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
