Research Of Fulfiprole Environmental Fate In The Paddy Fields And Risk Assessment For Aquatic Organisms

Flufiprole is a new pesticide of high efficient and low toxicity to fish and silkworm. In order to reveal the degradation mechanism and evaluate the risk of flufiprole to aquatic organisms after its application to the paddy field, the study investigates the degradation kinetics and mechanisms of Flufiprole in water and soil and the influencing factors. The absorption and migration behaviors of Flufiprole in soils were also studied. A multi-tiered ecological risk assessment method was established to study the environment behavior of flufiprole pesticide and its effects to aquatic organism in the field-fish pond-ecosystem. The main results and conclusion can be summed as follows:1. Degradation of flufiprole in the environment.Degradation of flufiprole in water via various mechanisms, hydrolysis and photolysis, and degradation in5different types of soils was investigated under laboratory conditions. Results show that flufiprole is rather stable and not easy to break down in acid and netural solutions, but is easy to hydrolyze in alkine solution, with half-life of26.7d in solution at pH9.0and50℃. Through identification of the hydrolytic products, it could be inferred that the degradation of flufiprole in water is alkali-catalyzed hydrolysis. Under the artificial light of an Xe lamp,in light intensity of4000lx and UV intensity of25μW·cm-2, the half-lives of flufiprole in pure water, Qinghuai River water and Ge Lake water was96.0min,63.0min and37.7min, respectively, and fipronil was its main photolytic product. The half-lives of flufiprole were much longer in aerobic soils compared to anaerobic condition. The results showed that flufiprole was degraded the fastest in fluo-aquic soil of Shanxi, the half-lives in aerobic and anaerobic conditions was89.3d and69.2d.2. Adsorption and migration of flufiprole in soils.Adsorption and migration of flufiprole in soil and affecting factors were studied with vibrating equilibrium method and thin-layer chromatography. Adsorption of flufiprole in5soil samples tested was well fitted with Freundlich model. The sorption capacity followed an order of black soil> paddy soil> fluo-aquic soil of Shanxi> red soil> yellow brown soil. Flufiprole was easy to be absorbed by soil (Kf values ranged from87.9to599.6). The flufiprole adsorption by soil belonged to physisorption with changes of free energy less than40KJ/mol, the main factor affecting the adsorption was organic matter content in the soil. Since the thin layer migration test Rf value of5soils ranged from0to0.17, flufiprole was not easy to migrate in soil. 3. Study on the safety of flufiprole to aquatic organisms as it was used in paddy field.A multi-tiered ecological risk assessment method was used to study the effect of flufiprole pesticide to aquatic organism in the rice paddy-fish pond ecosystem. Results showed that96h LC50of flufiprole to Eriocheir sinensis, Macrobrachium rosenbergii was0.40and0.011mg·L-1, respectively. After application, with the exception of a few drift losses, flufiprole main residues in rice plants and paddy water. The highest concentration of flufiprole in paddy water was0.034mg·L-1for simulation ecosystem and0.024mg·L-1for field ecosystem. Flufiprole degraded tardily in paddy field water with half-lives of5.0d and3.12d in simulation ecosystem and field ecosystem, respectively. When a part of paddy water was overflowerd into the treated fish-pond after24h, the highest concentration of flufiprole in adjacent fish-pond water reached0.0018mg·L-1in simulation ecosystem and0.0011mg·L-1in field ecosystem. Flufiprole degraded tardily in pond-water with half-lives of8.9d and7.2d in simulation ecosystem and field ecosystem respectively. It is suggested that flufiprole posed an potential risk to Macrobrachium rosenbergii and a low risk to fish and Eriocheir sinensis.