Removal of Oxamyl in Soil by Different Treatments

Document Type : Original Article

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Department of Pesticide Chemistry & Technology, Faculty of Agriculture, Alexandria University, Alexandria, P.O. Box 21545, Egypt

Abstract

The remediation of the oxamyl pesticide, applied, at a rate of 50 µg/gm soil and amended with different materials namely, Tergitol NP9 (nonionic surfactant), charcoal, lorandeat and iron fillings at rate of 300, 250, 250 and 300 Kg/Fadden, respectively, was investigated. The oxamyl residue levels in loamy sand was extracted at different time intervals after treatment based on the solid phase extraction (SPE) with methanol and then analyzed by HPLC. Only the peak corresponding to oxamyl was observed in the chromatogram and no intermediate metabolites  could be detected. At the end of the experiment (21 days), the dissipation percentage of oxamyl reached about 88, 78, 73 and 72% in soil amended with NP-9, Fe, lorandeat and charcoal, respectively. The rate of disappearance was 2 times higher than in unamended-soil, while Fe, lorandeat and charcoal  enhanced the dissipation rate by 1.77, 1.65 and 1.61 times, respectively. The disappearance rate constants and half-life values of the compound were obtained from the exponential decay equations. The decomposition of oxamyl in the control, charcoal and lorandeat followed the first order kinetics with t1/2 of about 22.08, 13.8 and 13.2 days. On the other hand, a biphasic model was assumed to explore the disappearance of oxamyl in soil amended with NP-9 and Fe where the rate of disappearance in the first phase was faster than the second phase. This is clearly reflected in the half-life (t0.5) values for the first and second phases, where the t0.5 values of oxamyl ranged from 3.3 to 12.7 and 6.5 to 15.6 days, respectively. The results demonstrated that using NP-9, Fe, charcoal and lorandeat may offer an efficient remediation treatment for oxamyl-polluted soil.

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