Global Mercury Assimilation by Vegetation

Assimilation of mercury (Hg) by vegetation represents one of the largest global environmental Hg mass fluxes. We estimate Hg assimilation by vegetation globally via a bottom-up scaling approach using tissue Hg concentrations synthesized from a comprehensive database multiplied by respective annual biomass production (NPP). As global annual NPP is close to annual vegetation die-off, Hg mass associated with global NPP approximates the transfer of Hg from plants to soils, which represents an estimate of vegetation-mediated atmospheric deposition. Annual vegetation assimilation of Hg from combined atmospheric and soil uptake is estimated at 3062 +/- 607 Mg yr(-1), which is composed of 2491 +/- 551 Mg yr(-1) from aboveground tissue uptake and 571 +/- 253 Mg yr(-1) from root uptake. Assimilation of atmospheric Hg amounts to 2422 +/- 483 Mg yr(-1) when considering aboveground tissues only. Atmospheric assimilation increases to 2705 +/- 504 Mg yr(-1) when considering that root Hg may be partially derived from prior foliar uptake and transported internally to roots. Estimated atmospheric Hg assimilation by vegetation is 54-137% larger than the current model and litterfall estimates, largely because of the inclusion of lichens, mosses, and woody tissues in deposition and all global biomes. Belowground, about 50% of root Hg was taken up from soils with currently unknown ecological and biogeochemical consequences.

Automated summary

This passage examines the global assimilation of mercury by vegetation, estimated through a comprehensive database and biomass production data. It found that the vegetation assimilation of atmospheric and soil uptake of Hg is 3062 +/- 607 Mg yr(-1, with atmospheric assimilation exceeding current model estimates by 54-137%.