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; State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun 130117, China.
State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun 130117, China.
Ecotoxicol Environ Saf. 2024 Oct 1;284:116895. doi: 10.1016/j.ecoenv.2024.116895. Epub 2024 Aug 15.
Neonicotinoids are widely used pesticides around the world, but the photolysis of neonicotinoids in cold agricultural region are still in blank. This paper aimed to study the influence of cold temperature over photolysis of neonicotinoids. To this end, the photolysis rates and photoproducts of dinotefuran and nitenpyram in water, ice and freeze-thawing condition were determined. Coupled with quantum chemistry calculation, the influence mechanisms of temperature and medium were investigated. The results showed the photolysis rates of neonicotinoids in water condition slightly declined with the lowered temperature due to the photolysis reactions were endothermic reactions. However, the photolysis rates increased by 89.8 %, 59.2 %, 49.4 % and 9.5 % for dinotefuran and nitenpyram in ice and thawing condition, respectively. This phenomenon was posed by the concentration-enhancing effect and change of photo-chemical properties of neonicotinoids in ice condition, which included lowered bond cleavage energy, lowered first excited singlet state energy and expanded light absorption range. The photolysis pathways of the two neonicotinoids did not change in different medium, but the concentration of carboxyl products was relatively higher than that of water condition due to the more amounts of reactive oxygen species in ice medium, which might increase the secondary pollution risk after ice-off in spring due to the higher ecotoxicity to nontarget organism of these photoproducts. The influence of cold temperature and medium change should be considered for the environmental fate and risk assessment of neonicotinoids in cold agricultural region.
新烟碱类杀虫剂在全世界范围内被广泛使用，但在寒冷的农业地区，新烟碱类杀虫剂的光解情况仍不清楚。本文旨在研究低温对新烟碱类杀虫剂光解的影响。为此，测定了水中、冰中和冻融条件下噻虫嗪和吡虫清的光解速率和光解产物。结合量子化学计算，探讨了温度和介质的影响机制。结果表明，由于光解反应是吸热反应，水中新烟碱类杀虫剂的光解速率随温度降低而略有下降。然而，在冰中和解冻条件下，噻虫嗪和吡虫清的光解速率分别增加了 89.8%、59.2%、49.4%和 9.5%。这一现象是由于冰中浓度增强效应和新烟碱类杀虫剂光化学性质的变化引起的，包括降低键断裂能、降低第一激发单线态能量和扩大光吸收范围。两种新烟碱类杀虫剂在不同介质中的光解途径没有改变，但由于冰介质中活性氧的数量较多，羧酸产物的浓度相对较高，这可能会增加春季融冰后二次污染的风险，因为这些光解产物对非靶标生物的生态毒性更高。在寒冷的农业地区，应考虑低温和介质变化对新烟碱类杀虫剂环境归宿和风险评估的影响。
