Seasonal and Spatial Distribution of Heavy Metals in the Bed ...

HEAVY METALS IN THE MARINE ENVIRONMENT

Seasonal and Spatial Distribution of Heavy Metals in the Bed Sediments of Polluted Tsurumi River K.M. Mohiuddin1,2, K. Otomo3, N. Shikazono1 1Laboratory of Geochemistry, School of Science for Open and Environmental Systems, Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, 2238522 Yokohama, JAPAN, [email protected] 2Department of Agricultural Chemistry, Faculty of Agriculture, Bangladesh Agricultural University, 2202 Mymensingh, BANGLADESH, [email protected] 3Laboratory of Geochemistry, School of Science for Open and Environmental Systems, Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, 2238522 Yokohama, JAPAN, [email protected] Abstract The Tsurumi is a class one Japanese river. It has a significant metal loading originating from urban environment. Sediments samples were collected from twenty sites on Winter, 2008 and Summer 2009 and analyzed to determine and compare the extent of heavy metal content viz. zinc (Zn), copper (Cu), lead (Pb), chromium (Cr), cadmium (Cd), nickel (Ni), cobalt (Co), arsenic (As), molybdenum (Mo) and strontium (Sr). Total trace metal concentrations were measured in the liquid extracts of the sediments by inductively coupled plasma mass spectrometry (ICP-MS). A widely used 5-step sequential extraction procedure was also employed for the fractionation of the metals. Concentration of Zn, Cu, Pb Cr and Cd were three to four times higher than that of standard values and downstream sediments are much more polluted than the upstream sites. Geochemical partitioning results suggest that the order of potential trace metal mobility in aquatic environment is: Cd > Zn > Pb > Cu > Co > Cr > Mo > Ni. The pollution load index (PLI) has been used to access the pollution load of different sampling sites. According to Intensity of pollution (IPOLL), Tsurumi River sediments are moderately to heavily contaminate by Zn, Pb and Co. EFc values demonstrated that the Cd content is enriched alarmingly in both season. The area load index and average PLI values of the river was 7.77, 4.93 in winter and 7.72, 4.89 in summer, respectively. If the magnitude of trace metal pollution in the river system increases consecutively, may have severe impacts on the aquatic ecology in the river. Key words: Seasonal Variation, Pollution assessment, Heavy metal, Tsurumi River, Water and sediment Introduction Trace metals are among the most common environmental pollutants, and their occurrence in waters and biota indicate the presence of natural or anthropogenic sources. The existence of trace metals in aquatic environments has led to serious concerns about their influence on plant and animal life. Trace elements are easily influenced by environmental factors such as surface runoff, groundwater, dissolution from sediment, deposition from the atmosphere and anthropogenic pollutants. Hence, trace metals may be sensitive indicators for monitoring changes in the water environment. Water of the river Tsurumi has been receiving significant amount of wastes containing base metals from municipal wastewaters, household garbage, industrial and vehicle discharges due to rapid urbanization and strong wildlife populations consequently the quality of water is being polluted. Recently Mohiuddin et al. (2010) reported that the dis15th ICHMET

tribution of trace metals in the downstream of Tsurumi River water and sediments are enriched alarmingly and may affecting aquatic ecology. Keeping these views in mind, this research work was conducted to determine the spatial distribution and winter and summer seasonal variation of trace metal content in polluted Tsurumi River sediments and to perform the sequential extraction procedure for partitioning of trace metals for determining the anthropogenic portion of trace metals. Materials and Methods Sediments samples were collected from twenty sites on winter, 2008 and summer 2009 (Table 1). For the determination of total trace metals (e.g. Zn, Cu, Pb, Cr, Cd, Ni, Co, As, Mo and Sr) the extraction was carried out in Teflon containers provided with screw stoppers as described by Tessier et al. (1979) and trace metals concentrations in the extract were determined by ICP-MS. A widely used 5-step 569


sequential extraction procedure described by Hall et al. (1996) was employed. The five steps are as follows: Step-1: AEC (Adsorbed/ Exchangeable/ Carbonate) Phase, Step-2: Amorphous Fe Oxyhydroxide, Step-3: Crystalline Fe Oxide, Step-4: Sulphides and Organics, Step-5: Silicates and Residual Oxides. Table 1. Location of different sampling sites of the downstream of Tsurumi River

