ISSN 0016-7029, Geochemistry International, 2017, Vol. 55, No. 10, pp. 935–945. © Pleiades Publishing, Ltd., 2017. Original Russian Text © Yu.G. Tatsii, V.N. Udachin, P.G. Aminov, 2017, published in Geokhimiya, 2017, No. 10, pp. 942–953.
Environmental Geochemistry of Mercury in the Area of Emissions of the Karabashmed Copper Smelter Yu. G. Tatsiia, *, V. N. Udachinb, c, **, and P. G. Aminovb, *** a
Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKHI), Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991 Russia b Institute of Mineralogy, Ural Brach, Russian Academy of Sciences, Ilmeny State Reserve, Miass, 456317 Russia cGeological Faculty, Branch of the Southern Ural State University, ul. Oktyabrya 16, Miass, Chelyabinsk oblast, 456318 Russia *e-mail:
[email protected] **e-mail:
[email protected] ***e-mail:
[email protected] Received February 16, 2017; in final form, March 23, 2017
Abstract⎯Mercury emissions during production of blister copper at the smelter Karabashmed are roughly estimated. The high mercury content in the atmospheric dust, soils, lake sediments of the Karabash geotechnogenic system shows that emissions of the plant are the main source of environmental contamination. The mercury content in soils of residential territory ranges within 0.2–11.4 mg/kg, reaching 15 mg/kg in soils of the impact zone. The maximum mercury content in the bottom sediments of Lake Serebry is 32 mg/kg. The high degree of contamination by other elements of emissions (Cu, Pb, Zn, As, Cd) is also demonstrated. Obtained results justify the need for the instrumental control of mercury in emissions. Keywords: mercury, emissions, environment, anthropogenic pollution, heavy metals DOI: 10.1134/S0016702917100093
INTRODUCTION It is generally accepted that mercury is an extremely dangerous contaminant. Practically in all countries, mercury and its compounds are ascribed to contaminants requiring the mandatory industrial control and environmental monitoring. In the Russian Federation, only mercury has been normatively determined in different environmental components as the substance of the 1st class hygienic danger and belongs to the “List of contaminants subjected to the state regulation in the area of environmental protection” (List…, 2015). This causes a need to studying of processes of mercury supply and behavior in the environment, revealing the scales and intensity of mercury contamination, and implementation of necessary environmental monitoring. Metallurgical plants are ascribed to the 1st category objects, which exert significant negative impact on the environment and are among the main sources of the mercury emission in atmosphere. In the technical report on the global mercury assessment (AMAP/UNEP, 2013), the mercury emissions by non-ferrous metallurgical plants (including copper smelters producing blister unrefined copper) are the second in abundance after the coal-fired power plants. According to data of ACAP (2005), the mercury emissions during the nickel and copper production in the
Russian Federation in 2001/2002 accounted for 14% of all mercury emissions. At the same time, mercury and its compounds were excluded from a list of substances subjected to control on plants, including copper smelters. On September 2014, The Russian Federation signed the Minamata Convention on mercury (Minamat Convention…, 2013), in which copper production is considered as one of the main sources of mercury emission. Within the framework of this Convention, inventories of the environmental mercury contaminations are preparing in Russia. This work includes carrying out of analytically proved researches on the basis of actual measurements of mercury emission from industrial objects. In view of the importance of meeting the international obligations of the Russian Federation, if significance of mercury emissions and releases for copper smelters will be justified, it will be necessary to consider additionally the mercury involvement in a list of marker elements for emissions and releases (ITS 3-2015). In the emissions of non-ferrous metallurgical plants in general and copper smelters, in particular, the main contaminants are sulfur dioxide, dust, nitrogen oxide, carbon oxide, metals and metalloids, and their compounds (depending on the composition of raw material, these are zinc, lead, copper, arsenic,
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cadmium, mercury, etc.). The most urgent ecological problem in relation with the copper production from raw material is SO2 emissions in flue gases forming during roasting and smelting of sulfide concentrates. Mercury is ascribed to the group of chalcophilic elements, which are typomorphic for copper smelter emissions. Sulfide ores usually used to obtain copper, lead, and zinc have relatively high Hg content, which is related to the affinity of these metals to sulfur. Most part of this Hg is released during roasting/smelting and together with SO2 is supplied in flue gases. The main volume of mercury is retained in the gas purification system, but some part is ejected into the atmosphere. Full inventory of global mercury emission during production of non-ferrous metals is absent. Partial assessments were made on the basis of available official data on emissions or emission coefficients and statistical data on the metal production and/or consumption of raw material (Pirrone