Co-Authors:
Yaron, B., Div. Soil Residues Chem., Inst. Soils Water, Agric. Res. Organ., Bet Dagan, Israel
Saltzman, S., Div. Soil Residues Chem., Inst. Soils Water, Agric. Res. Organ., Bet Dagan, Israel
Abstract:
Summarizing the present theoretical knowledge on the physicochemical interactions between parathion and soil constituents, the following practical conclusions concerning the behavior of parathion in the soil environment may be drawn: 1. Reaching the soil, parathion is distributed among the solid, liquid, and gaseous soil phases. In the absence of water, parathion is preferentially distributed in the solid phase. 2. The affinity for parathion of the constituents of the soil solid phase decreases in the order: organic matter > clay fraction (montmorillonite > attapulgite > kaolinite) > coarse fraction. 3. The hysteresis in parathion release from the adsorbed phase is due to its strong bonding to organic colloids. Hence, a build-up of long-lasting residues in soils is a possibility to consider. 4. The chemical degradation of parathion in soils is a slow process, the rate of which is dependent on the soil properties and environmental factors. 5. The chemical degradation of parathion in soils proceeds by the hydrolysis of the phosphate ester bond. The resulting nontoxic metabolites, mainly the phosphate moiety, may be retained by the soil colloids.