Uranium in Different Samples from Eastern ...

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ISSN 1878-5220

Volume 8 • 2014

Procedia - Earth and Planetary Science Vol. 8 (2014) 1–102

International Workshop “Uranium, Environment and Public Health” (UrEnv 2013) Editors: Teresa Albuquerque and Margarida Antunes

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Available online at www.sciencedirect.com

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ScienceDirect Procedia Earth and Planetary Science 8 (2014) 1

Introduction to the Special Issue of Procedia Earth and Planetary Science: UrEnv2013-Uranium, Environment and Public Health

The Iberian Peninsula (Portugal and Spain) has broad experience in the exploration and exploitation of radioactive minerals mostly related to mining activities. Nowadays these abandoned mines don’t have any environmental recovery plan and are very susceptible to major environmental problems, calling for continuous monitoring and control. The significant contamination, due to the nature of the associated chemical elements, their high mobility and radiological risk, requires the conception and implementation of appropriate remediation steps. The special issue of Procedia Earth and Planetary Science includes manuscripts of the presentations held at the International workshop UrEnv2013 - Uranium, Environment and Public Health, organized by the Polytechnic Institute of Castelo Branco (Portugal; 25th October, 2013). This International workshop was targeted to the presentation and debate of diverse case studies addressing its importance to the environment and public health. A very special acknowledgement to the reviewers: Abreu MM (ISA, Technical University of Lisboa; Portugal); Almeida JPF (Polytechnic Institute of Castelo Branco; Portugal); Carvalho PCS (FCT, University of Coimbra; Portugal); Danko A (FEUP, University of Oporto; Portugal); Góis J (FEUP, University of Porto; Portugal); Goovaerts P (BioMedware; Michigan); Nieto PJG (University of Oviedo; Spain); Silva C (FC, University of Lisbon; Portugal); Silva IC (Polytechnic Institute of Castelo Branco; Portugal); Sousa AJ (IST, Technical University of Lisbon; Portugal) and Taboada J (University of Vigo; Spain). We would wish to extend our sincere thanks to José Carlos Gonçalves (Vice-President of the Polytechnic Institute of Castelo Branco) for his very helpful and valuable scientific support. The International workshop UrEnv2013 was organized under the project Poctep (EU) Águeda “Caracterización ambiental y análisis de riesgos en cuencas transfronterizas: proyecto piloto en El río Agueda (ref. 0410_AGUEDA_ 3_E)" (2011 – 2013).

Editors,

Teresa Albuquerque Margarida Antunes

1878-5220 © 2014 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco doi:10.1016/j.proeps.2014.05.001


ScienceDirect Procedia Earth and Planetary Science 8 (2014) 2 – 6

International workshop “Uranium, Environment and Public Health”, UrEnv 2013

Sequential Gaussian Simulation of Uranium Spatial Distribution – a Transboundary Watershed Case Study Albuquerque MTDa*, Antunes IMHRa, Seco MFMa, Roque NMa, Sanz Gb a

Polytechnic Institute of Castelo Branco and CIGAR, Castelo Branco 6000, Portugal b Universidad de Vigo, Vigo 36310, Spain

Abstract The main purpose of this work is the uranium spatial distribution patterns in groundwater, within the Águeda river transboundary watershed (Portugal-Spain). Mineral resources occur distributed throughout the watershed, mainly sulphide and uranium minerals. Sixty-five groundwater samples were analyzed. Geostatistical modeling was used, throughout conventional variography and Sequential Gaussian Simulation algorithm, to model the groundwater uranium spatial distribution. A hundred simulations, differing in their initial random-number seed, were performed. Spatial uncertainty evaluation allowed the definition of future monitoring and sampling strategies as well as the measurement of remediation possibilities. Uranium hot spots are strongly embedded in the central area (Ciudad Rodrigo). © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

© 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco

Keywords: Groundwater; uranium; Gaussian simulation; spatial distribution; Águeda watershed

1. Introduction Uranium is a naturally occurring element present as a trace constituent in the earth's crust 1. However, uranium ore extraction produces tailings, containing large volumes of contaminated waste rocks and heap-leach residues accumulated in dumps at mine sites2-4. The discharges of uranium and associated radionuclides as well as heavy metals

* Corresponding author. Tel.: +351 272 339 300; fax: +351 272 339 399 E-mail address: [email protected]

1878-5220 © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco doi:10.1016/j.proeps.2014.05.002

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M.T.D. Albuquerque et al. / Procedia Earth and Planetary Science 8 (2014) 2 – 6

Six decades of uranium exploration and mining milling in Europe has resulted in a considerable legacy of waste rock piles, below-grade ore heaps and milling residues disposal sites – Uranium Mine and Mill Tailings (UMMT)5. The remediation of UMMT sites has two objectives: 1) to interrupt pathways to radiological and to non-radiological exposures; 2) to mechanically stabilize the sites against environmental processes, such as erosion 5. However, almost mining activities ceased without any environmental recovery plan and the rejected materials remain exposed to environmental conditions. Runoff superficial water dissolves substances from soils and sediments and allows their transport into groundwater, increasing trace element concentrations, such as uranium. Groundwater spatial trace elements distribution will allow the identification of potential contamination sources. The groundwater vulnerability assessment is a critical point in decision-making processes, aiming to land use and resource management optimization. Therefore, it is imperative the adoption of preventive measures as well as accurate monitoring processes. The establishment of spatial patterns for U contamination within the transboundary watershed of the Águeda River (Portuguese and Spanish territory) is the main goal of this paper. This study is part of on-going project AGUEDAEnvironmental models for territorial’s assessment and management: Águeda’s watershed case study to develop a methodology for environmental risks and human health.

2. Material and Methods The study area - Águeda watershed - is located in the central west area of the Iberian Peninsula, between Portugal and Spain (Fig. 1a), occupying a total area of 2600 km6. Anthropogenic activities grew exponentially in the last 50 years and the exploitation of natural resources, coupled with changes in consumer habits, induced environmental changes on the local population. Ciudad Rodrigo (Spain) is the main urban and farming region in the Águeda watershed (Fig. 1b).

a)

PORTUGAL

b)

SPAIN

●

●

Fig. 1. (a) Águeda Watershed location; (b) sampling design.

Ciudad Rodrigo

4


In the Águeda transboundary watershed were selected and collected a total of sixty-five groundwater samples, between 1 and 2 m below surface (during May 2012). Selected chemical element contents were analyzed in the Natural Resources and Agro-biology Institute (IRNASA, Salamanca; Spain). Uranium total groundwater content was determined by inductively coupled plasma mass spectrometry. Sequential Gaussian simulation was used for conditional stochastic simulation of the uranium groundwater concentration distribution. Sequential Gaussian simulation starts by defining the univariate distribution of values, performing a normal score transform of the original values to a standard normal distribution. Simulation of normal scores at grid node locations was done sequentially with simple kriging (SK) using the normal score variogram and a zero mean7,8. Once all normal scores were simulated, they were back-transformed to original grade values. For the computation the Space-Stat software V. 4.0.7 was used9.

3. Results and conclusions Selected results of multiple uranium simulated realizations are presented in figure 2. The evaluation of the spatial uncertainty allows to conclude that hot spots of U are strongly implanted in the central area of the Águeda watershed (Fig. 2), overlapping the urban area of Ciudad Rodrigo, where is located the principal U abandoned mines. Small variations, in the spatial patterns, can also be observed. Concerning the watershed’s comers, high spatial uncertainty can be observed as the simulated U hot spots shows high variability throughout the simulated realizations (Fig. 2), which could be related to uranium mine exploitations.

Fig. 2. Multiple uranium simulated realizations.


The average simulated map for uranium distribution together with the experimental omnidirectional variogram, and fitted parameters, are shown in figure 3. The average representation stresses the high content of U located in the central part of the Águeda river watershed (Figs. 2 and 3). Local north and east U hot spots can be also identified, with high spatial uncertainty associated though (Fig. 3).

a)

b)

U normal score omnidirectional variogram’s fitted parameters C0 (nugget effect) 0,38 C1 –sill - spherical model 0,44 C2 – sill - spherical 0,46 model Range 2100 m

Fig. 3. (a) Average simulated map of uranium content; (b) omnidirectional variogram and fitted parameters.

The obtained results points to the old mining activities as a clear environmental risk factor. These situations should be carefully monitored in future work as they can play an important role as an environmental liability. In addition, the fact that this watershed is shared by two different countries hampers its management and make long-term planning challenging. Future works spatial uncertainty evaluation allows to define future monitoring and sampling strategies as well as the measurement of remediation possibilities.

Acknowledgements This research was funded by the POCTEP project “Caracterización ambiental y análisis de riesgos en cuencas transfronterizas: proyecto piloto en el río Agueda” (Ref. CE: 0410_AGUEDA_3_E).

References 1. Zachara JM, Long PE, Bargar J, Davis JA, Fox P, Fredrickson JK, Freshley MD, Konopka AE, Liu C, McKinley JP, Rockhold ML, Williams KH, Yabusaki SB. Persistence of uranium groundwater plumes: Contrasting mechanisms at two DOE sites in the groundwater–river interaction zone. J Cont Hydro 2013; 147: 45-72. 2. Gómez P, Garralón A, Buil B, Turrero MJ, Sánchez L, De la Cruz B. Modeling of geochemical processes related to uranium mobilization in the groundwater of a uranium mine. Sci Total Environ 2006; 366: 295-309. 3. Mkandawire M. Biogeochemical behaviour and bioremediation of uranium in waters of abandoned mines. Environm Sci Pol Resea 2013; 20/11:

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7740-7767. 4. Neiva AMR, Carvalho PCS, Antunes IMHR, Silva MMVG, Santos ACT, Cabral Pinto MMS, Cunha PP. Contaminated water, stream sediments and soils close to the abandoned Pinhal do Souto uranium mine, central Portugal. J Geochem Explor 2014; 136: 102-117. 5. Falck WE. The long-term safety of uranium mine and mill tailing legacies in an enlarged EU. European Communities: JCR Scientific and Technical Reports; 2008. 6. Albuquerque MTD, Sanz G, Oliveira SF, Martínez-Alegría R, Antunes IMHR. Spatio-temporal groundwater vulnerability assessment – a coupled remote sensing and GIS approach for historical land cover reconstruction. Water Resour Manage 2013; 27: 4509–4526. 7. Deutsch CV. Geostatistical Reservoir Modeling. New York: Oxford University Press; 2002. 8. Goovaerts P. Geostatistics for natural resources evaluation. New York: Oxford. University Press; 1997. 9. Biomedware. Space-Stat software V. 4.0.7; 2013.




Assessment of Radon Concentrations Inside a High School Building in Guarda (Portugal): Legislation Implications and Mitigation Measures Proposed Antão AMa* a

Instituto Politécnico da Guarda, Guarda 6300, Portugal

Abstract The maximum accepted radon concentration in buildings represents the national reference level for radon and is an important parameter in the indoor air quality (IAQ). In Portugal, national regulations defines the maximum concentrations of 400 Bq/m3 of radon, being there search mandatory only in dwellings in granitic areas as Guarda district. With the aim of assessing the average values of indoor radon, it was made a study of radon concentrations inside of Instituto Politécnico da Guarda (IPG). It was used a continuous Radon Monitoring equipment for real-time measurements in two different periods – winter and summer. The results obtained show an IAQ for radon gas above 400 Bq/m3, with some seasonal variations, as well as variations related to the occupation of these divisions.According to that some mitigation solutions are proposed. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: indoor radon; cancer; granitic bedrock; convection air flow; Portugal

1. Introduction Recent studies1-3 on indoor radon and lung cancer in Europe, North America and Asia, provide strong evidences that radon causes a substantial number of lung cancers in the general population. Current estimates of the proportion of lung cancers attributed to radon, range from 3 to 14%4. According to Word Health Organization (WHO), radon is the second cause of lung cancer after smoking, growing this risk by 8% per 100 Bq/m 3 increase in measured radon concentration. The maximum accepted radon concentration in dwellings represents the national reference level for radon and is an important parameter in the indoor air quality (IAQ).The Handbook on indoor radon from WHO4, proposes a reference level of 100 Bq/m3 to minimize health hazards due to indoor radon exposure. * Corresponding author. Tel.: +351 271 220 100; fax: +351 272 222 690. E-mail address: [email protected]


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A.M. Antão / Procedia Earth and Planetary Science 8 (2014) 7 – 12

Other countries and associations1,5 have different values : Norway - New indoor radon limits for certain types of building have been recently adopted (100 Bq/m 3, x action required and 200 Bq/m3, maximum value accepted); WHO – if the radon reference level of 100 Bq/m3 cannot be implemented the chosen reference level should x not exceed 300 Bq/m3; x Austria - action levels for existing and new buildings are 400 and 200 Bq/m³, respectively ; x Switzerland – the Swiss Radiological Protection Ordinance set a guidance value of 400 Bq/m3 for the concentration of radon gas in dwellings; x Sweden – indoor radon limits for new buildings is 140 Bq/m3 and 400 Bq/m3 for reconstruction, being those limits compulsory; x UK - domestic Action Level is 200 Bq/m3; x Finland - the indoor radon concentration should not exceed 400 Bq/m3 in existing buildings, whereas new buildings should be built so that 200 Bq/m3 is not exceeded; Belgium - indoor radon action-level is 400 Bq/m3 and design level for new buildings is 200 Bq/m3. x In some countries such as Sweden, Switzerland and the Czech Republic, if the radon measurements indicate that this level is exceeded it is compulsory that action be taken to reduce the radon concentration. Other countries (Norway, Switzerland, the UK and the USA) impose radon measurements as part of a property transaction. In Portugal, national legislation, DL 79/20066, defines the reference concentrations of pollutants within the existing buildings, namely “… maximum concentrations of 400 Bq/m3 of radon, being there search mandatory only in dwellings in granitic areas, particularly in the districts of Braga, Vila Real, Porto, Guarda, Viseu e Castelo Branco”. It also defines for educational buildings a periodicity of auditing the radon level every two years. The Instituto Tecnológico e Nuclear (ITN) makes reference to the correlation between the granitic bedrock and high concentration zones of radon gas in Portugal7. Recent works8,9 indicate a strong correlation between high radon levels in dwellings of the Guarda region due to several factors such as: high U average content of the granitic rocks of this region; high radon levels in the soil gas at 80 cm deep; presence of uranium mineralizes faults and dikes that present high U contents and radon concentrations. Based on these assumptions, it was made a study of indoor radon concentrations in the School of Technology (ESTG) from Polytechnic Institute of Guarda (IPG), with the aim of assessing the average values and, in the case of these exceeds the regulations, to propose mitigating measures. This region was an ancient miner zone for uranium and radium exploration (Forte Velho, Tapada dos Mercados, Cruz da Faia and Tintinholho mines), being nowadays disabled. The ESTG is localized in a granitic rock massif that presents some superficial alteration with the production of a saprolite soil that serves as a foundation ground for the ESTG building. Besides that, the region has a cold climate with an average annual minimum temperature of -2,8ºC10 and an average of 40 days per year with temperatures below 0ºC, especially during November, December, January, February and March. This makes quite difficult to perform some mitigation measures of radon gas such as natural ventilation.

2. Methodology The indoor radon measurement was made in classrooms, laboratories, professor’s office, and caves. For this purposes we used a continuous Radon Monitoring equipment (Radon Monitor 1029 from SUNNUCLEAR CORP.), that record real-time continuous measurements of radon gas, air temperature, humidity and pressure. It is an active device, similar to ionization chamber that is used for inside measurements of radon emanation. The scintillation counts are processed by electronics and values are stored in the instrument’s memory and posterior download to a PC. The measurements were made in two different time periods – November/December (cold season) and May/September (hot season) during the normal operating period of school, with students and professors moving in and out. The equipment was located in a corner of the rooms to prevent air currents and works continuous during the measurement period. This methodology permits relate the radon values with the temperatures and humidity that exists at the time of measuring, and also to know where the radon gas came from.

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3. Bedrock characterization 3.1 Geological framework of the region The Guarda granite, as well as the surrounding granites is derived from the partial melting of relatively hydrated sediments, considered as sin-orogenic, sin-F311. The ESTG building is located in a porphyroid coarse grain granitic rockmass, monzonite type (Fig. 1). There are granitic rocks from deep origin, resulting of the melting of materials that are installed in the shear zones Carbonífero Dúrico-Beirão and Vigo-Régua)11. It is a very fractured old rockmass due to the alpine faults that cross through. The field work done allowed defining four joint systems – three subverticals and one sub horizontal12. Figure 1b shows the main vertical joint systems characteristics obtained with the DIPS® software in the study zone. The study zone presents a morphology shaped by the work of the Alpine fault systems, with a NE-SW orientation (Fig. 1a), and by the influence that ancient glaciers, with more than 20000 years old, left on the terrain13. The current climatic environment has provided the superficial weathering of the rock material in a saprolite soil with high porosity. In the field the rockmass is weathered on the surface and in some cases more deeply with transformed into a regolith material. The alteration of these rocks tends to decrease with depth, being highly conditioned by the joint network systems and morphological characteristics of the terrain.

a 1

2

3

4

5

15

16

17

18

19

6

7

8

9

10

11

12

13

b

14

Fig. 1. (a) Geological framework of the region. Legend: 1- Porphyroid granites and granodiorites; 2-Monzonite porphyroid granites; 3-Granites and granodiorites; 4-Biotitic quartz diorites and granodiorites; 5-Biotitic granites; 6- Muscovite-biotite granites; 7-granite-gneiss; 8-Early biotite granites; 9-Quartzites of Armonicano; 10-“Malpica” formation; 11- “Beiras” complex; 12-“ Almaceda” formation; 13-“Rosmaninhal” formation; 14-Conglomerates; 15-Arcoses; 16-Quartz Veins; 17-alluvium; 18-Glacial deposits; 19- Faults; (b) Analysis of the joints systems with the DIPS ® software.

