The behaviour of the organophosphorous pesticide pirimiphos-methyl in soil/water systems

This research describes the abiotic degradation of pirimiphos-methyl (0-2-diethyl-amino-6-methylpyrimidin-4-yl-0,0-dimethylphosphorothioate) under controlled conditions in aqueous solutions and in soil/water slurries.;The kinetics of hydrolysis of pirimiphos-methyl was determined in alkaline solutions. The second-order rate constant was 2.57 x 10--3 M--1s--1 at 25.0°C, but the rate was significantly enhanced at elevated temperatures.;A microfitration---HPLC technique was employed to study the uptake and degradation of pirimiphos-methyl in aqueous slurries of---well-characterized soils from the Middle Belt region of Nigeria. Sorption kinetics of the pirimiphos-methyl were described in terms of fast and slow process!;Disappearance of the pesticide was due to both sorption and degradation by hydrolysis in the presence of the soil matrix. The phase distribution of the product species was measured along with that of the original pesticide. (Abstract shortened by UMI.).