An Empirical approach for ecological risk assessment of pesticides in surface and groundwater using monitoring data

• Pesticides were found in 82% of surface water and 60% of groundwater sites. • A new acute RQ method improves risk assessment using toxicity values and assessment factors. • Cluster analysis identified key pesticides: chlorantraniliprole (surface) and acrinathrin (ground). • Targeting these pesticides improved classification accuracy, achieving over 87% agreement. Pesticide contamination in aquatic environments poses significant ecological risks, necessitating accurate assessment methods to guide effective management strategies. This study aimed to develop an ecological risk assessment method for pesticides in surface and groundwater that better reflects actual field conditions. Traditional risk assessment methods, such as the Toxicity Exposure Ratio (TER) and chronic Risk Quotient (RQ chronic )have limitations that may overestimate risks and fail to capture transient exposure patterns. Our findings showed that traditional RQ assessments indicated potential risks at 29% of surface water sites and 33% of groundwater sites, with RQ values exceeding 1. To address these limitations, we developed an acute risk assessment approach (RQ acute ) and utilized cluster analysis. According to the RQ acute assessment, only one surface water site and ten groundwater sites had RQ values greater than 1, with acrinathrin and chlorantraniliprole identified as primary contributors to groundwater risk. This research demonstrates that the acute risk assessment approach, combined with cluster analysis, enhances the accuracy and practicality of ecological risk assessments for pesticides in aquatic environments. The proposed method aligns more closely with real-field situations, facilitating the identification of high-risk pesticides and sites, and supports the development of targeted management strategies to optimize resource utilization and improve environmental protection in agricultural water bodies.