Determination of persistent organic pesticide residues in lake Bassotu, Hanang', Manyara region, Tanzania

This study reports on pesticides residues studies conducted at Bassotu lake, Hanang', Manyara region. In this study a total of 12 water samples, and 13 sediment samples were collected, and analysed by GC for pesticide residues. Water samples were drawn a few centimetres below the surface into air tight Teflon capped 11, bottles or with plastic cape lined with aluminium foil and Sediment samples were collected in the entrance of run off and areas where eroded materials are deposited. Samples were extracted by use of liquid-liquid phase extraction procedure for water samples and solid phase extraction for sediment samples. All samples were analyzed by gas chromatography. Fenithrothion, a-endosulfan, f3- endosulfan, and endosulfan sulphate were identified in the samples of all matrices, in the mean concentrations of 20.88 µg/l, 0.49 2.41 µg/1 and 14.33 respectively, in water, and 1604.76 fig/g, 26.95 µg/g, 116.44 nig, and 204.14 µg/g, respectively, in sediments. According to WHO Drinking Water Guidelines; a health-based value of 20 µg/litre can be calculated for endosulfan on the basis of an Acceptable Daily Intake (ADD of 0.006 mg/kg of body weight (WHO, 2003). The concentration of endosulfan in this study is below WHO drinking water guidelines. Thus, No significant contamination was noted in the lake. The study has shown that residues of Organochlorine (OC) are present in the Bassotu Lake. Residue analyses also showed that higher organochlorine pesticides and their residues were generally more accumulated in the sediment samples. Thus, it can be concluded that sediments could be a good indicator and informative for the presence of pesticide residues pollution in aquatic environment. As this study was a screening study, it is recommended that a more detailed study of distribution of the OC be conducted so as to qualify the quality of the water from Bassotu Lake for domestic and animal use.