A Preliminary Evaluation of the DDT Contamination of Sediments in Lakes Natron and Bogoria (Eastern Rift Valley, Africa)
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Dichlorodiphenyltrichloroethane (DDT) is still used in Africa for the indoor control of malaria and it may represent a potential hazard for wildlife. The littoral sediments of two alkaline-saline lakes, Natron (Tanzania) and Bogoria (Kenya), in the Eastern Rift Valley, supporting large populations of lesser flamingos (Phoeniconaias minor), were analysed for DDT residues. Physical–chemical analyses (temperature, conductivity, pH and dissolved oxygen) were also performed on the water of the two lakes and in the tributaries of Lake Natron, to evaluate the influence of the environmental variables on pollutant occurrence. At Lake Natron, around 1 km from the sediment collection sites, tree leaves of Acacia tortilis were also collected. The main metabolite found in all sediment samples was pp’DDE, whilst equal concentrations of pp’DDT and pp’DDE were measured in acacia leaves. The levels of DDTs measured in the sediments were within 5.9–30.9 ng g−1 d.w., reaching the maximum value in a tributary of Lake Natron. On the whole, the contamination of Lake Natron and Lake Bogoria basins seems to be quite moderate. Nevertheless, the pp’DDE/pp’DDT ratio equals 1 in the Acacia tortilis leaves, which makes one suppose that the input of the parent compound was rather recent and could have been from aerial transport or dust from relatively close-by old pesticides storage sites.
KeywordsObsolete contaminant pollution Soda lakes Sediments Acacia leaves Tanzania Kenya
This research was partially funded by the British Council DELPHE 291 ‘FIELD IT’ FOR EAST AFRICA Project (University of Nairobi, Kenya). It was conducted under research permits from the Tanzanian Wildlife Research Institute and the Kenyan National Council for Science & Technology to Dr David Harper. We thank the staff of his project ‘Rift Valley Lakes Exploration & Research’ (RiVLER) for maintaining the camp, food and accommodation. We would also like to thank AfriCover for providing some of the data used to make the maps.
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