Comparison of atmospheric mercury speciation and deposition at nine sites across central and eastern North America

• Published in: Journal of Geophysical Research: Atmospheres Vol. 115; no. D18
• Main Authors: Engle, Mark A., Tate, Michael T., Krabbenhoft, David P., Schauer, James J., Kolker, Allan, Shanley, James B., Bothner, Michael H.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 27.09.2010; American Geophysical Union
• Subjects: Air pollution; Anthropogenic factors; atmospheric mercury; Atmospheric sciences; Boundary layers; diel patterns; Dry deposition; Earth sciences; Earth, ocean, space; Emissions; