Effects of pH on the environmental fate of [14C]aldicarb in an aquatic microcosm

The role of pH in determining the environmental fate of [14C]aldicarb was examined in an aquatic microcosm. Only minor amounts of the radiochemical were absorbed by aquatic organisms at any pH. Of the radioactivity absorbed, greater than 75% was rapidly metabolized and incorporated into tissues. Minor differences in the in vivo spectrum of aldicarb and metabolites as a function of pH were discerned for fish; the quantitative and qualitative distribution of aldicarb and its metabolites was identical for the other organisms across the pH levels. The most notable difference in metabolite spectrum appearing in the water as a function of pH was the absence of aldicarb sulfone at pH 4 on Day 6. In contrast, aldicarb sulfoxide was found as the major metabolite and aldicarb was completely lacking at all three pH levels. Since aldicarb sulfoxide is biologically active, disappearance of the parent compound does not eliminate hazard. The general effects of pH on the environmental fate of aldicarb are negligible on Day 6 but may be more pronounced at other time periods.