Development And Case Study Of Aquatic Ecological Risk Assessment Technique For Using Pesticides In Paddy Fields

As a necessary step in the registration of pesticides applied in rice paddy, aquatic ecological risk assessment has provided powerful technical support in environment safety administration of these pesticides. Nowadays, surface water bodies surrounding paddy fields are seriously polluted by pesticides applied in rice paddies in China, but the basis of aquatic ecological risk assessment of pesticides applied in paddy field is very weak. Therefore, it’s necessary to carry out aquatic ecological risk assessment research of pesticides applied in paddy field.In this paper, primary studies on ecological risk assessment procedure, methods and assessment technique were carried out basing on the studies of abroad and combined with the characteristics of pesticides pollution of surface water in our country. And as a result, methods and procedure of aquatic ecological risk assessment of pesticides in paddy field as well as a set of assessment technique were established. The procedure includes three phases:problem formulation, analysis and risk characterization; and the process includes four tiers of each tier three important techeniques including effect evaluation, exposure assessment and risk characterization were developed.Based on the procedure and assessment technique, impact of azoxystrobin on aquatic organisms in the pond nearby paddy field was carried out. Firstly, the Med-Rice spreadsheet model was used to predict the risk, the result showed the exposure concentrations of azoxystrobin was2.766μg/L, the toxicity endpoint values (96h LC50,48h LC50,48h LC50) of azoxystrobin to Carassius auratus, Macrobrachium nippoensis and Eriocheir japonica sinemis were0.57,1.06and>1000mg/L, then calculated the risk quotient, which was0.0044、0.0025.<2.6×10－6, Then used PRAESS to predict, the exposure concentrations of azoxystrobin was3.32μg/L, the risk quotient was0.0047.0.0031、<3.3×10－6, and then paddy field modeling system concerning the risk assessment of azoxystrobin applied in rice paddy to aquatic organisms was conducted, the exposure concentration of azoxystrobin in fishpond was3.00μg/L,15days after applied in paddy field, the treatment group mortality of Carassius auratus, Macrobrachium nippoensis and Eriocheir japonica sinensis were0,2.5% and12%, the results indicated that the risk of azoxystrobin to Carassius auratus, Macrobrachium nippoensis and Eriocheir japonica sinensis were low and models predicted well with modeling system. The study results of paddy field modeling system could not only validate models, but also provide scientific basis for the safety of the use of azoxystrobin in paddy field.Finally, Med-Rice spreadsheet model was used to predict the risk of common used pesticides for rice paddies in our country and seven pesticides with moderate to high risk to aquatic organisms were screened, they are chlorpyrifos, profenofos, abamectin, triazophos, diazinon, carbendazim, and acetochlor.