Particulate mercury in a suburb of the Yangtze River Delta, China: Characteristics, sources and health risk assessment

This study investigates the characteristics, sources, and health risks of particulate-bound mercury (PBM) in PM₂.₅ from a suburban site in Nanjing, within the Yangtze River Delta, China. Seasonal sampling conducted in 2019 revealed a mean PBM concentration of 106 ± 115 pg/m³, with the highest levels in autumn. The PBM/PM₂.₅ ratio indicated significant anthropogenic influence. The estimated annual dry deposition flux of PBM was 39.86 μg/m²/yr. Health risk assessment determined that the non-carcinogenic risks from PBM exposure were below the safety threshold (Hazard Index < 1) for both children and adults. However, children were found to be more vulnerable, with risk levels approximately 11 times higher than adults, primarily through the ingestion pathway. Back-trajectory analysis indicated that air masses influencing the site originated from local, regional, and long-range sources. The findings underscore that while current PBM levels pose minimal immediate health risks, the heightened susceptibility of children and the significant dry deposition flux warrant continued monitoring and further investigation into the complete atmospheric mercury cycle in this economically vital region.