et al., 1996; Pacyna et al., 2006, 2010). According to some researchers (Hylander and Herbert, 2008), emission coefficients applied in these calculations are clearly underestimated, which is related to the uncertainties due to the absence of experimentally measured coefficients for different processes, reliable data on emissions, especially for countries where national expert assessments are absent. This was taken into account during last global mercury assessment (AMAP/UNEP, 2013), which resulted in a significant increase of emission coefficients during blister copper production. The solution of ecological problems is based on the objective information on the real state of the environment (water, terrestrial, and air) and its change in response to the anthropogenic impact. However, in spite of the uninterrupted mentioning of significant mercury content in ores and concentrates, the reliable information on the mercury content in raw materials, emissions, discharges, and wastes of specific plants and the entire non-ferrous metallurgy in the Russian Federation is absent. Literature data on the environmental mercury load in the area of operation of smelters are precious little. The Karabashmed smelter (Chelyabinsk district) is the Russia’s third ranking plant on the blister copper production after the Copper plant in Norilsk and the Sredneural’skiy copper smelter (SUMZ) in Revda. In 2014, this plant produced 102000 t of black blister copper (ITS 3-2015) and continues to increase capacities. For the last 15 years, the smelter was cardinally renovated with modernization of production technology: replacement of furnace and converters, mounting a gas purification system with baghouses, electrostatic precipitators, and wet scrubber, launching the sulfuric acid plant and production of sulfuric acid. At the same time, not all flue gases are supplied for recycling. According to official data for 2012, almost fourth part of the gases was ejected into the atmosphere without purification. A new sulfuric acid plant has been
launched in 2016 to decrease significantly emissions, assuming that all gases after smelting will be passed through a gas purification system. Pyrometallurgical extraction of copper provides transition of most part of mercury from concentrate into a gas phase and, then, together with SO2, dust, and metal oxides into the gas purification system. Different cleaning methods are applied to remove dust from flue gas–dust mixture during obtaining of copper matte at the smelting stage in Ausmelt furnace. Their aim is maximum dust removal before supply of gases in the sulfuric acid plant to produce the highquality sulfuric acid. However such systems of gas desliming are also applied to decrease the mercury content before emission of flue gases in stack after gas purification (ITS 3-2015). The aim of this work is to estimate the atmospheric emissions of mercury during production of blister copper at the Karabash copper smelter and its further accumulation and redistribution in the different structural blocks of geosystem under conditions of the elevated aerial mercury load. MATERIALS AND METHODS As mentioned above, mercury and its compounds were excluded from a list of controlled substances. Therefore, the mercury content in the flue gases at the Karabashmed smelter is not controlled and the systems of mercury removal from them are absent. For this reason, the mercury content in the emissions was estimated on the basis of available data on volumes of blister copper production, raw material, and mercury content in it, as well as the presence of flue gas purification systems. Sampling. Copper concentrates were collected on the raw material handling location after averaging and reduction following procedures generally accepted for works with large-scale technological samples. Atmospheric precipitates. Samples of dry depositiojs (atmospheric dust) were sampled during field works in August, 2013. They were taken from the window sills of the recessed balconies at the third floor, from different sides of the building: from the eastern side faced to the Karabash copper smelter (KCS) and, from the western side with a street view. Construction of the building completely excludes the passage of rain and snow on the window sills, which was also confirmed by the character of samples. The weight of samples collected from the surfaces (~50 cm2) was 2.52 g in the western side and 0.54 g in the eastern side, which can be explained by addition of road dust in the first case. The distance to the KCS is approximately 2.5 km. Sampling of rain precipitations have been carried out during 2007–2013; background precipitates were collected at a distance of 25–30 km from KCS, as well as in the Karabash itself. Anthropogenic precipitations
