Study On Environmental Behavior And Pollution Features Of Chiral Pesticides Enantiomers

About more than 30% commonly used pesticides are chiral in China. The two enantiomers have the same physical and chemical properties, however their bioactivity, toxicity, and absorption, distribution and degradation in organisms and the environment are usually totally different. Therefore, it is necessary to investigate the enantioselective behaviors of the enantiomers of chiral pesticides in the environment. In this work, we studied the enantioselective degradation and stability of chiral herbicides S-metolachlor, ethofumesate, napropamide and fluazifop-butyl in order to evaluate the environmental risks and supply some data for optical pure product development. The main works are as follows.The chiral separation and residue analysis method of S-metolachlor were developed. The degradation of S-metolachlor in soil and corn plant in Anhui and Heilongjiang province was investigated. The degradation of S-metolachlor in soils was much slower than that in maize plants, and the half-lives of S-metolachlor in soils ranged from 12.0 to 12.4 d, while the half-lives in corn plants only ranged from 0.80 to 1.10 d. The degradation of S-metolachlor in Anhui corn plant was faster than that in Heilongjiang corn plant. We also studied the stability of S-metolachlor, the results showed that S-metolachlor was configurationally stable in the degradation in soil and corn plants indicating there was no isomerization.Chiral separation of ethofumesate enantiomers was achieved on a chiral HPLC column, and an accurate and efficient sample pretreatment method was established. The degradation of ethofumesate in soils and sugar beet plants in Ningxia, Anhui, Heilongjiang and Inner Mongolia were investigated. The results showed that the degradation of ethofumesate in soils was much slower, and the half-lives was from 14.44 to 63.01d, and the degradation rates in four soils were difference, k (Anhui)>k (Heilongjiang)>k (Inner Mongolia)> k (Ningxia). Compared with soils, the degradation of ethofumesate in sugar beet plants was much faster, and the half-lives was from 0.75 to 1.94 d. Enantioselective degradations of ethofumesate were found. In Ningxia sugar beet plant, (-)-ethofumesate dissipated faster than (+)-ethofumesate, while (+)-ethofumesate showed a faster degradation in Inner Mongolia sugar beet plant.The stereoselective degradation and transformation of the enantiomers of the herbicide fluazifop-butyl were studied to investigate the environmental behavior and chiral stability of the optical pure product. Chiral separation and prepare of fluazifop-butyl enantiomers was achieved on a chiral HPLC column, and a validated enantioselective residue analysis methods were developed. The stereoselective degradation of the enantiomers of the herbicide fluazifop-butyl in Beijing, Heilongjiang and Anhui soil were studied. The results showed that R-(+)-fluazifop-butyl was preferentially degraded in Beijing soil, but in Anhui soil, S-(-)-fluazifop-butyl dissipated faster. R-(+)-fluazifop-butyl was chiral stable in the process of degradation in soils. The effects of pH on the degradation showed fluazifop-butyl enantiomers degraded faster in alkaline conditions, while in acidic water fluazifop-butyl enantiomers degraded slower. There was significant enantioselectivity of the degradation of fluazifop-butyl in Shangzhuang Reservoir, S-(-)-fluazifop-butyl dissipated faster. Under field condition, the enantioselective dissipation of fluazifop-butyl in tomato, cucumber, pakchoi, rape and soil was investigated. S-(-)-fluazifop-butyl dissipated faster than R-enantiomer in tomato and cucumber, while R-(+)-fluazifop-butyl showed a faster degradation in pakchoi, rape and soil. The enantioselective dissipation of fluazifop-butyl in rabbit plasma in vivo and in vitro was investigated. Fluazifop-butyl was rapid degraded to fluazifop, formation and degradation of fluazifop was obvious selectivity. To confirm the results in vivo, enantioselective metabolism of fluazifop-butyl in plasma in vitro was investigated. The results showed that was fluazifop-butyl metabolized quickly and the metabolic process were significantly enantioselective, S-(-)-fluazifop-butyl dissipated faster than R-enantiomer. In all experiments, R-(+)-fluazifop-butyl only degraded to R-(+)-fluazifop, indicating that the degradation of R-(+)-fluazifop-butyl with chiral stability.The chiral separation of napropamide enantiomers was achieved by a chiral HPLC method, and their absolute configurations were confirmed by optical rotatory dispersion (ORD). The stereoselective degradation of napropamide in tomato, cucumber, rape, cabbage and soil were investigated. Napropamide dissipated rapidly in vegetables with half-lives only of 1.13-2.21 days, but much more slowly in soil with half-live of 11.95 d. Slight stereoselective degradation of the two enantiomers was only observed in cabbage, and there was no enantioselectivity in other vegetables and soil. The two individual enantiomers were prepared by HPLC, based on which the phytotoxicity of the enantiomers of napropamide to cucumber, soybean, and the bioactivity to the target weeds poa annua and festuca arundinacea were studied. The results showed napropamide could inhibit the normal growth of soybean and cucumber. To a certain extent, napropamide could induce the oxidative stress in soybean and cucumber, because the activities of SOD and CAT in cucumber and soybean were obviously inhibited by napropamide, and (-)-napropamide was more toxic than (+)-napropamide. For the target weeds poa annua and festuca arundinacea, (-)-napropamide was more active than (+)-napropamide.