Hydrological seasonality reshapes sources and health risks of potentially toxic elements in a megacity river system of the Beijing-Tianjin-Hebei urban agglomeration.

Hydrological seasonality causes significant shifts in the sources and health risks of potentially toxic elements in Beijing-Tianjin-Hebei urban river systems, with arsenic posing the highest risk.

• Why it matters: Understanding how seasonal hydrological changes influence PTE behavior is crucial for effective pollution management and public health protection in rapidly urbanizing regions.
• What they did: The study analyzed PTEs over a full hydrological year in a typical reclaimed water-influenced river system, identifying seasonal variations in sources, distribution, and risks through field sampling and Monte Carlo simulations.
• The result: Findings reveal higher pollution severity in the dry season but greater health risks from arsenic during the wet season, leading to a proposed management framework for targeted, season-specific pollution control.