Data supporting: [Beyond Dilution: How East Asian Monsoon Reshapes Bisphenol Fate and Risk via Source-Dependent Pathways]

The conventional paradigm in contaminant hydrology holds that flood events uniformly dilute pollutants, thereby reducing environmental risk. This study challenges that view by demonstrating that in complex river basins with spatially heterogeneous pollution sources, such as the Pearl River Basin, the East Asian monsoon acts as a differential processor. It reshapes contaminant fate and risk through source-dependent pathways. Using the Foshan reach of the Pearl River Basin as a natural laboratory, we reveal a stark dichotomy: industrial point sources are the dominant contributor in the Beijiang River (47% of the BPs load), whilst agricultural non-point sources are the dominant contributor in the Xijiang River (85%). Monsoon floods triggered divergent consequences. In the industrial Beijiang, however, elevated late-flood-season temperatures activated a “thermally amplified sediment release” mechanism. Supported by substantial sediment BPs reservoirs and field-observed shifts in partition coefficients consistent with thermal desorption, this inferred process likely contributed to a 4.6-fold increase in aqueous BPA concentrations, paradoxically elevating ecological risk during high-flow periods. Consequently, high ecological risk (RQ≥1.0) concentrated in lower Beijiang, directly mapping the industrial source-sediment legacy-thermal release cascade. Furthermore, BPAP posed a moderate human health risk during floods, potentially reflecting the emerging challenge of unregulated substitution of BPA with analogues whose environmental behavior remains poorly understood. We synthesise these findings into a predictive “source-process-risk” framework, which posits that effective risk mitigation in multifunctional basins requires a paradigm shift from uniform dilution-based assumptions to spatially explicit, process-informed management strategies that account for how climate dynamics differentially unlock legacy pollution.