Distribution of organochlorine pesticides and polychlorinated biphenyls present in surface sediments of the Sabaki and Tana estuaries, Kenya

Abstract

Polychlorinated biphenyls (PCBs) and Organochlorine pesticides (OCPs) in the surface sediments of the Sabaki and Tana estuaries were studied to determine distribution as well as their ecological risk. The concentration range of PCBs and OCPs were 0.65-9.29 ng/g dw and 0.47-9.84 ng/g dw, respectively. Sabaki Bridge in the Sabaki River and Tana 4 in the Tana River recorded high levels of both PCBs and OCPs. The calculated values of DDD+DDE/ DDT showed that the presence of DDT from both the rivers is a result of historical input. The ecotoxicological impact of sediment pollution by PCBs and OCPs was assessed using sediment quality guidelines specified by the Canadian Council of Ministers of the Environment. The concentration values for PCB, HCB, Heptachlor epoxide, and Chlordane in this study indicate low ecological risk to sediment dwelling organisms. DDT showed an adverse biological effect to sediment dwelling organisms. As a result, there is a need to establish a programme for monitoring persistent organic pollutants in Kenya, so that any elevation in concentration above the environmental quality standards can be detected and appropriate actions taken to minimize potential adverse effects to the environment and public health.