State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun 130117, China; Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions, Heilongjiang Province Collaborative Innovation Center of Cold Region Ecological Safety, School of Geographical Sciences, Harbin Normal University, Harbin 150025, China.
Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions, Heilongjiang Province Collaborative Innovation Center of Cold Region Ecological Safety, School of Geographical Sciences, Harbin Normal University, Harbin 150025, China.
Aquat Toxicol. 2023 Apr;257:106443. doi: 10.1016/j.aquatox.2023.106443. Epub 2023 Feb 20.
Neonicotinoids are widely used pesticides that contaminate aquatic environments. Although these chemicals can be photolyzed under sunlight radiation, it is unclear for the relationship between photolysis mechanism and toxicity change in aquatic organisms. This study aims to determine the photo-enhanced toxicity of four neonicotinoids with different main structures (acetamiprid, and thiacloprid for cyano-amidine structure, imidacloprid and imidaclothiz for nitroguanidine). To Achieve the goal, photolysis kinetics, effect of dissolved organic matter (DOM) and reactive oxygen species (ROSs) scavengers on photolysis rates, photoproducts, and photo-enhanced toxicity to Vibrio fischeri were investigated for four neonicotinoids. The results showed direct photolysis plays a key role in the photo-degradation of imidacloprid and imidaclothiz (photolysis rate constants are 7.85 × 10 and 6.48 × 10 min, respectively), while the photosensitization process of acetamiprid and thiacloprid was dominated by ·OH reactions and transformation (photolysis rate constants are 1.16 × 10 and 1.21 × 10 min, respectively). All four neonicotinoid insecticides exerted photo-enhanced toxicity to Vibrio fischeri, indicating photolytic product(s) posed greater toxicity than their parent compounds. The addition of DOM and ROS scavengers influenced photo-chemical transformation rates of parent compounds and their intermediates, leading to diverse effects on photolysis rates and photo-enhanced toxicity for the four insecticides as a result of different photo-chemical transformation processes. Based upon the detection of chemical structures of intermediates and Gaussian calculations, we observed different photo-enhanced toxicity mechanisms for the four neonicotinoid insecticides. Molecular docking was used to analyze the toxicity mechanism of parent compounds and photolytic products. A theoretical model was subsequently employed to describe the variability of toxicity response to each of the four neonicotinoids.
新烟碱类杀虫剂是广泛使用的农药，会污染水生环境。尽管这些化学物质在阳光辐射下可以光解，但水生生物中光解机制与毒性变化之间的关系尚不清楚。本研究旨在确定具有不同主要结构的四种新烟碱类杀虫剂（乙虫腈和噻虫嗪的氰基脒结构，吡虫啉和噻虫啉的硝基亚甲基结构）的光增强毒性。为了实现这一目标，研究了四种新烟碱类杀虫剂的光解动力学、溶解有机物（DOM）和活性氧（ROS）清除剂对光解速率、光产物以及对发光菌的光增强毒性的影响。结果表明，直接光解在吡虫啉和噻虫啉的光降解中起关键作用（光解速率常数分别为 7.85×10 和 6.48×10 min），而乙虫腈和噻虫嗪的光敏化过程则由·OH 反应和转化主导（光解速率常数分别为 1.16×10 和 1.21×10 min）。四种新烟碱类杀虫剂对发光菌均表现出光增强毒性，表明光解产物比其母体化合物具有更大的毒性。DOM 和 ROS 清除剂的添加影响了母体化合物及其中间产物的光化学转化速率，从而由于不同的光化学转化过程，对四种杀虫剂的光解速率和光增强毒性产生了不同的影响。基于中间产物的化学结构检测和高斯计算，我们观察到四种新烟碱类杀虫剂具有不同的光增强毒性机制。采用分子对接分析了母体化合物和光解产物的毒性机制。随后采用理论模型描述了四种新烟碱类杀虫剂的毒性响应变化的可变性。
