A source-informed framework for prioritizing emerging contaminants in complex watersheds: Hazard-exposure integration and field stress testing.

Regional management of emerging contaminants (ECs) is constrained by expanding chemical space, diverse sources, and limited monitoring coverage. We developed a source-informed regional prioritization framework integrating intrinsic hazard and exposure evidence. Intrinsic hazard comprised persistence, bioaccumulation, ecotoxicity, and human-health hazard, while exposure combined regional occurrence evidence, local emission potential derived from outfall and sector information, and a fate-adjusted relative exposure score. The two domains were geometrically integrated to generate a watershed-specific priority inventory. Applied to an industrially complex watershed, the framework ranked 423 candidate ECs and identified 80 priority compounds, with Tier I including PFOS, several PCBs, BPA, and PFOA. Targeted PFAS and PCB monitoring provided a field stress test across distinct mobility and partitioning regimes. Framework-derived ranks were significantly concordant with empirical RQ ranks (Kendall's τ=0.58-0.71, p < 0.001), and the top five framework-priority compounds accounted for 89.2% of cumulative empirical RQ within the measured subset. Sensitivity analyses showed that the priority structure remained generally stable under tested source-scoring, fate-model, and MCDA perturbations. The resulting inventory supports targeted monitoring, source tracing, and priority control in the study watershed.