Organochlorine Pesticides (OCPs) Contaminants in Sediments from Karachi Harbour, Pakistan

Abstract

Mangrove swamps, intertidal mudflats and creeks of backwaters represent main feature of Karachi harbour area. Karachi harbour sediment is under continuous influence of untreated industrial effluents and domestic waste discharged into the Harbour area via Lyari River. Sediment samples from sixteen locations were collected to evaluate the levels of contamination of organochlorine pesticides (OCPs) in Karachi harbour and adjoining areas. It has been observed that residual concentrations of various organochlorine pesticides were considerably higher in the semi-enclosed area of the upper Harbour in the vicinity of the discharge point of Lyari River. The residue of DDT mainly its metabolites (DDE and DDD) were widely distributed and have been detected in most of the sediment samples in relatively higher concentrations as compared to other OCPs. The higher levels of the DDTs would attribute to low tidal flushing of the area. The high proportion of pp′-DDE in the most sediment sampled (41–95%) suggested old inputs of DDTs in the environment. Ratio of ∑DDT and DDT was in the range of 0.04 –0.24 at all locations which also reflects that the discharges of DDT were negligible in the Harbour area. This may be due to the restrictions being implemented on the use of DDTs and Pakistan has also switched over to natural pest control or using safer formulas. The data obtained during the study showed that concentration levels of other pesticides such as HCHs, HCB and Cyclodienes in the sediment were generally lower than the threshold levels known to harm wildlife by OCPs. The results clearly indicate that elevated concentration of organochlorine pesticides (OCPs) in the marine sediment of Karachi harbour and adjoining area was localized and much lower than the concentrations reported from neighbouring and regional countries which suggests/confirms that the present use of pesticide in Pakistan is environmentally safe