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in August, 2013, were collected at approximately 2.5 km from emission point under unfavorable meteorological conditions. Samples were collected using plastic rain collectors. Values of pH were measured in situ, and then samples were filtered under vacuum through 0.45-mm Millipore membrane filters (Udachin et al., 2010). Immediately after collection, samples for heavy metals were acidified by HNO3 and preserved at 4°C. Soils. Field and laboratory studies of metal-contaminated soils and soil samples were carried out according to the Methodical Instructions (1981). Soil sampling during surveying seasons 2010-2014 was conducted in accordance with GOST 17.4.3.01-83 and GOST 17.4.4.02-84. Surface samples from the interval 0-10 cm, including horizons А0 (litter) and А, were used for the assessment of pollution through atmospheric deposition. Water was sampled according to GOST P 51592– 2000 from a depth of 0.5 m, filtered, measured рН, acidified by HNO3, and stored at 4°C. The bottom sediment cores were taken from the deepest parts of Lake Serebry and the Berezovskii reach of Lake Seliger (background lake). After sampling, the core was cut into layers 1, 2, 5, or 10 cm thick, packed in plastic sachets, and preserved at temperature of 4°C. Sampling localities of soil and bottom sediments are shown in Fig. 1. Fish. Bream (Abramis brama L.) was taken as bioindicator. Five species 300–500 g in weight were studied in each lake. Gills, liver, kidneys, muscles, and skeleton were collected for analysis. The samples were prepared by decomposition in concentrated HNO3 with addition of hydrogen peroxide (Gashkina et al., 2015). Bioaccumulation in fish was estimated as compared to that of Lake Seliger located far from metallurgical complexes and considered as “background”. Analytical methods. Concentrations of trace elements in samples of rain, lake water, soil, bottom sediments, and tissue and organs of fishes after proper sample preparation were determined by ICP-MS and ICP-AES. Mercury in solid samples was determined by cold vapor atomic absorption with pyrolitic volatilization and preconcentration on gold trap. The analysis was carried out at the certified analytical laboratories of the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences (Moscow), Institute of Mineralogy of the Ural Branch of the Russian Academy of Sciences (Miass), and Institute of Problems of the Technology of Microelectronics and Ultrapure Materials, Russian Academy of Sciences (Chernogolovka). RESULTS AND DISCUSSION Assessment of mercury emissions. The impossibility of direct measurements of mercury emission, as well as disagreement between official data on SO2 emissions and data obtained using cosmic survey (Fioletov et al., GEOCHEMISTRY INTERNATIONAL
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2016) permit only qualitative assessment of minimal Hg emissions from total production of blister copper, processed raw material, and the presence of flue gas purification system. Copper concentrate is supplied at smelter from four sources: Mikheevskiy GOK, Aleksandrinsk Mining Company, ORMET Company, and Aktyubinsk Copper Company. The mercury contents in the concentrates are approximately 2.9, 1.2 (2.5), 4.4 (4.4), and 7.7 (1.3) mg/kg, respectively (in brackets—results of 2011). Since proportions of concentrates from different sources are unknown, the mean Hg concentrations from the first three sources (3 mg/kg) were taken for assessment of minimally possible emissions. This corresponds to the Hg concentrations in most of the usually used copper concentrates (Hylander and Herbert, 2008). Copper concentration in all concentrates was taken corresponding to the content in concentrate from Mikheevskiy GOK (22%). In this case, 489 000 t of concentrate containing at least 1500 kg Hg is required to produce 100000 t of blister copper (in 2014 KCS produced 102.64 kilo t (ITS 3-2015) at generally accepted extraction of 93%. This mercury at temperature of roasting and smelting passes into flue gases and partially in slag. Around 4% goes in slag (60 kg), whereas 96% are removed in gases, from which, as mentioned above, one fourth is ejected into the atmosphere without treatment, and these gases contain approximately 360 kg Hg (Fig. 2). Other part of gases is supplied for processing in the purification system, which involves bag filters, electrostatic precipitators, wet skrubbers, and, at last, sulfuric acid plant. Mercury removal efficiency in such system according to the average assessments of AMAP/UNEP (2013) accounts for 95%, but can reach more than 99% according to some data (Wu et al., 2016). In our calculations, we took that the efficiency of the existing system was 98%, which is 22 kg additionally. Thus, according to minimum calculations, excluding possible mercury emission into the atmosphere from metallurgical slag and wastes, almost 400 kg mercury is ejected into the atmosphere during production of 100000 t black copper at KCS. With allowance for these assumptions and the high degree of uncertainty, this amount can be much greater: the average copper content in the concentrates can be less than 22%, while the average mercury content in concentrate is higher. It should be noted that 400 kg mercury is sufficiently high value, which is inferior only to the emissions of copper, lead, and zinc. However, this value yields the emission coefficient of 0.82 g Hg/t concentrate and 4.0 g Hg/t blister copper, which is close to values for developed countries. If all flue gases are passed through a gas purification system and sulfuric acid workshop, over 100 kg mercury will be ejected into the atmosphere (emission coefficient is approximately 1.0 g Hg/ t Cu). 2017
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Fig. 1. Sampling localities in the territory of the Karabash geoanthropogenic system. s—litter sampling points; d—soil sampling points; m—bottom sediments sampling points.
