| Abstract
| - Concentrations of chlorinated pesticides were analyzed inair (biweekly 1997−1998), water, and precipitation atLake Malawi, in southeast Africa. The pesticides in air inSenga Bay on the southwest shore of Lake Malawiwere not extensively weathered, implying recent use.Elevated levels of heptachlor, chlorobenzenes, aldrin, anddieldrin were detected periodically, which indicated useon a regular basis. Annual average concentrations for thosepesticides ranged from 31 to 257 pg/m3. Levels of HCHs,DDTs, chlordanes, and α-endosufan in air at Senga Baywere comparable to those of the Laurentian Great Lakes,ranging from 24 to 40 pg/m3. Considering air−water gasexchange and wet deposition, the net fluxes of chlorinatedpesticides to the lake surface were depositional.Concentrations of chlorinated pesticides in the waterfrom Lake Malawi were relatively low compared to theLaurentian Great Lakes and Lake Baikal. This indicates rapidtransformation of chemicals in the water column, whichwas further supported by high metabolite-to-parent ratios.The results suggests that tropical regions may act asboth a global source and sink for chlorinated pesticides,since removal processes may be faster compared to temperateand Arctic regions.
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