The Distribution Of Organochlorine Pesticide Residues In The Marine Environment Along The Coastal Region Of Kenya

Abstract

Samples of seaweed, water, sediment and nine species of fish were collected from Kenya's coastal sites at Kilifi, Malindi, Sabaki River, Tana River and Lamu Bay between May 1998 and January 1999. The samples were examined for the presence of lindane, aldrin, dieldrin, «-endosulfan, endrin, DDT, DDE and DDD residues using a gas chromatograph equipped with a 63Ni-electron capture detector. Standard methods were used for sampling, sample extractions, clean up and analysis (UNEP/F AO/IAEA, 1982; UNEP/IAEA, 1982). The study revealed that in the 258 samples analyzed lindane, aldrin, DDT and DDE were the most frequently present (57-100%) while o.-endosulfan, dieldrin, DDD and endrin were either absent (e.g endrin) or rarely detected. In the seaweed samples, from Malindi the residue levels ranged from 0.054 ng/g for u-endosulfan to 8.22 ng/g for lindane. A mong the weeds the waterweeds from river Sabaki recorded the highest mean concentration for aldrin (11.900 ng/g). The concentrations of the insecticide residues were lowest in water samples probably due to the high dilution at the sources. These varied from 0.025 ug/l for DDD from river Tana to 1.834 )..lg/lfor endrin from Kilifi Creek. The highest concentration of I!DT and DDE in water was -0.491 and 0.386 ug/l respectively . from Malindi samples. Sediments contained the highest concentrations of pesticide . residues, with the highest being DDT (59 ng/g) detected from Kilifi Creek samples while . - the lowest was for aldrin (0.584 ng/gj.from Lamu Bay samples. IV Among the species of fish studied, Siganus rivulatus emerged the best accumulator of the insecticide residues. The fish had the highest mean concentration of 1011 ng/g for DDT and second highest mean concentration of 418 ng/g for DDD in the fat extracts. Carcharhinus macloti had the lowest amount of residue with aldrin at a mean lipid concentration of 17.9 ng/g. There was no general trend established for the levels of concentrations of the insecticide residues in seaweeds, sediments and fish with the seasonal variations. For water samples the total load of the insecticide residues per volume of water was high in the wet season and low in the dry season. The generally low levels of organochlorine pesticide residues detected In this study suggest that there is no large-scale pollution of the marine environment from commercial and agricultural activities at the Kenyan coast. The organochlorine pesticide residues found are likely to be a result of some local pollution coupled with some global transport. The increasing population and industrialization in Kenya will undoubtedly increase pesticide pollution into the marine 'environment. Hence, monitoring of pesticide residues should continue, but more important, education of the general public as to the hazards associated with the use of such compounds is essential for the long-term mitigation of the problems.