DEGRADATION KINETICS OF ORGANOPHOSPHORUS AND ORGANONITROGEN PESTICIDES IN DIFFERENT WATERS UNDER VARIOUS ENVIRONMENTAL-CONDITIONS

The evolution of a mixture containing 19 organophosphorus (OF) and organonitrogen (ON) pesticides at ppb level was studied over a g-month period in different water types (ultrapure water, natural seawater, river water, filtered Fiver water) and under various conditions. The degradation kinetics were monitored in closed bottles in darkness at two temperatures (T = 6 and 22 degrees C) and in a system exposed to natural sunlight (variable temperature). The mixture was analyzed by gas chromatography coupled with a nitrogen phosphorus detector (GC/NPD). Energy activation (E(a)) and half-lifetimes (t(1/2)) were determined. Very different degradation behavior with respect to physicochemical conditions and molecular structures of the pesticides was observed. These experiments confirm that half-lives of OP pesticides can be more than several months and consequently lead to lasting environmental pollution.