A Comparative Study On Different Models For Groundwater Pesticide Exposure

Pesticide groundwater risk assessment is an important conpnent of pesticide environmental assessment and a necessary step in pesticide registration. It helps to mitigate and manage pesticide enviromental risk. In the risk assessment, exposure models have been used to estimate the pesticide concentrations in the groundwater. The USA and the EU have developed different exposure models that are used in their pesticide registration system. Pesticide environmental risk assessment in our country started late, but developed rapidly in recent years. Cooperated with EU scientists, China has developed a groundwater pesticide exposure model China-PEARL based on EU model PEARL and China-PEARL starts to be used for pesticide environmental risk assessment.This study aims to run pesticide groundwater risk assessment model PRZM-GW of USEPA with the data of our standard scenario. By comparing the exposure analysis of PRZM-GW to China-PEARL, verify the authority of China-PEARL, and find out the main factors that affect the results of models to provide reference for the construction of our own groundwater exposure model with completely independent intellectual property right.Weifang scenario for PRZM-GW was established to evaluate the pesticide groundwater risk in China by using the data of Weifang standard scenario in China-PEARL and other data required. On this basis,56pesticides applied on5crops in145application methods were calculated by SCI-GROW, PRZM-GW and China-PEARL in weifang scenario. Then risk was characterized with RQ which is calculated by guidance value GV. RQ was used to determin if the risk of pesticide was acceptable or not.The comparative analysis on PRZM-GW and China-PEARL shows that:1. The groundwater risk of8pesticides,13application methods was unacceptable. PRZM-GW shows that the pesticides with unacceptable risk included atrazine, acetochlor, alachlor, fomesafen, omethoate and carbendazim. And the pesticides with unacceptable risk evaluated by China-PEARL included carbendazim, fomesafen, carbofuran and dimethoate. Among them, carbendazim and fomesafen were assessed unacceptable risk by both PRZM-GW and China-PEARL.2. Comparison of the effects of pesticide properties on model PEC betwenn PRZM-GW and China-PEARL was made. Koc has the biggest effect on PEC. Koc>400L kg-1could be adopted as a preliminary determination of PEC<0.1μg L-1. The PEC show clearly linearly correlation with logged soil aerobic half-life. The PEC of the both models increase steeply when soil aerobic half-life>10d. Hydrolysis half-life is used in PRZM-GW and determines the variation trend of pesticide concentration in groundwater. Solubility in water is an input option of China-PEARL which affects lightly on PEC.3. The PEC of two models were linear with the application rate of pesticide.Through the comparative study above, SCI-GROW might underestimate the risk of some pesticides with extremely high risk on account of its tight range of PEC distribution. So, it is not recommended that to use SCI-GROW for pesticide groundwater risk assessment in our country. As the official model of USEPA that used in pesticide registration, PRZM-GW has public approval. And the predicting tendency of PRZM-GW and China-PEARL was highly consistent. It verifies the credibility of China-PEARL. The conservation of PRZM-G and China-PEARL was ranged, that is PRZM-GW> China-PEARL. The PEC of China-PEARL are closer to reality. It is consistent with the Tier that China-PEARL is applied in.