Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE-21335 Lüneburg, Germany.
Sci Total Environ. 2015 Feb 15;506-507:369-79. doi: 10.1016/j.scitotenv.2014.11.025. Epub 2014 Nov 24.
Even appropriately used, pesticides can enter the surface and groundwater by several routes where photochemical degradation along with biotic processes contributes to their fate, resulting sometimes in the formation of stable transformation products (TPs). Yet, little is known about S-metolachlor (SM) transformation in the aquatic environment. Furthermore, commercial formulation of a pesticide might have different physical and biological properties compared to its pure grade. The present study assessed the biodegradability of the pure SM and its commercial product Mercantor Gold(®) (MG) by employing two OECD biodegradation (301D, F) tests. Photolysis in water was investigated by using a Xe lamp. Subsequently the biodegradability of the photolysis mixtures was examined. The primary elimination of SM was monitored and structures of its TPs were elucidated by HPLC-UV-MS/MS. Additionally, a set of in silico prediction programs was applied for supporting analytical results and toxicity assessment of SM and TPs. S-metolachlor and Mercantor Gold(®) were not biodegraded. HPLC-UV analysis showed higher elimination of SM in MG compared to pure SM during photolysis. A total of 10 photo-TPs of SM and MG were identified. According to MS data and in silico predictions, chemical structures were proposed for all found photo-TPs. Likewise for the parent compounds, no biodegradation has been observed for their photo-TPs. However, in the 301F test new bio-TPs have been generated from photo-TPs which were observed for the first time according to authors' best knowledge. The results suggest that the MG formulation does not affect the biodegradation process, but it influences the photolysis efficiency and potentially might result in faster formation of TPs in the environment. This study also demonstrates that photo-TPs can be further transformed into new products due to bacterial activity in the water phase. Moreover biotransformation might lead to an increased toxicity compared with the parent compound.
即使使用得当，农药也可以通过多种途径进入地表水和地下水，其中光化学降解与生物过程共同作用决定了它们的命运，有时会形成稳定的转化产物（TPs）。然而，人们对水生态环境中 S-甲草氯（SM）的转化知之甚少。此外，与纯品相比，农药的商业制剂可能具有不同的物理和生物特性。本研究采用 OECD 两种生物降解（301D、F）试验评估了纯 SM 和其商业制剂 Mercantor Gold(®)（MG）的可生物降解性。通过 Xe 灯研究了水的光解，随后检查了光解混合物的可生物降解性。监测了 SM 的初步消除，并通过 HPLC-UV-MS/MS 阐明了其 TPs 的结构。此外，还应用了一组计算机预测程序来支持 SM 和 TPs 的分析结果和毒性评估。SM 和 Mercantor Gold(®)均未发生生物降解。HPLC-UV 分析表明，在光解过程中，MG 中 SM 的消除率高于纯 SM。共鉴定出 SM 和 MG 的 10 种光转化产物（TPs）。根据 MS 数据和计算机预测，为所有发现的光转化产物提出了化学结构。与母体化合物一样，其光转化产物也未观察到生物降解。然而，在 301F 试验中，根据作者的最佳知识，首次从光转化产物中生成了新的生物转化产物（TPs）。结果表明，MG 制剂不会影响生物降解过程，但会影响光解效率，并可能导致环境中 TPs 的形成更快。本研究还表明，由于水相中细菌的活性，光转化产物可以进一步转化为新产物。此外，与母体化合物相比，生物转化可能导致毒性增加。