3.2 Rock material characterization It is monzonitic two mica granite, with large predominance of biotite, coarse grained, porphyritic texture, with an average size of the matrix crystals of 7 mm and the feldspar megacristals having lengths between 45 to 70 mm. The main minerals are quartz, microcline, oligoclase, biotite, albite and muscovite, having been observed as accessories the apatite, the zircon and the magnetite. The kaolinite, sericite and chlorite are the most abundant secondary minerals14. The characterization of the granitic material with weathering grades from I to IV15, was done after a surface geological reconnaissance. This characterization showed some different physic characteristics depending on the degree of weathering. In the more weathering grades the porosity ranges between 7,3 and 14 %, while in the

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fresh rock its range between 0,5 and 1 %12,16. The Fissuration Index (IF) 17, also showed important variations with duplicate values between the fresh rock and the more weathering grades, which denotes an intense material fissuration in this weathering grade. In the fresh or less weathered rock, the presence of fractures even closed is rare, not observing cracks in their minerals. In the medium and high weathering granitic rocks, the cracking and fissuration are very sharp, leading to a loss of cohesion of the rock material and its subsequent transformation into a saprolite soil12, which allows the radon emanation to the atmosphere and to the interior of buildings. Different studies18 shows that U is mainly primary and resides in accessory minerals, being mobilized by post-magmatic processes. Secondary sites of U include grain boundaries, cleavage traces and micro fractures that facilitate radon emanation 4. Building characterization The ESTG building consists of two floors and is developed mainly in length. Has an under surface basement (cellar), offices and laboratories on the 1st floor and classrooms and professor’s offices on the 2nd floor. It is a framed structure building with the external walls made of two individual brick panels, and the interior walls formed by one single panel. The indoor doors are made of wood fiber plates with a honeycomb structure. The windows are glazed with simple aluminium frame with double glass and thermal break. Table 1 shows the areas and volumes of the divisions where measurements were made. Table 1. Areas and volumes of the measured divisions. Division

Area (m2)

Volume (m3)

Cellar

161,10

342,20

Professor's office

25,90

77,70

Classroom

103,15

309,45

5. Results and discussion 5.1 Results The results obtained for this campaign are presented in figures 2 and 3. Figure 2 shows the concentration of gas radon and temperature values in a professor’s office and in the ESTG building cellar. Figure 3 illustrates the concentration values of gas radon and temperature measured in a classroom and at the ESTG cellar obtained in the hot season. Table 2 shows the statistic parameters for the measurements made in the two places during May and September (hot season) and November /December (cold season). Table 2. Statistical parameters for the measurements made in the two divisions in the hot and cold season. Division

Professor's office 76 (Bq/m3) Hot season

Cold season

Cellar (Bq/m3) Hot season

Cold season

Average

478,73

521,16

1288,74

2141,11

Standard deviation

113,53

214.26

449,71

427,81

Maximum value

860,40

918,80

2409,1

3279,7

Minimum value

282,200

51,0

468,10

1033,7

11


b

a Fig. 2. Values of radon gas concentration and temperatures obtained in the cold season for (a) a professor’s office 76; (b) the ESTG building cellar.

a

b

Fig. 3. Values of radon gas concentration and temperatures obtained in the hot season for (a) a professor’s office 76; (b) the ESTG building cellar.

5.2 Discussion The measures presented in Fig.2 were done in November/December – the cold season19, with the heaters working inside the building. Outside the air temperature varies by at least 10 to 15 ºC less. This makes a slight indoor sub pressure, which allows the air to come from the foundation settlement to the cellar and them to the second floor where the professor´s offices are. This is the last floor with no open windows or door, so the air becomes tapered there. The results obtained in the hot season and presented in Fig.3, shows values of radon gas concentrations less than those obtained during the cold season for the same room/floor. This may suggest a minor entrance of radon gas to the building in the hot season. In fact, during this season there are not sub pressures of the building due to their heating. Also during this season the windows and interior doors are usually open for air circulation and ventilation. The saprolite soil of the ESTG building foundation has a porosity that allows a rapid gas emanation to the open air. This air, with high concentrations of radon gas, it comes to the cellar and them from convection air flow to the other upper floor of the building. The values in table 2, showed that the highest values are in the cellar during the cold season. In the Professor’s office the highest values are also during this season, which denotes a very poor ventilation. 6. Mitigation measures The occupants of the building are subject to continued exposure resulting in an accumulated effective dose, that can provide significant risks to the health of its occupants. In the light of the results obtained, which allow the existence of a risk, some measures and methodologies are proposed to keep radon levels within the admissible

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values. As the building is already built and in use, we propose some mitigation solutions being in mind, there is an old construction located in a very cold region. Different authors propose the use of forced ventilation through the execution of ventilation pipes inside the cellar to the rock mass, for placement of a depression mechanical ventilation system that drive the air of this zone to the exterior of the building20,21. It also proposed a PVC membrane having at least 6 mm thick according to EPA22,23 to coat the cellar ground and the buried walls of the basement. 7. Final considerations The results obtained from this campaign show an IAQ for radon gas above the maximum reference level for the national regulations (400 Bq/m3). Additionally, there are also seasonal variations, as well as variations related to the occupation of these locations by the inhabitants. In function of the values obtained in the different places analyzed (cellar and 1st floor), we conclude that migration of radon is from the saprolite soil of the foundation, to the interior of the basement and to the upper floors, commanded by the variations in pressure and temperature existing inside the building. Some mitigation solutions are proposed being in mind, there is an old educational building in a very cold region, to the natural ventilation is not an appropriate methodology for lower the radon values. It proposes a depression mechanical ventilation system associated with a PVC membrane to coat the cellar ground and walls. Measurements of radon should be made frequently to assess the functioning of these measures. References 1. IRPA (International radiation Protection Association). Proceeding from the Third European Congress. Radiation protection – science, safety and security. www.irpa.net; 2010. 2. Lazo E., Smith R, Coates R, Andersen R, Asano Y, Chapple C-L, Faulkner K, Hefner A, Hill M, Jones R, Larsson C-M, Liebenberg G., Liland A, McKinlay A, Menzel H-G, Perks C, Rodriguez M, Schieber C, Shaw P, Visage A, Wakeford R, Ye S-J. The state of radiological protection; views of the radiation protection profession: IRPA13, Glasgow. J Radiol Prot 2012; 32: 489-524. 3 Field RW, Steck DJ, Smith B, Brus C, Fisher E, Neuberger J, Platz C, Robinson R, Woolson R, Lynch C. Residential Radon Gas Exposure and Lung Cancer. American J Epidemiology 2000; 151, 11: 1091-1102. 4 WHO (World Health Organization). Handbook on indoor radon: a public health perspective. Ed. H. Zeeb & F. Shannoun; 2009. 5 EPA. Building Radon Out. A Step-by-Step Guide On How to Build Radon-Resistant Homes. In http://www.epa.gov/radon/images/hmbuyguidsp.pdf; 2001. 6 DL 79/2006 de 4 de abril. Regulamento dos Sistemas Energéticos de Climatização em Edifícios. Portugal; 2006. 7 ITN. Radão: Um Gás Radioactivo de Origem Natural. Portugal; 2005. 8 Neves LJPF, Avelans SCC, Pereira AJSC. Variação sazonal do gás radão em habitações da área urbana da Guarda (Portugal Central). IV Congresso Ibérico de Geoquímica-XIII Semana de Geoquímica, Lisboa; 2003. p. 307-309. 9 Pereira AJSC, Neves LJPF. Radon In Portugal. 9th Int. Symp on Metal Ions in Biology and Medicine. 2006. Abstr Book; O-1. 10 IPMA. Normais climatológicas 1971-2000. (www.ipma.pt/oclima/normais.clima/1971-2000/010/). Accessed on 27/12/2013. 11 Ferreira N, Iglesias Ponce de Léon, M, Noronha F, Ribeiro A, Ribeiro ML. Granitóides da Zona Centro Ibérica e seu enquadramento geodinâmico. In: Bea, F., Carnicero, A., Gonzalo, J.C., López Plaza, M. & Rodrigues Alonso, M. D. (Eds). Geologia de los Granitoides e Rocas Associadas del Macizo Hespérico. Editorial Rueda, Madrid, 1987. p. 37-51. 12 Antão AM. Comportamento geotécnico do granito da Guarda relacionado com a sua alteração. PhD. Thesis, Coimbra; 2004. 318 p. 13 Ferreira N, Vieira G. Guia Geológico e Geomorfológico do Parque Natural da Serra da Estrela. Ministério da Economia, IGM e ICN, 2000. 14 Teixeira C, Martins JA, Medeiros JA, Pilar L, Carvalhosa A, Ferro MN. Notícia explicativa da folha 18-C, Guarda. Carta Geológica de Portugal 1/50000. SGP, Lisboa; 1963. 15 IAEG. Rock and soil description and classification for engineering geological mapping. Report of the IAEG Commission on Eng. Geol. Mapping. Bull of Int. Assoc. Eng. Geol. 1981; 24: 235-274. 16 Ferreira MQ, Antão AM. Caracterização química e mineralógica do estado de alteração do granito da Guarda. VI Congresso Nacional de Geologia. Rev Ciências Terra 2003. V: 24-25. 17 Delgado Rodrigues, J. Laboratory study of thermally-fissured rocks. Memória nº 583, LNEC, Lisboa, 13pp., 1983. 18 Pereira AJSC, Neves LJPF, Godinho MM. Suportes do urânio no granito das beiras – implicações para o potencial de emanação do radão .II Congresso Ibérico de Geoquímica-XI Semana de Geoquímica, Lisboa; 1999. p. 137-140. 19 Fonseca AR, Pimenta E. O gás radão no departamento de engenharia civil da ESTG. Projeto de fim de curso; 2010. 155 p. 20 Ferreira MJMM, Coelho MJP. O radão em edifícios – minimização da perigosidade. Universidade Fernando Pessoa: Porto; 2011. 21 Roserens GA. Radon:15 ans d’expérience; 150 assainissements. http://Kheops.champs.cstb.fr/Radon/Doc/7%20radon%20en%Suissex.pdf; 2004 22 EPA. Passive Radon Control System for New Construction. www.epa.gov; 1995. 23 RADPAR. Radon Prevention and Remediation. 2012 . http://web.jrc.ec.europa.eu/radpar/




Uranium and Arsenic Spatial Distribution in the Águeda Watershed Groundwater Antunes IMHRa*, Albuquerque MTDa, Seco MFMa, Oliveira SFa, Sanz Gb a

Polytechnic Institute of Castelo Branco and CIGAR, Castelo Branco 6001-909, Portugal b Universidad de Vigo, Vigo 36310, Spain

Abstract The high spatial variability of groundwater contaminants is a non-stationary process, as spatial variability is strongly dependent on several externalities. The herein work shows a first approach to the construction of spatial distribution patterns for sensitive contaminants in groundwater, within the transboundary watershed of the Águeda River. The obtained results points out to the old mining activities as a serious environmental risk factor. The obtained maps showed to be suited for assessing the environmental impact of the considered contaminants and could facilitate the improvement of local groundwater systems’ management and the development of specific monitoring activities. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selectionand and peer-review under responsibility the Instituto Politécnico Castelo Branco. Selection peer-review under responsibility of the of Instituto Politécnico de CastelodeBranco Keywords: Uranium; Arsenic, groundwater; mining area; Águeda watershed, geochemical maps.

1. Introduction Mining can be regarded as a potentially harmful activity to groundwater. The extraction of uranium ore produces tailings, large volumes of contaminated waste rocks and heap-leach residues accumulated in the dumps at mine sites. The discharges of uranium and associated heavy metals and metalloids from waste and tailing dumps in abandoned uranium mining and processing sites pose contamination risks to surface and groundwater 1,2 leading to contamination of stream sediments and soils2-5.

* Corresponding author. Tel.: +351 272 339 900; fax: +351 272 339 901. E-mail address: [email protected]


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In wet climates, acid mine drainage development and leaching of dumps are dominant pathways of contaminants into the surrounding environment. Most mining operations ceased its activities without any environmental recovery plan and the rejected materials remain exposed to environmental conditions. Surface water runoff contributes for some substances dissolution and allows their transport into groundwater. Therefore, groundwater can be affected and altered with an increasing of the concentrations of heavy metals, such as U and As. The U and As spatial groundwater’s spatial patterns concerning the transboundary watershed – Portuguese and Spanish territory - of the Águeda river is the core issue of this manuscript. This survey is part of on-going project AGUEDA- Environmental models for territorial’s assessment and management: Águeda’s watershed case study to develop a methodology for environmental hazards and human health assessment. The spatial distribution of these factors will permit the identification of potential pollution sources, taking into account the primary activities in the subject area: agriculture, mining, industrial or urban activities. The groundwater vulnerability assessment is a critical point in decision-making processes, aiming to land use and resource management optimization. Therefore, it is imperative the adoption of preventive measures as well as accurate monitoring processes.

2. Águeda River Watershed The Águeda River catchment (total area of 2600 km2) is situated in the central west portion of the Iberian Peninsula between the Portuguese district of Guarda (310 km2) and the Spanish provinces of Salamanca and Caceres (2290 km2)6. Anthropogenic activities grew exponentially in the last 50 years. Ciudad Rodrigo (Spain) is the main urban and agricultural area in the Águeda watershed. Mineral resources occur distributed throughout the watershed; mainly sulphides and uranium minerals associated to granitic intrusions together with detrital iron and associated sedimentary materials7. The exploitation of natural resources, coupled with changes in consumer habits, induced environmental changes with long-term consequences on the local population6. Mining activities constituted one of the principal human activities in the Águeda watershed area particularly uranium mineral explorations 7. Nowadays, mining explorations have ceased and there has not been any significant outgrowth work in the field. The tailings and rejected materials were deposited along the ground and are not covered by vegetation. They are exposed to the air and water that can change the environmental geochemistry of surface streams and groundwater. In addition, this watershed is shared by two different nations (Portugal and Spain), which can difficult manage and planning activities.

3. Methodology A total of 75 samples of groundwater was collected in the Águeda watershed area along a sampling grid of 7.5 x 7.5 km, during May 2012 (Fig. 1). Water from wells was collected between 1 and 2 m below the waterline. Temperature, pH, ORP, electrical conductivity (EC) and dissolved oxygen (DO) were analyzed “in situ”. Nitrates, phosphates, As, B, Ba, Ca, K, Mg, Mn, Na, Sr and U contents were determined in the Natural Resources and Agrobiology Institute (IRNASA, Salamanca; Spain). Analytical techniques include inductively coupled plasma mass spectrometry (metals and uranium) and atomic absorption (arsenic). Groundwater’s quality spatial patterns, concerning to metals and metalloids concentrations in groundwater, were constructed using geochemical and geostatistical approaches, using the Geostatistical Analyst of ArcMap 10 8. U and As showed a strong association stresses in the performed Principal Components Analysis (Fig.2). Spatial patterns were then represented through a geostatistical interpolation procedure (Gaussian kriging with backtransform algorithm).

I.M.H.R. Antuneset al. / Procedia Earth and Planetary Science 8 (2014) 13 – 17

Fig. 1. Groundwater sampling points collected in the Águeda River watershed. y - groundwater samples location. PT – Portugal; ES – Spain.

4. Results and Conclusions The U distribution shows its dependence to the U-mines influence showing hotspots in the central region of the Águeda watershed. Arsenic shows a distinct behavior relative to other trace elements, but a strong association with U, which can be observed in the performed Principal Components Analysis (Fig. 2). The occurrence of these two factors can be associated with mining activities in the region9. The U distribution map shows that hotspots are mainly concentrated in the central part of the area, which coincide with abandoned mine activities sites (Fig. 3). The As distribution shows a smoother distribution but still with higher values occurring in the central area, also related to their proximity to the mineralization and old mining activities (Fig. 3). However, the smoother arsenic distribution, all along the Águeda watershed area, can be supported by the evidence that arsenopyrite (arsenic sulfide mineral) is not the most relevant mineral of the mineralized veins, and occurring associated with other sulfide minerals, as it has been confirmed in other mine areas10. In the northern and southern parts of the Águeda watershed it is possible to identify clusters of moderate to high concentrations of U and As, which will be the target of a detailed future study. The obtained results points out of an older mining activity as a serious environmental risk factor. Gaussian kriging with backtransform algorithm, allowed the interpolation, to the all study area with outliers weight attenuation and final representation in the original variables space, allowing ulterior results validation and subsequently providing a robust tool11 for risk assessment within the study area and therefore allowing the future network monitoring design in a more robust and appropriate way.

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Fig. 2. PCA F3-F4 factorial plan.

(a)

(b)

Fig. 3. Geochemical distribution maps for the Águeda river watershed: (a) Uranium; (b) Arsenic.

I.M.H.R. Antuneset al. / Procedia Earth and Planetary Science 8 (2014) 13 – 17

Future work will be focused on the evaluation related to the probability of these elements to exceed a specific threshold (e.g., water supply values or background contents10). Groundwater’s temporal characterization is another issue expected to be overcome with sampling campaigns during the winter season. The definition of seasonal patterns for the contaminant spatial distribution will be useful for determining its dependence with precipitation and infiltration.

Acknowledgements This research was funded by the POCTEP project “Caracterización ambiental y análisis de riesgos en cuencas transfronterizas: proyecto piloto en el río Agueda” (Ref. CE: 0410_AGUEDA_3_E).

References 1. Gómez P, Garralón A, Buil B, Turrero MJ, Sánchez L, De la Cruz B. Modeling of geochemical processes related to uranium mobilization in the groundwater of a uranium mine. Sci Total Environ 2006; 366: 295-309. 2. Neiva AMR, Carvalho PCS, Antunes IMHR, Silva MMVG, Santos ACT, Cabral Pinto MMS, Cunha PP. Contaminated water, stream sediments and soils close to the abandoned Pinhal do Souto uranium mine, central Portugal. J Geochem Explor 2014; 136: 102-117. 3. Lottermoser BG, Ashley PM, Costelloe MT. Contaminant dispersion at the rehabilitated Mary Kathleen uranium mine, Australia. Environm Geol 2005; 48: 748-761. 4. Lottermoser BG, Ashley PM. Physical dispersion of radioactive mine waste at the rehabilitated Radium Hill uranium mine site, South Australia. Aust J Earth Sci 2006; 53: 485-499. 5. Kipp GG, Stone JJ, Stetler LD. Arsenic and uranium transport in sediments near abandoned uranium mines in Harding County, South Dakota. Appl Geochem 2009; 24: 2246-2255. 6. Albuquerque MTD, Sanz G, Oliveira SF, Martínez-Alegría R, Antunes IMHR. Spatio-temporal groundwater vulnerability assessment – a coupled remote sensing and GIS approach for historical land cover reconstruction. Water Resour Manage 2013; 27: 4509–4526. 7. Sánchez-González S, García-Sánchez A, Caravantes P, Rodríguez-Cruz MS, Sánchez-Martín MJ, Rodríguez ISR. Caracterización y análisis de impactos ambientales en la cuenca del rioÁgueda. In: Francisco Campos Sánchez-Bordona, editor. Cuenca del rio Águeda un território para dos Países. Servicio de Publicaciones. Universidad Europea Miguel de Cervantes Valladolid; 2013. p. 35-64. 8. ESRI. ArcGIS Desktop, Version 9.3. Environmental Systems Research Institute, 329 Washington: Inc. Reedlands; 2004. 9. Seco MFM. 2014 Caraterização ambiental e análise de riscos na bacia hidrográfica do rio Águeda. Msc in Sistemas de Informação Geográfica em Recursos Agro - Florestais e Ambientais – Especialização em Análise de Informação Geográfica (Unpublished thesis), ESA/IPCB, Castelo Branco: Portugal; 2014. 10. Antunes IMHR, Albuquerque MTD. Using indicator kriging for the evaluation of arsenic potential contamination in an abandoned mining area (Portugal). Sci Total Environ 2013; 442: 545–552, 11. Saito H, Goovaerts P. Geostatistical interpolation of positively skewed and censored data in a dioxin contaminated site. Environ Sci Techn 2000; 34 (19): 4228-4235.

