The Behavior Of Pesticide Residues In Ophiopogonis, Chrysanthemun And Cultivated Soil

Radix Ophiopogonis and Chrysanthemum are the most characteristic traditional Chinese herbal medicines in Zhejiang province.In order to evaluate the safety of pesticides used on Radix Ophiopogonis and Chrysanthemum,the analytical methods of chlorpyrifos,carbendazim,chlorfluazuron and imidacloprid,degradation of chlorpyrifos,carbendazim,chlorfluazuron and imidacloprid in Ophiopogon, Chrysanthemum and cultivated soils were studied.The results showed that dynamics of chlorpyrifos,carbendazim,chlorfluazuron and imidacloprid followed the first order kinetics.The half-lives of chlorpyrifos,carbendazim in Ophiopogon and cultivated soil were 2.75～3.65 d(chlorpyrifos in soil),2.69～4.29 d(chlorpyrifos in leaf),3.06～7.07 d(carbendazim in soil) and 3.60～5.35 d(carbendazim in leaf) respectively,and the concentration of chlorpyrifos or carbendazim in fresh Radix Ophiopogonis increased quickly during the first few days,and peaked at 2～3 d then decreased,with half lives of 2.62～4.36 d(chlorpyrifos) and 2.01～3.60 d(carbendazim).The effect of temperature on chlorpyrifos,carbendazim in soil and dry Radix Ophiopogonis showed that the half-lives of chlorpyrifos were 4.29～10.18 d(soil,10～30℃), 13.33～20.32(dry root,5～20℃) and the half-lives of carbendazim were 6.54～13.13 d(Soil,10～30℃),28.29～35.18 d(dry root,5～20℃),which indicated that effect of temperature on chlorpyrifos and carbendazim in soil and dry Radix Ophiopogonis was significant.If 0.675 kg ai/hm~2 chlorpyrifos was sprayed two times a year,the minimum preharvest interval of 18 d was sufficient to ensure the chlorpyrifos residues in dry Radix Ophiopogonis not exceed the proposed MRL of 0.1 mg/kg.If 0.675 kg ai/hm~2 carbendazim was sprayed two times a year,the minimum preharvest interval of 15 d was sufficient to ensure the carbendazim residues in dry Radix Ophiopogonis not exceed the proposed MRL of 0.1 mg/kg.The half-lives of chlorfluazuron in chrysanthemum and soil were 6.64～8.68 d(soil),3.69～4.40 d(fresh fetal chrysanthemum),3.66～4.24 d(fresh chrysanthemum flowers);The half-lives of imidacloprid in chrysanthemum and soil were 4.89～6.38 d(field soil),3.44～3.98 d(fresh fetal chrysanthemum),2.10～2.21 d(fresh chrysanthemum flowers).The effect of temperature on chlorfluazuron,imidacloprid in soil and dry chrysanthemum showed that the half-lives of chlorfluazuron were 12.44～15.23 d(soil,10～30℃),41.75～48.46(dry chrysanthemum,5～20℃) and the half-lives of imidacloprid were 10.09～13.30 d(soil,10～30℃),15.33～23.98 d(dry chrysanthemum,5～20℃).If 1500 times 5%chlorfluazuron was sprayed two times a year,the minimum preharvest interval of 20 d was sufficient to ensure the chlorfluazuron residues in the dry chrysanthemum not exceed the proposed MRL 0.1 mg/kg.If 40 g ai/hm~2 imidacloprid was sprayed two times a year,the minimum preharvest interval of 15 d was sufficient to ensure the imidacloprid residues in the dry chrysanthemum not exceed the proposed MRL of 0.1 mg/kg.