百菌清在马铃薯中的最终残留及土壤中消解动态研究

On residue of chlorothalonil in harvested potato and its dynamic degradation mechanism in soil

为评价百菌清在马铃薯上的使用安全性及土壤中的消解动态残留,建立了百菌清在马铃薯及土壤中的残留分析方法,2016—2017年在湖南长沙和河北石家庄两地进行了720 g/L百菌清悬浮剂在马铃薯上的施用,分析了其有效成分百菌清在马铃薯上的消解动态和最终残留。马铃薯、土壤样品用体积比为1∶1的丙酮-乙腈的混合液振荡提取,提取液经盐析、浓缩后用乙腈定容,气相色谱法检测。结果表明,在添加水平为0. 02 mg/kg、0. 20 mg/kg和2. 00 mg/kg时,马铃薯中百菌清残留量检测方法的添加回收率为81. 1%～110. 5%,相对标准偏差(RSD)为4. 4%～11. 9%;土壤中百菌清残留量检测方法的添加回收率为82. 4%～111. 6%,RSD为6. 3%～10. 9%。百菌清在马铃薯上以高剂量(3 240. 0 g/hm^2)、低剂量(2 160. 0 g/hm^2) 2个剂量分别施药3次和4次,最后一次施药后7 d、14 d、21 d的马铃薯的最大残留量均值分别为0. 084 mg/kg、0. 026 mg/kg、0. 020 mg/kg。百菌清在土壤中的残留消解动态规律符合一级动力学反应模型,其消解半衰期为3. 63～8. 35 d,在土壤环境中较易降解。

Intends to establish a residue analysis method for assessing and degratation of the chlorothalonil in the potato and the soil so as to increase the safe application of chlorothalonil in thesoil and the dynamic mechanism of the residue digestion in it,we managed to apply the digestion dynamics to the study of the final residues of chlorothalonil in the potato after 720 g/L chlorothalonil suspension in the potato in Changsha,Hunan and Shijiazhuang,Hebei,respectively,in 2016 and 2017.On the purpose,we have extracted potato and soil samples by the mixture of acetone and acetonitrile(1:1,V/V),and,then,filtered via the Brinell funnel.The filtrate has been collected and vibrated in a stopper container with sodium chloride,and then acetone-acetonitrile phase and water phase can be stratified.And,then,when half of the solution has been concentrated to a degree of nearly half in dry state,the mixture can be fixed to 5.0 mL with acetonitrile and removed into the sampling bottle for observation and inspection via the gas chromatograph.The results of the test tend to show that there can be found a proper linear relation between the peak area and the mass concentration rate of chlorothalonil in a range of 0.01-2.0 mg/L,with the standard curve being equal to y=10352 x-59.5,and R^2=0.9996.At the additional levels of 0.02 mg/kg,0.20 mg/kg and 2.00 mg/kg,the sfforementioned method for the residue determination in the potato can also be put into the categorical range of 81.1%-110.5%,with the relative standard deviation(RSD)being 4.4%-11.9%.Besides,the method for the residue determination in the soil can also be added with a recovery range being of 82.4%-111.6%,and the relative standard deviation(RSD)being 6.3%-10.9%.Thus,the final residue testing results have revealed that chlorothalonil can also be managed to be dealt with the potato both at high(3 240.0 g/hm^2)and low dose(2 160.0 g/hm^2)3 times and 4 times,respectively,with the maximum residue mean time length for the potato treated for a period of 7 days,14 days and21 days when it was adopted in a ratio of 0.084 mg/kg,0.026 mg/kg and 0.020 mg/kg respectively,which have not been found higher than the MRL established by any other countries and regions in the world.The soil digestion dynamic testing results show that the digestion process of chlorothalonil in the soil tends to be a gradual reduction process and the dynamic regularity of the residue digestion in the soil proves consistent with the first-order kinetic reaction model.The half-life of the chlorothalonil residues prove to be 3.63 days to 8.35 days.And,in comparison,the half-life of the chlorothalonil residues in Changsha2016-2017 turn to be 8.35 days and 3.63 days and in Shijiazhuang 2016-2017,6.33 days and 5.64 days,respectively.Thus,it can be concluded that chlorothalonil is by nature easy to be degraded in the soil environment but not lead to the cumulative residue pollution in it.