Pesticide residues in the surface runoff

Tay, Teck Pin (2005) Pesticide residues in the surface runoff. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

The purpose of this study is to investigate the amount of pesticide washed out under the influence of different rainfall intensities and different time intervals between the pesticide application and the first rainfalL Three different rainfall intensities were simulated on an experimental plot and administered in different time intervals after pesticide application. Both the surface runoffs and the soil samples were taken for pesticide analysis in the laboratory. The extracted pesticide from both the water and the soil samples were later determined by gas chromatography with flame phosphorus detector. Generally, the results show a similar trend of pesticide wash out in the surface runoff. There was no significant different in the wash out of pesticide in the surface runoff among the three rainfall intensities studied. All the three rainfall intensities had shown that the l-h and 2h time intervals after the pesticide application, were more susceptible to being washed out in the runoff. It was observed that there was a significant different (p<0.05) in the pesticide amount between the short hour time intervals and the long hour time intervals runoff. Parallel to most studies, most of the pesticide was found to have accumulated in the soil after high frequencies of pesticide applications. The soil in the light rainfall intensity had adsorbed the most amount of pesticide. Comparatively, the soil under the heavy rainfall intensity had the least amount of pesticide adsorbed among the three rainfall intensities. Nonetheless, the amount of pesticide found in the soil of all the three rainfall intensities was ranging from 1.06 mg/kg to 9.44 mg/kg. The observation had concluded that in the long hour time intervals degradation processes and the crystallization of the pesticide on the soil particles had accounted for the lower amount of pesticide washed out in the surface runoff. Thus, for the amount of pesticide washed out in the surface runoff, the time interval between the pesticide application and the first rainfall was the major factor.

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