五氟磺草胺在稻田中的消解动态及残留特性

建立了超高效液相色谱-质谱联用检测五氟磺草胺在水稻植株、稻田土壤、田水和糙米中残留的分析方法，结合田间试验研究了五氟磺草胺在稻田环境中的消解及残留特性，并对稻米中五氟磺草胺残留的膳食暴露进行了初步评估。结果表明:在0.005~0.5 mg/L范围内，五氟磺草胺的质量浓度与对应的峰面积间呈良好线性关系，检出限（LOD）为0.001~0.002 mg/kg，定量限（LOQ）为0.003~0.005 mg/kg。在0.005~0.5 mg/kg添加水平下，五氟磺草胺在水稻植株、稻田土壤、田水和糙米中的平均回收率在89%~106%之间，相对标准偏差在2.8%~8.5%之间。浙江、福建和黑龙江2年3地的田间试验表明:0.025%五氟磺草胺颗粒剂在水稻植株、稻田土壤和田水中的消解半衰期分别为1.5~3.3，3.0~4.7和1.6-3.0 d，说明该药剂在稻田环境中消解速率较快。以五氟磺草胺有效成分含量37.5和56.3 g/hm2分别施药1次，于水稻成熟期采样检测，发现其在糙米中的残留量低于0.005 mg/kg，表明其膳食摄入风险很低，该研究结果可为五氟磺草胺风险评估提供一定参考。

Dissipation and residue characteristic of penoxsulam in rice paddy

A qualitative and quantitative method using UPLC-MS/MS was developed for the analysis of penoxsulam residues in rice paddy samples including rice plant, paddy water, soil and brown rice. The residue and dissipation of penoxsulam in the rice paddy were investigated for dietary risk assessment of residual penoxsulam in brown rice. Based on the analytical approach, the satisfied linearity was obtained in the concentration ranged from 0.005 mg/L to 0.5 mg/L with the limit of detection(LOD) from 0.001 mg/kg to 0.002 mg/kg and the limit of quantification(LOQ) from 0.003 mg/kg to 0.005 mg/kg. With the spiked concentrations of 0.005 to 0.5 mg/kg, the average recoveries varied from 89% to 106% with the relative standard deviation (RSD) from 2.8% to 8.5%. Those results indicated that this new method has favorable accuracy, precision and sensitivity, which meets the demand of pesticide residue analysis and is applicable for effective monitoring the penoxsulam residual in rice paddy field. The results of residue dynamics indicated that the half-lives of penoxsulam in rice plant, paddy soil and water were 1.5-3.3 d, 3.0-4.7 d, and 1.6-3.0 d, respectively. Hence, penoxsulam belongs to a class of readily-degradable herbicide in the rice paddy environment. After the application of 0.025% penoxsulam granules twice with the dosage at 37.5 g a.i./hm² and 56.3 g a.i./hm², respectively, the highest residues of penoxsulam in brown rice were lower than 0.005 mg/kg and the dietary risk was low in which the risk quotient was 2.22×10^-4, which was obviously lower than risk threshold. Taken together, our data can be used as an important methodological and statistical basis for the further integrated evaluation of dietary risk and MRL formulation.