农药水解半衰期的pH值敏感性评价

pH value sensibility evaluation of pesticides hydrolysis half-life

为了量化环境pH值变化对农药半衰期的影响程度,基于不同环境pH值下的农药半衰期数据,建立了农药半衰期的pH值敏感性指数评价方法,并根据指数大小将敏感性分为3A、2A、1A、0、1B、2B和3B共7个等级。利用该方法对305种农药水解半衰期进行的评价结果:pH值敏感性指数在-1.67~3.31,指数平均值为0.50,指数绝对值平均值为0.60。多数农药的水解半衰期pH值敏感性指数为正值,在环境pH值提高时会促进水解。其中氨基甲酸酯类、二苯醚类和芳氧苯氧丙酸酯类除草剂,氨基甲酸酯类和拟除虫菊酯类杀虫剂,二甲酰亚胺类和苯并咪唑类杀菌剂尤为显著。而三嗪类和磺酰脲类除草剂则比较独特,总体上有随着pH值的降低水解加快的趋势。农药半衰期的pH值敏感性指数,能直观地反映环境pH值变化对农药半衰期的影响程度。

In order to quantify the influence of environmental pH value changes on pesticide half-life,a pH value sensibility index evaluation method was established based on pesticides half-life data under different environmental pH values.The sensibility was divided into seven grades including 3A,2A,1A,0,1B,2B and 3B according to the index.The results of the evaluation of the hydrolysis half-life of 305 pesticides showed that the pH value sensibility index ranged from-1.67 to 3.31,the average was 0.50,and the average of absolute value for index was 0.60.The pH value sensibility index of the hydrolysis half-life of most pesticides was positive,which will promote hydrolysis when the pH value increased in the environment.Carbamate,diphenyl ethers and aryloxyphenoxypropionate herbicides,carbamate and pyrethroid insecticides,dicarboximidies and benzimidazole fungicides were particularly significant.However,triazine and sulfonylurea herbicides were unique and had a tendency to accelerate hydrolysis when the pH value decreased.The pH value sensibility index of pesticide half-life can directly reflect the influence degree of environmental pH value change on pesticide half-life.