Levels of organochlorine pesticides in five species of fish from Lake Ziway, Ethiopia

Abstract

The Ethiopian Rift Valley (ERV) lakes region is an agricultural area in Ethiopia with intense year-round irrigated framing where widespread legal and illegal pesticide use was documented. The aim of the study is to assess tissue concentration of organochlorine pesticides (OCPs) in fillets of fives species of fish from Lake Ziway, an ERV lake. The influence of trophic position and fish size on accumulation of OCPs was investigated. Sample preparation for the analysis of OCPs was done following the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method and OCPs were analyzed using gas chromatography and compound specification was made using mass spectrometry. Dichloro-diphenyl-trichloroethanes (DDTs) were dominant among investigated OCPs. 4,4’-dichloro-diphenyl-dichloro-ethylene (p,p’-DDE) was the predominant DDT metabolite constituting about 99.2% of total DDTs. Historic DDT input was suggested as the source of current DDT contamination dominated by p,p’-DDE. Geometric mean value of p,p’-DDE varied from 1.07 to 3.64 ng g–1ww. Species variation in accumulation of p,p’-DDE was found that could result from differences in trophic level, lipid content, age, specific habitat, and feeding habit. Carassius carassius occupying a higher trophic position and with relative high lipid content had the highest p,p’-DDE levels. Positive associations between log-transformed p,p’-DDE, and total length were found for C. carassius and Cyprinus carpio. p,p’-DDE was biomagnified through the local food web. Generally, the levels of DDT in the present study are lower than levels reported from lake Ziway in earlier studies. The present findings may contribute contemporary OCP contamination data in investigated fish species.