Fate of pyribambenz propyl (ZJ0273) in anaerobic soils revealed by position-specific 14C labeling.

Pyribambenz propyl, or ZJ0273, is a new and widely used pyrimidynyloxybenzoic herbicide; however, its behavior and safety in anaerobic soils remain poorly understood. In this study, ZJ0273 was labeled with (14)C on its benzoate-, pyrimidyl- and benzyl- rings respectively, and applied to anoxic flooding soils to characterize its anaerobic fates. Over the 100 d incubation, the amended (14)C-ZJ0273 was slightly mineralized to (14)CO2 (<4%) or redistributed into the overlaying water (<10%), with the majority of the (14)C (82-98%) remaining in the soil. The residues in soil underwent a gradual transformation from extractable residues (ER) to bound residues (BR), with the percentage of (14)C-BR increasing from 1.1 to 2.5% at day 5 to 23.2-47.2% at day 100. The proportion of (14)C-ER, (14)C-BR and (14)CO2 depended both on the soil property and the labeling position. Generally, ZJ0273 has the highest tendency to form BR in fluvio-marine yellow loamy soil, and the mineralization on both the benzoate and benzyl rings tends to be more extensive in red-clayed soil than the other soils. The ring-specific labeling (14)C on three aromatic rings respectively provides full molecular information and yield information on sub-molecular level, i.e., the benzoate ring was generally more susceptible to cleavage than the pyrimidyl or benzyl rings (P<0.01).