Full Length Research Paper
Organochlorine and organophosphorus pesticide residues in water and sediment from Yala/Nzoia River within Lake Victoria Basin, Kenya Safina Musa1*, John Wageni Gichuki2, Phillip Okoth Raburu3 and Christopher Mulanda Aura4,5 Kegati Aquaculture Research Station, Kenya Marine and Fisheries Research Institute, P. O. Box 3259-40200, Kisii, Kenya. 2 Kenya Marine and Fisheries Research Institute, P. O. Box 1881-40100, Kisumu, Kenya. 3 Chepkoilel University College, Moi University, P. O. Box 1125-30100, Eldoret, Kenya. 4 Kenya Marine and Fisheries Research Institute, P.O. Box 81651-80100, Mombasa, Kenya. 5 Laboratory of Marine Bioresource and Environment Sensing, Hokkaido University, Minato-cho, Hakodate, Hokkaido 041-8611, Japan. Accepted 29 September, 2011
This study set out to survey pesticide usage and concentrations of their residues in lower Yala/Nzoia catchment areas of Lake Victoria, Kenya during the dry and rainy seasons of 2009. Water and sediment samples were analyzed for selected organochlorine and organophosphorus pesticide residues using gas chromatography equipped with electron capture detector. The findings of the survey showed that the banned organochlorines are still being used in the catchment. Pesticide residue levels of organochlorines in water samples from Yala/Nzoia Basin were below detection limit (BDL) both during the rainy and dry seasons. The residue levels detected in sediment samples collected during the rainy season ranged from 0.05 to 59.01 µgkg-1, whereas during the dry season, they ranged from BDL-24.54 µgkg-1. The concentrations of dieldrin and p,p’-DDD were notably higher (p < 0.05) than aldrin and p,p’DDT, respectively, in most of the samples. No organophosphates were detected in any of the water and sediment samples. Organochlorine residues detected in sediment in both seasons were below the World Health Organization recommended guidelines. Therefore, it was concluded that there were neither environmental nor human health hazards posed by these compounds in the water and sediments. Key words: Organochlorine, organophosphorus, residues, Lake Victoria.
INTRODUCTION The use of pesticides has certainly increased agricultural production, and improved longevity and quality of life. Coupled with these successes are a number of side effects. Pesticide use is still indispensable in Kenya in the area of agricultural production and public health vector control. However, the toxicity of these compounds and their presence in the environment pose grave issues that obliges the development of methods that will increase agricultural productivity and disease vector control with minimal environmental contamination and side effects to non-target species. Previous research conducted on sediments, micro-invertebrate organisms from both marine and freshwater ecosystems in Kenya have continually revealed contamination by pesticides (Barasa, 1998; Everaarts et al., 1997; Getenga et al., 2004; Mugachia et al., 1992; Munga, 1985; Wandiga et al., 2002). Levels of pesticide contamination at the top of the food chain in the basin have been exhibited by presence of residues in the cow and human milk, and bird eggs (Kahunyo et al., 1986; Kanja, 1988; Kituyi et al., 1997; Wandiga and Mutere, 1988). Potential risks of pesticide use in the tropics may differ from those in the widely studied temperate regions. It is
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Musa et al.
generally assumed that the climatic conditions in the tropics facilitate the breakdown of bioactive compounds, thus avoiding most of the side effects of pesticides. Kenya, like most other developing countries, is at the crossroads of environmentally sustainable agricultural...