Flumioxazin separately 14C-labeled at 1,2-positions of the tetrahydrophthalimide moiety or uniformly labeled at the phenyl ring was exposed to two algae and duckweed via the water layer and water milfoil via the water layer or bottom sediment for 14 days to investigate uptake and metabolic profiles in these aquatic plants. While 14C-flumioxazin received immediate hydrolysis through maleimide ring opening and amide bond cleavage with its hydrolytic half-life of <1 day in both water and sediment, the 14C-plant uptake was ≤4.7% of the applied radioactivity (%AR) with water exposure for all plants and 0.9%AR with sediment exposure for water milfoil. No 14C-translocation between shoot/leaves and roots occurred in water milfoil. The components of 14C residues in plants were common among the species, which were the above hydrolysates and their transformation products, that is, dicarboxylic acid derivative metabolized via hydroxylation at the double bond of the cyclohexene ring followed by sugar conjugation with its counterpart amine derivative via acid conjugations.
Keywords: aquatic plants; conjugation; flumioxazin; metabolism; sediment exposure; water exposure.