FATE OF RIMSULFURON IN THE ENVIRONMENT

The fate of C-14-labeled rimsulfuron in aqueous and soil environments was examined. Hydrolysis was first-order, pH-dependent, and accelerate d at higher temperatures. Rimsulfuron degraded rapidly in pH 5, 7, and 9 buffer solutions (25 degrees C) with half-lives of 4.7, 7.2, and 0. 4 days, respectively, primarily through contraction of the sulfonylure a bridge. Soil metabolism studies also showed rapid decomposition by b ridge contraction with half-lives of 24.5 (laboratory) and 5.7 (field) days. The degradation rate and metabolic pathway did not change when aqueous solutions (pH 7 or 9) or soil was kept in the dark or exposed to light. A faster degradation rate in light-exposed pH 5 aqueous solu tion was observed. Rimsulfuron was moderately adsorbed on soils with h igh levels of clay or organic matter. Although soil TLC suggested rims ulfuron could be mobile, minimal mobility was observed under field con ditions. Rimsulfuron residues (>0.01 ppm) were not observed in rotatio nal crops grown in rimsulfuron-treated soil.