丙硫克百威及其主要代谢物在棉田中的残留降解研究

将20% 丙硫克百威乳油施于棉田, 采用气相色谱分析技术研究了丙硫克百威及其主要代谢产物在棉田中的残留降解情况。结果表明: 1) 丙硫克百威在棉田土壤和棉叶中可很快降解转化为克百威, 克百威在棉叶中的最大残留值出现在施药后当天, 在棉田土壤中出现在施药后3d, 说明丙硫克百威在棉叶中的降解速率快于在棉田土壤中; 2) 克百威可进一步转化为3-羟基克百威, 后者在棉叶和棉田土壤中的残留量表现为先升后降, 到第10 天才达最大值,明显滞后于克百威最大值出现的时间; 3) 丙硫克百威和克百威在棉叶和棉田土壤中的降解过程符合Ct= C0·e-kt方程, 它们在棉叶中的降解半衰期为3.6～4.4d, 在棉田土壤中则为10.4～11.9d; 4) 当丙硫克百威的用量按有效成份计为200～400g/hm2, 每季棉花施药3～4 次(每次间隔7d) , 最后一次施药距采收时间分别为20、30d时, 丙硫克百威(含克百威和3-羟基克百威) 在棉籽和棉田耕层土壤中的残留量均小于0. 5 mg/kg。

Study on the Residue and Degradation of Benfuracarb and its Ma in Metabolites in Cotton Field

The residue and degradat ion of benfuracarb and its main metabo lites were studied by gas chromatography, after 20% benfuracard EC had been applied to the cotton field. The results are as follows: (1)Benfuracarb could degrade to carbofuran rapidly in the cotton field so ils and cotton leaves. The h ighest residue of carbofuran in the cotton leaves came out in the same day of the insect icide applied, but the highest residue in the cotton field so il came out in the third day after the insecticide applied. It shows that the degradation rate of benfuracrb in the cotton leaves is faster than in the cotton field soil. (2)Carbofuran could degrade to 3-hydroxycarbofuran. The 3-hydroxycarbofuran’s residue levels in the cotton field soil and cotton leaves increase at first, and then decrease. Its highest residue came out in the 10th day, and clearly later than that of carbofuran. (3) The degradation of benfuracarb and carbofuran in cotton field soil and cotton leaves could be described with the equation: Ct= Co·e-kt, the half life of them 3.6～4.4 days in cotton leaves, and 10.4～11.9 days in the soil. (4)When 200～400 g/hm2 of benfuracarb (a. i) were app lied 20 days and 30 days before the harvest, the residue of benfuracarb ( included benfuracarb, carbofuran and 3-hydroxycarbofuran) was all less than 0.5 mg/kg in cotton-seed or in the tillage soil of cotton field.