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.

Trends in Water Quality in a Tropical Kenyan River-estuary System: Responses to Anthropogenic Activities

“…For the last five decades, rivers and estuarine systems have witnessed spatial-temporal variations in terms of water quality parameters and sediment loads that have drastically impaired these ecosystems [1,[20][21][22][23][24][25] Elevated agricultural activities, urbanization, industrialization, deforestation, river impoundments, and unregulated water abstractions have contributed to poor water quality downstream due to excessive nutrient and sediment loads [23,24]. It is estimated that over 350,000 chemical substances and about 70,000 undocumented ones are in regular application globally [26] (Wang et al, 2020).…”

“…It is against the above backdrop that there is an urgent need to assess and monitor changes in environmental variables/factors in relation to anthropogenic impacts to rivers and estuaries along the south coast of Kenya in the WIO region to inform its management for sustainable utilization of its resources. Despite the fact that a number of studies have been concentrated in the north coast of Kenya [21,23,43], no comprehensive studies have been undertaken along the south coast rivers and estuaries of Kenya in the region to document the sources of pollution and their impacts. Physico-chemical water quality attributes measured monthly based on numerous sampling sites throughout the larger south coast estuary of Kenya in the WIO region, were used in this study to investigate river-estuarine water quality on a spatial scale.…”