Global Mercury Emissions from Open Biomass Burning Estimated Using a Mass-Balance Approach

Mercury (Hg) emissions from open biomass burning (OBB) represent a significant component of global atmospheric Hg cycling. Previous estimates have relied on the emission factor (EF) approach, which carries substantial uncertainties due to its inherent limitations. Here, we developed a mass-balance model to re-estimate global Hg emissions from OBB during 2010–2019, enabling quantification of emissions from individual vegetation tissues. Our results indicate that global annual Hg emissions average 280 Mg yr^–1 (ranging 93–803 Mg yr^–1), including 129 Mg yr^–1 from vegetation-derived combustion, 81 Mg yr^–1 from litterfall combustion, and 70 Mg yr^–1 from peatland fires. Emissions exhibit strong latitudinal and longitudinal variability, with hotspots in central Africa, the Indo-China Peninsula, and boreal Asia. By category, the largest contributors are Africa (49%) among continents, savannas (29%) among biomes, and leaves (58%) among vegetation-derived emissions. Seasonal peaks occur in January, March, and August, while total annual emissions remain relatively stable over the decade, despite extreme anomalies such as the 2015 Indonesian fires. This approach reveals distinct emission sources and high spatial heterogeneity, providing a more accurate and nuanced assessment of Hg emissions from global OBB.