土壤中毒死蜱及主要代谢产物的降解与生态风险

为探讨施用农药毒死蜱后土壤中毒死蜱及其主要降解产物3，5，6-三氯吡啶-2-酚（TCP）污染分布特征，评估农田土壤环境中毒死蜱及TCP的环境风险，以玉米、小麦和大豆3种作物农田为研究对象，开展旱地农田田间试验。通过对施用后不同时间农田土壤中毒死蜱浓度检测发现，土壤中毒死蜱均在前期消解较快，后期逐渐变缓。小麦、大豆、玉米种植土壤中毒死蜱的半衰期为7.86~24.84 d（均小于30 d），消解速率常数为0.027 9~0.088 2 d^-1。前期均表现为0~5 cm土壤中毒死蜱残留量最大，15~20 cm土壤中毒死蜱残留量最小，即随着深度的增加土壤中毒死蜱的残留量逐渐降低；随着时间的延长，0~10 cm土壤中毒死蜱残留量逐渐减少，10~20 cm土壤中毒死蜱残留量逐渐增加。TCP比母体毒死蜱更容易迁移，对环境的污染风险较高。随着毒死蜱施用剂量的增加，小麦、大豆、玉米3种作物种植土壤中毒死蜱及TCP的短期和长期生态风险均增大。超推荐剂量施用毒死蜱导致毒死蜱及TCP产生较高的短期和长期生态风险，TCP生态风险在3种作物农田中均达到了高风险等级。

Degradation characteristics and ecological risk of chlorpyrifos and results of its degradation in dryland soils

The environmental pollution risk of chlorpyrifos and TCP in dryland soils is getting increased attention. Chlorpyrifos and TCP distribution characteristics after the application of chlorpyrifos in the field areas of corn, wheat, and soybean crops were discussed, and their environmental risks concerning soil pollution were assessed. After its application, it was observed that chlorpyrifos in soils removed quickly in the early stage and its spread gradually slowed down. The half-life of chlorpyrifos in wheat, soybean, and corn-growing soils was 7.86 d to 24.84 d(all<30 d)and the digestion rate constant was 0.027 9 d^-1 to 0.088 2 d^-1. In the early stage, chlorpyrifos residue is highest in the 0~5 cm soil layer and lowest in the 15~20 cm soil layer. With the increase in the depth of soil, chlorpyrifos residue gradually decreased. The residue of chlorpyrifos in the 10~20 cm layer of soil gradually increased in later stages. Furthermore, TCP is more liable to be removed, and thus the risk of environment pollution is high. With the increase in the dosage of chlorpyrifos, short-term and long-term ecological risks of chlorpyrifos and TCP showed an increase in the soils growing wheat, soybean, and corn crops. When the superrecommended dosage was administered to the these three crops, chlorpyrifos and TCP had higher short-term and long-term ecological risks, with the TCP ecological risk reaching maximum risk level in all the three crops.