Occurrence of Typical Organophosphate Esters in the Largest Tributary of the Yellow River with Water Supply and Irrigation Functions: Spatiotemporal Variation, Potential Sources, and Risk Assessment

Organophosphate esters (OPEs) are extensively present in aquatic environments and are ecologically hazardous. In this study, we investigated the spatiotemporal variation, potential sources, and ecological risk of seven typical OPEs in water samples collected from the largest tributary of the Yellow River during the wet, dry, and normal seasons. All target OPEs were detected; triethyl phosphate (TEP) and tris(2-chloroethyl) phosphate (TCEP) were the most commonly detected target compounds (100%). The results indicated that the total concentration of OPEs ranged from 0.73 to 2023.62 ng/L in water. Concentrations of OPEs were significantly higher in the normal season (12526.27 ng/L) and wet season (12047.81 ng/L) than in the dry season (7886.37 ng/L). The spatial distribution was dominated by Cl-OPEs and Aryl-OPEs, which were mainly concentrated in the central and lower sections with frequent urban activities. Principal component analysis and Spearman’s correlation analysis demonstrated that urban wastewater discharge, industrial production, and atmospheric wet deposition were potential sources of OPEs. The species sensitivity distribution and assessment factor were used for the ecological risk assessment of OPEs. The OPEs presented low ecological risk (RQ < 0.01) at different periods. However, tris(2-butoxyethyl) phosphate (TBEP) and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) posed relatively higher ecological risks.