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Uranium Contents in the Lithological Formations of Santiago Island, Cape Verde Cabral Pinto MMSa*, Silva MMVGb, Ferreira da Silva Ea, Miranda Pa, Marques Ra,c, Prudêncio Ia,c, Rocha Fa b

a Geobiotec Research Centre, Aveiro, 3810-193, Portugal Geociences Centre, University of Coimbra, Coimbra 3000-272, Portugal c C2TN, IST, Univ. Lisboa, EN10, Bobadela, Portugal

Abstract We present the uranium contents in the different lithological formations of Santiago. The island is constituted by basalticbasanite rocks, but phonolitic-trachytic rocks also occur. The highest contents of uranium occur in the phonolitic-trachytics rocks of Ancient Complex and Pico Antónia Formations, and also in other formations of heterogeneous materials, which have phonolitictrachytics fragments, reaching 62.8 μg.g-1 of uranium. These contents are much higher than those of the MORB (0.047-0.18 μg g1) and OIB (1.02 μg.g-1) and even higher than those of the upper crust. The source of uranium in the rocks of Santiago is related with the occurrence of zircon © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

© 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection andpeer-review peer-review under responsibility the Instituto Politécnico deBranco Castelo Branco. Selection and under responsibility of theof Instituto Politécnico de Castelo

Keywords: Uranium; lithostratigaphical formations uranium contents; uranium source; Santiago Island; Cape Verde

1. Introduction The Cape Verde Islands are located in the Macaronesia region in the eastern shore of the Atlantic Ocean, 500 km



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west from Senegal’s Cape Verde Peninsula, after which the archipelago was named—between the latitudes 17°13′N (Santo Antão Island) and 14°48′N (Brava Island) and the longitudes 22°42′W (Boa Vista Island) and 25°22′ W (Santo Antão Island). The Cape Verde Archipelago is composed by 9 inhabited islands plus one uninhabited. The land areas vary from 35 km2 (Santa Luzia Island, uninhabited) to 991 km2 (Santiago Island). Over half of the archipelago’s population lives in the Santiago Island. The 40Ar/39Ar data indicate that the volcanic evolution of Santiago spread from 4.6 Ma (the major submarine phase) to 1.1-0.7 Ma (the late volcanic activity), with most of the sub aerial volcanism taking place from 3.3 to 2.2 Ma1,2. The periods of intense volcanic activity, which caused the growth of the island, are separated by erosion and sedimentation periods, materialised by intercalated sedimentary formations. After the initial phase of submarine volcanism, the volcanic building emerged and the volcanism became sub aerial. Isotopic data (Sr-Nd-Hf and Pb), major and trace elements data of rock samples from Santiago were present 3,4 in order to constrain the mantle source. The island of Santiago is the largest of the Cape Verde archipelago, with a length and width of 54.9 km and 29 km respectively, and reaching an altitude of 1392 m. Climatic conditions and erosion are some of the natural problems of the Cape Verde archipelago. Furthermore, human influence on the surficial environment has often proven to be inappropriate and with a strong impact. The knowledge of the natural geochemical variability is essential for the suitable resolution of economic, environmental, planning, medical and legal issues. The need for building a database of georeferenced geochemical information that comprises the surficial environment of the island of Santiago was the main motivation for carrying out this study. A geochemical survey of 252 rock samples, 339 stream sediment samples and 249 soil samples from the island of Santiago was conducted, following the guidelines of the International Project IGCP 259 not only at the sampling stage, but also in the subsequent stages of preparation, analysis, data treatment and mapping5,6. A textural analysis was also carried out, and the mineralogical composition of about 25% of the samples was studied5. In this work we present the uranium contents in the different lithological formations of Santiago Island, Cape Verde and try to understand its source.

2. Lithostratigraphic formations The lithological cartography of Santiago Island was published7 and together with other works8, helped to establish the volcano-stratigraphic sequence of the island. The oldest formation (Complexo Antigo - CA), spread through the island is essentially a dense very altered dyke complex, but intrusions of foid gabbroic and alkaline sienitic rocks, intravolcanic breccias, phonolites, trachytes, carbonatites and piroxenites also occur. The submarine volcanism is expressed by the Flamengos Formation (FL) which discordantly overlaps the CA and it occurs essentially in the centre and south of the island, particularly on the northeast slope (Fig. 1). The basaltic mantles (limburgites, basanites and basanitoides) are formed by the stacking of pillow-lavas, with subordinated breccias and intercalated tuffs. The breaccia form compact deposits and, in general, they are much altered into clay materials. The Orgãos Formation (CB) is essentially a very compact volcano-sedimentary unit, formed by a breccia/conglomerate with a sandstone matrix and may correspond to lahares. Some of the clasts result from CA erosion. The cement contains carbonated and zeolitic material, of secondary origin. The Eruptive Complex of Pico da Antónia (PA) is the geological formation with the largest development on the island representing more than half of the surface of Santiago Island (Fig. 1). This unit is essentially formed by thick sequences of basaltic lava flows, intercalated by pyroclastic material and the flows are essentially subaerial, but with some submarine pillows-lavas in the coast5,6. This formation also contain dikes, volcanic necks, domes and pyroclastic material of phonolitic-trachytic compositions. The Assomada Formation (AS) is constituted by basaltic mantles (basanites) and some basaltic pyroclastes, originated from exclusively sub-aerial activity. These lavas fill valleys and are, with the 50 cinder cones of the Monte das Vacas Formation (MV), the most recent manifestation of volcanism in Santiago Island4. The quaternary formations have a small spatial representation, are ancient and modern alluvium, torrent deposits, sand dunes and also limestone.

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3. Methods - field sampling, sample treatment and chemical analysis A geochemical survey of 152 rock samples from Santiago Island was conducted to cover all the lithological formations of the island in order to collect simultaneously rock, soil and stream sediment samples5,9. The guidelines of the International Project IGCP 259 were followed at the stages of sampling, preparation, analysis, data treatment and mapping for soils and stream sediments samples. The collection of rocks aimed to the chemical characterization of the different lithological units of Santiago Island. Thus, for each different geologic unit we selected at least five sampling points. The location of sampling points was dependent on representatively but also on accessibility, as Santiago have a very rough relief and a poor road network.

Fig. 1. Geological cartography of Santiago Island, Cape Verde, modified7.

The physical preparation of the rock samples was performed in the Geosciences Department in University of Aveiro (Portugal) and in the Earth Sciences Department in University of Coimbra (Portugal). In the laboratory, rock


samples (~2 kg of rock) were cleaned, crushed in a hydraulic press, then in a jaw mill to minus 2 mm and finally in an agate mill to minus 75 Pm. To clean the mill between each sample, about 30 g silica were crushed for 5 minutes and the mill was cleaned with tape water and 96 % ethanol. The contents of U in rock samples were obtained by instrumental neutron activation analysis (INAA) at the Portuguese Research Reactor, in Sacavém. Two reference materials were used in the evaluation of U concentration by INAA: sediment GSD-9 and soil GSS-4 from the Institute of Geophysical and Geochemical Prospecting (IGGE). Reference values were taken from data tabulated10. The samples and standards were prepared for analysis by weighing 200–300 mg of powder into cleaned high-density polyethylene vials. Irradiations (6 h) were performed in the core grid of the reactor11, at a thermal flux of 3.34 x 1012 n cm-2 s-1; фepi/фth = 1.4%; фth/фfast = 12.1. More details of the analytical method could be found12-15.

4. Results The contents of U determined in the various formations of the Santiago Island ranges from below the detection limit to 62.8 μg g-1 (Table 1). The lowest U contents were found in the CC limestone (0.37 μg g-1) and CC terraces (1.20 μg g-1), while the highest U contents ( up to 62.8 μg g-1) were found in the CC alluvium, which results from the erosion of CA rocks (Table 1).

Table 1. Concentrations of uranium (μg g-1) from different rocks of Santiago Island. x

n=18 n=16 n=16 n=39 n=15 n=8 n=9 n=9 n=14

S Max Min CA (basaltic-basanitic rocks) 2.78 2.49 8.08 < ld CA (phonolitic-trachytic rocks) 4.64 2.87 11.10 0.35 FL 1.39 0.68 2.56 < ld PA (basaltic-basanitic rocks) 1.48 0.74 3.42 < ld PA (phonolitic-trachytic rocks) 2.97 0.75 4.03 1.07 AS 1.83 0.83 2.32 < ld MV 1.61 0.99 3.77 < ld CB 1.71 0.52 2.35 < ld CC (terraces) 1.20 0.63 2.36 < ld CC (Limestones)

n=5

0.37

n=3

39.65

0.18 0.50 CC (Alluvion of CA) 32.61 62.80

0.25 2.36

x – mean; s – standard deviation; min – minimum; max – maximum; n – number of samples; ld- detection limit. Magmatic formations: CAAncient Internal Eruptive Complex formation, FL-Flamengos formation, PA-Pico Antónia formation, AS-Assomada formation, MV-Monte das Vacas formation; Sedimentary formations: CB-Orgãos, CC- Quarternary rocks (e.g. limestone and alluvium).

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The CA and PA formations present two very distinct groups of rocks, one with contents of Fe2O3 (T) ranging from 9.89% to 18.40% and the other group with Fe2O3 (T) contents ranging from 1.94% to 5.60%5. These two groups correspond to basaltic-basanitic and phonolitic-trachytics rocks, respectively. The phonolitic-trachytics rocks of CA and of PA are richer in U than the basaltic-basanitic rocks of the same respective formation (Table 1) and those from CA have high U contents with an average of 4.64 μg g-1 but reaching 11.1 μg g-1. These contents are much higher than those of Middle Ocean Ridge Basalt (MORB: 0.047-0.18 μg g-1) and Ocean Island Basalt (OIB: 1.02 μg g-1)16 and even higher than those of the upper crust (2.7 μg g-1)17. The Flamengos Formation (FL), representative of the submarine volcanism, has the lavas with the lowest U contents (1.39 μg g -1), while the Complexo Antigo Formation has the highest U contents (Table 1). The basaltic-basanitic rocks from PA, the Assomada (AS), Monte das Vacas (MV) and Orgãos (CB) formations rocks have similar U contents (Table 1). Their average U contents are higher than MORB and OIB. So all the volcanic rocks from Santiago Island are enriched in uranium specially those of phonolitictrachytic compositions. It was also found enrichment in the most incompatible elements in the lavas from Santiago 4. The baseline value maps of U in soils and stream sediments of Santiago Island were defined9 and according to them, uranium in Santiago topsoil and stream sediments has a geogenic origin and there is no contamination of this metal in these two sampling media. The highest uranium contents in the analysed rocks are probably related with zircon as this mineral was found in the stream sediments of CA, PA and CC alluvium7. The high correlation between the contents of U and Zr5 also seem indicate that the source origin of U in the rocks of Santiago is related to the zircon occurrence.

References 1. Holm PM, Grandvuinet T, Friis J, Wilson JR, Barker AK, Plesner S. An 40Ar–39Ar study of the Cape Verde hotspot: temporal evolution in a semi-stationary plate environment. J Geophys Research: solid Earth 2008; 113: B8. 2. Ramalho RAS. Building the Cape Verde Islands. Springer Thesis- Recognizing Outstanding Ph.D. Research. Springer 2011; 207 pp. 3. Barker AK, Holm PM, Peate DW, Baker JA. Geochemical stratigraphy of submarine lavas (3–5 Ma) from the Flamengos Valley, Santiago, Cape Verde. J Petrol 2009; 50: 169–193. 4. Barker AK, Holm PM, Peate DW, BakerJA. A 5 million year record of compositional variations in mantle sources to magmatism on Santiago, Southern Cape Verde archipelago. Contrib Mineral Petrol 2010; 160: 133-154. 5. Cabral Pinto MMS. Geochemical mapping of Santiago Island with a low/medium sampling density. PhD tesis, Univ Aveiro 2010; 410 p. 6. Cabral Pinto MMS, Ferreira da Silva EA, Silva MMVG, Melo-Gonçalves P. Uranium of Santiago Island (Cape Verde) topsoil: estimated background value map and environmental risk assessment. (Submitted in J African Earth Sci in August 2013. 7. Serralheiro A. A Geologia da ilha de Santiago (Cabo Verde). Bol Museu Lab Mineral Geol Fac Ciências Lisboa 1976; 14 (2). 8. Matos Alves CA, Macedo JR, Celestino Silva L, Serralheiro A, Peixoto Faria AF. Estudo geológico, petrológico e vulcanológico da ilha de Santiago (Cabo Verde). Garcia de Orta, Serv Geol, Lisboa 1979; 3 (1-2): 47-74. 9. Cabral Pinto MMS, Ferreira da Silva EA, Silva MMVG, Dinis PA. Estimated Background Values Maps of Uranium in Santiago Island Topsoil and Stream Sediments. Procedia Earth and Planetary Sciences 2014. (Submitted in this Special Issue). 10. Govindaraju K. Compilation ofworking values and sample description for 383 geostandards. Geostand Newslett 1994; 18: 1-158. 11. Dung HM, Freitas MC, Santos JP, Marques JG. Re-characterization of irradiation facilities for k0-NAA at RPI after conversion to LEU fuel and re-arrangement of core configuration. Nucl Inst Methods Phys Res 2010; 622: 438-442. 12. Dias MI, Prudêncio MI. Neutron activation analysis of archaeological materials: an overview of the ITN NAA laboratory, Portugal. Archaeometry 2007; 49 (2): 381-391. 13. Gouveia MA, Prudêncio MI, Morgado I, Cabral JMP. New data on the GSJ reference rocks JB-1a and JG-1a by instrumental neutron activation analysis. J Radioanal Nucl Chem 1992; 158: 115-120. 14. Gouveia MA, Prudêncio MI. New data on sixteen reference materials obtained by INAA. J Radioanal Nucl Chem 2000; 245: 105-108. 15. Prudêncio MI. Ceramic in ancient societies: a role for nuclear methods of analysis. In: Koskinen, Axel N. editors, Nuclear Chemistry: New Research. Nova Science Publishers, Inc., New York, 2009; 51-81. 16. Sun SS, McDonough WF. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. Geol Soc 1989; 42: 313-345. 17. Rudnick RL, Gao Sx. Composition of the continental crust. Treatise on geochemistry 2003; 3: 1-64.




Estimated Background Values Maps of Uranium in Santiago Island Topsoil and Stream Sediments. Cabral Pinto MMSa*, Ferreira da Silva EAa, Silva MMVGb, Dinis PAc a

University of Aveiro, Department of Geosciences, Geobiotec Research Centre, Aveiro 3810-193, Portugal b Geociences Centre, University of Coimbra, Coimbra 3000-272, Portugal c IMAR-CMA, University of Coimbra, Coimbra 3000-272, Portugal

Abstract We present maps of estimates of background values of uranium in the soils and stream sediments of Santiago Island, Cape Verde, delineate their main sources, relate them with the geology of the island, and assess their environmental risks. We use an index to numerically access the environmental risk of U, which we denominate by Environmental Risk Index. Values of this index higher than one were only found in three soil sampling points, all for agricultural purposes. So, U in Santiago topsoil and stream sediments has a geogenic origin and there is no contamination of uranium in these two sampling media. Published by Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license 2014The TheAuthors. Authors. Published by Elsevier © 2014 (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: Uranium; soils; stream sediments; Estimated Background Value; Environmental Risk Index; Santiago Island; Cape Verde

1. Introduction National geochemical surveys have been a priority in many countries given the importance and applicability of the resulting geochemical databases1,2. These surveys provide the natural state of the environment3-6 and allow the discrimination between geogenic sources and anthropogenic pollution8,9 which is useful for mineral exploration,



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agriculture, geomedicine, and other fields. A reliable geochemical baseline can only be established if pristine sites are sampled. Santiago Island is the main island of Cape Verde, a developing country with an incipient industry a subsistence agriculture, were the anthropogenic contamination is supposed to be low. It is thus a pristine region for geochemical surveys in volcanic basic rocks, related with a mantle plume, which is located in the Atlantic Ocean. In this paper we present baseline value maps, referred to as Estimated Background Value (EBV) maps, of U in soils and stream sediments of Santiago Island, delineate their main source, and relate them with the lithology of the island. Furthermore, we assess the environmental risk of this potentially toxic element using an index, the Environmental Risk Index (ERI) proposed by9, that numerically evaluates the enrichment of the concentration of the studied metal in relation to permissible levels defined by the Canadian legislation12 for agricultural and residential purposes for Santiago soils.

2. The study area The archipelago of Cape Verde is located in the Macaronesia region, on eastern Atlantic, about 500 km west of the coast of Senegal. Santiago Island is composed mainly by volcanic rocks. The pyroclasts have reduced importance, the lavas occupy most of the island, and the phaneritic rocks occur in small areas. Sedimentary rocks also occupy small areas. Metamorphic rocks are rare and are associated to incipient contact metamorphism. In Santiago island occur seven main lithostratigraphic formations10 (Fig. 1a): CA – Ancient Internal Eruptive Complex (intrusive dykes of basaltic-basanite or phonolitic-trachytic composition, and some carbonatite masses); Flamengos (submarine formation, basaltic-basanite lavas); CB - Órgãos (sedimentary formation, primarily conglomerates and breccias, which correspond to lahars); PA - Pico Antónia (submarine and subaerial formation, basaltic-basanite lavas, pyroclasts, phonolitic-trachytic); AS - Assomada (subaerial formation, basaltic-basanite lavas); MV - Monte das Vacas (50 pyroclastic cones) and CC – Quaternary (limestone, gravel, sand).

3. Methods 3.1 Field sampling, sample treatment, chemical analysis, and analytical control Composite samples of the soil and stream sediments were collected from 249 and 337 sites, respectively, at a density of 0.3 site/km2, covering the major soil types as well as the major rock types in Santiago Island. On each site a composite sample made up of five grabs was collected over an area of about 100 m2 for soils and spaced approximately 50 m along the water line for stream sediments. The sampling sites were selected to represent pristine samples. The samples were oven dried at < 4 ºC, sieved through a 2 mm plastic sieve, homogenized and quartered, and milled in an agate mortar to < 75 Pm. The chemical analysis was performed in the ACME Analytical Laboratories, Ltd, Vancover, Canada. Each sample was digested in aqua regia and analysed by inductively coupled plasma-mass spectrometry (ICP-MS). The results were subjected to several data quality tests10.

3.2 Maps of Estimated Background Value fields We use the term Estimated Background Value, EBV, of uranium to refer to the estimate of the “true” Background Value of that metal at the sampling locations and also at all points of the interpolated spatial field. For soils, the mapping of the EBVs was performed by ordinary kriging using a theoretical model of spatial continuity fitted to the experimental variograms calculated for U. Cross validation was carried out to assess whether the fitted model was suitable for the experimental variogram. The root-mean-square error (RMSE) was used to measure the differences between values predicted by the model and the actual values. The RMSE ranges from 0 to infinity, with 0 corresponding to the ideal.


The spatial distribution of the content of U in stream sediment points (spatial locations) is not a spatially continuous field. The content of a particular point is representative of that point only, although it has also the contribution of the points located upstream in the stream line. Because of this, the spatial distribution of each element is mapped using dot points and not contour lines. Spatial distributions of U content were mapped following the recommendations of8. The diameter of the symbols were classified in 8 classes defined by the following intervals: [minimum-P10[; [P10P25[; [P25-P50[; [P50-P75[; [P75-P90[; [P90-P95[; [P95-P97.5[; [P97.5-maximum], where Px is the x-th percentile value.

3.3 Environmental risk assessment In this section we assess the environmental risk of U in soils providing a numeric measure of the risk. Despite these estimated fields are geochemical background fields, the natural concentration of the studied metal in some areas of the island may be too high for agricultural and/or residential purposes. For U, the Environmental Risk Index (ERI) for agricultural or residential purposes is measured by ERI(s) = C(s) / P, where C(s) is the U content observed at sampling site s, and P represent the permissive level of that element, according the Canadian Legislation. The permissible level is the element concentration in the soil, above which the soil is considered to be unsafe for some purpose; e.g. agricultural, residential, industrial, commercial, etc.5,11,12.

