Initial Estimates of Soil Mercury Emissions Induced by Soil Heating During Global Wildfires

Wildfires, increasingly frequent extreme events driven by global change, have significantly accelerated the release of mercury (Hg) stored in soils. However, a systematic quantification of Hg emissions from topsoil heating during global wildfires has been lacking. This study proposes a novel method for estimating these emissions, based on quantitative formulas that link soil heating depths with fire temperature and fire radiative power. Our results estimate that annual soil Hg emissions from topsoil heating during 2008–2019 were 98.1 Mg yr⁻¹ (24.5–290.0 Mg yr⁻¹). Emission hotspots were predominantly located in northern high-latitude (25%) and tropical regions (41%). In high-latitude regions, substantial historical Hg accumulation in soils, combined with rising wildfire frequency and intensity, contributed to significant emissions. In tropical regions, frequent wildfires and high atmospheric Hg deposition were the main drivers. This study provides crucial data to enhance global Hg emission inventories and improves the understanding of how wildfires impact global Hg cycling.