FATE OF CHLORPYRIPHOS AND ENDOSULFAN IN SOIL
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Date
2003
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AAU, Anand
Abstract
Chlorpyriphos and endosulfan were applied @ 5.0 μg g-1 soil in a laboratory experiment to study their persistence in sandy and sandy loam soil with and without glucose treatment. Adsorption of these insecticides in the soils and their downward movement in the PVC columns filled with sandy and sandy loam soils were also carried out in the laboratory as well as microplot conditions to work out the risk of ground water pollution. Chlorpyriphos and endosulfan showed first-order dissipation in both sandy and sandy loam soils with and without glucose treatment. The halflife values for chlorpyriphos irrespective of glucose treatment in sandy and sandy loam soils ranged from 10.0 to 10.6 and 14.3 to 14.7 days, respectively. The half-life values for total-endosulfan, α - endosulfan and β - endosulfan in sandy soil without glucose treatment were 35.4, 13.9 and 28.9 days, respectively, the correspondmg values in glucose treated sandy soil were 31.7, 17.4 and 27.4 days. The half-life values for total-endosulfan, α - endosulfan and β - endosulfan in sandy loam soil without glucose treatment were 59.0, 20.6 and 41.8 days, respectively, the corresponding values in glucose treated sandy loam soil were 41.8, 19.4 and 35.4 days. Chlorpyriphos showed biphasic mode of dissipation in sandy soil with and without glucose treatment and in glucose treated sandy loam soil, whereas it was monophasic in case of sandy loam soil without glucose treatment. Total-endosulfan showed monophasic mode of dissipation, α - Endosulfan and β - endosulfan showed biphasic mode of dissipation in glucose treated sandy and sandy loam soils, whereas it was monophasic in case of sandy and sandy loam soils without glucose treatment. Endosulfan on degradation was converted to endosulfan sulphate, which is a persistent metabolite. Degradation of chlorpyriphos and endosulfan enhanced initially with glucose application and it was marginally higher in glucose treated soils as compared to soils without glucose treatment. Adsorption of chlorpyriphos, α - endosulfan and β - endosulfan was studied on sandy and sandy loam soils. Chlorpyriphos showed maximum adsorption on both the soils followed by β - endosulfan and α - endosulfan. Organic matter content of the soil was predominantly responsible for adsorption of the insecticides, which was evident by low KOC values of the insecticides for sandy loam soil. Soil column study carried out for one month period revealed little movement of chlorpyriphos beyond 6 cm depth in sandy loam soil in the laboratory experiment and no movement beyond 6 cm depth in sandy soil in laboratory as well as microplot conditions and in sandy loam soil in microplot condition, however quite low amount of endosulfan reached upto 30 cm soil depth in the laboratory and microplot study in sandy loam soil, while, there was little movement of endosulfan beyond 12 cm depth in sandy soil in laboratory as well as microplot conditions. None of the insecticides were detected in the leachates.
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Agricultural Chemistry and Soil Science, A Study