Occurrence and distribution of Organochlorine Pesticide Residues in Water and Sediments of Earthen Fish Ponds in South Western Kenya

Abstract

Abstract. Persistent organochlorine residues in the environment are a threat to ecological health of
aquatic organisms and pose a health risk to both animals and human consumers. Organochlorine
pesticides were determined in water and sediments collected during wet and dry season from selected
riverine and earthen fish pond sites in high altitude catchment areas within Kuja River (Kenya)
between August 2016–May, 2017. Analysis of DDT and metabolites, Hexachlorocyclohexanes
(HCHs) isomers and cyclodienes using a gas chromatograph (GC), and electron capture detector
(ECD), confirmed using GC - Mass Spectrometry (MS). Mean (± Standard error) results of DDTs,
cyclodienes and HCHs in pond waters were:- below detection level (BDL) to 0.27±0.03g/L, BDL
to 0.11±0.00g/L, and 4.39±1.01g/L respectively; and BDL to 0.23±0.01g/L, 1.20±0.005g/L,
and 1.71±0.02g/L in river water respectively. Sediment mean OCPs contents were significantly
(p<0.05) higher for Dieldrin (3.043±0.43g/kg), Endrin (2.56±0.460g/kg), Heptachlor
(3.61±0.02g/kg) DDT (2.97±1.32g/kg), Endosulfan (6.31.27±1.051g/kg), Methoxychlor (2.15±
1.641g/kg) and Lindane (2.96±1.32g/kg), respectively. A longitudinal spatial distribution pattern
was noted for both water and sediment OCPs contents, demonstrating that cyclodienes are
predominant contaminants in point and non-point sources in water courses. The study recommends
continuous monitoring of OCPs in upstream catchment areas for informed management and policy
decisions on pesticide use.