4. Results and discussion The U contents in Santiago topsoil ranges from 0.10 μg/g to 2.20 μg/g, with an average of 0.79 μg/g and a standard deviation of 0.30. Table 1 shows the parameters of the theoretical model fitted into the experimental variogram. The U concentrations in Santiago stream sediments ranges from 0.20 μg/g to 2.30 μg/g, with an average of 0.68 μg/g and a standard deviation of 0.24. The comparison of the EBV maps with the geological map suggests that the spatial distribution of the EBVs is more controlled by the geological material in the soils than in the stream sediments (Fig. 1a-c). The U EBVs appear to be highly correlated to phonolitic-trachytics rocks of Pico Antónia and Ancient Internal Complex Formations, and also with pyroclastic deposits of Monte das Vacas and Assomada Formations. Contrarily, the Orgãos Formation is depleted in uranium. The comparison of the stream sediments U dot map with the geology (Fig. 1 a, c) shows that a clear chemical characterization of stream sediments in different geological formations is difficult, since the chemical composition of each sample is determined by the chemical composition of its watershed. The soils and stream sediments in the central-east region of the island have the lowest U contents (Fig. 1a-c). Figure 1 (d) and (e) shows the ERI field obtained for U for agricultural (a) and residential (b) purposes in Santiago soils. Only the ERI map of U for agricultural uses in soils presents regions above the legislated permissible values. This figure shows that there are very few places with concentrations of U above the levels allowed by Canadian legislation. The low U is due to fact that Santiago Island is composed mainly by lavas originated by mantelic partial fusion, which are depleted in lithophile elements. The levels of U in Santiago have a geogenic origin, showing no contamination in this metal.

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Fig. 1. (a) Geological cartography of Santiago Island; Spatial distribution of the EBV of U (μg/g) in Santiago: (b) soils; (c) stream sediments; Environmental Risk Index (ERI) of U (μg/g) soils for: (d) agriculture; (e) residential.

Table 1. Parameters of the theoretical models of spatial continuity fitted to the experimental variogram of uranium

Parameters

Model

C0

C

Range

Dir.

Anis.

RMSE

Uranium

Exp.

0.025

0.0275

2,500

N10ºE

1.2

1.16

Anis., geometrical anisotropy = major axis/minor axis; C, sill for the structure; C0, nugget effect; Dir., major direction of spatial continuity; model, theoretical model fitted to the experimental variogram (Sph., spherical; Exp., exponential); Range, major range in meters.


References 1. Garret RG, Reimann C, Smith DB, Xie X. From geochemical prospecting to international geochemical mapping: a historical overview. Geoch, Explor, Environ, Analysis 2008; 8: 205-217. 2. Smith DB, Reimann C. Low-density geochemical mapping and the robustness of geochemical patterns. Geoch: Explor, Environ, Analysis 2008; 8: 219-227. 3. Appleton JD, Ridgway J. Regional geochemical mapping in developing countries and its application to environmental studies. App Geoch 1993; 2: 103-110. 4. Xie Xuejing X, Xuzhan M, Tianxiang R. Geochemical mapping in China. Journal of Geochemical Exploration 1997; 60 (3): 99-113. 5. Reimann C, Caritat P. Chemical Elements in the Environment - Factsheets for the Geochemist and Environmental Scientist. ISBN 3-540-636706. Springer–Verlag, Berlin, Germany, 1998; 398 p. 6. Salminen R, Batista MJ, Bidovec M, Demetriades A, De Vivo B, De Vos W, Duris M, Gilucis A, Gregorauskiene V, Halamic J, Heitzmann P, Lima A, Jordan G, Klaver G, Klein P, Lis J, Locutura J, Marsina K, Mazreku A, O’Connor PJ, Olsson SA, Ottesen R.-T, Petersell V, Plant JA, Reeder S, Salpeteteur I, Sandström H, Siewers U, Steenfelt A, Tarvainen T. Geochemical Atlas of Europe. Background Information, Methodology and Maps 2005;. Part 1 (526 p) and Part 2 (690 p). 2005. Geochemical Atlas of Europe. Background Information, Methodology and Maps. Part 1 (526 p) and Part 2 (690 p). 7. Darnley A.G, Björklund A, Bølviken B, Gustavsson N, Koval PV, Plant JA, Steenfelt A, Tauchid M, Xie Xuejing. A Global Geochemical Database For Environmental and Resource Management. Recommendations for international geochemical mapping. Final report of IGCP project 259, 1995; UNESCO Publishing. 8. Albanese S, De Vivo B, Lima A, Cicchella D. Geochemical background and baseline values of toxic elements in stream sediments of Campania region (Italy). J Geoch Explor 2007; 93: 21-34. 9. Cabral Pinto MMS, Ferreira da Silva EA, Silva MMVG, Melo-Gonçalves P. Uranium of Santiago Island (Cape Verde) topsoil: estimated background value map and environmental risk assessment. Submitted in J Afri Earth Sci, August 2013. 10. Serralheiro A. A Geologia da ilha de Santiago (Cabo Verde). Boletim Museu Laboratório Mineralógico Geológico Faculdade de Ciências de Lisboa 1976; 14 (2). 11. Ministry of the Environment. Soil, Ground Water and Sediment Standards for Use. Canadian Legislation. Under Part XV.1 of the Environmental Protection Act; 2011. 12. Dutch legislation VROM. Circular on target values and intervention values for soil remediation. Netherlands Government Gazette, No. 39, Ministry of Housing, Spatial Planning and Environment, Directorate General for Environmental Protection, Department of Soil Protection, The Hague Widerlund A, Shcherbakova; 2000.

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Release, migration, sorption and (re)precipitation of U during a granite alteration under oxidizing conditions Cabral Pinto MMSa*, Silva MMVGb, Neiva AMRb a b

University of Aveiro, Department of Geosciences, Geobiotec Research Centre, Aveiro 3810-193, Portugal Department of Earth Sciences and Geociences Centre, University of Coimbra, Coimbra 3000-272, Portugal

Abstract

A study of release, migration, sorption and (re)precipitation of U during alteration under oxidizing conditions were carried out in U minerals from a granite and hydrothermal quartz veins. U-bearing minerals can be related with precipitation from faults or solubilization and remobilization minerals by meteoric waters. The hot meteoric fluids dissolved (the remaining) uraninite, coffinite, thorite, etc. in the granite and apatite, monazite, xenotime in the quartz veins. These fluids were responsible for the growth of U-bearing minerals in the hydrothermal quartz veins, by adsorption or by precipitation. The neoformation associated to weathering could be a mechanism of U concentration. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: Uranium; uranium migration; secondary uranium phosphate mineralization, Portugal.

1. Introduction Uranium is a structural constituent in nearly two hundred mineral species1 and more than two hundred uraniumbearing mineral phases were compilated by2. Uranium could be an energy resource and play a role in environmental problems associated with the disposal of radioactive waste materials, mining contamination and remediation of contaminated sites. Uraninite is the most important uranium mineral in terms of abundance and economic value3 and




the principal ore mineral in the Portuguese uranium mineral deposits4. In general, it occurs in granites, pegmatites and associated quartz veins and is unstable in acid and oxidizing conditions like those found in acid hydrothermal and meteoric fluids. It is easily dissolved and probably the most important source of dissolved U in groundwater emanating from weathered granite terrains5-10. Other U-minerals from rocks (e.g. thorite, huttonite, thorianite, monazite, titanite, xenotime, allanite, zircon) and their alteration by acid hydrothermal or meteoric fluids is also a source of dissolved U in hydrothermal fluids or surface waters and groundwater. Many uranium deposits are derived from the dissolution of these uranium minerals9, 11-14. The principal mechanism of dissolution of U from minerals is oxidation: The principal oxidant is Fe3+(15), which is produced by the oxidation of pyrite, and usually found associated with uranium minerals. The uranyl ion (UO22+) and its complexes are soluble in water and can be transported over distances up to kilometres. Changes in aqueous chemistry, temperature, and pressure lead to the precipitation of new uranium minerals, such as uranyl oxyhydroxides, carbonates, silicates, phosphates, etc. 3, 12 A systematic study using scanning electron microscopy and electron microprobe is now presented in uranium minerals and uranium-bearing minerals from the Variscan peraluminous biotite granite and from the related hydrothermal brecciated quartz veins in order to study the release, migration, and sorption and (re) precipitation of U under oxidizing conditions.

2. Geological setting A coarse- to very coarse-grained porphyritic biotite Variscan granite is located in central Portugal and forms the border of the Beiras batholith. The granitic magma intruded the Beiras Group, a Cambrian metassedimentar sequence of phyllites and metagraywakes, with intercalations of metasandstones and metaconglomerates. The granitic intrusion produced a contact metamorphic aureole with an outer zone of porphyroblastic micaschist, and an inner discontinuous zone of hornfels. Close to the contact, the granite shows a plane-linear fabric due to the N-S to 10ºE orientation of feldspar phenocrysts caused by magmatic flux. NE-SW and also some NW-SE aplite, aplite-pegmatite and pegmatite veins and numerous quartz veins cut the granite. The uranium quartz veins cut the country phyllites and are thin, brecciated, aligned along the N45ºW direction of phyllite flux cleavage, and contact granite-country rock. They fill old NW-SE faults in the interception of this fault system with late N20-25º W faults, but also occurs disseminated in the phyllite at vein walls. The U-mineralization consists of secondary U-phosphates, mainly saleeite and meta-saleeite and this epithermal U-mineralization overlays a hydrothermal wolframite-sulphide mineralization and the paragenetic sequence12.

3. Results Uraninite is magmatic and occurs mainly in the unaltered granite, is rare in the altered granite and was not found in the mineralized quartz veins. Uraninite from the altered granite is fractured and hydrated, has the radioactive damage halos filled with late pyrite, U-S-bearing phases and Fe oxyhydroxides (Fig. 1a, b) and its analytical totals are lower than in the uraninite from the unaltered granite(12). The alteration zones and crystal rims are poorer in U (86.7 wt.% UO2) than the cores and unaltered zones (90.2 wt.% UO2) and some uraninite crystals are replaced by coffinite, U[SiO4]1-x(OH)4x, which results from uraninite alteration (Fig. 1c). The U contents in coffinite crystals range between 65.0 wt.% UO2 in the rims to 84.0 wt.% UO2 in the cores of crystals. Thorite, (U,Th)SiO4, was found in all the granite samples and its composition is variable from 0.5 to 10.4 wt.% UO 2. Some thorite seems to be primary, whereas the other is related to the granite alteration and replaces apatite and monazite, is associated with xenotime, (YPO4), and fills fractures of several minerals (Fig. 1d, e, f). In the altered granite, thorite has low UO2 contents (0.46 wt.%) in fractured crystal zones. Monazite from the altered granite has a pervasive porosity and some crystals were formed by alteration of apatite, and are frequently replaced by thorite (Fig. 1e). Monazite and xenotime from altered granite and hydrothermal veins have lower U contents than these minerals from unaltered granite. In the altered granite, xenotime crystals are zoned, with cores richer in U than the rims. Apatite from the altered granite is fractured, shows dissolution and has lower U and P contents than apatite from unaltered granite. In quartz veins, apatite crystals are replaced by

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uranium phosphates (Fig. 1g) and have high U contents (~1.1 wt.% UO2) 12 . In quartz veins, zircon rims have an extraordinary U enrichment (up to 18 wt.% UO2) compared to cores (up to 0.33 wt.% UO2) 12. The most altered rims of chlorite and anatase from quartz veins are partially replaced by U-bearing Fe oxyhydroxides (Fig. 1h), containing up to 5.7 wt.% UO2. Meteoric water warmed by deep circulation through granite faults, shear zones and quartz veins became enriched in U, P and Mg due to the solubilization of mainly uraninite, coffinite, thorite and monazite, apatite, chlorite. Uranium from these solutions was later adsorbed on Fe oxyhydroxides, weathered surfaces of anatase, zircon and apatite, or precipitated as saleeite and meta-saleeite at the surface of Fe minerals (Fig. 1g, i) and at apatite weathered surface due to local saturation.

Fig 1. Backscattered images of minerals from the Variscan granite and related mineralized hydrothermal quartz veins, Central Portugal. (a) crystal of uraninite (U), rimmed by a radioactive damage zone filled with U-Fe-bearing phases (U-Fe-phase) and pyrite (Py), enclosed in quartz (Q); (b) crystal of uraninite (U), rimmed by a radioactive damage hallo filled with U-Fe-S-bearing phases (U-Fe-phase) and pyrite (Py), enclosed in quartz (Q) and associated biotite (B); (c) corroded crystal of coffinite (Cof) enclosed in fractured quartz (Q), associated with an Pb oxide (Pb); (d) fractured crystal of monazite (Mon), replaced by thorite (Th) and xenotime (Xe), enclosed in biotite (B); (e) fractured crystal of apatite (Ap), replaced by monazite (Mon), which is replaced by thorite (Th), enclosed in biotite (B) and associated muscovite (M); (f) fractured crystal of apatite (Ap), replaced by thorite (Th) rimmed by ilmenite (il), enclosed in biotite (B) and chlorite (Cl); (g) uranium phosphates (S) replacing apatite (Ap), filling quartz (Q) fractures with also chlorite (Cl); (h) chlorite (Cl) weathered to Fe oxyhydroxides (Fe) associated with quartz (Q); (i) uranium phosphates (S), filling fractures in the mineralized quartz (Q) veins, associated with U-rich Fe oxyhydroxides (Fe-U) and pyrite (Py) and Fe oxyhydroxides,(Fe).


4. Discussion and conclusions Uranium-bearing minerals in the unaltered granite are uraninite, thorite, xenotime, Ce-monazite. Zircon and apatite also present some U. The textural, mineralogical and chemical changes found in this research show that uraninite, coffinite, thorite, xenotime, Ce-monazite, zircon, apatite, chlorite, anatase, from granite and/or hydrothermal mineralized quartz veins are altered, dissolved and vacuolated. The rims of uraninite, coffinite, thorite, xenotime and Ce-monazite, are poorer in U than respective cores, indicating uranium removal to the fluid, while the altered rims of zircon, apatite, chlorite and anatase crystals are richer in U than respective cores. The enrichment in U is related to the presence of Fe minerals, Fe oxyhydroxides and altered apatite. The U-mineralization in the quartz veins occurs in the intersection of two fault systems and the paragenetic sequence has three phases. The first phase originated silicates, sulphides, wolframite and phosphates (apatite, xenotime and monazite), the second is dominated by silicates while the precipitation of the U-phosphates occurs in the third supergenic phase, associated with Fe oxyhydroxides12. The large and deep Variscan faults and shear zones in the granite were reactivated by the Alpine tectonism and gave rise to a deep circulation of meteoric waters within the granite and along the quartz veins. The waters were heated up and became enriched in uranium by solubilization, and locally the completely remobilization of U-bearing minerals4. These hot meteoric fluids dissolved uraninite, coffinite, thorite, monazite, xenotime and apatite in the biotite granite and apatite, monazite and xenotime in the quartz veins, which became enriched in U and P. The leaching of uranium from fertile granites represents a major source of uranium to hydrothermal fluids13. These fluids were responsible for the growth of a new mineral assemblage in the hydrothermal quartz veins, where the dissolved U was fixed on the altered surface of minerals, like zircon and apatite, by adsorption11, or by precipitation as uranium minerals, such as saleeite and meta-saleeite. The neoformation of discrete minerals on high-surface area weathering products, rather than direct elemental adsorption, could be a major mechanism in U secondary concentration16. Phosphorous resulted from the dissolution of apatite, monazite and xenotime from the granite and mineralized quartz veins and Mg mainly from chlorite alteration were released to the fluid. The precipitation of U-phosphates occurred at the surface of anatase and Fe oxyhydroxides, released from altered chlorite and sulphides, and at the altered apatite surface. As groundwater is undersaturated with respect to uranyl phosphates, such as saleeite 17, simple solubility-controlled precipitation was not the major mechanism, but only one for the formation of the Umineralization12. This precipitation at the surface of the new Fe-minerals was the main factor responsible for U retention within the quartz veins leading to the uranium phosphate mineralization. However, saleeite was also found replacing U-rich apatite and apatite is rare in the mineralized quartz veins, because it was replaced by monazite and U-phosphates. The hydrothermal fluid is rich in U and Mg and saleeite and meta-saleeite precipitated at apatite weathered surface. The immobilization of U(VI) from aqueous solutions in a solid phase by interaction with apatite has been studied, and the dominant mechanisms are: dissolution-precipitation or sorption onto the apatite surface with formation of amorphous or microcrystalline U phases18,19. The uranium released from uraninite (and thorite?) in the early hydrothermal alteration of the granite was immobilized in coffinite. Later, meteoric hot fluids, circulating through reactivated deep faults, promoted a high dissolution of (remaining) uraninite, coffinite, thorite, xenotime, monazite in the granite and quartz veins and became enriched in uranium. The alteration of monazite and apatite from the granite and the mineralized quartz veins released P to the fluid, while Mg and Fe were released from the weathering of chlorite and sulphides. Close to the surface, where oxygen content is high, the brecciated quartz veins are structural traps where Fe is immobilized as Fe oxyhydroxides. These Fe oxyhydroxides precipitated in fractures, pores and rims of the altered zircon, anatase and chlorite. The precipitation of U-phosphates occurs at the surface of these Fe oxyhydroxides and in the weathered surface of apatite, immobilizing the uranium. The Fe oxyhydroxides can also have adsorbed some U, P and Mg, and its transformation to hematite or goethite leads to the precipitation of U-phosphate minerals. The uptake of U by Si/Al/Fe gels could also occur12.

