Beyond Steady-State: An Integrated Framework Unveils BPAP as the Highest-Risk Bisphenol in a Dynamic River System

The paradigm for managing emerging contaminants is shifting from static concentration control toward dynamic risk forecasting. However, this transition is hindered by the lack of mechanistic models that can link nonlinear environmental processes to holistic risk prioritisation. Here, we present an integrated modelling framework that resolves driver collinearity, integrates multimedia risks, and apportions pollution sources. The framework combines three novel components: an Environmental Condition Index (ECI) to quantify synergistic environmental influences on contaminant release, an extended dual-media Toxicological Priority Index (ToxPi) for holistic risk integration, and an enhanced Positive Matrix Factorisation model (PMF-DMC) for spatially resolved source attribution. Applied to a complex watershed in the Pearl River Basin, the framework revealed a critical risk priority reversal: bisphenol AP (BPAP) emerged as the top-priority control pollutant, contrary to concentration-centric assessments that identified bisphenol A (BPA). This reversal underscores the inherent limitations of concentration-centric regulation and demonstrates the necessity of adopting dynamic, process-informed frameworks for managing emerging contaminants. The framework's transferable design establishes it as a predictive and adaptive tool for risk governance, offering a methodological advance for ecological modelling in non-stationary environments.