Atmospheric precipitates. Dust–gas emissions from KCS are the main factor of anthropogenic impact on the environment of the Karabash geotechnogenic system (aerial type of technogenesis) through dry and wet precipitates, which are the main concentrators and temporal depository for aerosol microadmixtures. Karabash is located in the flat valley extending from the southwest to the northeast. Orientation of mountainous ranges with heights up to 600 m and the predominance of western winds creates a complex pattern of redistribution of atmospheric industrial emis-
sions, and causes their precipitation in the urban territory when wind is absent. The main stack of the plant is 127 m high, which is 100–120 m below the eastern range. Therefore, the eastern mountainous framing of the town serves as its orographic barrier at the prevailing direction of emission, prevents their rapid removal, and facilitates formation of inversion (smog) situations. Owing to topographic peculiarities, unfavorable meteorological conditions and temperature inversions result in the precipitation of significant part of emissions within intermontane valley.
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100% 24% 360 kg
Concentrate
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1500 kg Hg 4% Slag
Emissions Roasting/smelting Without purification 6%
Emissions1%
66%
5%
Converter
Gas purification
15 kg Wastes
1% Slag
59% 6% Sulfuric acid plant
Blister copper
5% Wastes
Emissions 0.5% kg
0.5% Sulfuric acid
Fig. 2. Evaluative scheme of the mercury fluxes during blister copper production at Karabashmed.
Analysis of samples of atmospheric dust confirmed that its composition is dominated by S, Cu, Cd, Pb, Zn, As, Hg, the elements of KCS emissions. Note that the content of these elements in sample taken from the eastern side of the building faced toward KCS is approximately 1.5 times higher than their contents in the dust sample taken from the opposite side. The contents of such elements as Co, Cr, and Ni, in both the samples are approximately at the same level. The mercury content in the eastern sample of dust accounted for 3.8 mg/kg, which exceeds MAC for soils of 2.1 mg/kg (GN 2.1.7.2041-06) and background contents of 0.15 mg/kg, which were determined by us for the lower parts of the humic–accumulative horizons of the gray forest soils unaffected by atmospheric contamination. In order to estimate the anomalous concentrations of heavy metals and metalloids in atmospheric dust, the enrichment factors relative the Earth’s crust were calculated with normalizing to Sc (Reimann and Caritat, 2000), which accounted for 1427 for Cd, 857 for As, 487 for Cu, 398 for Pb, and 182 for Zn. The average contents of elements in the Earth’s crust were taken for calculation from Kasimov and Vlasov, (2015), while for Sc and Hg were used values 15.6 and 0.065 mg/kg, respectively (Grigor’ev, 2009). The mercury enrichment factor accounted for 67, which is much lower than for other elements, which however supports the anthropogenic origin of mercury in the dust. It should be emphasized that around half of mercury is ejected as elementary Hg°, the life time of which in the atmosphere varies from few days to 1.5 years and which can be transported over significant distances. Fractionation of samples over particle size (Ermolin et al., 2016) revealed the highest mercury content GEOCHEMISTRY INTERNATIONAL
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in >10 μm fraction. This may indicate that mercury in dust occurs as particles rather than adsorbed on their surface. In the last case, the highest concentration would be found in the finest fraction. This assumption is also supported by the fact that the mineralogical composition of the emissions, in addition to others, includes “primary” minerals of reworked concentrates: pyrite, chalcopyrite, sphalerite, and galena, while toxic elements in particulate emissions occur mainly in tightly bound form (Williamson et al., 2004). In samples of the studied dust, only 0.7% Hg occur in soluble form, whereas soluble forms of S, Zn, Cu, As, and Cd accounted for 46.1, 11.1, 1.9, 4.1, and 1.5%, respectively (Fedotov et al., 2016). Taking into account that the total concentrations of these elements in the studied samples are extremely high (Cd 0.1, As 4.2, Pb 5.9, Cu 11.5, Zn 11.9, S 15.5 g/kg), such dust may represent a serious danger for health. Leaching of contaminants from the air contributes to wet precipitation. The mercury content in the rain water can vary in a wide range, often showing extremely low concentrations both in the background and anthropogenic rains (below detection limits). Dissolved species of elements in atmospheric precipitates, however, can be confidently subdivided into background and anthropogenic ones. Air masses transferring rains with background concentrations of trace elements are supplied either from the west (central Russia) or from the southwest, while rains with anomalous concentrations are characterized by directions along the Uralian Range, especially in the regions with metallurgical production (Udachin et al., 2010). Clear geochemical indicator of the environment can be enrichment factor, which can differ by ten and more times for the same elements in the back2017
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Concentration, mg/kg
350
Hg
Height, m asl
Concentration, mg/kg
940
2000
Cu Pb Cr Ni
1000
0
100 200 300 400 500 600 Distance, m
Fig. 3. Change of heavy metal concentrations as a result of soil slope wash.
