Enrichment and fractionation of heavy metals in bed sediments of River Narmada, India |
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Authors: | C K Jain Harish Gupta G J Chakrapani |
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Institution: | (1) National Institute of Hydrology, Roorkee, 247 667, India;(2) Indian Institute of Technology, Roorkee, 247 667, India;(3) Present address: Centre for Flood Management Studies, National Institute of Hydrology, G. S. Road, Sapta Sahid Path, Mathura Nagar, Dispur, Guwahati, 781 006, India |
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Abstract: | A metal fractionation study on bed sediments of River Narmada in Central India has been carried out to examine the enrichment
and partitioning of different metal species between five geochemical phases (exchangeable fraction, carbonate fraction, Fe/Mn
oxide fraction, organic fraction and residual fraction). The river receives toxic substances through a large number of tributaries
and drains flowing in the catchment of the river. The toxic substances of particular interest are heavy metals derived from
urban runoff as well as municipal sewage and industrial effluents. Heavy metals entering the river get adsorbed onto the suspended
sediments, which in due course of time settle down in the bottom of the river. In this study fractionation of metal ions has
been carried out with the objective to determine the eco-toxic potential of metal ions. Although, in most cases (except iron)
the average trace/heavy metal concentrations in sediments were higher than the standard shale values, the risk assessment
code as applied to the present study reveals that only about 1–3% of manganese, <1% of copper, 16–19% of nickel, 4–20% of
chromium, 1–4% of lead, 8–13% of cadmium and 1–3% of zinc exist in exchangeable fraction and therefore falls under low to
medium risk category. According to the Geo-accumulation Index (GAI), cadmium shows high accumulation in the river sediments,
rest of other metals are under unpolluted to moderately polluted class. |
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Keywords: | Heavy metals River Narmada Sequential extraction Tessier scheme Geo-Accumulation Index Risk assessment code |
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