Browsing by Author "Stephens, Justina"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    GLC analysis of endosulfan and other chlorinated pesticide residues in cotton products soil and water
    (University of Dar es Salaam, 1987) Stephens, Justina
    Soil, water, cottonseed crude oil and cottonseed animal feed collected from the Western Cotton Growing Area (W.C.G.A.) of Tanzania were analysed for organochlorine pesticides and their metabolites by gas chromatography using an electron capture detector. Fourteen top soil samples from four different points in Mabuki farm in the W.C.G.A. were collected eleven days after the second foliar spray on cotton, of 35$ thiodan, and then one day and five days after the third spray, and lastly at harvest, three months after the sixth and final thiodan application. Endosulfan I, endosulfan II, endosulfan sulfate, p,p'-DDE, p,p'-DDD and p,p'-DDT were detected and quantified in the soil. For each soil sample, endosulfan I was much less than endosulfan II, while endosulfan sulfate was the highest of all the three. There was a rapid decrease in total endosulfan (sum of endosulfan T, endosulfan II, and endosulfan sulfate) five days after the third application of thiodan, and an overall gradual decrease in this value three months after the final application. p,p'-DDE residues were very low and sometimes undetectable, while p,p'-DDD had highest values. Total DDT (sum of p,p'-DDE, p,p'-DDD and p,p'-DDT) in soils collected thirteen months after its final application was much less than in soils collected eight months after the final DDT application. In all the five water samples analysed, neither the Mabuki farm pond water, nor Lake Victoria water had detectable endosulfan residues. However, the pond and the lake water samples collected two months after the heaviest rains (table 2) and run-offs had detectable DDT residues: 0.0025 ppm in one pond water, and 0.0008 ppm, 0.004 ppm in two Lake Victoria water samples collected thirteen months after the last 40% DDT and phenthoate mixture foliar spray on cotton. Among the six cottonseed crude oil samples from the Vegetable Oil Industries Limited (VOIL) analysed, endosulfan (0.045 ppm) was detected in only one sample, which was from seeds ginned six months back, and stored at room temperature. Two other crude oil samples had 0.077 ppm and 0.229 ppm total DDT residues respectively. Crude oil from seeds ginned eleven months back had neither endosulfan nor DDT residues detected. One out of three VOIL cottonseed cake samples analysed had 0.0498 ppm of endosulfan II and two had 0.014 ppm and 0.0124 p-;p'-DDD respectively. The cottonseed cake was from cottonseeds ginned six months back. It was generally found that endosulfan rapidly oxidizes to the sulfate, which in turn gradually disappears from the environment and from the cottonseed products. DDT on the other hand, had relatively large concentrations and was more frequently detected in almost all the samples analysed.