Atmospheric Mercury Variability at a High-Altitude Site in East China: The Significant Role of Temperature-Driven Natural Source Contributions

Both anthropogenic activities and natural sources can affect the atmospheric mercury concentrations; however, their contributions are not accurately quantified. Here we present online measurements of total gaseous mercury (TGM) at a high-altitude mountaintop (1545 m asl) in East China. Statistically significant differences in TGM concentrations were observed during the cold season (2.35 ± 0.65 ng m–3), the 2022 Beijing Winter Olympics (2.09 ± 0.43 ng m–3), and the warm season (3.61 ± 1.78 ng m–3). Most air pollutants generally decreased from cold to warm seasons, whereas TGM concentrations clearly increased with rising temperatures. A trained generalized additive model revealed that anthropogenic emissions dominated TGM variability in the cold season, while the east-south wind directions and temperature-driven natural sources played the leading role in the warm season in association with long-range transport. Scenario analyses replacing individual variables in the warm season indicated that contributions from anthropogenic emissions slightly decreased, while natural emissions associated with elevated temperature increased TGM by 0.83 ng m–3 on average, accounting for ∼23% of total TGM concentration. Our findings highlight the significant role of natural source emissions, which are nonlinearly driven by temperature, in the variability of atmospheric mercury in the upper air of developed regions in the context of declining anthropogenic emissions and global warming.