Distribution of endosulfan in water, sediment and fish from Warri river, Niger delta, Nigeria

This article presents the first attempt to quantify the levels and distribution pattern of endosulfan, an organochlorine pesticide in surface water, sediment and fish ( Chrysichthys furcatus and Tilapia zilli ). The samples were collected from three stations (Ovwian, Ekakpamre and Ovu) of Warri River in the western Niger Delta of Nigeria in 2006 during the dry and wet seasons (January–August). A total of 96 samples made up of 24 samples each for water, sediment and fish were analysed in this study. The pesticide levels were analysed using high performance liquid chromatography (HPLC model CECIL 1010) to elucidate its distribution in various environmental compartments. The ranges of concentrations of the pesticide in the matrices were: 0.01–9.23 μg/l (water), 0.06–11.98 μg/gdw (sediment), 0.01–15.06 μg/gdw ( Chrysichthys furcatus) and 0.01–1.80 μg/gdw ( Tilapia zilli ). From this result, decreasing order of occurrence of the pesticide is as follows: fish > sediment > water. The concentrations observed in fish ( Chrysichthys furcatus ) were higher than the levels observed in sediment and water suggesting bioaccumulation of the pesticide by the fish. Spatial variations occurred with downstream stations having statistically higher concentrations in all matrices at P  < 0.05. Seasonal variations occurred with higher concentrations in dry season for water and sediment only, while the fish species had higher concentrations in the wet season. The observed values of endosulfan were above the ecological bench marks (0.02 μg/l) recommended by Nigeria Environmental Protection Agency and European Union. They were also relatively higher than those in previous studies on the Nigerian environment, an observation that calls for regular monitoring of the Niger Delta water bodies.