| Abstract
| - Carfentrazone-ethyl (CF-E) is an aryl triazolinone reduced-risk herbicide for use on corn, wheat,and soybean. As part of the assessment of its metabolic fate, the aerobic aquatic metabolism of[14C]CF-E at a concentration of 0.22 μg/g was investigated. Two separate aquatic sediments (siltyclay loam and clay loam soils, flooded with water) were used in the study. At each of eight samplingsthroughout the 30-day study, the distribution of radioactivity between surface water, sediment,and volatile fractions was assessed. At zero time, the majority of the applied radioactivity wascontained in the water layer (83−90%), declining to 70−80% after 30 days. This was coupled withan increase in the percent radioactivity in the soil layer from 4−6% at day 0 to 13−19% after 30days. Nonextractable soil residues and volatile degradation products were formed in negligibleamounts. Analysis of the incubation extracts from either aquatic sediment indicated a rapidconversion (<2 days) of the parent CF-E ester to carfentrazone−chloropropionic acid. Over time,increasing amounts of a cascade of acidic degradation products comprising >90% of the appliedradioactivity were formed. Identification of these degradation products was initially achieved throughchromatographic comparison with reference synthetic standards and subsequently confirmed usingLC-MS analysis. A degradation pathway for CF-E under aerobic aquatic conditions is proposed. Keywords: Aerobic; aquatic; metabolism; aryl triazolinone; carfentrazone-ethyl; Aim
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