Water quality criteria derivation and ecological risk assessment for organophosphorus pesticides

Organophosphorus pesticides (OPPs) are a group of neurotoxic compounds that can cause neural dysfunction, overstimulation, paralysis, and even death to numerous non-target organisms. Despite their potential ecological impacts, there is a lack of research on water quality criteria (WQC) for OPPs, which hinders the risk assessment for these pollutants. This study aimed to derive short-term and long-term water quality criteria (SWQC and LWQC, respectively) for eight common OPPs through the species sensitivity distribution (SSD) methodology. The ecological risk of these compounds in aquatic environments was consequently assessed using a four-level tiered approach. The results showed that the derived SWQC ranged from 0.0245 μg/L (chlorpyrifos) to 18.6 μg/L (dimethoate), while the LWQC ranged from 0.326 ng/L (chlorpyrifos) to 0.354 μg/L (dimethoate). OPPs were widely recorded in different waters with concentrations up to 40.9 μg/L. The tiered approach results indicated that most OPPs had a low acute risk but a severe chronic risk. The estimated chronic hazard quotients (HQ) were calculated with a maximum of 4782, the exceedance probabilities with a maximum of 97.6%, and the overall probabilities (ORP) with a range of between 0.08% and 11.5%. These findings suggest that the contamination of OPPs in aquatic environments warrants further concern.