ground and anthropogenic precipitates. At the same time, the composition of anthropogenic precipitates may significantly vary depending on weather, wind direction, distance from the emission source, and other parameters. Sampling of such precipitates is complicated by the rapid removal of anthropogenic particles from air during rain. In addition, a frequent change in wind direction makes it difficult “to catch” maximally anthropogenic rain. For the same reasons, the average composition of anthropogenic precipitates is difficult to determine. However, obtained results demonstrate the range of mercury contents in different precipitates. In particular, the mercury contents are from below detection limit to 0.008 μg/L in the background sediments, and from below detection limit to 1.7 mg/L in the anthropogenic precipitates. The characteristic example is rainfall sampled in August, 2013, at 2.5 km from emission source. In sample collected at the end of multiday period of drizzly rain, the mercury content was 0.034 mg/L. Anthropogenic sample of rainstorm initially showed a multiple elevation of almost all contaminants (up to hundreds and thousands of times). Mercury is not detected at all. Soils. Zonal type of soils in the Karabash area is the gray forest soils, which in natural conditions are subneutral or weakly acid, are characterized by the low sum of exchange cations, and the absence of carbonates, which determines their initial buffering and potentially weak ability to resist to anthropogenic
loads. Long-term impact of acid rains led to the significant change of main soil-forming processes: increase of soil acidity and, as a result, degradation, disintegration, and removal of accumulated humus, i.e. chemical erosion of the soil (Udachin et al., 2014). The high ranker and low thickness of soil profile make such soil more amenable to destruction during elimination or partial destruction of vegetation (Stepanov et al., 1992). Intense degradation processes led to the formation of the impact (2–4 km across) and buffer (4–8 km) natural–anthropogenic zones on the territory adjacent to the smelter. The destruction of mechanism providing stability of soil cover in the impact zone (technogenic wasteland) resulted in the development of plane and linear erosion on slopes and almost full absence of natural vegetation and soil cover. Therefore, the further migration of chemical elements from emissions after their deposition on the surface and erosion products is driven by their transfer in form of solutions, colloids, and suspended particulate matter during rainwash and in soil runoff (Udachin et al., 2014). It can be assumed that elements precipitated during rain and snow melting could be washed out by water flows downslope. This is confirmed by the results of sampling on the western slope of Zolotaya Mount, which demonstrated a significant enrichment in the elements of emission toward the slope base. In this case, the mercury content increases by more than an order of magnitude, from 0.11 to 3.40 mg/kg (Fig. 3). The uppermost sampling point is located at a distance slightly less than 2 km southeast of emission source. Under conditions of the complete absence of humic–accumulative soil horizon and intense slope erosion, this may indicate a gradual erosion of precipitated from atmosphere mercury and its migration mainly in suspended form into subordinate areas of sedimentation zones. It is characteristic that the main element contaminants present in smelter emissions (Cu, Zn, As, and Pb) behave by the similar manner. The buffer zone can be conditionally subdivided into two subzones: dead soil covering birch forest and degraded forests. The subzone of the dead soil covering birch forest was distinguished on the basis of morphological characteristics of the birch (Betula pendula), which are most resistant to the smelter emissions, the absence of grass (grass–shrub) and partially moss layers. The inner part of the buffer zone adjacent to the impact zone is permanently subjected to the surface smoke pollution. Therefore, birch in this area is low, crooked, while in the outer part it is higher and without trunk deformations in the external part. Soil samples taken in the buffer zone showed a wide scatter of mercury content (0.2–4.7 mg/kg) and did not reveal unambiguous correlation with distance from emission source. It is possible that the emission impact was overlapped with geological features of this gold-bearing region with sulfide mineralization.
