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Fate characterization of a novel herbicide ZJ0273 in aerobic soils using multi-position ¹⁴C labeling

Wang, Haiyan, Ye, Qingfu, Yue, Ling, Han, Ailiang, Yu, Zhiyang, Wang, Wei, Yang, Zhengmin, Lu, Long
Science of the total environment 2009 v.407 no.13 pp. 4134-4139
herbicide residues, environmental fate, pesticide persistence, degradation, radiolabeling, carbon, radionuclides, mineralization, soil pH, acid soils, alkaline soils, aerobic conditions
ZJ0273, propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate, is a novel herbicide being developed for use on rape crops. The environmental behavior and fate of ZJ0273, however, are not well understood. In this study, multi-position ¹⁴C-labeled compounds (B-ZJ0273 and C-ZJ0273) were used to investigate the fate of ZJ0273 in aerobic soils, and compare their differences in extractable residues (ER), bound residues (BR), and mineralization. ER for both ¹⁴C labels followed a similar dissipation trend in the same soil, and results showed a strong effect of soil pH, with the ER level being significantly higher in acidic soils than neutral or alkaline soils. The disappearance of parent compound followed first-order dynamics for both labels in the same soils. No difference in BR was observed between the two ¹⁴C-labels. BR increased with time and reached 17.5-35.3% of applied ¹⁴C in the three soils after 100-d incubation, which is much smaller than the non-accumulative criteria (70%) as stated in the directives by the Commission of the European Communities. Mineralization to CO₂ also depended closely on the soil type, with the cumulative mineralized fraction being substantially greater in the neutral and alkaline soils than in the acidic soil. Results also showed that cumulative mineralization rates of the two labels in the acidic soil were much smaller than those in the neutral and alkaline soils. Mineralization of C-ZJ0273 (1.2-9.9%) was found to be more extensive than that of B-ZJ0273 (0.5-6.6%), suggesting that benzyl ring was more susceptible to cleavage than pyrimidine ring. The use of multi-position labeling proved to be valuable; it served the purpose of validating the rigorousness of experimental protocols, and provided insights into the behavior and fate of the different molecular fragments.