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References 1. Fleischer M, Mandarino JA. Glossary of Mineral Species The Mineralogical Record, Tucson, Arizona; 1995. 2. Smith Jr DK. Uranium mineralogy. In De Vivo B, Ippolito F, Capaldi G, Simpson PR, editors. Uranium Geochemistry, Mineralogy, Geology, Exploration and Resources. Institute of Mining and Metallurgy, London; 1984. p. 43–88. 3 Finch R, Murakami T. Systematics, Paragenesis of U minerals. In Burns PC, Finch R, editors. Ribbe PH, series editor. Uranium: Mineralogy, Geochemistry and the Environment. – Reviews in mineralogy; 1999. 38: 91–180. 4 Cotelo Neiva JM. Jazigos portugueses de minérios de urânio e sua génese. – In MRPV Ferreira, editor. Engineering Geology and Geological Resources. Book in honour to Prof. J. M. Cotelo Neiva. Coimbra University Press (written in Portuguese); 2003. 1: 15–76. 5. Basham IR, Ball TK, Beddoe-Stephens BD Michie, UMcL. Uranium-bearing accessory minerals and granite fertility: II. Studies of granites from the British Isles. In: Compte-rendu méthodes de prospection de l’uranium; Symposium sur les méthodes de prospection de l’uranium — examen dur programme AEN - AIEA de R & D. Organ. Econ. Coop. and Develop., Paris; 1982.p. 398-413. 6. Poty B, Leroy J, Cathelineau M, Cuney M, Friedrich M, Lespinasse M, Turpin L. Uranium deposits spatially related to granites in the French part of the Hercynian orogen. In Vein Type Uranium Deposits, IAEA-TC-361, International Atomic Energy Agency, Vienna; 1986. p.215-246. 7. Cuney M, Friederich M. Physicochemical and crystal-chemical controls on accessory mineral paragenesis in granitoids: implications for uranium metallogenesis. Bull Mineral 1987; 110: 235–247. 8. Tischendorf G, Förster H-J. Hercynian granite magmatism and related metallogenesis in the Erzgebirge: A status report. In Kv. Gehlen, DD Klemm, editors. Mineral Deposits of the Erzgebirge/Krusˇne´ hory (Ge rmany/Czech Republic. Monograph Series on Mineral Deposits 1994; 31: 5-23. 9. Plant JA, Simpson PR, Smith B, Windley BF. Uranium ore deposits-products of the radioactive earth. Uranium: Mineralogy, Geochemistry and the Environment. In PC Burns, RJ Finch, editors. Uranium: Mineralogy, Geochemistry and the Environment, vol. 38. Rev. Mineral., 1999. p. 255–319. 10. Förster H-J. The chemical composition of uraninite in Variscan granites of Erzgebirge, Germany. Mineral Mag 1999; 63: 239–252. 11. Hecht L, Cuney M. Hydrothermal alteration of monazite in the Precambrian crystalline basement of the Athabasca Basin (Saskatchewan, Canada): implications for the formation of unconformity-related uranium deposits. Mineral Deposita 2000: 35: 791–795. 12. Cabral Pinto MMS, Silva MMVG, Neiva AMR. Geochemistry of U-bearing minerals from the Vale de Abrutiga uranium mine area, Central Portugal. N Jb Mineralogie 2008; 185/2: 183-198. 13. Tartèse R, Boulvais P, Poujol M, Gloaguen E, Cuney M. Uranium mobilization from the Variscan Questembert syntectonic granite during fluid-rock interaction at depth. Econ Geol 2013; 108: 379-386. 14. Mercadier J, Annesley IR, McKechnie CL, Bogdan TS, Creighton S. Magmatic and metamorphic uraninite mineralization in the western margin of the Trans-Hudson Orogen (Saskatchewan, Canada): a uranium source for uncondormity-related uranium deposits? Econ Geol 2013, 108, 1037-1065. 15. Abdelouas A., Lutze W, Nuttall HE. Uranium contamination in the subsurface; characterization and remediation. Rev Mineral Geoch 1999; 38(1): 433-473. 16. De Putter T, Charlet JM, Quinif Y. REE, Y and U concentration at the fluid–iron oxide interface in late Cenozoic cryptodolines from Southern Belgium. Chem Geol 1999; 153: 139–150. 17. Pinto MMSC, Silva MMVG, Neiva AMR. Pollution of Water and Stream Sediments associated with the Vale de Abrutiga Uranium mine, Central Portugal. J Mine Water Environ 2004; 23: 66–75. 18. Jeanjean J, Rouchaud JC, Tran L, Fedoroff M. Sorption of uranium and other heavy metals on hydroxyapatite. J Radioanalytical Nuclear Chemistry 2005; 201: 529-539. 19. Simon FG, Biermann V, Peplinski B. Uranium removal from groundwater using hydroxyapatite. Appl Geochem 2008; 23: 2137–2145.




The National Radioactivity Monitoring Program for the Regions of Uranium Mines and Uranium Legacy Sites in Portugal Carvalho FP a* a

Instituto Superior Técnico/Laboratório de Protecção e Segurança Radiológica, Universidade de Lisboa, Estrada Nacional 10, km 139, Bobadela 2695-066, Portugal

Abstract Following closure of the uranium mining company, the areas of former radium and uranium mines were assessed for environmental radioactivity, stable metals and public health impact. Concentrations of radionuclides were found highly enhanced in milling tailings, in mine drainage, and in some surface water streams. An environmental remediation plan was advised and it is ongoing. Furthermore, field surveys are annually carried out and results reported to the Government, the European Union, and made available to the public. This monitoring program enabled assessing the radiological risk, and every year contributes to substantial improvement of radiological safety of population and environment. © Published by Elsevier B.V. This 2014The TheAuthors. Authors. Published by Elsevier B.V.is an open access article under the CC BY-NC-ND license ©2014 (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: uranium sites; milling tailings; radioactivity; environmental remediation; radiation dose

1. Introduction In Portugal, between 1908 and 2001, 60 deposits of radioactive ore were extracted for the production of radium and uranium. On 2001, with the closure of Empresa Nacional do Urânio (ENU-SA), the assets of this company were transferred to the Empresa de Desenvolvimento Mineiro (EDM), State holding company under the Ministry of Economy for the mine sector. The environmental remediation works of uranium legacy sites were entrusted to EXMIN,

* Corresponding author. Tel.: 351 219 946 332; fax: 351 219 550 117. E-mail address: [email protected]


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F.P. Carvalho / Procedia Earth and Planetary Science 8 (2014) 33 – 37

a society initially set up by EDM for the remediation, under the supervision of the State Follow up Commission (CAC) with representatives of Ministries of Economy, Environment, Science & Technology, and Health set up by the DecreeLaw 198A/2001. Later, after approval of the general remediation plan and several site specific remediation plans by the CAC, the EXMIN ceased functions and the remediation activities were directly ascribed to EDM1,2. The Nuclear and Technological Institute (ITN), now IST/CTN, was charged to implement the monitoring of environmental radioactivity in regions impacted by extraction of radioactive ores during the phases of exploitation, closure, and requalification, such as established in the Decree Law 165/2002 article 14. To this purpose in 2006 was set up a regular monitoring programme of environmental radioactivity in the areas of old uranium mines and milling sites which started implementation in 2007. This programme carries out extensive environmental surveys for determination of radionuclide concentrations, especially those of the uranium series, and ambient radiation doses. Results of this national monitoring programme are annually reported to the Government, released to the public, and transmitted to the European Union as required by the EURATOM Treaty, articles 35 and 36. Regular monitoring of these regions is needed to ensure the updated assessment of environmental radioactivity and to generate scientifically sound information for radiological protection of the population and environment, including protection of the quality of natural resources, such as, water, soils, and agriculture and animal products.

2. Past research and monitoring activities in uranium regions The current and regular national monitoring of uranium regions, implemented since 2007, was not the beginning of the environmental and radioprotection work carried out in this field. The Department of Radiological Protection and Safety (DPSR) had already carried out during the previous 20 years periodic monitoring of environmental radioactivity and published institute reports on the impact of active uranium mining. That work, although thoroughly done, suffered limitations inherent to the spectrometry equipment and knowledge available at that time about key radionuclides, such as 210Po and 222Rn. Notwithstanding, it was an important contribute to keep institutional control on mining and milling waste, to improve waste management, and to figure out the radioactive impact on the environment 3 With the closure of ENU-SA and cessation of all mining and milling activities in 2001, a new period would start. During decades radioactive waste was controlled and mining concession areas were of restricted access and surveyed by the Junta de Energia Nuclear (JEN) and later by the Empresa Nacional de Uranio (ENU). With closure, the abandon could lead to a major disruption in waste management and in surveillance of properties and facilities and, thus, to a major change in radiation protection measures. There was a need to follow this change and prevent loss of institutional control on radioactive waste. The need for assessment of sites and for an eventual remediation plan in order to meet radiation protection goals was put forward 4(Fig. 1). The assessment of radioactivity levels in the uranium mining areas was resumed by the time of discontinuing the uranium production activities through a research project aimed at identifying the uranium mining and milling waste in those regions and the potential radiological exposure risks. This project was supported by an IAEA Technical Cooperation project (POR/9/014, 2001-2003) and allowed for revisiting and referencing all the uranium legacy sites, measuring ambient radiation doses, and analyzing the composition of wastes left on site by past mining and milling activities. A clear picture about characteristics of sites, types of contamination, and need for remediation was obtained and consolidated. This project concluded with an International Workshop jointly organized by ITN/DPSR and the IAEA, in Sacavém, 11-13 February 2004, on the “Environmental Contamination from Uranium Production Facilities and Remediation Measures” (Proceedings published by the IAEA in 2005) 3. This assessment was followed by the research project entitled “Study of Effects of Uranium Mining Residues on the Public Health” (MinUrar Project), funded by the Ministry of Health as a result of a recommendation approved by the Parliament (Recommendation to the Government Nº34/2001). The MinUrar project (2003-2006) was jointly implemented by the Nuclear and Technological Institute (ITN/DPSR), the National Health Institute and the Geological Survey and carried out an in-depth study of the uranium residues impact and its effects on the environment and public health.


Fig. 1. Uranium mining areas in Portugal, periodically surveyed for environmental radioactivity. Open circles indicate old uranium mines.

3. Results of the MinUrar project The MinUrar project was implemented through three main axes: environmental radioactivity, heavy metals, and impact on public health5. Investigation on environmental radioactivity levels showed that mining and milling tailings at Canas de Senhorim/Urgeiriça contained high concentrations of uranium family radionuclides (Table 1). For instance, the concentrations of 226Ra in mill tailings reached 25 kBq kg-1 whereas in sludge from ponds used to treat acid mine water, 238U concentrations reached about 42 kBq kg-1. The areas receiving surface runoff and drainage from milling tailings displayed enhanced concentrations of those radionuclides also, and concentrations in the most contaminated soils were up to 200 times higher than concentrations in agriculture soils of the region. The same trend was observed with the ambient radiation doses that reached values of 41 mSv a-1 on uranium tailings at Urgeiriça and decreased to 2.5 mSv a-1 on agriculture fields. Clearly, the uranium milling tailings were a source of radiation originating external radiation dose rates largely exceeding the regional radiation background and the additional dose limit of 1 mSv/year to members of the public (Directive 96/29/Euratom). Furthermore, due to the very high radium (226Ra) concentrations in the waste, tailings were a powerful source of radon (222Rn) and radioactive dust. Atmospheric processes and surface runoff following heavy rains, would gradually contribute further to disperse the radionuclides from the milling tailings in the surrounding environment. Radionuclide concentrations determined in agriculture products, indicated higher values in these areas. Radioactivity in drinking water was also elevated in some investigated counties and especially in water from private supplies (wells) in some areas near Canas de Senhorim, and Cunha Baixa. Suspended dust particles in surface air at Canas de Senhorim carried also higher radionuclide concentrations than air dust in other counties. Therefore, if the area of milling tailings was left without control and with no remediation, this could originate an exposure to radionuclides and radiation doses exceeding the maximum permissible limits for the safety of the population and compromise the quality of environmental resources of this region 5. The dispersion of heavy metals and other inorganic contaminants in the area of Canas de Senhorim was detected mainly in the hydrographical basin of streams receiving drainage from the mining facilities and milling tailings and, thus, it was concluded that uranium ore processing had left its fingerprint in the environment through enhanced concentrations of co-occurring stable metals, such as lead and zinc5.

35

36

F.P. Carvalho / Procedia Earth and Planetary Science 8 (2014) 33 – 37 Table 1. Radionuclide concentrations (Bq kg-1 ±1SD) in uranium waste at Urgeiriça mine and mill site after closure of ENU-SA Company. 238

U

Milling tailings, Barragem Velha Sludge ponds, Barragem Nova

235

U

234

U

230

Th

226

Ra

210

Po

232

Th

2530±94

118±12

2876±105

10337±598

24717±2039

20354±681

412±32

41598±1228

1959±67

40182±1187

13390±613

1690±150

1176±43

386±22

Spoil heap, Santa Barbara

6108±173

276±14

6175±175

8052±282

3608±133

3501±112

112±7

Waste heap by the ore mill

38316±1154

1717±67

38247±1152

30115±113

15569±707

30824±1147

426±21

211±7

10±1

201±7

128±6

140±8

227±8

117±6

Soil, Aldeia de Aguieira

A soil from the region is shown for comparison.

Regarding the effects from exposure to waste from past uranium mining activities on human health, the results indicated the existence of a negative impact on populations’ health living near the uranium mining and milling areas, although a direct cause-effect relationship could not be established5. By the end of MinUrar project results supported recommendations made in the final report which included the implementation of an environmental remediation plan, the periodic environmental radioactivity monitoring in the areas impacted by the uranium residues, as well as the follow up of remediation works, and radiological surveillance of the environment in the post-remediation5.

4. Outline of a remediation programme The need for environmental remediation of former uranium sites was foreseen and proposed for enhanced radiation protection of the public3,6. Following the sound recommendations made by MinUrar project in 2005, the implementation of a remediation plan for the abandoned mines, including radioactive and non-radioactive mines was approved and entrusted by the Ministry of Economy to EDM. This plan achieved the rearrangement and confinement of radioactive waste in Urgeiriça in the period 2005-2007. Other mine sites, such as Valinhos and Espinho, were cleaned up and requalified and, remediation of Cunha Baixa site is ongoing and others, such as Quinta do Bispo mine site may follow7,8.

5. Regular monitoring of uranium regions This radioactivity monitoring programme of the former uranium mining and milling areas currently takes into account the main five mining areas in the center of the country, where most of the mining and milling waste is deposited and to where the waste from small mines is planned to be relocated and stored. This monitoring plan takes into account the potential transport of radionuclides from mining and milling waste into ground water and rivers crossing the region and possible transfer pathways of radionuclides along the food chain to man. Samples collected yearly in the region include soils, vegetables, well water used for irrigation, drinking water from public supplies, atmospheric dust, and radon in surface air. The sampling areas encompass the main mines and milling tailings areas and rivers receiving discharges and surface runoff. Occasional samples of milk, poultry and cooked meals are purchased in the area for radio analytical measurements. The focus of environmental monitoring has been maintained in the main mine areas, i.e., Urgeiriça, Quinta do Bispo, Cunha-Baixa, Bica, Castelejo, Mortórios, with occasional visits to and sampling in other areas. A thorough monitoring has been made of the main rivers receiving mine water discharges, especially the River Mondego. The main radionuclides of the uranium series, namely the alpha emitters uranium isotopes, 230Th, 226Ra, 210Po and 210Pb (beta emitter) are systematically determined in the samples through radiochemical analyses and alpha spectrometry measurements. A periodic analytical quality control programme is implemented through participation in international interlaboratory comparison exercises organized by the IAEA and EU, and routine analyses of certified reference materials. The results consistently are of good quality and show accurate and precise determination of radionuclides2,4,9.


The results of the monitoring are included in the Annual Report on the environmental radioactivity surveillance, delivered to the authorities and released to the public by the ITN (now IST/CTN). These reports show extensive tables with radionuclide concentrations in all type of samples totalizing around 400 radionuclide measurements per year 9. Results from several years of monitoring enabled identifying hot spots of radioactive waste, areas with wells showing too high radionuclide concentrations for use in irrigation and consumption, and kitchen gardens with vegetable products not suitable for human consumption. Appropriate recommendations have been made to the population concerned. In general, the population is not exposed to high values of external radiation doses and, with few exceptions, is supplied nowadays with water suitable for human consumption.

6. The need to plan the post remediation phase A few sites of uranium mining legacy were remediated so far, including the Urgeiriça site where the uranium mill was operated and most of the milling waste deposited. The milling waste pile Barragem Velha was confined with a multi-layer cover and the remediated site was fenced in 2007. This area is now of restricted access and requires maintenance and continuous radiation monitoring that is carried out by EDM. Other areas were cleaned up at Urgeiriça including mill facilities, warehouses, terrains and roads. A public park was build up on the terrains of the former ENU. The mine drainage and seepage from the waste pile are recovered and treated in an automated water treatment plant at Barragem Nova8. Mine sites as Valinhos and Espinho were cleaned up and re-engineered to make them suitable for new uses and are intended to be released from institutional control. Other areas, such as Cunha Baixa, are under remediation and Quinta do Bispo is planned for remediation soon. The issue still open to finding a suitable solution is the future use and control of these areas. There is a need for custody of remediated sites and permanent radiological surveillance, at least until confirmation that remediation works were sufficient to reduce radon concentration in the air, offer efficient shield against gamma radiation, and that are stable solutions providing long term confinement for solid and liquid effluents. The regular national monitoring programme implemented by the IST/LPSR ensures every year, as required by national legislation and by the EURATOM Treaty, that mine sites, soils, rivers and atmosphere are controlled for radioactivity, and that water, agriculture and animal products (meat, milk, cheese) from the region are suitable for human consumption and, thus, for trade and export. Due to the long lived radionuclides present in the uranium waste, waste confinement and management need to be effective in keeping them apart from the biosphere for long time (centuries). In this regard, international recommendations for enhanced radiation safety and regulatory control have been agreed and provide suitable guidance applicable to uranium legacy10. References 1. Batista AS. The programme for remediation of contaminated sites: its regulation and follow-up in Portugal. In: International Atomic Energy Agency. Proceed. of an International Workshop on Environmental Contamination from Uranium Production Facilities and Remediation Measures held in Lisbon 11-13 Feb 2004.Vienna; 2005. p. 223-232. 2. Carvalho FP. Past uranium mining in Portugal: legacy, environmental remediation and radioactivity monitoring. In: IAEA. The Uranium Mining Remediation Exchange Group (UMREG). Selected Papers 1995–2007. IAEA, Vienna, STI/PUB/1524; 2011. p. 145-155. 3. Carvalho FP, Madruga JM, Reis MC, Alves JG, Oliveira JM, Gouveia J, Silva L. Radioactive survey in former uranium mining areas in Portugal. In: AIEA. Proceed. of an International Workshop on Environmental Contamination from Uranium Production Facilities and Remediation Measures, held in Lisbon 11-13 Feb 2004. Vienna; 2005. p. 29-40. 4. Carvalho FP. Environmental remediation of old uranium mining sites and radioprotection goals. Radioprotecção 2003; vol II-III: 159-165. 5. Falcão JM, Carvalho FP, Leite MM, Alarcão M, Cordeiro E, Ribeiro J. MinUrar-Minas de Uranio e seus Resíduos. Efeitos na Saúde da População. Relatório Científico I (Julho/2005) and II (Fevereiro/2007). Publ. INSA, INETI, ITN. (http://www.itn.pt/docum/pt_bib_reltec.htm). 6. Carvalho FP. Uranium in Portugal: the end of mining exploitation and environmental contamination (In Portuguese). Industria & Ambiente 2003; 30: 7-11. 7. Nero JM, Dias JM, Torrinha AJ, Neves LJ, Torrinha JA. Environmental evaluation and remediation methodologies of abandoned radioactive mines in Portugal. In: International Atomic Energy Agency. Proceed. of an International Workshop on Environmental Contamination from Uranium Production Facilities and Remediation Measures held in Lisbon 11-13 Feb 2004. Vienna; 2005; p. 145-158. 8. Empresa de Desenvolvimento Mineiro. The Legacy of Abandoned Mines. Lisboa; 2011 (ISBN: 978-972-95226-2-8) 9. Instituto Tecnológico e Nuclear. Relatório Programas de Monitorização Radiológica Ambiental. UPSR A, nº38/2011; 2001. (http://www.itn.pt/docum/relat/radiolog/rel-vig-radiol2011.pdf) 10. IAEA. Release of sites from Regulatory Control on Termination of Practices. Safety Standards Series No. WS-G-5.1. AIEA, Vienna; 2006.

