摘要
Trace metal concentrations were investigated in a recent sediment core collected from the Rehri Creek area of the Karachi coast, Sindh - Pakistan. The core was sliced horizontally at 2.5-cm intervals to determine grain size, sediment composition, pH, organic matter, and acid-leachable trace metals: cadmium, chromium, copper, lead, and zinc. The trace metals were analyzed by ICP. To separate anthropogenic from geogenic input, several approaches were made, including comparison with sediment quality guidelines--ecotoxicological sense of heavy metal contamination and classification by quantitative indexes. Grain-size analysis and sediment composition of core sample show a sandy nature with neutral pH. Elemental sequence (ES) of the trace metals is in the order of Zn (19.2-109.56 ppm) 〉 Si (66.46-101.71 ppm) 〉 Ba (12.05-26.86 ppm) 〉 As (8.18-17.36 ppm) 〉 Ni (4.2- 14.69 ppm) 〉 Cr (3.02-9.62 ppm) 〉 Pb (2.79-6.83 ppm) 〉 Cu (2.2-5.29 ppm) 〉 Co (0.9-2.05 ppm). Thus it is likely that the area may face a serious threat of metal pollution with the present deposition rates unless stringent pollution control norms are adopted. The Sediment Geo-accumulation Index shows that there is no Cr, Cu, Ni, Pb, Zn, or Fe pollution; however, the former index and the Pollution Load Index indicate arsenic pollution in the sediments.
Trace metal concentrations were investigated in a recent sediment core collected from the Rehri Creek area of the Karachi coast, Sindh - Pakistan. The core was sliced horizontally at 2.5-cm intervals to determine grain size, sediment composition, pH, organic matter, and acid-leachable trace metals: cadmium, chromium, copper, lead, and zinc. The trace metals were analyzed by ICP. To separate anthropogenic from geogenic input, several approaches were made, including comparison with sediment quality guidelines--ecotoxicological sense of heavy metal contamination and classification by quantitative indexes. Grain-size analysis and sediment composition of core sample show a sandy nature with neutral pH. Elemental sequence (ES) of the trace metals is in the order of Zn (19.2-109.56 ppm) 〉 Si (66.46-101.71 ppm) 〉 Ba (12.05-26.86 ppm) 〉 As (8.18-17.36 ppm) 〉 Ni (4.2- 14.69 ppm) 〉 Cr (3.02-9.62 ppm) 〉 Pb (2.79-6.83 ppm) 〉 Cu (2.2-5.29 ppm) 〉 Co (0.9-2.05 ppm). Thus it is likely that the area may face a serious threat of metal pollution with the present deposition rates unless stringent pollution control norms are adopted. The Sediment Geo-accumulation Index shows that there is no Cr, Cu, Ni, Pb, Zn, or Fe pollution; however, the former index and the Pollution Load Index indicate arsenic pollution in the sediments.
基金
supported by International Atomic Energy Agency through its Projects Pak-13930 and RAS 7/016