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Global 3‐D land‐ocean‐atmosphere model for mercury: Present‐day versus preindustrial cycles and anthropogenic enrichment factors for deposition
Author(s) -
Selin Noelle E.,
Jacob Daniel J.,
Yantosca Robert M.,
Strode Sarah,
Jaeglé Lyatt,
Sunderland Elsie M.
Publication year - 2008
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2007gb003040
Subject(s) - environmental science , biogeochemical cycle , mercury (programming language) , deposition (geology) , atmosphere (unit) , atmospheric sciences , hydrology (agriculture) , environmental chemistry , geology , meteorology , chemistry , geography , paleontology , sediment , computer science , geotechnical engineering , programming language
We develop a mechanistic representation of land‐atmosphere cycling in a global 3‐D ocean‐atmosphere model of mercury (GEOS‐Chem). The resulting land‐ocean‐atmosphere 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 −1 for present day), soil volatilization (550 Mg a −1 ), and evapotranspiration (550 Mg a −1 ). 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.