Results and Discussion Average concentration along with standard deviation of total trace metal viz. Zn, Cu, Pb, Cr, Cd, Ni, Co, As, Mo and Sr contents in winter and summer sediments are presented in Table 6. The trace metals were also compared with background and toxicological reference values. The average concentration for trace metals in summer samples is lower than winter samples, which may be due to the dilution effect of the surplus water in summer. 570

The standard deviation for Zn, Cu, Pb, Cr and Ni, is higher which reflects the variation in sites to sites. Detailed values designate the presence of higher amount in downstream and lower amount in upstream. The average concentration of Zn, Cu, Pb, Cr, Cd greatly exceeded the geochemical background (shale standard and continental crust) as well as Japanese river sediment average. Whereas mean concentration of Ni, Co, As, Mo and Sr were almost similar to the standard value. However, when compared with effect-based toxicological level i.e. Toxicity reference values (TRV) of US EPA the situation was also quite alarming for Tsurumi river sediments because for all the trace metals values were several fold higher, which indicate that the levels of trace metals found in the sediments of the river General Geochemical Fractionation Trends The order of importance of different geochemical fractions of trace metals in Tsurimi River winter and summer sediment samples were almost similar. The order obtained for the winter samples of the study were: Zn: AEC >> amorphous Fe oxyhydroxide > silicates and residual > crystalline Fe oxide > sulphides and organics Cu: amorphous Fe oxyhydroxide >> silicates and residual > crystalline Fe oxide sulphides and organics > AEC Pb: amorphous Fe oxyhydroxide >> silicates and residual > AEC ~ crystalline Fe oxide > sulphides and organics Cr: silicates and residual > amorphous Fe oxyhydroxide ~ crystalline Fe oxide > sulphides and organics > AEC Cd: AEC >> silicates and residual > amorphous Fe oxyhydroxide Co: amorphous Fe oxyhydroxide > silicates and residual > AEC > sulphides and organics > crystalline Fe oxide Ni: silicates and residual >> amorphous Fe oxyhydroxide > AEC > crystalline Fe oxide > sulphides and organics Mo: crystalline Fe oxide > sulphides and organics > silicates and residual > AEC > amorphous Fe oxyhydroxide These findings suggest that the order of potential trace metals mobility in the aquatic environment of Tsurumi River is: Cd > Zn > Pb > Cu > Co > Cr > Mo >Ni

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Table 2. Comparison of Trace metal concentration (µg g-1) in Tsurumi river sediment winter and summer samples

aTurekian and Wedepohl (1961); bTaylor (1964); cUS EPA (1999) and dGamo (2007).

Assessments of Anthropogenic Pollution Index of Geoaccumulation (Igeo) and Pollution Intencity (IPOLL) The geoaccumulation index Igeo values were calculated for different metals as introduced by Muller (1969), which is Igeo = Log2 [Cn/( 1:5 *Bn)] where Cn is the measured concentration of element n in the sediment and Bn is the geochemical background for the element n. The factor 1.5 is introduced to include possible variations of the background values that are due to lithologic variations. Karbassi et al. 2008 proposed modification in Igeo calculation and suggest the equation as follows IPOLL = Log2 [Bc/Lp]; Where Bc and Lp are indicative of pollution intensity, bulk concentration and lithogenous portion, respectively. Bc was computed by subtraction of the anthropogenic portion of metals from bulk concentration. Since there was not any need in these evaluations to use the shale metal concentrations, the constant factor (1.5) was eliminated. Here, chemical partitioning results is substituted for the mean crust and shale levels. The calculated Index of geoaccumulation (Igeo) and Pollution Intencity (IPOLL) of the trace metals in the winter and summer sediments of the river Tsurumi and their corresponding contamination intensity are illustrated in Fig. 1. 15th ICHMET

Figure 1. Comparison of Igeo and IPOLL values The Igeo and IPOLL values for winter samples are higher than summer samples and IPOLL values were always higher than Igeo values for same elements. Igeo values Zn, Cu, Ni and Mo exhibited in class 1 and 2, indicating uncontaminated to moderately contaminated sediments. Whereas, Pb and Co lies in zero class indicates unpolluted sediment quality. On the other hand, the IPOLL values for reflects a bit alarming results Zn, Pb and Co in class 3 i.e. moderately to heavily contaminated sediments and Cu, Cr, Ni and Mo in class 1 and 2, indicating uncontaminated to moderately contaminated sediments. 571


