Distribution of trace metals in inter-tidal sediment along Karachi coast, Pakistan
Abstract
Marine sediments are endpoints for trace metals emitted from anthropogenic sources and provide an archive for studying trace metal pollution. Contaminated sediments are a significant environmental problem affecting marine environments throughout the country. Most assessments of water quality have focused on water-soluble compounds, with relatively little attention paid to sediment, a repository for sorbed contaminants. The primary goal of this study was to determine the concentrations and spatial distribution of metals in marine sediments along Karachi coast. In the present study sediments samples from inter tidal along Karachi coast were analyzed on the ICP-EOS for trace metal concentration analysis using sediment standards namely SL-I, SL-3 and SL-5. Sediment samples were collected from pollution receipt zone namely; (i) Layari River outfall zone, (ii) Karachi Harbour Area (iii) Manora Channel Mains and open sea zone namely: (i) Manora Channel Exit (ii) North-West Coast of Karachi (iii) South East Coast of Karachi. In general, concentrations of toxic metal in sediment pertaining to Lavari River mouth area and the Karachi Harbour area (which are pollution recipient areas) were higher as compared to toxic metal contents in sediments from other areas facing open sea (Nom-West Coast and South East Coast) and entrance to Manora Channel. In open sea zone, concentration of Cn Cid, M, Pb, V and Zn were higher in sediments of Manora Channel exit as compare to South East Coast and North West Coast. Manne sediments belonging to the South-East coast off Karachi have relatively high concentrations of these toxic elements except (Pb, Sr, U) as compared to the North-West coast. Metal concentrations in surficial sediment shows that Karachi Harbour area is polluted area, Elevated concentrations of Cr (320 ppm), Ni (56 ppm), Sr (449 ppm), 7.21 (666 ppm), Pb (49 ppm) and U (I .66 ppm) occur in this area. Sewage and industrial wastes are the main sources of heavy metal pollution in Karachi Harbour. However, contamination in Karachi coast is not critical but heading towards it. Studies suggest incorporation of quick remedial measures to combat pollution in shallow environments off Karachi Coast.
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