Global 3‐D land‐ocean‐atmosphere model for mercury: Present‐day versus preindustrial cycles and anthropogenic enrichment factors for deposition

Abstract

[1] We develop a mechanistic representation of land-atmosphere cycling in a global 3-D ocean-atmosphere model of mercury (GEOS-Chem). The resulting land-oceanatmosphere model is used to construct preindustrial and present biogeochemical cycles of mercury, to examine the legacy of past anthropogenic emissions, to map anthropogenic enrichment factors for deposition, and to attribute mercury deposition in the United States. Land emission in the model includes prompt recycling of recently deposited mercury (600 Mg a À1 for present day), soil volatilization (550 Mg a À1), and evapotranspiration (550 Mg a À1). The spatial distribution of soil concentrations is derived from local steady state between land emission and deposition in the preindustrial simulation, augmented for the present day by a 15% increase in the soil reservoir distributed following the pattern of anthropogenic deposition. Mercury deposition and hence emission are predicted to be highest in the subtropics. Our atmospheric lifetime of mercury against deposition (0.50 year) is shorter than past estimates because of our accounting of Hg(0) dry deposition, but recycling from surface reservoirs results in an effective lifetime of 1.6 years against transfer to long-lived reservoirs in the soil and deep ocean. Present-day anthropogenic enrichment of mercury deposition exceeds a factor of 5 in continental source regions. We estimate that 68% of the deposition over the United States is anthropogenic, including 20% from North American emissions (20% primary and <1% recycled through surface reservoirs), 31% from emissions outside North America (22% primary and 9% recycled), and 16% from the legacy of anthropogenic mercury accumulated in soils and the deep ocean.

Effect of climate change on air quality

“…Volatilization of mercury from the ocean is directly affected by warming (lower solubility of elemental mercury) and would also be affected by changes in ocean biology and circulation (Strode et al, 2007;Sunderland and Mason, 2007). Increased volatilization of soil mercury could potentially be of considerable importance, as the amount of mercury stocked in soil (1.2 Â 10 6 Mg) dwarfs that in the atmosphere (6 Â 10 3 Mg) and in the ocean (4 Â 10 4 Mg) (Selin et al, 2008). Soil mercury is mainly bound to organic matter (Ravichandran, 2004).…”

Distribution of mercury in coastal marine sediments of China: Sources and transport

“…Current global atmospheric deposition of mercury (Hg) has been estimated to be three times higher than preindustrial levels (Selin et al, 2008). The anthropogenic Hg emission of China is the largest in the world owing to its rapid industrialization and urbanization in the last several decades, taking up approximately 30% of the global Hg emission (Pacyna et al, 2010;Wu et al, 2006).…”

Rapid oxidation of mercury (Hg) at volcanic vents: Insights from high temperature thermodynamic models of Mt Etna's emissions

“…The anthropogenic Hg flux is of the same order (2200-4000 Mg yr −1 ; Selin, 2009;Pirrone et al, 2009); the most significant of these flux sources is coal combustion, but metal production, waste incineration and artisanal gold mining are also important (Mason, 2009). The total atmospheric burden of Hg has more than doubled from~1600 to 1800 Mg in pre-anthropogenic times (Mason et al, 1994;Lamborg et al, 2002) to~5000 Mg at the present day (Selin et al, 2008) due to these industrial activities. This significant increase in atmospheric Hg is reflected in archives such as lake sediments, peat bogs and ice records which show a 2-to 4-fold increase in the past 150 years (Lindberg et al, 2007;Farmer et al, 2009).…”