Figure 2. Variation in PLI values of different sampling sites of Tsurumi river winter and summer sediment samples Pollution Load Index The pollution load index (PLI) proposed by Tomlinson et al. (1980) has been used in this study to measure PLI in sediments of the river Tsurumi. PLI values of sediments of the studied region vary from site to sites and season to season. The figure 2 reflects the decreasing trend of PLI from downstream to upstream. The PLI values for winter and summer ranged from 2.2-10.1 and 1.6-11.1, respectively. Some sites of down and midstream showed higher PLI values in summer, which may the reflection of prolonged existence of polluted water in river mouth as they cannot mix easily with Tokyo bay water due to high tide. The area load for winter and summer is almost same having 7.77 and 7.76 respectively and Cd, Zn, Pb, As and Mo were the major 5 pollutants contributing towards the relatively high PLI for this area. Conclusion A detailed examination on geochemical fractionation, comparison with different standards, toxicological reference values and backgrounds indicate that Zn, Cu, Cd, Pb, Cr and Cd and to a lesser extent Ni, Co, As, Mo and Sr are anthropogenically enriched in Tsurumi River sediments. This study has revealed that the order of potential trace metals mobility in the aquatic environment of Tsurumi River is in the order of Cd > Zn > Pb > Cu > Co > Cr > Mo > Ni. Various environmental parameters are varied with location and season. Variation in overall pollution load is not so significant in winter and summer season, but downstream is severely polluted. As enhanced con572

centrations of trace metals are recorded in most populated urban areas as well as close to industrial establishments, indicating that their concentrations have been strongly affected by anthropogenic influences. According to IPOLL, Tsurumi River sediments are moderately to heavily contaminate by Zn, Pb and CoThe area load index and average PLI values of the river was 7.77, 4.93 in winter and 7.72, 4.89 in summer, respectively; Which indicate that the river sediments are in polluted condition and in summer pollution load is lower than winter, may be due to dilution effect of surplus water.. Acknowledgements The presenting author thankfully acknowledges the Ministry of Education, Culture, Sports, Science and Technology, Japan, for financial support in the form of Monbukagakusho Scholarship. References Gamo, T. (ed.) (2007). Environmental Geochemistry. (In Japanese) Baihu-kan, Japan, 118-119. Hall, G. E. M.; Vaive, J. E.; Beer, R. and Hoashi, M. (1996). Selective leaches revisited, with emphasis on the amorphous Fe oxyhydroxide phase extraction. Journal of Geochemical Exploration, 56, 59-78. Karbassi, A. R.; Monavari, S. M.; Nabi Bidhendi Gh. R.; Nouri J. and Nematpour K., (2008). Metal pollution assessment of sediment and water in the Shur River. Environ Monit Assess, 147, 107-116

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Karbassi, A. R.; Monavari, S. M.; Nabi Bidhendi Gh. R.; Nouri J. and Nematpour K., (2008). Metal pollution assessment of sediment and water in the Shur River. Environ Monit Assess, 147, 107-116 Muller, G., (1969). Index of geoaccumulation in sediments of the Rhine River. GeoJournal, 2(3), 108 - 118. Muller, G., (1969). Index of geoaccumulation in sediments of the Rhine River. GeoJournal, 2(3), 108 - 118. Mohiuddin, K. M.; Zakir, H. M.; Otomo, K.; Sharmin, S. and Shikazono, N. (2010) Geochemical distribution of trace metal pollutants in water and sediments of downstream of an urban river. International Journal of Environmental Science and Technology, 7(1), 17-28. Muller, G., (1969). Index of geoaccumulation in sediments of the Rhine River. GeoJournal, 2(3), 108 - 118. Taylor, S. R., (1964). Abundances of chemical elements in the continental crust: a

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new table., Geochimica et Cosmochimica Acta. 28 (8), 1273-1285. Tessier, A.; Campbell, P. G. C.; Bisson, M., (1979). Sequential extraction procedure for the speciation of particulate trace metals., Analytical Chemistry. 51(7), 844-851. Tomlinson, D. C.; Wilson, J. G.; Harris, C. R.; Jeffrey, D. W., (1980). Problems in the assessment of heavy-metal levels in estuaries and the formation of a pollution index., Helgoland Marine Research. 33, 566-575. Turekian, K. K.; Wedepohl, K. H. (1961). Distribution of the elements in some major units of the earth's crust., Geol. Soc. Am. Bull. 72, 175 - 192. US EPA (1999). U.S. Environmental Protection Agency, Screening level ecological risk assessment protocol for hazardous waste combustion facilities. Vol. 3, Appendix E: Toxicity reference values. EPA 530-D99001C.

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