Abstract: Pesticides are applied at high frequency during rice cultivation, and drained into the surrounding water bodies periodically from paddy water. Therefore, pesticide pollution in rice production can cause potential risk to the surrounding surface water. Risk assessment for pesticides used in rice paddy could provide scientific basis for the decision-making of pesticides environmental safety management. Exposure assessment is the key step of risk assessment. The exposure assessment models for pesticides used in paddy fields were summarized in present researches, including RICEWQ, Tier I Rice and PFAM models of the United States, MED-RICE and SWAGW models of the European Union, Aquatic PEC, PADDY model series and PCPF model series of Japan, TOP-RICE and PRAESS models of China, respectively. The background of model development, the conceptual models, the calculation formulas, the input parameters, the output results, and the characteristics and application of models were introduced. Differences of these models were compared from the aspects of simulation level, prediction accuracy and simulation scale. Limitations of existing models have been analyzed. Lastly, key points of future researches are put forward, including to complete and improve the rice-surface water exposure scenario system, to strengthen the validation of models and the comparison of prediction results between different models, and to develop Large-scale watershed integrated simulation models.

Key words: pesticide, rice paddy, surface water, exposure assessment model