A quantitative appraisal of Lyari river effluent, Karachi, Pakistan

This study explores the extent and possible sources of chemical contamination in Lyari River, Karachi. During the study, samples were collected from eight different locations during pre- and post-monsoon periods. The samples were analyzed for chemical parameters and heavy metals and compared with National Environmental Quality Standards (NEQS). Among all the sites, L-8 was the most polluted site as the site represents Lyari River outfall through which the river finally merges to the Arabian Sea. The concentration of all the parameters were higher (TSS, BOD, COD, cyanide, oil and grease, phenol, Pb, Ni, Cu, Cd and Cr) compared to NEQS. The concentration of metals were in the order of Ni > Cr > Cu > Cd > Pb > As. As such, no significant differences in the concentration of pollutants were observed during the pre- and post-monsoon periods. These results suggest that the Lyari River is grossly polluted with untreated domestic and industrial effluents, which presumably contribute toxicity to the marine ecosystem.