Improved Mechanistic Modeling of Global Vegetation-Mediated Mercury Deposition

Vegetation-mediated dry deposition of gaseous elemental mercury (Hg0) is a critical component of global Hg cycling, yet large uncertainties persist in quantifying its fluxes. We implemented an improved mechanistic scheme in a chemical transport model, integrating physically based stomatal and mesophyll conductance algorithms with an integrated leaf area index (LAI) database to enhance the simulations of global Hg0 dry deposition. Compared with traditional semiempirical parametrizations, the new scheme more accurately reproduced diverse literature-derived field observations, particularly in Asia and the Amazon region. The model estimated a global vegetation-mediated Hg0 dry deposition flux of 2257 Mg yr–1, with hotspots in tropical rainforests and industrialized regions of Asia driven by enhanced vegetation activity and intensive regional anthropogenic emissions. These results demonstrate that our mechanistic model representations, evaluated by the diverse literature-derived field observations, can substantially reduce uncertainties and improve the understanding of atmosphere–biosphere Hg cycling.