Temporal and Spatial Distribution, Pollution Characteristics, and Ecological Risk Assessment of Organophosphate Esters (OPEs) in the Water Body of Poyang Lake Inlet

As critical conduits for pollutant enrichment and transformation, lake inlets govern the biogeochemical cycling of emerging contaminants. This study investigated the occurrence, spatiotemporal heterogeneity, and source–sink dynamics of 15 organophosphate esters (OPEs) in the major inflowing rivers of Poyang Lake, China. Using UPLC–MS/MS, positive matrix factorization (PMF), and risk quotient (RQ) modeling, we identified the mechanisms driving pollutant distribution across three hydrological periods. Alkyl-OPEs (58.19%) and chlorinated OPEs (40.42%) dominated the contaminant burden, with TCPP and TEP identified as the primary congeners. Concentrations exhibited a distinct seasonal gradient, with higher levels during the dry season and lower levels during the wet season, controlled by seasonal hydrological dilution versus evaporative and stagnant accumulation. PMF indicated that source contributions shifted with hydrology: intense wet-season precipitation flushed non-point sources from waste and electronic products (45.1%), while reduced dry-season flow concentrated mixed inputs from agricultural runoff and ship traffic (50.7%). Ecological risk assessment identified EHDPP, TCrP, and TCPP as high-risk contaminants (RQ ≥ 1.0), posing direct threats to aquatic population. These findings highlight the need for adaptive, season-specific management of emerging contaminants at the river–lake interface, specifically by implementing enhanced interception of surface runoff during the wet season and enforcing stringent regulations on localized shipping emissions during the dry season to protect freshwater ecosystems.