塩素処理における有機りん系農薬の類型別反応性とオキソン体への変換について

Abstract

The reactivities of the P=S type organophosphorus pesticides (OPs) and their oxons with chlorine were investigated. The reactivity of diazinon, a typical OP, with chlorine was higher at low pHs and high chlorine concentrations but was not affected by initial diazinon concentration. The dominant reaction was the neutral reaction at pHs 7.2-8.5, whereas it was both the neutral and the acid-catalyzed reaction at pH 5.9. The main chlorination product, diazinon-oxon, was not affected by diazinon concentration, chlorine concentration or pH. The reactivities of ten OP species with chlorine were investigated under water treatment conditions. Eight of ten OPs transformed into their oxons at high rates (72-103%), although the reactivities of these OPs with chlorine differed. On the other hand, two amidates, namely butamifos and isofenphos, transformed into their oxons at 50%, and the remaining 50% was composed of hydrolysates (i.e., 5-methyl-2-nitrophenol for butamifos and isopropyl salicylate for isofenphos) and chlorinated derivatives of hydrolysates. Finally, ten oxons were examined to determine their reactivities with chlorine. After 24 hours, three oxons chlorinated were degraded by 20-30% compared with them nonchlorinated, but the other oxons were not degraded to that extent. From these results, drinking water quality control must account for stabilities of residual oxons of OPs in chlorination, particularly for those with strong toxicities.