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Table 1. Content of some elements in soils of residential area of the town of Karabash Element As Cd Cu Hg Ni Pb S Sb Zn
Range, mg/kg 38.4–1450 3.5–42.3 404–10 494 0.20–11.4 27.2–828 106–3393 201–17552 4.5–239 436–9062
Rate of exceeding
% of soils with elevated content
8–232 3.5–2 6–159 1.3–6 1–18 1.6–52 1.2–110 3–44 4.4–82
100 100 100 60 90 100 100 100 100
MAC1, mg/kg
APC2, mg/kg
2 – – 2.1 – 32 160 4.5 –
5 1 66 – 40 65 – – 110
Class of danger3
1 Hygienic norms “Maximally Permissible Concentrations (MPC) of chemical substances in soil”. GN 2.1.7.2041-06. 2 Hygienic norms “Approximately Permissible Concentrations (APC) of chemical substances in soil”. GN 2.1.7.2511-09. 3 GOST 17.4.1.02-83 “Nature protection. Soils. Classification of chemical substances for control of contamination”.
1 1 2 1 2 1 2 1
Gosstandard,
Moscow, 1983
A good indicator of atmospheric contamination is the forest litter horizon of the soil profile. It is known that the thickness of the forest litter in the buffer zone under conditions of strong atmospheric contamination increases by more than four times as compared to the background regions (Vorobeichik, 1995). This is related to the fact that anthropogenic impact decreases the rate of biochemical processes and suppresses or completely terminates the destruction of organic matter in the litter. This causes a change of fractional composition of litter up to the disappearance of traces of live supersoil cover. Litter samples taken in the zone of dead soil covering birch forest in the inner part of the buffer zone and consisting mainly of the birch fall with no traces of decomposition showed an extreme accumulation of heavy metals as compared to the upper soil layer practically for all elements (Gashkina et al., 2015). On the catchment of Lake Serebry, the mercury concentration in the litter of dead soil covering birch forest was five times higher than that of the top soil layer. Beyond the buffer zone, where decomposition of organic matter of litter is stabilized, situation changes and mercury concentration in the top soil horizon becomes higher than in the litter. Of particular concern are soils of the residential zone, which is almost completely localized in the impact and inner part of the buffer zone. In this area, the distribution of mercury, unlike other element contaminants, was strongly controlled by not only anthropogenic emissions but also by gold mining with amalgamation. Detailed ecological-geochemical survey carried out in 1990–1991 in Karabash (Nesterenko, 2006) revealed that KCS during its activity supplied in the environment (mainly in soil) the huge amounts of metals and metalloids, including mercury, which formed spacious anomalies in soil. The most contamGEOCHEMISTRY INTERNATIONAL
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inated and largest mercury anomaly occupies the entire western part of the town. It spans the peaks and near-peak facies of slopes with depressed birch and slopes with dead soil covering birch forest. In the northeastern part of the town, the anomaly of the same intensity but much smaller in area is confined to peaks and near-peak parts and slopes with highly eroded talus, which are completely devoid of soil cover and plant. In 2013, over 30 samples were taken from the residential territory of the town (Fig. 1). Their analysis showed a wide scatter of element contents. In all samples, typomorphic anthropogenic elements from KCS emissions exceed MAC and APC; this fraction for mercury is 60% (Table 1). The humus content in the urban soil is very low (2–4%). The highest contents (4.1–4.5%) were found in the southern part, which coincides also with the elevated mercury content in this area. Obtained distribution in general is similar to the previously obtained one (Nesterenko, 1997), however, some points have the higher contents. More detailed survey is required to provide a full pattern, but even available results revealed the high degree of soil contamination on the urban territory. It is characteristic that “pure” soil brought for vegetable bed at farmland gradually degrades, with increase of heavy metals in it. According to our data, the mercury concentrations in such soil increased by approximately three times for ten years. Lakes. Lake Serebry was studied as an example of water source which supplies water for the northern part of the town of Karabash and is directly and indirectly subjected to the anthropogenic air impact. The lake is surrounded by the dead soil covering birch forest from the inner part of the buffer zone and located 5 km north of smelter, where, according to windrose, only 15% of air mass are transferred. However, owing to the specific topography, unfavorable meteorologi2017
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Depth, cm
0 2 4 6 8 10 12 14 16
200 400 600 800
0
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Concentration, mg/kg 600 0 40 80
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0
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Breaking of smelter; 1989–1998
Cu
As
Pb
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60 0 2 4 6 8 10 12 14 16
Fig. 4. Concentration profile of Cu, As, Hg, and Pb in the bottom sediments of Lake Serebry.
