Dissipation Residue And Ecological Toxicology Evaluation Of Hexaconazole In Paddy Field

The residues and the dissipation dynamic rules of hexaconazole in rice plant,rice husk,brown rice,paddy water and soil were studied in this paper.Also studied the toxicology effect of hexaconazole in zebrafish,and evaluated the security of hexaconazole in the paddy field environment through by the acute toxicity indexes,so as to provide scientific experiment datas for the rational use and the pollution effective control of hexaconazole in paddy field.The main results were as follows:1.The detection methods of hexaconazole in brown rice,rice husk,rice plant,paddy water and soil were established.The samples were extracted by methanol,n-hexane and methylene chloride,column chromatography purification,and then detected by gas chromatography(with electron capture detector).The limit of detection(LOD)was 2.0×10-11g,and the limit of quantification(LOQ)was 0.005 mg/L for paddy water,0.02 mg/kg for soil,plant,rice and rice husk.The fortified concentration of hexaconazole in rice plant,rice husk,brown rice and soil were 0.02mg/kg,0.2mg/kg and 2.0mg/kg,the fortified concentration of hexaconazole in paddy water was 0.005mg/kg,0.05mg/kg and 1.Omg/kg.The adding recovery levels ranged from 82.75%to 103.68%,the relative standard deviations ranged from 1.87%to 5.86%.This method has good sensitivity,high accuracy,so it can be used to the residues detection of hexaconazole in rice plant,rice husk,brown rice,paddy and soil.2.From 2013 to 2014,the dissipation dynamic rules of hexaconazole in rice plant,paddy water and soil in different natural environmental condition in Changsha,Nanjing and Zhengzhou were studied.The results showed that the dissipation rules were all consistented with first order kinetics equation,and the half-lifes of hexaconazole in rice plant,paddy water and soil were 4.12?7.33 days,2.89?7.17 days and 11.77?23.18 days,respectively.So as to say,the hexaconazole belongs to easily degradable pesticide.3.From 2013 to 2014,the concentration of 50%hexaconazole wettable powder were 75 and 112.5 g a.i/ha,applied 2 or 3 times in different natural environmental condition in Changsha,Nanjing and Zhengzhou.The final residual tests results show that when the recovery intervals were 15 days and 30 days,the residues in rice were less or more than the MRL of China(0.1 mg/kg);when the recovery interval was 45 days,the residues in rice were all less than the MRL(0.1 mg/kg).In order to ensure the eating safety of rice,we recommended that the dose should not exceed 75 g a.i/ha,the drug delivery times should not exceed 2 times,the applying pesticide spray interval was 7 days,the harvest interval was 45 days.4.The acute toxicity of 50%hexaconazole wettable powder in zebrafish was studied in this paper.The test results show that the median lethal concentration(LC50)of 50%hexaconazole wettable powder in zebrafish in 24 h,48 h,72 h,96 h were 7,20 mg a.i/L,6.90 mg a.i/L,6.90 mg a.i/L and 6.90 mg a.i/L,respectively.According to the acute toxicity evaluation standards of chemical pesticides in fish,the acute toxicity of 50%hexaconazole wettable powder in zebrafish was poisoning.