School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, 24060, USA.
J Environ Qual. 2022 Nov;51(6):1270-1281. doi: 10.1002/jeq2.20402. Epub 2022 Sep 20.
Soil organic matter (SOM) retains and attenuates many contaminants; however, its interactions with neonicotinoid insecticides under field conditions remain poorly understood. The goal of this study was to determine if SOM influences the persistence or leaching of two neonicotinoid insecticides: thiamethoxam (TMX) and its transformation-product clothianidin (CLO). Thiamethoxam-coated soybean [Glycine max (L.) Merr.] was planted into a clay soil containing different soil organic carbon (SOC) concentrations. Leachate and soil samples were collected for 10 wk after planting and were analyzed for insecticide concentrations using liquid chromatography-tandem mass spectrometry. Single and multiple linear regressions were performed between SOC, leaching volumes, and measured insecticide concentrations, focusing on rainfall events near the beginning, middle, and end of the study. Correlations were also tested between SOC and cumulative mass of leached insecticides. Neither SOC nor per-event leachate volumes explained variability in TMX leaching or residual CLO concentrations in soils; however, by the conclusion of the study residual thiamethoxam concentrations in soil were negatively correlated with cumulative volume of leached water. Initially, the concentration and total mass of leached CLO were significantly and negatively correlated with SOC content; however, this effect faded with time. Leachate dynamics also affected CLO transport, with positive correlations between leachate volume and CLO concentration during the latter events. This analysis demonstrates that SOM can reduce peak loading of neonicotinoids but may not alter cumulative leaching over the entire growing season.
土壤有机质（SOM）能保留和削弱许多污染物；然而，其在田间条件下与新烟碱类杀虫剂的相互作用仍知之甚少。本研究的目的是确定 SOM 是否会影响两种新烟碱类杀虫剂（噻虫嗪和其转化产物噻虫胺）的持久性或淋溶。噻虫嗪包衣大豆[Glycine max（L.）Merr.]种植在含有不同土壤有机碳（SOC）浓度的粘壤土中。种植后 10 周内采集淋溶液和土壤样品，并使用液相色谱-串联质谱法分析杀虫剂浓度。在研究开始、中期和结束时附近的降雨事件前后，对 SOC、淋溶量和测量的杀虫剂浓度之间进行了单因素和多因素线性回归。还测试了 SOC 与淋溶杀虫剂累积质量之间的相关性。SOC 或单次淋溶体积都不能解释噻虫嗪淋溶或土壤中残留 CLO 浓度的变化；然而，到研究结束时，土壤中残留的噻虫嗪浓度与淋溶水的累积体积呈负相关。最初，淋出液中 CLO 的浓度和总量与 SOC 含量呈显著负相关；然而，这种影响随着时间的推移而减弱。淋出液动态也影响 CLO 的传输，在后几个事件中，淋出液体积与 CLO 浓度呈正相关。这项分析表明，SOM 可以减少新烟碱类杀虫剂的峰值负荷，但在整个生长季节内可能不会改变累积淋溶量。
