Residue dynamics of pyroxasulfone in the soil and its safety assessment on following plants
In this paper,ultra performance liquid chromatography(UPLC-PDA)was used to detect the residue dynamics of pyroxasulfone in soil,and the risk of phytotoxicity of pyroxasulfone in soil to following plants was evaluated by indoor pot experiment.The results showed that the accuracy of the method was high.The average recovery of pyroxasulfone was 83.76％-90.63％and RSD was 1.96％-6.69％.The degradation equation was CT=0.338 1e-0.006 1T and the half-life was 113.6 d.The toxicity of different content of pyroxasulfone in soil to 32 plants was determined.The results showed that when the content of pyroxasulfone in soil was 0.1 mg/kg,the inhibition rate of fresh weight of Taraxacum mongolicum,amaranth,lettuce,astragalus sinicus,tomato,spinach,okra and fennel was higher than 50％,and the risk of residual pesticide damage in soil was extremely high.The inhibition rate of fresh weight of Shanghai green,mung bean,mustard,chrysanthemum,cabbage,lettuce,pepper,eggplant,sorghum,rice,sesame and cucumber plants was 30％-50％,which was of high residual phytotoxicity risk.The inhibition rate of fresh weight of rape,clover and tobacco was 10％-30％,which was of the risk of medium residual pesticide damage.The inhibition rate of sunflower,soybean,corn,wheat,cotton and fresh weight was less than 10％and the risk of pesticide residue in soil was low.The toxicity test results of some plants showed that the IC30 and IC90 values of pyroxasulfone on spinach were 0.009 mg/kg and 0.491 mg/kg,respectively,and those on sorghum were 0.093 mg/kg and 0.726 mg/kg,respectively,indicating that the combination of the two plants can serve as indicator plants for pyroxasulfone residues in soil.IC10 values of pyroxasulfone on Alfalfa,wheat,soybean,and corn were 1.063,0.911,1.101,and 3.724 mg/kg,respectively,which were twice as much as the initial deposition of pyroxasulfone in the field(0.712 mg/kg).The above results indicate that pyroxasulfone is highly safe to alfalfa,wheat,soybean and corn,which are considered safe crops for subsequent crop rotation after using pyroxasulfone.
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