cal conditions and temperature inversions result in the precipitation of most part of emissions within intermontane valley. Significant part of elements precipitated with emissions on the drainage area is discharged into the lake owing to the surface erosion. The main hydrochemical parameters of the lake waters are as follows: рН 6.5–7.5, color index 10–20° Pt–Co, and salinity less than 100 mg/L (Deryagin, 2010). The chemical composition of surface waters in the zone of plant activity strongly differs from that of natural waters and reflects the character of anthropogenic pollution. Concentrations of most elements in the Lake Serebry water exceed many times the contents of these elements in Lake Seliger regarded as the background. The Seliger water meets requirements to drinking waters in terms of considered elements, whereas the Serebry water does not meet these requirements in terms of arsenic (25.5 μg/L) and stibium (5.52 μg/L), and exceeds norms of fishery basins for five elements: 5 times for Pb, 23 times for Cu, 8 times for Zn, 3.4 times for Mn, and 4 times for Hg. Under existing hydrochemical conditions, elements supplying in lake with atmospheric falls and surface runoff form complexes with organic matter, or are adsorbed on mainly iron and manganese hydroxide particles, and finally are involved in the bottom sediments. Toxic elements deposited in the lake sediments create chronic contamination. The contents of most chalcophile elements in the bottom sediments of Lake Serebry are two orders of magnitude higher than those of Lake Seliger. Most of the elements are accumulated in the top layer of bottom sediments (Fig. 4). Maximum mercury concentration recorded in the top layer was 32 mg/kg. The mercury enrichment factors in the top (0–2 cm) layer relative to their content in layer corresponding to the preindustrial period for different cores vary from 150 to 250. According to Norms and Criteria … (1996), such contents of Hg, Cd, Pb, Cu, Zn, and As in bottom sediments correspond to the IV class of contamination (dangerous contamination). Under the influence of microorganisms, mercury in
bottom sediments may pass into methylated form, transforming into more toxic alkyl compounds. Fish. Assessment of element bioaccumulation in the physiological systems of fishes of Lake Serebry as indicator of environmental contamination is finally the assessment of aerial impact of copper smelter on hydrobionts through a chain of emissions–atmospheric precipitates–soil–lake (water, bottom sediments)–fish. Fishes, as other organisms, are able to accumulate elements in much more amounts as compared to their content in water, and degree of their accumulation can be estimated from the value of bioaccumulation: ratio of element content in certain organ or tissue to that in water. This is of special importance for mercury, because it is accumulated as methylmercury in fish organism. Obtained results showed that mercury in fish is accumulated mainly in muscles and liver. The mercury contents in fish did not exceed norms in the Sereby and Seliger lakes. The maximum accumulation would be expected in breams from Lake Serebry, where water and especially bottom sediments are strongly contaminated by mercury. However, the mercury contents in all organs and tissues of breams from Lake Seliger are several times higher (Fig. 5), while bioconcentartion in liver and kidneys is over 8000 (around 600 in Lake Serebry) higher with respect to its content in water (Gashkina, 2015). This can be explained by the antagonistic effect of selenium. Selenium possesses anticarcinogenic and antimutagenic effect and is able to suppress the toxic effect of mercury, forming mercury selenide. Although Se content in water is low, its contents in organs and tissues of fishes of Lake Serebry is significant, while bioconcentration in liver is more than 10000. Strong accumulation of selenium in breams possibly prevents excessive mercury accumulation. Experimental addition of selenium in lake water demonstrated a decrease of methylmercury in muscles of perch and pike with simultaneous increase of selenium content (Hultberg, 2002). In addition, in view of the high sulfur content in atmospheric sediments, soil, and bottom sediments at neu-
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μg/L 0.05
1.0 Hg
0.04
0.6
0.03
0.4
0.02
0.2
0.01
Concentration, ppm DW
0.8
0
0 Gills
Liver
Water
Kidney Muscles Skeleton μg/L 0.6
20 Se Concentration, ppm DW
0.5 15 0.4 0.3
10
0.2 5 0.1 0
0 Gills
Liver
Water
Kidney Muscles Skeleton
Lake Serebry
Lake Seliger
Fig. 5. Hg and Se concentrations in the organs and tissues of bream from the Serebry and Seliger lakes.
