Investigation of degradation of carbamate pesticides adsorbed on soil under the impact of sunlight

The degradation rates of two carbamate pesticides adsorbed on humus-rich and clay-rich soils were examined under sunlight by applying dry and wet conditions. Bothpesticides degraded faster under wet conditions compared to the corresponding ratesobtained under dry conditions. Both pesticides adsorption on clay-rich soil degradedfaster compared to the cases adsorbed on humus-rich soil. The intermediate productsof degradation were mainly the result of the hydrolysis of the pesticides which wasthe main reasen for faster degradation under wet conditions. It was concluded thatthe loose, three dimensional structure of humic acids bound the pesticide and thewater molecules strongly by using its polar functional groups which caused aretardation of the hydrolysis of pesticides molecules. On the other hand, the lewis-acid sites on clay might have catalysed the hydrolysis of the pesticide moleculesadsorbed on clay-rich soil.Keyword : Carbamate, Clay, Humus, Soil, HydrolizeII