37




Radioactivity in Soils and Vegetables from Uranium Mining Regions Fernando P. Carvalhoa*, João M. Oliveiraa, Margarida Maltaa a

Instituto Superior Técnico/Laboratório de Protecção e Segurança Radiológica, Universidade de Lisboa, Estrada Nacional 10, km 139, 2695-066 Bobadela LRS, Portugal

Abstract Samples of soils, irrigation water, and vegetable products from three areas were analyzed for radionuclides. These areas are located in the basins of Ribeira da Pantanha, Ribeira do Castelo and streams tributaries to Ribeira de Inguias, all receiving drainage from old uranium mines. Results showed enhancement of radionuclide concentrations, especially 226Ra, in vegetables from kitchen gardens in these areas when compared with reference areas upstream the mine’s discharge points. The main source and transfer pathway of radionuclides to plants was the irrigation water used, rather than the soil. Non-contaminated products were obtained in these areas when irrigation was made with non-contaminated water from deep wells, instead of water from surface streams and irrigation wells contaminated with mine drainage. Guidelines for radionuclide concentrations in irrigation water and soil are needed. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: Uranium; Radium; Polonium; Mine drainage; Soil to plant transfer.

* Corresponding author. Tel.: 351-21-994 6332; fax: 351-21-955 0117. E-mail address: [email protected]


Fernando P. Carvalho et al. / Procedia Earth and Planetary Science 8 (2014) 38 – 42

1. Introduction Radiological exposure of humans to radionuclides from uranium mining and milling waste depends upon the environmental dispersion of uranium waste and radionuclide transfer pathways. These pathways include the transfer of radionuclides from uranium waste to soils and from soils to plants, and then radionuclide ingestion with the diet of local populations. This diet may include agriculture products from former uranium mining areas of the center of Portugal, especially those located along streams and rivers that receive U-mine drainage. In these hilly areas farms generally are of small area co-existing with forest and agro-forest farms and most horticultural garden farms are for family consumption. These garden soils are concentrated in alluvial deposits of rivers and generally are rich in organic matter and high in silica content. Irrigation is essential for the production and this is ensured either with water pumped from surface streams or from irrigation wells. These irrigation wells tap surface aquifers and generally were dug near the streams and water lines. This paper reports results on radioactivity levels in soils, irrigation water, and vegetables grown in agriculture plots near former uranium mining in the center of Portugal and located in the catchment of streams and rivers flowing through those areas. 2. Materials and Methods Three areas were investigated: one near the Urgeiriça and Valinho mines in the county of Nelas, other near the mines of Cunha Baixa and Quinta do Bispo in the Mangualde county, and a third one near the Vale de Arca, Carrasca, Pedreiros and Bica old uranium mines in the Sabugal county (Figure 1).

Figure 1 – Maps of the study areas with location of sampling stations. A, Mondego River basin; B, Zêzere River basin.

In the first area were located old uranium mines, mining waste, milling plant facilities, milling tailings plus unprocessed low grade ore and rubbles from the dismantling of the chemical plant. All these materials were concentrated in one single place, the milling tailings Barragem Velha, and the waste capped in 2005-6. The area, with about 10 ha, was reshaped, a multilayer cover put in place, and the area fenced. Nearby, at Barragem Nova, a waste water treatment plant (ETAM) was refurbished and automated to carry on neutralization and radionuclide co precipitation with barium chloride. Sludge from mine and waste water treatment is deposited at Barragem Nova. Acid mine drainage and acid seepage from the milling tailings are now collected and treated in this ETAM, and treated water released into Ribeira da Pantanha stream which flows through the area. After cleanup of the area of Valinhos mine, a small dam was build up on Ribeira da Pantanha and the artificial lake formed there is intended to became a leisure and picnic area. Stretching the Ribeira da Pantanha, there are several areas with agriculture and pasture for ovine and bovine cattle. An area of kitchen gardens does exist at the Caldas da Felgueira village and

39

40


Ribeira da Pantanha stream water is used for irrigation. The site U1, with similar characteristics but upstream the mine zones was used as a reference area (Figure 1). In the second area, in the Mangualde county, two large mines Quinta do Bispo and Cunha Baixa have for many years released untreated and treated drainage into the Ribeira do Castelo stream. Agriculture is abundant in this area, especially near Cunha Baixa and in alluvial soils along the Castelo stream. Water from this stream and from irrigation wells dug near the stream is used for irrigation. Most agriculture plots are kitchen gardens, but one large apple orchard does exist at Cunha Baixa village. At the time of this survey no environmental remediation had been initiated in these mines. Station CB1 a similar kitchen garden at the village of Mesquitela and on the banks of the Ribeira do Castelo stream was used as a reference site (Figure 1). In the third area, in the Sabugal county, four old uranium mines are located in a valley running NNE-SSW from Águas Belas to the historic village of Sortelha. The valley is drained by two streams, Quarta-feira and Valverdinho, which merge into the Ribeira de Inguias stream, and further south this one discharges into the River Zêzere. In the valley and along the streams there is abundant agriculture production which uses water from wells dug on stream banks for irrigation. Most production of agriculture plots are for family consumption, but wide productions of maize and wine do exist as well. Samples of water from irrigation wells, soil from the agriculture plots, and plants from the available production were collected in the three areas on May 2010. Some agriculture plots were located close to the mines and others at km from the mines, along the streams receiving drainage from mine areas. Water samples were filtered through 142 mm diameter, 0.45 μm pore size membrane filters, and filtered water and suspended particulate matter were analyzed separately. Soil bulk samples of the top 30 cm layer were collected and sieved in the laboratory. The size fraction less than 63 μm was used for radioanalysis. Vegetables (lettuce, cabbage, tomatoes, rtc.) were cleaned and washed with tap water in the laboratory and tubers and fruits peeled off, as for consumption. Samples were freeze dried and aliquots of homogenized material retaken for radioanalysis. Radionuclides were determined in all samples applying radiochemical separation of radionuclides, electrodeposition and radiation measurement by alpha spectrometry. The procedures followed are described in detail elsewhere1,2,3. 3. Results and Discussion Results of radionuclide determinations are shown in Tables 1, 2 and 3, for part of the samples analyzed. Due to space constraints only a few results are shown. In the area of Nelas county, radionuclide concentrations determined in all vegetables and especially in lettuce showed a trend with concentrations increasing down the Pantanha stream from near Urgeiriça to a maximum at Caldas de Felgueira (Table 1). While, for example, 238U in lettuces at the reference station U1 was 51.6±2.0 mBq/kg, at Caldas de Felgueira it was 771±22 mBq/kg (wet weight). This increase goes along with the increase in radionuclide concentrations in bottom sediments and water in the stream. Although radioactive discharges into the stream at Urgeiriça have decreased after implementation of waste water treatment, radionuclide concentrations in the stream materials are still measurable, especially in bottom sediments which will keep a record of past effluent discharges for years. Pumping water and mud from the stream into the kitchen gardens has facilitated radionuclide transfer to vegetables4,5,6. In the Cunha Baixa area (Table 2) many agriculture plots have irrigation wells with acidic water contaminated with radionuclides from Cunha Baixa mine seepage. Agriculture plots along the water line from Quinta do Bispo mine also showed contamination although this water was used for irrigation. Soils and vegetables from agriculture plots in these areas all showed radionuclide concentrations enhanced in comparison to values determined at the reference station C1 (Table 2). Common garden products, such as lettuces, displayed higher concentrations near the Cunha Baixa mine. However, apple production in the orchard near Cunha Baixa (#C5) which used as irrigation water a deep aquifer free of radioactive contamination, showed no enhanced radioactivity levels when compared with #C2, confirming water as the main source of radionuclides accumulated in plants6. Several km downstream along Ribeira do Castelo (C#5), radionuclide concentrations in soils and agriculture products showed concentrations with no contamination from the mines. In the Águas Belas-Sortelha valley the agriculture soils along the Quarta-feira stream showed enhanced concentrations from dispersion of waste materials from Vale de Arca mine by surface runoff into the stream (Table

41


3). The same was observed in some soils around the Bica mine. Agriculture production near these mines displayed higher radionuclide concentrations especially of radium. In vegetable products from Bica area 226Ra was near three times higher than in the reference station and the product displaying the highest radium concentrations was the watercress, near Quarta-feira village (QF#2). Previous research in the area around the Bica mine has indicated contamination of the aquifer and advised continued water treatment to neutralize acidity and precipitate radionuclides 7,8,9. Table 1. Activity concentrations of radionuclides in soils (Bq/kg dry weight), irrigation water (mBq/L) and vegetables (mBq/kg wet weight) from Ribeira da Pantanha basin (Sites: 1, Algeraz; 2 Valinhos; 3,Vale Escuro; 4,Urgeiriça; 7, Caldas de Felgueira). Sample

238

Id.

U

235

U

234

U

230

Th

226

Ra

210

Pb

210

Po

232

Th

Reference Soil

#U1

198±6

9.6±0.9

201±6

456±19

395±46

302±12

302±12

178±9

Water

#U1

70.7±2.1

3.3±0.2

69.9±2.1

1.5±0.6

38.4±2.4

88.6±2.8

12.2±0.5

0.22±0.03

Lettuce

#U1

51.6±2.0

2.1±0.3

52.3±2.0

59.0±14.2

189±12

119.5±5.2

67.4±3.6

17.6±6.9

Lettuce

#U3

87.4±4.5

4.6±0.9

90.5±4.6

48.7±2.5

718±114

171±5

183±5

24.3±1.6

Lettuce

#U4

124±4

38.4±0.7

128±4

94.0±14.4

1754±194

156.3±6.6

53.0±2.6

30.4±7.1

Lettuce

#U7

771±22

35.5±2.9

766±22

227±16

2963±419

706±22

197±9

39.6±4.7

Carrots

#U7

834±33

27.7±4.3

849±34

160±10

1830±181

390±41

253±12

20.5±2.8

Table 2. Activity concentrations of radionuclides in soils (Bq/kg dry weight), irrigation water (mBq/L) and vegetables (mBq/kg wet weight) from Ribeira do Castelo basin (Sites: 1, Mesquitela; 2, Gomes; 3, Aida; 4, Figueiredo; 5, Pisão; 6; Adelino; 7 Qta Carvalhais) 238

235

234

230

Po

232

#C1

314±10

15.0±1.6

316±11

560±24

512±52

567±26

567±26

132±8

Irrig water

#C1

44.4±1.1

2.1±0.1

43.7±1.1

0.86±0.06

37.0±2.8

37.1±1.5

4.7±0.2

0.13±0.02

Lettuce

#C1

437±12

21.4±1.6

462±12

253±17

683±35

527±13

122±4

80.0±6.5

Apple

#C2

45.4±1.8

1.8±0.3

47.1±1.9

24.6±1.4

1627±54

157±5

216±9

3.7±0.5

Lettuce

#C3

3231±136

147±10

2988±126

500±22

1205±178

9141±454

3162±150

28.9±1.7

Apple

#C3

31.5±1.5

1.20±0.4

29.4±1.4

30.0±8.1

1305±70

115±5

668±25

5.2±3.5

Lettuce

#C4

1142±31

50.5±3.8

1100±30

381±23

3359±248

1159±44

931±18

49.9±5.7

Apple

#C5

5.2±0.5

0.26±0.11

6.6±0.6

7.2±0.7

287±16

16±2

107±9

3.6±0.5

Lettuce

#C6

193±8

6.6±1.2

197±8

153±10

3309±226

714±24

294±8

36.2±4.1

Apple

#C6

3.2±0.3

0.14±0.06

4.8±0.4

4.6±0.4

555±30

63.7±6.8

63.9±2.6

1.8±0.3

Lettuce

#C7

803±23

34.6±3.2

758±22

624±34

6260±768

1752±67

2479±122

277±18

U

Pb

210

Soil

U

Ra

210

Id.

U

Th

226

Sample

Th

Table 3. Activity concentrations of radionuclides in soils (Bq/kg dry wt) and vegetables (mBq/kg wet wt) from Águas Belas-Sortelha valley and Ribeira de Inguias basin (Sites: 1, Águas Belas; 2, Vale de Arca; 4, Bica; 5, Quarta-Feira; 6; Caldeirinhas; 7, Caria). Sample

Id.

238

U

235

U

234

U

230

Th

226

Ra

210

Pb

210

Po

232

Th

Soil

#QF1

763±24

37.3±3.2

762±24

666±42

795±64

551±19

551±19

139±10

Lettuce

#QF1

194±6

7.9±0.9

205±6

176±9

460±30

400±30

430±10

75±4

Lettuce

#QF2

158±6

6.1±0.9

154±6

1607±115

8300±1435

346±22

262±19

415±52

Water cress

#QF2

2842±62

133±5

2852±62

904±37

7312±832

2428±67

3734±131

135±7

Lettuce

#QF4

369±9

17.7±1.0

366±9

60.6±4.3

614±106

41.2±1.8

97.0±10.0

25.3±2.2

42


Lettuce

#QF5

77.1±3.4

1.8±0.4

67.6±3.2

43.1±10.5

671±50

185±15

170±6

15.6±6.5

Lettuce

#QF6

108±4

4.3±0.7

Lettuce

#QF7

112±5

4.8±09

114±5

102±6

3578±415

51.7±2.4

17.8±0.8

35.9±2.6

121±5

83.4±5.0

2042±160

406±29

210±6

42.2±3.4

These results confirm previous reports on these areas, including the fact that not all plants are similar accumulators of radionuclides from water and soil, and some may even preclude root absorption and exclude radioelements. Soil composition may also play a role in concentration of radionuclides by plants 6,10,11.

4. Conclusions In the three areas investigated, enhanced radionuclide concentrations were measured in soils and agriculture products, especially vegetables from plots near old uranium mines and their waste piles. The increment of radionuclide concentrations varied amongst sites, but the previous work suggested that the vehicle of radionuclidetransfer to plants was the use/dispersion of contaminated mine waste and, in particular, mine drainage 6. Acid and radioactive mine drainage seeped into the surface aquifer and many irrigation wells, supply contaminated water. Furthermore, surface wells dug near the waterlines receiving mine drainage are recharged with contaminated water from the streams which expands contamination through use in irrigation. In contrast to this, agriculture products grown near mine areas but irrigated with water from deep bore holes showed no radioactive contamination. Also the products from agriculture plots located further away from the mines and grown with clean surface water showed normal (background) radionuclide concentrations. These results suggested that non-contaminated agriculture products may be grown if mine water and drainage from the mines is not used as irrigation water. Once all the mine water discharges will be treated, the quality of surface waters will improve and the transfer of radionuclides to vegetables in agriculture plots might be prevented more efficiently. Nevertheless, guidelines establishing radioactivity limits for several types of water, including irrigation water and soils totally lack in national legislation which renders advice and regulatory control of water and soil use very difficult. References 1. Carvalho FP, Oliveira JM. Alpha emitters from uranium mining in the environment. J Radioanal Nucl Chem 2007; 274: 167-174. 2. Oliveira JM, Carvalho FP. A Sequential Extraction Procedure for Determination of Uranium, Thorium, Radium, Lead and Polonium Radionuclides by Alpha Spectrometry in Environmental Samples. In: Proceedings of the 15th Radiochemical Conference. Czechoslovak Journal of Physics 2006; 56(Suppl. D): 545-555. 3. Carvalho FP, Oliveira JM, Lopes I, Batista A. Radio nuclides from past uranium mining in rivers of Portugal. J Environ Radioact 2007; 98: 298-314. 4. Carvalho FP, Oliveira JM, Malta M. Analyses of radionuclides in soil, water and agriculture products near the Urgeiriça uranium mine in Portugal. J Radioanal Nucl Chem 2009; 281:479-484. 5. Carvalho FP, Oliveira JM, Faria I. Alpha Emitting Radionuclides in Drainage from Quinta do Bispo and Cunha Baixa Uranium Mines (Portugal) and Associated Radiotoxicological Risk. Bull Environ Contam Toxicol 2009; 83:668-673. 6. Carvalho FP, Oliveira JM, Neves MO, Abreu M M, Vicente E M.. Soil to plant (Solanum tuberosum L.) radionuclide transfer in the vicinity of an old uranium mine. Geochem: Explor Environ, Anal 2009; 9: 275-278. 7. Carvalho FP, Oliveira JM, Falck W E. Geochemistry of radionuclides in groundwaters at the former uranium and radium mining region of Sabugal, Portugal. In: B. Merkel and M. Schipek editors. The New Uranium Mining Boom. Challenge and lessons learned. Springer-Verlag Berlin; 2011. p. 81-90. 8. Carvalho FP, Madruga MJ, Reis MC, Alves JG, Oliveira JM, Gouveia J, Silva L. Radioactivity in the environment around past radium and uranium mining sites of Portugal. J Environ Radioact 2007; 96: 39-46. 9. Carvalho FP. Environmental remediation and the legacy of uranium mining waste in Portugal and Europe-Lessons to retain. Adv Mater Res 2010; 107: 157-161. 10. Neves MO, Abreu MM, Figueiredo V. Uranium in vegetable foodstuffs: should residents near the Cunha Baixa uranium mines site (Central Northern Portugal) be concerned? Environ Geochem Health 2012; 34: 181-189. 11. Pulhani VA, S. Dafauti AG, Hegde RM, Sharma UC, Mishra. Uptake and distribution of natural radioactivity in wheat plants from soil. . J Environ Radioact 2005; 79, Issue 3, Pages 331–346.




Intake of Radionuclides with the Diet in Uranium Mining Areas Carvalho FPa*, Oliveira JMa, Malta Ma a

Instituto Superior Técnico/Laboratório de Protecção e Segurança Radiológica, Universidade de Lisboa, Estrada Nacional 10, km 139, Bobadela 2695-066, Portugal

Abstract To assess the ingestion of radionuclides from uranium mining and milling tailings and other sources related to the legacy of uranium mining, several meals from villages in the region were analyzed. For comparison, it was analyzed a meal prepared with non-local products. Local homemade meals contained much higher radioactivity than the comparison meal. The highest concentrations were consistently those of 226Ra followed by uranium and 210Po. Ingestion of local foods by the most exposed population group (critical group) might exceed the recommended dose limit for members of the public, i.e., being higher than 1 mSv/year above the natural radioactive background. © Published by Elsevier B.V. This 2014The TheAuthors. Authors. Published by Elsevier B.V.is an open access article under the CC BY-NC-ND license © 2014 (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: Uranium mines; uranium waste; radioactivity; agriculture; radionuclide ingestion; radiation dose

1. Introduction The environmental radiological monitoring of old uranium mine regions is performed annually by the IST/LPSR in order to fulfill European Union Member State obligations derived from the EURATOM Treaty, in particular Articles 35 and 361. The aim of such monitoring program is to keep updated knowledge on environmental radioactivity, to identify undue exposure of population members to ionizing radiation from uranium mining and milling waste, and to identify dispersion and transfer pathways of radionuclides from those wastes in order to abate

* Corresponding author. Tel.: 351 219 946 332; fax: 351 219 550 117. E-mail address: [email protected]


44

F.P. Carvalho et al. / Procedia Earth and Planetary Science 8 (2014) 43 – 47

radiation exposure of Population. Radioactivity exposure pathways of humans include external radiation, inhalation of radon and dust, and ingestion of radionuclides with the diet. In uranium mining and milling areas the existence of spoil heaps and mine drainage into water streams, may easily lead to accumulation of uranium series radionuclides in vegetables and other agriculture products, thus entering the food chain2-6. Although vast surveys of the areas around old uranium mines have been performed for monitoring the dispersal of radionuclides in the environment, the most realistic assessment of the radionuclide intake is the direct measurement of radioactivity in meals cooked by local families. In a preliminary study using this method we collected meals in villages near uranium mine sites and analyzed them for radionuclides. Radionuclide activity concentrations determined were used to compute the radiation dose through ingestion for adults and children.

