3种烟碱类杀虫剂在土壤中的降解吸附特性及对地下水的影响

采用室内模拟实验方法,以太湖水稻土、江西红壤和东北黑土为代表性土壤,研究了噻虫啉等3种烟碱类杀虫剂在土壤中的降解、吸附特性,并利用GUS（Ground Ubiquity Score）指数分析了其对地下水污染的影响。结果表明,3种烟碱类杀虫剂在3种土壤中均较易降解,降解半衰期在5～31d之间,属于易降解农药,降解特性与土壤理化性质及农药本身性质有关。3种烟碱类杀虫剂在江西红壤、太湖水稻土与东北黑土中的吸附较好地符合Freundlich方程,Kd值在0.30～14.70之间,KOC在42.8～1750.9之间,属难吸附农药。吸附性强弱与农药本身溶解性和土壤有机质含量有关,水溶性越强吸附越弱,有机质含量越高,吸附性越强。3种烟碱类杀虫剂在太湖水稻土中的GUS值均小于1.8,而在江西红壤中,其GUS值均大于1.8,这3种杀虫剂在江西红壤中均有一定的淋溶性,对地下水均有一定的污染风险。

The Degradation and Absorption of Neonicotinoid Pesticides in Soils and Its Effect to Groundwater

Adsorption and degradation of three kinds of neonicotinoid pesticides in Taihu paddy soil, Jiangxi red soil and black soil were systematically studied using indoor simulation experiments, based on which the impact of neonicotinoid pesticides on groundwater was assessed with GUS index. The results showed that the three neonicotinoid pesticides were quickly degraded in the soils. The degradation half-life times was between 5 and 31 days, indicating they are easily biodegradable. Their degradation behavior attributed to both soil properties and the nature of pesticides themselves. The absorption of the three neonicotinoid pesticides on the selected soils followed Freundlich isotherm. The Kd values were between 0.30 and 14.70, KOC values between 42.8 and 1 750.9, which indicated these pesticides are difficult to be adsorbed. The extent of adsorption is related to the solubility of pesticides and soil organic matter content. High water-soluble pesticides showed high rates of adsorption. The pesticides also prefer to adsorb on soil with high organic matter content. GUS index of the three kinds of neonicotinoid pesticides in paddy soils at Taihu Lake region was less than 1.8. While at Jiangxi red soil, the value was over 1.8, which underscores the potential risk of groundwater contamination due to leaching.