College of Resources and Environment, Hunan Agricultural University, Changsha 410028, China.
College of Resources and Environment, Hunan Agricultural University, Changsha 410028, China.
Ecotoxicol Environ Saf. 2022 Apr 15;235:113424. doi: 10.1016/j.ecoenv.2022.113424. Epub 2022 Mar 18.
The occurrence of pesticides and their metabolites in the environment can alter the ecological relationships between aquatic food chains. Fipronil is a broad-spectrum insecticide which release in the environment may harm the non-target organisms. However, the toxicity and biotransformation of its two enantiomers are far from fully understood. The present study aimed to investigate the aquatic toxicity and environmental behavior of fipronil at enantiomeric level using two freshwater algae, Scenedesmus quaclricauda (S. quaclricauda), and Chlorella vulgaris (C. vulgaris) through an integrative approach the transformation process of the individual enantiomer isolated and in racemic form. The 72 h-EC values of rac-, R-, S-fipronil varied from 3.27 to 7.24 mg L with R-fipronil posing a more significant effect on algal growth inhibition. Chlorophyll a was more susceptible to fipronil exposure than chlorophyll b and carotenoids. Enantioselective alterations on physiological and biochemical parameters (chlorophyll a, chlorophyll b, carotenoids, and the activities of antioxidant enzyme catalase (CAT) and superoxide dismutase (SOD)) were also observed. The half-lives (T) of R-fipronil and S-fipronil in algae culture were 3.4-3.5 d and 4.0-4.9 d, respectively. By the end of the 17-d exposure, the enantiomer fractions (EFs) increased to 0.59, indicating a preferential depuration of R-fipronil. The metabolites monitoring showed the fipronil sulfide was the main metabolite followed by fipronil sulfone. The results revealed that the enantiomers of fipronil pose enantiospecific behaviors induced by these two algae, with the R-enantiomer more toxic to algal growth and favorable in degradation. These analyses are beneficial for understanding the ecological effect of chiral pesticide in aquatic environment, and the enantiomeric differences of the toxicity, degradation and the formation of toxic metabolites could be helpful for the eco-environmental risk evaluation.
环境中农药及其代谢物的存在会改变水生食物链的生态关系。氟虫腈是一种广谱杀虫剂，其在环境中的释放可能会对非靶标生物造成危害。然而，其两种对映异构体的毒性和生物转化还远未完全了解。本研究采用两种淡水藻类——斜生栅藻（Scenedesmus quaclricauda，S. quaclricauda）和普通小球藻（Chlorella vulgaris，C. vulgaris），通过整合的方法，从对映体水平上研究了氟虫腈的水生毒性和环境行为，研究了从单个对映体和外消旋体中分离出的对映体的转化过程。 rac-、R-、S-氟虫腈对 72 h-EC 值的影响范围为 3.27-7.24 mg/L，其中 R-氟虫腈对藻类生长抑制的影响更为显著。叶绿素 a 比叶绿素 b 和类胡萝卜素更容易受到氟虫腈的暴露。还观察到生理生化参数（叶绿素 a、叶绿素 b、类胡萝卜素以及抗氧化酶过氧化氢酶（CAT）和超氧化物歧化酶（SOD）的活性）的对映选择性变化。R-氟虫腈和 S-氟虫腈在藻类培养物中的半衰期（T）分别为 3.4-3.5 d 和 4.0-4.9 d。到 17 天暴露结束时，对映体分数（EF）增加到 0.59，表明 R-氟虫腈优先被降解。代谢物监测表明，氟虫腈硫醚是主要代谢物，其次是氟虫腈砜。结果表明，氟虫腈对映体在这两种藻类的诱导下表现出对映体特异性行为，R-对映体对藻类生长的毒性更大，有利于降解。这些分析有助于了解手性农药在水生环境中的生态效应，以及毒性、降解和有毒代谢物形成的对映体差异有助于生态环境风险评估。