tral рН, mercury in Lake Serebry can be bounded with sulfur compounds. Obtained results on the mercury contents are given in Table 2. Noteworthy is some disagreement: the mercury content in the atmospheric dust is 3.8 mg/kg, and reaches 15 and 32 mg/kg in soils and bottom sediments, respectively. This is rather related to the fact that prior to modernization of technological process, the high-mercury dust and gas after blast smelting were ejected in the smelter stack. After launching of Ausmelt furnace in 2006, the most part of the dust supplied in emissions from converters was characterized by much lower mercury contents, while dust–gas mixture of smelting stage passes through a gas purification system. Therefore, data on the Hg content in GEOCHEMISTRY INTERNATIONAL
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atmospheric dust are ascribed to the contents in the modern emissions of mainly converter dust, while Hg contents in soils and bottom sediments represent integral characteristics on heavy metals and mercury during historical period. In this respect, noteworthy is the mercury profile in the bottom sediments (Fig. 4), with minimum for all elements corresponding to pause in the plant activity; in recent years, after launching of the Asumelt furnace, the mercury content in the top layer decreases. CONCLUSIONS Obtained data on the mercury content in the atmospheric dust, soils, and lake bottom sediments of the 2017
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Table 2. Mercury content in the main segments of the Karabash geotechnogenic system Main segments
Hg content
Emissions of the copper smelter (estimated at 2015)) Emissions at complete reworking of flue gases (assessment) Atmospheric dust (2.5 km from pipe) Fraction of soluble form in dust Content in soils of impact zone Content in soils of the buffer zone Content in soils of the residential zone Water of Lake Serebry Maximum concentration in the top layer of bottom sediments of Lake Serebry Average content in muscles of breams from Lake Serebry
~400 kg/yr Around 100 kg 3.8 mg/kg 0.7% Up to 15 mg/kg 0.2–4.7 mg/kg 0.2–11.4 mg/kg 0.04 μg/L 32 mg/kg 0.19 mg/kg of dry weight
Karabash geotechnogenic system indicates the presence of powerful mercury source—emissions of the Karabashmed copper smelter. The mercury content in 60% of soils of the residential area exceeds MAC, while contents of mercury and other heavy metals in the bottom sediments of Lake Serebry, one of the drinking water sources, are ascribed to a class of dangerous contamination. At the same time, the mercury content in fish is lower than MAC, which is likely explained by the elevated selenium content. Assessment of the mercury content in the KCS emissions with allowance for its content in copper concentrate and existing gas purification system showed that from 100 kg Hg (complete processing of flue gases) to 400 kg Hg (incomplete processing, 2015) may be ejected into the atmosphere during production of blister copper. Together with other heavy metals and metalloids (Cu, Pb, Zn, As, Cd), mercury is ascribed to main contaminants in plant emissions. Obtained estimates highlighted the necessity of involvement of mercury in a list of marker elements for obligatory control of emissions. Unfavorable situation in terms of mercury and other metals and metalloids requires large-scale study of behavior of elements in emissions and discharges of the plant. ACKNOWLEDGMENTS The study of phase and element compositions of copper concentrates was financially supported by the Russian Science Foundation (RSF) No. 14-17-00691. REFERENCES ACAP. Assessment of Mercury Releases from the Russian Federation. Arctic Council Action Plan to Eliminate Pollution of the Arctic (ACAP), Russian Federal Service for Environmental, Technological and Atomic Supervision & Danish Environmental Protection Agency (Danish EPA, Copenhagen, 2005). AMAP/UNEP. Technical Background Report for the Global Mercury Assessment 2013. Arctic Monitoring and Assess-
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