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.