We use historical anthropogenic emissions since 1840 to drive the accumulation of mercury in soils (Streets et al. 2011). Most emissions over that time period come from European and North American industry and mining, but the relatively long lifetime of Hg0 in the atmosphere results in a more hemispherically distributed accumulation in soils. The greatest magnitude of anthropogenic mercury accumulation occurs in the slowly overturning soil pools, while the greatest relative enhancement is in the most labile soil pools. We find that soil respiration more than doubles from the preindustrial period to the present due to the accumulation of anthropogenic mercury.
To examine atmosphere-terrestrial feedbacks in the biogeochemical cycling of mercury, we couple the GEOS-Chem atmosphere-ocean model with the GTMM. We update the model's air-land interface by including more mechanistically based dry deposition and surface photoreduction and revolatilization processes. We test the sensitivity of model results to uncertainties in the affinity of mercury to different soil pools and the fraction of mercury released upon soil respiration. Finally, we evaluate the model with comparison to field observations of mercury and carbon concentrations in vegetation, leaf litter, and soils across a range of ecosystems in the United States. Where observations are available, we compare modeled surface fluxes to measured dry deposition, throughfall, and washoff. We examine the seasonal and interrannual variability of modelled atmosphere-terrestrial mercury exchange and comment on the implications for long-term climate change.