2. Materials and Methods The collaboration of several families regularly consuming vegetables and legumes from their kitchen gardens was requested. These were located in the village of Cunha-Baixa, close to the old uranium mine with the same name, and in the village of Caldas de Felgueira, on the banks of Ribeira da Pantanha stream flowing through the Urgeiriça mining and milling area7. To the families were given plastic boxes with tight closure for collection of homemade meals. These consisted of vegetable soups, a popular diet item for daily consumption, made with vegetable products from their kitchen gardens. A total of 8 meal samples were obtained, 6 from Cunha Baixa and 2 from Caldas de Felgueira. For comparison, a meal was purchased in a restaurant in the region where food was prepared with products purchased in the supermarket and originated in non-local production. This reference meal was composed of a cabbage soup and a dish of rice, salad and pork meat. Meals were kept frozen until freeze drying in the laboratory. The resulting dry powder was thoroughly homogenized and sample aliquots were taken for analysis of uranium and thorium isotopes, 226Ra, 210Pb and 210Po. The chemical separation of radioelements and their determination by alpha spectrometry, as well as the analytical quality assurance procedures followed are described in detail elsewhere8-11. Activity concentrations of radionuclides are given in Bq/kg (fresh weight). The committed effective radiation doses for adult and children were computed using the concentrations determined in the meals and the activity to dose conversion factors recommended by the International Commission on radiological Protection (ICRP) and adopted by the EU and the IAEA12,13.

3. Results and Discussion Results of radionuclide analysis in the meals showed larger concentrations of uranium series (238U) radionuclides than thorium series (232Th) radionuclides (Table 1). The average activity concentration of each radionuclide in these meals may be compared with concentrations determined in the reference meal (Table 2). Generally, radionuclide concentrations in the meals from villages were significantly higher than in the reference meal. For example, on average, 226Ra concentrations were 20 times, and 210Po concentrations were 60 times higher than in the reference meal. In the case of Cunha-Baixa this was due to the use of vegetables produced in kitchen gardens near the mines and mines waste heaps in the preparation of family meals. Kitchen gardens at Cunha-Baixa are located in fields along the water stream receiving discharges of mine drainage. Water from this water stream and from irrigation wells nearby is contaminated with acid seepage from past uranium mining activities and contains relatively high concentrations of dissolved radionuclides, such as uranium and radium14. The kitchen gardens at Caldas de Felgueira were irrigated with water from the Ribeira da Pantanha stream, which for many years received drainage and wastewater from Urgeiriça mine and milling area15. Radionuclides that were consistently high in all meals were 226Ra, followed by uranium isotopes (238U, 235U, 234U) and 210Po. This ranking of radionuclide accumulation in vegetables is the same as determined in analyzed fresh products from the region, i.e., without cooking8,15. Radium-226 in the meals from the villages averaged 5258±6356 mBq/kg (fresh weight) which can be compared with the reference soup with 262±22 mBq/kg fresh weight. The main

45


dish of the reference meal with rice and pork meat was even lower, with 38.3±4.6 mBq/kg. It was also noticed that the meals from Caldas da Felgueira were higher in 226Ra activity concentrations than those of Cunha-Baixa (Table 1). The accumulation of radionuclides from mine drainage, and especially the accumulation of 226Ra by wild plants growing on sludge and agriculture crops had been reported before, and it was related to irrigation with contaminated water16-18. Table 1. Activity concentrations of radionuclides (mBq/kg fresh weight) in family meals from villages near uranium mines. Sample

Origin

238

U

235

U

234

U

230

Th

226

210

Ra

210

Pb

Soup #4

Cunha Baixa

223±7

10.2±1.1

212±7

53.8±6.6

6764±649

172±12

Soup #5

Cunha Baixa

340±11

15.7±1.8

330±11

290±16

4787±308

Soup #6

Cunha Baixa

266±10

12.4±1.6

285±10

140±22

2367±151

Soup #7

Cunha Baixa

189±7

8.5±1.2

186±7

63.3±12.5

Soup #8

Cunha Baixa

10.6±0.7

0.25±0.07

11.7±0.7

88.5±27.1

Soup #9

Cunha Baixa

6.8±0.3

0.16±0.04

6.9±0.3

8.1±0.9

Soup #10

Caldas da Felgueira

1624±48

78.5±6.3

1577±47

428±92

1282±64

Soup #11

Caldas da Felgueira

310±13

21.9±3.3

289±12

138±10

19966±3353

Maximum

-

1624

78.5

1577

428

19966

Minimum

-

6.8

0.16

6.9

8.1

136

Mean

-

371

18

362

151

5258

Standard deviation

-

521

25

506

140

6356

232

Po

Th

145±9

15.8±3.5

280±18

174±9

14.2±2.0

153±8

144±11

23.9±9.8

5187±757

141±13

1255±25

2.4±0.3

1578±188

95.0±8.8

39.2±2.3

0.9±0.4

136±6

210±16

4.1±0.2

0.16±0.11

185±13

170±9

44.8±18.9

15.2±1.1

7.9±0.6

8.8±2.4

280

1255

44.8

15.2

4.1

0.16

156

242

14

78

415

15

Table 2. Activity concentrations of radionuclides (mBq/kg fresh weight) in a restaurant meal cooked with non-local products. Sample

Origin

238

U

235

U

234

U

230

Th

226

Ra

210

Pb

210

Po

232

Th

Soup

Caldas da Felgueira

12.3±1.0

0.51±0.16

16.2±1.1

255±202

262±24

20.6±1.7

4.1±0.4

17 years old) the annual average dose from ingestion would be 0.71 mSv/year with a maximum of 2.1 mSv/year. These estimates of the annual dose rate due to the ingestion of local foods are one order of magnitude higher than for the reference meal (Tables 3 and 4). The largest contribution to radiation dose from the diet comes from the 226Ra in vegetables (Fig. 1). It was noticed also that 210Po concentration in vegetables from villages was higher than in the reference meal and therefore the relative contribution of this radionuclide to dose was higher as well. 4. Conclusions The determination of radionuclides, mostly of the uranium family, in homemade soups prepared with vegetables and legumes from local production in villages near old uranium mines, showed that local population has higher radionuclide intake than populations at large and must be considered the most exposed (critical group) amongst the general population. This higher intake comes from the transfer of radionuclides originated in uranium waste to vegetables grown in the family kitchen gardens, followed by consumption. Previous work has shown that dispersion of radionuclides with water used for irrigation is the main pathway for the uptake of radionuclides, such as 226Ra, by plants16, 17. The computation of the radiation dose due to radionuclides ingested with the diet indicated that there are

46

F.P. Carvalho et al. / Procedia Earth and Planetary Science 8 (2014) 43 – 47 Table 3. Effective radiation dose extrapolated to annual basis (mSv/year) for members of the population computed on the basis of the analyzed meals from uranium mine areas. Sample

Origin

Absorbed radiation dose from ingestion (mSv/year) Age group: 2-7 years

Age group: > 17 years

1.9

0.81

Cunha Baixa

1.6

0.67

Cunha Baixa

0.93

0.37

Soup#4

Cunha Baixa

Soup#5 Soup #6 Soup #7

Cunha Baixa

3.3

1.1

Soup #8

Cunha Baixa

0.51

0.21

Soup #9

Cunha Baixa

0.21

0.069

Soup #10

Caldas da Felgueira

0.87

0.34

Soup #11

Caldas da Felgueira

4.6

2.1

Maximum

-

4.6

2.1

Minimum

-

0.21

0.069

Mean

-

1.7

0.71

1.5

0.65

Standard deviation

critical groups that may receive through ingestion an annual effective dose exceeding the maximum recommended limit i.e., 1 mSv/year from radionuclides and exposures related to practices. Table 4. Effective radiation dose extrapolated to annual basis (mSv/year) for members of the public computed on the basis of the comparison meal made with non-local products (restaurant).

Sample

Origin

Absorbed radiation dose from ingestion (mSv/year) Age group: 2-7 years

Age group: > 17 years

Soup

Restaurant

0.09

0.036

Main dish

Restaurant

0.12

0.04

Fig. 1. Relative contribution of radionuclides to radioactivity determined in soups prepared with vegetables from different origins.


47

This preliminary study was based on a small number of meals collected in villages of the uranium region, and a larger investigation on local diets and encompassing more villages is now underway. Notwithstanding, these findings advice focused attention on mine drainage and irrigation water, including specific measures to control the quality of irrigation water in order to abate radionuclide accumulation in agriculture products and to reduce human exposure through ingestion of agriculture products.

References 1. EURATOM Treaty at http://eur-lex.europa.eu/en/treaties/dat/12006A/12006A.htm (accessed 9-3-2014). 2. Carvalho FP. Past uranium mining in Portugal: legacy, environmental remediation and radioactivity monitoring. In: IAEA. The Uranium Mining Remediation Exchange Group (UMREG). Selected Papers 1995–2007. Vienna, STI/PUB/1524; 2011. p. 145-155. 3. Carvalho FP, Oliveira JM, Libânio A, Lopes I, Ferrador G, Madruga JM. Radioactivity in Public Water Supplies in the Uranium Mining Regions in Portugal. In: AIEA. Proceed. of an International Workshop on Environmental Contamination from Uranium Production Facilities and Remediation Measures, held in Lisbon 11-13 Feb 2004. Vienna; 2005. p. 41-51. 4. Carvalho FP, Madruga JM, Reis MC, Alves JG, Oliveira JM, Gouveia J, Silva L. Radioactive survey in former uranium mining areas in Portugal. In: AIEA. Proceed. of an International Workshop on Environmental Contamination from Uranium Production Facilities and Remediation Measures, held in Lisbon 11-13 Feb 2004. Vienna; 2005. p. 29-40. 5. Carvalho FP, Madruga MJ, Reis MC, Alves JG, Oliveira JM, Gouveia J, Silva L. Radioactivity in the environment around past radium and uranium mining sites of Portugal. J Environ Radioact 2007; 96: 39-46. 6. Carvalho FP, Oliveira JM, Lopes I, Batista A. Radio nuclides from past uranium mining in rivers of Portugal. J Environ Radioact 2007; 98: 298314. 7. Carvalho FP, Oliveira JM, Malta M. Radioactivity in Iberian Rivers with Uranium Mining Activities in their Catchment Areas. Procedia Earth and Planetary Science 2014 (submitted in this volume). 8. Carvalho FP, Oliveira JM. Alpha emitters from uranium mining in the environment. J Radioanal Nucl Chem 2007; 274: 167-174. 9. Oliveira JM, Carvalho FP. A Sequential Extraction Procedure for Determination of Uranium, Thorium, Radium, Lead and Polonium Radionuclides by Alpha Spectrometry in Environmental Samples. In: Proceedings of the 15th Radiochemical Conference. Czechoslovak Journal of Physics 2006; 56 (Suppl. D): 545-555. 10. Carvalho FP, Oliveira JM. Performance of alpha spectrometry in the analysis of uranium isotopes in environmental and nuclear materials. J Radioanal Nucl Chem 2009; 281: 591-596. 11. Pham MK, Benmansour M, Carvalho FP, Chamizo E, Degering D, Engeler C. Certified Reference Material IAEA-446 for radionuclides in Baltic Sea seaweed. Appl. Radiat. Isot. 2013 (Available online 20 November 2013). 12. ICRP. Age-dependent Doses to Members of the Public from Intake of Radionuclides, Part 5, Compilation of Ingestion and Inhalation Dose Coefficients. ICRP Publication Nº 72, Ann. ICRP 26, Elsevier Science, Oxford, UK; 1996. 13. COUNCIL DIRECTIVE 2013/59/EURATOM of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionizing radiation. 14. Carvalho FP, Oliveira JM, Faria I. Alpha Emitting Radionuclides in Drainage from Quinta do Bispo and Cunha Baixa Uranium Mines (Portugal) and Associated Radiotoxicological Risk. Bull Environ Contam Toxicol 2009; 83: 668-673. 15. Carvalho FP, Oliveira JM, Malta M. Analyses of radionuclides in soil, water and agriculture products near the Urgeiriça uranium mine in Portugal. J Radioanal Nucl Chem 2009; 281: 479-484. 16. Carvalho FP, Oliveira JM, Neves MO, Abreu MM, Vicente EM. Soil to plant (Solanum tuberosum L.) radionuclide transfer in the vicinity of an old uranium mine. Geochem: Explor Environ, Anal 2009; 9: 275-278. 17. Carvalho FP, Oliveira JM, Malta M. Radionuclides in plants growing on sludge and water from uranium mine water treatment. Ecol Eng 2010; 37:1058-106. 18. Carvalho FP. Environmental Health Risk from Past Uranium Mining and Milling Activities. In: C.A. Brebbia, editors. Environmental Health Risk IV. UK; 2007. p 107-114.




Radioactivity in Iberian Rivers with Uranium Mining Activities in their Catchment Areas Fernando P. Carvalhoa*, João M. Oliveiraa, Margarida Maltaa a

Instituto Superior Técnico/Laboratório de Protecção e Segurança Radiológica, Universidade de Lisboa, Estrada Nacional 10, km 139, 2695-066 Bobadela LRS, Portugal

Abstract Rivers flowing through the uranium mining region of Portugal, such as the Mondego and Zêzere rivers, receive drainage from areas of old uranium mines. The international River Águeda, a tributary to River Douro, has also important uranium mining and milling facilities in its catchment basin in Spain. In order to assess the radioactive contamination of these river basins resulting from uranium mining waste, uranium series radionuclides were measured in water, suspended particulate matter, and riverbed sediments. Results showed that significant radioactivity enhancement took place in sections of these rivers. This contamination persisted long time after environmental remediation implemented at some mine sites and cessation of mine discharges. The persistent risk of waste leaching and dam failure requires continued monitoring of radioactivity levels in these rivers. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

© 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: Uranium mining; mine drainage; river sediments; radioactivity.

1. Introduction The uranium mining industry in Portugal, mostly concentrated in the Centre North of the country, generated about 20 million tons of mining waste plus 5 million tons of milling tailings and sludge resulting from treatment of acid mine waters1. Most of uranium mining and milling waste materials were deposited on surface and have been exposed to weathering for many years. Following seasonal rains, surface runoff carrying leachates and particulate materials from these waste piles have the potential to cause enhancement of environment radioactivity levels and may reach streams

* Corresponding author. Tel.: 351-21-994 6332; fax: 351-21-955 0117. E-mail address: [email protected]



and main rivers. In the last few years, some of these uranium legacy sites, such as the Urgeiriça mine and milling site were remediated and radioactive waste was confined and covered with a multi-layer cap. The vital importance of river water for ecosystems health and sustained economic activities, such as agriculture and supply of drinking water for humans, requires proper industrial waste management and continuous environmental surveillance. Rivers flowing through the uranium mining region, namely the rivers Dão, Vouga, Távora, and the Mondego received water drainage from areas of old uranium mines during decades. Results on radioactivity assessment of these rivers were reported for 2006 2. The catchment areas of River Mondego and River Zezere with their main tributaries, plus the international River Águeda all receiving drainage from uranium mining areas were assessed on 2010 for radioactive contamination. Partial results of the radiological risk assessment for these river basins regarding uranium mine waste is reported herein. 2. Materials and Methods There are several old uranium mines with large amounts of uranium wastes in the catchment basins of rivers Mondego, Zezere and Agueda (Figure 1). The main ones are Urgeiriça and Valinhos mines near the Ribeira da Pantanha stream, and Cunha Baixa and Quinta do Bispo mines near the Ribeira do Castelo. Both Pantanha and Castelo streams are tributaries to River Mondego. The mining and milling area of Urgeiriça was remediated and since 2007 at least, there are no discharges of untreated effluents into Ribeira da Pantanha. In the catchment of River Zêzere there are four main old mines, Vale de Arca, Carrasca, Pedreiros and Bica draining into the streams Valverdinho and Quartafeira, which merge into Ribeira de Inguias - Ribeira de Caria, tributaries to River Zezere. The Iberian River Águeda has its source in Spain and receives drainage from uranium mines near Saelices el Chico, before becoming the border between the countries and joining the River Douro in Portugal. Sampling was carried out in May 2010 in Mondego and Zezere basins. Results for the Águeda are from 1996-2000, and 2007, and were unreported. River water and bottom sediments were sampled at several locations in each river, including the tributaries referred to above. Water samples of about 10-15 L each were pressure filtered on site through 142 mm diameter, 0.45 μm pore size membrane filters, on Teflon coated filter systems. Filtered water was stored in polyethylene drums and acidified at pH pH pzc. The aim of this work was to study the distribution pattern of U in soils, and surface water of an extensive area where there are several U deposits and extensive outcrops of black shale as the main U anomaly origin. In addition, gamma radiation measurements, uranium mobility, bioavailability and relation to soil properties were studied in order to assess the level of U pollution as well as its environmental risk.

2. Materials and methods 2.1 Study area This study was carried out in a region, the river Agueda basin (Salamanca province of Spain and Guarda district of Portugal) where there are numerous deposits of uranium, which occur in fracture areas in shale and schist of the pre-ordovician schist-greywacke complex (CEG) that forms part of the paleozoic basement of the Hesperian Massif4. The Saelices, Alameda del Gardón, Gallegos de Agañán, Carpio de Azaba, and Villar de la Yegua are the most important of these deposits. There is generally a clear tectonic control of the mineralization following shears, faults and breccia zones; this fracturation has been assigned an Alpine age5 as well as the associated hydrothermal processes that caused the U mineralization. In addition, there are other smaller U-quartz veins deposits hosted in hercynian granites that are situated in Casillas de Flores, La Puebla de Azaba, Sobradillo, San Felices de los Gallegos y Bañobarez. The principal ore minerals are pitchblende (UO 2) and coffinite [SiO4U(OH)4], accompanied by alteration products such as gummite (uranium oxides), U-phosphates (autunite, torbernite, sabugalite) and Usulphates (uranopilite, zippeite). Gangue minerals include pyrite and marcasite. The mining activities in Saelices deposit, including static and dynamic acid lixiviation, started in 1960 and finished in 2000, and produced huge amounts of wastes composed of barren rocks (mainly shales, schists and quartz), impoverished ore minerals, and mud rich in sulphates and iron oxides. The restoration of the Saelices mine included geomorphologic remodelling and recovering of the new surface with a layer of powdered arkoses and sandstones to prevent leaching by runoff, as well as addition of topsoil with organic and fertilizers amendments to promote revegetation with grass and other plant species to prevent surface erosion of this area. Rain water is stored in several ponds located at different topographical levels to control its low pH due to weathering of the abundant pyrite, as well as the discharge to the Águeda river, avoiding its radioactive contamination. The climate of this region is continental, with Atlantic influence; annual average precipitation is around 500 mm and very irregular and usually absent in July and August, so, during the dry season, the hydric balance is clearly

S. Sánchez-González et al. / Procedia Earth and Planetary Science 8 (2014) 93 – 97

negative, which propitiates the drying of ponds at Saelices mine site, avoiding water discharge into the Agueda river. 2.2 Sampling and analysis Water samples from rivers, streams, pounds, and surface wells regionally distributed, and topsoil around these wells were collected during March and April 2012. The soil samples were dried at 50 °C, mixed and homogenized and sieved through a 2-mm screen. The < 2 mm fraction was used to determine the main soil properties: pH was determined potentiometrically in a soil paste saturated with water; organic matter was determined by dichromate oxidation using the Tiurin method and %N by Kjeldahl method. Cation exchange capacity (CEC) was determined according to the ammonium acetate method, and particle size distribution (sand, silt, and clay) was analyzed by the pipette method. Water-soluble U in soil samples was measured as follows: Soil and Milli-Q water were mixed in 1:10 proportion and the mixed solution was shaken for 24 h using a rotary shaker. The solution was centrifuged at 3000 rpm; and then the supernatant was collected and filtered using 0.45 μm filters. The U concentration in the supernatant solutions, as well as, in water samples was determined using the ICP-MS method. Gross α activity in water samples was determined by α-spectrometry. Dose equivalent measurements (gamma radiation) were taken in situ at 1 m height with a Geiger counter (Lamse, Mod. Eris1R; Madrid, Spain), along the entire Águeda river basin, the measurement points were 552. The SPSS v.12.0 software package was used for all statistical analyses. 3. Results and discussion The median of the gamma dose equivalent (Fig.1) is very higher than the reported background of the Salamanca6 province 0.11 μSv/h, Guarda7 district 0.12 μSv/h or the worldwide average8 0.07 μSv/h, and range 0.06 – 1.50 μSv/h, with a median value of 0.18 μSv/h. The data varies mainly depending on the contents of U in the soil which in turn depends on the lithology of the soil parent material: on the CEG lower unity (Agadones area) the range is 0.06 – 0.36 μSv/h and the median 0.16 μSv/h; CEG upper unity (Argañan area) range 0.10 – 1.50 μSv/h median 0.28 μSv/h; granites 0.09 – 0.40 μSv/h median 0.20 μSv/h. Also it should be noted that some important anomalies are linked to some mining exploration works such as at Alameda del Gardón or Villar de la Yegua (3-5 μSv/h) and Carpio de Azaba (6.5 μSv/h) . It is not the case of the Saelices mine since has been restored and covered with a thick layer of barren shale and arkosic materials. In addition, it was observed that some local gamma radiation anomalies are related to regional alpine fracturation sites and outcropping areas of black shales.

Fig. 1. Map of gamma radiation dose equivalent in the Agueda river basin (circle indicate points with elevate gamma radiation > 1 μSv/h).

95

96


The radiological situation of the basin is not of immediate concern, except at the mining exploration sites with elevated external hazard index: annual effective dose 6.13 mSv/year versus world average 0.06 mSv/year, and a lifetime cancer risk of 284 x 10-4 versus world average 2.8 x 10-4. Therefore, environmental remediation at these sites should be planned and implemented. In river and stream samples the U concentration are lower (Fig. 2-A) range 8 μg/L (guideline limit for drinking water established by German Environment Protection Agency). Most samples are located in areas of black shale outcropping. In water samples of Agueda River downstream of the Saelices mine the uranium concentration is higher than upstream. A model for the mobilization of uranium in these waters is proposed. This involves the percolation of oxic waters through the fractured rocks, leading to the oxidation of pyrite and arsenopyrite and the precipitation of iron oxyhydroxides. This in turn leads to the dissolution of the primary pitchblende and, subsequently, to release of U (VI) species in water. These U (VI) species are retained by iron hydroxides and then can be mobilized by carbonate complexation. The U contents in shallow wells range from 0.1 to 79.5 μg/L with a median of 0.4 μg/L (Fig.2-B). However, normal U worldwide concentrations in natural waters1,9 do not exceed 0.4 μg/L, being those samples closest to the mining areas which have higher contents about 10-79.5 μg/l in similar form to other uraniferous areas10. Moreover, in a deep borehole hydraulically connected to mineralized quartz-veins (Gallegos de Argañan) the U content is 284 μg/L. The concentration of water-soluble U (or bioavailable) in soils regionally distributed in the Agueda river basin with no influence of mining works, ranges between 1 and 137 μg/L with a median of 9 μg/L, (Fig. 2-C). Except for the organic matter content and iron oxide content, there was no single soil parameter significantly explaining the water-soluble U in soils.

Fig. 2. Boxplot distribution of U in water (A, rivers and streams; B, Shallow wells) and soil (C, soils) samples.

The high U concentrations in Saelices mining ponds (25- 50 mg/L) indicate that these bodies of water constitute extreme environments. Even in areas influenced by mining activities, the U concentration 11 is usually about 3.5 mg/L, and the concentration limit established by the U Mill Tailings Remediation Action (UMTRA) in the USA is 0.5 mg/l. The uranium contamination can be caused by U lixiviation from the mining area. The main U source might be mining spoils of shale and schist, and waste mud of the acid leaching pads, with U contents up to 200 mg/kg. The gross α (>100 mBq/L) and β (>1000 mBq/L) activities12 in these waters originate from 238U and its daughter 226Ra, which is more mobile than uranium in supergene processes causing a relative enrichment of this element in water. In spite of the probable fractionation of 226Ra during weathering process there are a good correlation between α total activity in water samples (range 55-1800 mBq/L) and uranium concentration.


The PCA (Principal components analysis) of waters samples shows an association of U, As and pH (Fig. 3), which can indicate an increase of U solubility with increasing pH, linked to the formation of highly soluble negatively charged carbonate complexes, since the maximum adsorption13 of U on FeOOH occurs at pH around 5.5. Moreover, uranium might show similarity with the arsenic mobilization since AsO4H= is released in solution14 when the pH is > 5. In addition, the formation of uranyl-arsenate complexes has been proved by spectroscopy15; so, theses complexes can propitiate the transport of both elements together16. Fig. 3. Factorial plane: PC1 (54,9% of total variability and PC3 (8.5% of total variability.

Acknowledgements Acknowledgments: This work was funded by the EU co-financed by FEDER and POCTEP Program 2007-2013 (Ref. CE: 0410_AGUEDA_3_E). The software SPSS and ESRI-ArcGIS were used in the statistical and spatial analysis. References 1. Rogers JJ, Adams JA. Uranium: abundance in natural waters. In K.H. Wedepohl, editors. Handbook of Geochemistry. Springer. New York; 1978. 2. Gavrilescu M, Pavel LV, Cretescu I. Characterization and remediation of soils contaminated with uranium. J Hazar Mat 2009; 163: 475–510. 3. Echevarria G, Sheppard MI, Morel JL. Effect of pH in the sorption of uranium in soils. Environ Radioactivity 2001; 53: 257-264. 4. Arribas A. Sobre el origen de las mineralizaciones españolas de uranio en rocas metasedementarias. Bol Geol Min 1987; 48: 705-711. 5. Both RA, Arribas A, Saint-André B The origin of breccia hosted uranium deposits in carbonaceous metasediments in the Iberian Peninsula. Econ Geol 1994; 9: 584-601. 6. Quindos Poncela LS, Fernández PL, Gómez Arozamena J, Sainz C, Fernández JA. Natural gamma radiation map (MARNA) and indoor radon levels in Spain. Environ Intern 2004, 29: 1091– 1096. 7. Amaral EM, Alves JG, Carreiro JV. Doses to the portuguese population due to natural gamma radiation. Radiation Protection Dosimetry 1992. 45: 541-543. 8. UNSCEAR. Report. Sources and effects of ionizing radiation. New York; , 2000. 9. Palmer MR, Edmond JM. Uranium in river water. Geoch Cosmoch Acta 1993.5/7: 4947-4955. 10. Neiva AMR, Carvalho PCS, Antunes IMHR, Silva MMVG, Santos ACT, Cabral Pinto MMS, Cunha PP. Contaminated water, stream sediments and soils close to the abandoned Pinhal do Souto uranium mine, central Portugal. J Geochem Explor 2014; 136: 102-117. 11. Desssouki TCE, Hudson JJ, Neal BR, Bogard MJ. The effects of phosphorus additions on the sedimentation of contaminants in a uranium mine pit-lake.Water Research 2005; 39: 3055–3061. 12. Gutierrez-Villanueva JL. Radon concentration in air, soil and water in a granitic area: instrumental developments and measurements. PhD Thesis. University of Valladolid, Spain; 2008. 13. Vandenhove HC. Gil-García A., RigolM, Vidal. New best estimates for radionuclide solid–liquid distribution coefficients in soils. Part 2. Naturally occurring radionuclides. J Environ Radioactivity 2009; 100: 697–703. 14. Garcia-Sanchez A, Alvarez-Ayuso E, Rodriguez F. Sorption of As (V) by some oxyhydroxides and clays minerals. Application to its immobilization in two polluted mining soils. Clay Miner 2002; 37: 187– 194. 15. Gezahegne WA, Hennig C, Tsushima S, Planer-Friedrich B, Scheinost AC, Merkel BJ. EXAFS and DFT investigations of uranyl arsenate complexes in aqueous solution. Environ Sci Technol 2012; 46: 2228-2233. 16. Nair S, Merkel BJ. Transport of uranyl and arsenate in the presence of SiO2, Al2O3, TiO2 and FeOOH. Goldschmidt 2012 Conference Abstract; 2012.

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Uranium in different samples from Eastern Macedonia – a case study Petra Vrhovnika, Todor Serafimovskib, Nastja Rogan Šmuca, Matej Doleneca, Goran Tasevb, Tadej Doleneca a

Faculty of Natural Sciences and Engineering, University of Ljubljana, Department of Geology, Aškerčeva cesta 12,1000 Ljubljana, Slovenia b Faculty of Mining, Geology and Polytechnics, University “Goce Delčev–Štip”, Goce Delčev 89, 2000 Štip, Macedonia

Abstract

Content of uranium in the Sasa tailings dam material varies from 1.8 to 5.5 mg kg-1. Sasa tailings dam failure cause discharge of material in the Lake Kalimanci. The uranium content in surficial lake sediments in years, before the tailings dam failure varied from 2.4 to 5.4 mg kg-1 and after the failure from 3.6 to 10.4 mg kg-1. Meanwhile Lake Kalimanci water contains lower concentrations of uranium (0.9-1.1 μg ml-1). Water from Lake Kalimanci is being used for irrigation of the nearby Kochani valley, where the uranium content in soils varies from 73 to 182 mg kg-1. © Published by Elsevier B.V. This © 2014 2014The TheAuthors. Authors. Published by Elsevier B.V.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco. Selection and peer-review under responsibility of the Instituto Politécnico de Castelo Branco Keywords: uranium pollution; health effects; FYR Macedonia

1. Introduction The toxicity of uranium to humans and other living organisms has been of interest since the 1800s1. The vast majority of uranium that is free in the environment, and thus a possible source of human exposure, comes from the use of depleted uranium munitions2. The next main source of uranium exposure is presented by uranium rich deposits or other metal deposits connected with uranium. Historically, most epidemiology connected with uranium mining has focused on mine workers and radon exposure, although a smaller emerging literature has begun to form

* Corresponding author. Tel.: +386 1 4704620; fax: +386 1 4704560. E-mail address:[email protected]


Petra Vrhovnik et al. / Procedia Earth and Planetary Science 8 (2014) 98 – 102

around environmental exposure in residential areas and nearby (uranium and other metal) mining facilities3. Humans can be exposed to uranium by inhaling dust in the air or by ingesting contaminated water and food. Generally concentrations of uranium in the air are very low, but long term exposure can also lead to serious health effects. Uranium has toxic effects functions on the cardiovascular system, liver, kidneys, muscles and nervous system, but can also damage skin, bones and other parts of the human body3,4. Uranium, after entering human body, is usually absorbed from the intestine or lungs, enters the bloodstream and is rapidly deposited in the tissues (predominantly kidney and bone) or is excreted in the urine. Serbo-Macedonian Masiff contain two main ore deposits in the Osogovo Mountains, the Sasa-Toranica and Zletovo-Kratovo ore deposits, which are connected by the same geology catchment (Fig. 1a-b). It comprises highly metamorphic rocks containing gneiss, micas, amphibolites ilvaite skarns and schists. A typical mineral assemblage around the Sasa Mine area is represented by ore minerals: pyrite, galena, sphlareite, sometimes chalcopyrite and traces of ceruzite, anglesite and malachite. Next to the active Sasa mine, uranium origin can be also linked to the small uranium deposit in the south-west slopes of Osogovo Mountains which extends into the SMM. Uranium deposit in the Zletovska Reka region is related to Tertiary calc alkaline volcanics and belongs to low- to medium-temperature hydrothermal uranium deposits with small admixtures of other ore minerals5. A concentration of uranium in different granitoid complexes from SMM ranges from 2.8 to 10 mg/kg6. The present study was conducted over a wide area in Eastern FYR Macedonia, where several active mines are located. The main objective of this research was to evaluate concentrations of uranium in different samples from a wide area in NE FYR Macedonia and to assess the possible effects of uranium on human health.

99

100


Fig.1. (a) Study area; (b) basic geological composition of research area.

2. Materials and methods 2.1 Sampling and sample preparation Six surficial samples from the Sasa tailings dam were taken in October 2003. The surfaicial samples were collected in plastic bags and stored in the laboratory at 4oC. The samples were dried at 50oC for 48 hours. They were than sieved through a 0.315 mm polyethylene sieve and homogenised by a mechanical agate grinder to a fine powder for further analysis. Sufaicial sediment samples from Lake Kalimanci were taken before the accident in August 2001. The sampling collection was resumed in September 2007 four years after the accident happened. The sediment pH ranged between 5.5 and 7.5, and redox potential ranges were between -325 mV and +180 mV. The samples were collected with plastic corers (a tube 10 cm long with a 7 cm internal diameter), and were tightly packed into self-locking polyethylene bags. Water samples from Lake Kalimanci were collected at all twelve sampling sites at the same time as the fish collection. Water samples were filtered using a hand-pump on site through a 0.45μm membrane filter paper into pre-cleaned sample bottles. After immediate acidification with concentrated HNO 3, the samples were stored in a cooling box (< 4oC) until analysis. The sampling of the paddy soils from the Kochani valley was carried out between the villages Orizari and Krupište in autumn 2005. The paddy soils were sampled using a plastic spade to avoid any metal contamination and each sample comprised a composite of five sub-samples taken within 1 x 1 m2 square.

2.2 Analyses The geochemical analysis of the Sasa tailings dam material, the Lake Kalimanci surficial sediments and soil samples were processed at the commercial ACME Laboratories in Vancouver, Canada, using inductively coupled plasma mass spectrometry (ICP/MS). The accuracy and precision were assessed using international reference materials. A sequential extraction analysis was also applied in ACME Laboratories, to reveal the mobility and bioavailability of U in lake sediments.

3. Results and discussion

101


The north-east FYR Macedonia region is very rich in numerous metal deposits, among which Pb-Zn mines are currently heavily exploited. Next to lead and zinc, copper and gold are also very important in this region. Pb-Zn mines in north-east FYR Macedonia are some of the largest in Europe and consequently produce vast tailing dams. Due to wind transfer of the tailings dam material all over the Makedonska Kamenica and Kochani valley regions the U content was determined for such material. Results revealed that U content in Sasa tailings dam material varies from 1.8 to 5.5 mg/kg. In the 2003 the Sasa tailings dam failure occurred and caused an intensive flow of waste material through the Kamenica River valley and deposited in Lake Kalimanci. Since water from this lake is used for the irrigation of paddy fields in Kochani valley, sediments before and after the failure were studied. The U content in surficial sediments from Lake Kalimanci ranged from 2.4 to 5.4 mg/kg before the tailings dam collapse (Fig 2a) and from 3.6 to 10.4 mg/kg after the failure (Fig. 2b). Meanwhile a sequential extraction procedure revealed that the majority of U was found to be associated with the exchangeable fraction (F2) (Fig. 3). This indicates that U is highly mobile and bioavailable under normal conditions. a

b

2001 10,00 5,00 -

2007 U mg/kg

I-1 I-5 II-6 III-6 V-1 VI-5 VII-4 VIII-4

U mg/kg

20 10 0

Fig. 2. (a) Uranium content in the surficial lake sediments before the tailings dam failure (2001); (b) Uranium content in the surficial lake sediments after the tailings failure (2007).

100%

0% I-4 II-3 III-3 Water-soluble fraction F1

V-7 VI-11 VII-11 Exchangeable fraction F2

VIII-8

Fig. 3. Percentage U removed after each step of the sequential extraction procedure applied to sediments from Lake Kalimanci.

Lake Kalimanci waters were also examine and results showed low concentrations of U (0.9 – 1.1 μg/ml). As mentioned above, water from Lake Kalimanci is being used for the irrigation of nearby agricultural area, thus U the content in soils from Kochani valley was determined, and found to vary from 73 to 182 mg/kg. This is much higher than in the lake sediments and water. U is thus originate by other sources than the lake environment itself, but is most likely correlated with the small scaled uranium deposits in the south-west slopes of Osogovo Mountains, near Zletovska Reka region (Fig. 1a).

4. Conclusions The Sasa tailings dam failure occurred in year 2003 and the majority of the waste material was subsequently discharged through the Kamenica River Valley to Lake Kalimanci. Uranium concentrations defined in the Sasa tailings dam material varies from 1.8 to 5.5 mg kg-1. The uranium content in surficial lake sediments measured before the tailings dam failure ranged from 2.4 to 5.4 mg kg-1 and from 3.6 to 10.4 mg kg-1 after the accident. A sequential

102


extraction procedure revealed that the majority of uranium was associated with the exchangeable fraction (F2), indicating high mobility and bioavailability of uranium under normal environmental conditions. Meanwhile, Lake Kalimanci water contains lower concentrations of uranium (0.9-1.1 μg ml-1). Water from Lake Kalimanci is being used for irrigation of the nearby Kochani valley, where the uranium in soils varies from 73 to 182 mg kg-1.

Acknowledgements This work has been supported by the research programme “Geochemical and structural processes – P1-0 195” founded by the Slovenian Research Agency (ARRS) and the University “Goce Delcev” Stip, Faculty of Mining, Geology and Polytechnics, Department of Mineral Deposits. We would like to give our sincere thanks to Dr. Maria Teresa Durães Albuquerque and Dr. Isabel Margarida Horta Ribeiro Antunes. References 1. Hodge HC, Stannard N, Hursh JB. Uranium, plutonium, transplutonium elements. Handbook of experimental pharmacology, vol 36. Springer, New York; 1973. 2. Briner W. The toxicity of depleted uranium. Int.J.Environ.Res. Public Health 2010; 7 (1): 303-313. 3. Brugge D & Buchner V. Health effects of uranium: new research findings. Rev. Environ. Health 2011; 26(4): 231-249. 4. Taylor DM & Taylor SK. Environmental uranium and human health. Rev. Environ. Health 1997; 12 (3): 147-157. 5. Lazarov P, Jelenkovic R, Serafimovski T. Geology and model of genesis of the Zletovska reka uranium deposits, Republic of Macedonia. Plate tectonic aspects of the alpine metallogeny in the carpatho-Balkan region. Proceedings of the annual meeting – Sofia. UNESCO – IGCP project, No. 356. Vol.1; 1996 6. Jelenkovic R, Serafimovski T, Lazarov P. Uranium mineralization in the Serbo-Macedonian Masiff and the Vardar zone: Types and Distribution Pattern. Plate tectonic aspects of the alpine metallogeny in the carpatho-Balkan region. Proceedings of the annual meeting – Sofia. UNESCO – IGCP project, No. 356. Vol.1; 1996.

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