Rice Pesticides Ecological Risk Assessment Utilizing Standardized Aquatic Microcosm Simulating Aquatic Ecosystems In Yangtze Delta Paddy Area

Based on the deep study on the structure of water ecological communities in typical paddy fields in Zhejiang Province we have established a Standardized aquatic microcosm governed by zooplankton community,and with typical sediments and submerged macrophyte.And the reproducibility and stability of the system are studied.The results show that the standardized microcosm system is well reproducible and the system can be stably maintained for no more than 35 days.In the typical ecological system of Zhejiang Province the chlorpyrifos,butachlor and triadimefon residues were highest.We use the standardized aquatic microcosm to assess their effects on aquatic ecosystems and obtain no observed effect concentration of zooplankton community level(NOECcommuntiy).NOECcommuntiy of chlorpyrifos was 0.83/0.55 ?g/L(nominal concentration/actual concentration).NOECcommuntiy of butachlor was greater than 640/549.59 ?g/L.The NOECcommunity of triadimefon was greater than 2500/2078.88 ?pg/L.According to the actual exposure concentrations of the three pesticides in the typical rice area aquatic ecosystems in Zhuji City Zhejiang Province,chlorpyrifos actual exposure concentration was much greater than its NOECcommunity.It was considered that chlorpyrifos had high ecological risk on the zooplankton community in the local aquatic ecosystem.And the actual exposure concentration of butachlor and triadimefon was lower than that of NOECcommunity so it was considered that the ecological risk was low.A set of research model for studying the effects of pesticide mixture exposure on ecological communities was established:orthogonal test design(set exposure concentration combination treatment)-standardized microcosm(mixed exposure test)-PCA analysis(quantification of zooplankton community succession)-redundancy analysis(analysis of mixture fraction contribution to the total effect)-ANOVA(analysis significance of difference).The effect of mixed exposure of chlorpyrifos ·butachlor-triadimefon on the level of zooplankton community was studied using of the model.The results showed that the mixed exposure of the three pesticides resulted in a significant change in the zooplankton community when the exposure concentration of chlorpyrifos butachlor and triadimefon did not exceed NOECcommunity.It was speculated that the three pesticide mixed exposures produced synergistic synergies(Zooplankton community level)and the predominantly synergistic effect is butachlor.In order to evaluate the risk of pesticide in the environment the risk factors of the mixed exposure were established.The model of the chlorpyrifos-butachlor-triadimefon was studied by using the Standardized aquatic microcosm-orthogonal experiment design and multivariate statistical analysis.The results showed that the mixed exposure of the three pesticides resulted in a significant change in the zooplankton community when the exposure concentration of chlorpyrifos butachlor and triadimefon did not exceed NOECcommunity.It was speculated that the three pesticide mixture exposure has synergies on zooplankton community level.