ABSTRACT
The persistence of OC pesticides in Kenyan soils has been extensively studied (Sleischer and Hopcraft, 1984; Wandiga and Natwaluma, 1984; Wandiga and Mghenyi, 1988; Lalah et al., 1994; Ng’ang’a, 1994). Table 4.11 shows the rate of loss of DDT, DDE, and lindane in Kenyan soils. The accumulated evidence for the tropics indicates that OC pesticide persistence is lower than is found in temperate climates (Wandiga, 1996). This conclusion is consistent with levels described above. For instance, based on the quantity of OC pesticides used in the Hola irrigation scheme in the Tana District, one would predict higher concentrations in marine species where the Tana River enters the Indian Ocean. Given the high organic content of sediments along the Kenyan coast as a result of heavy upstream soil erosion, one would expect that the movement of OC pesticides to other areas as a result of ocean action would be minimal. However, the distribution of γ-HCH along the continental slope observed by Everaarts et al. (1996) confirms that pesticide movement from shallow coastal areas to deep ocean exists. The effect of low levels of DDT and its metabolites on marine life, wildlife, and the surrounding ecosystems have drawn the attention of the authors. Recently the authors initiated studies to examine the distribution and effect of DDT in the marine environment, using a laboratory-based marine ecosystem.
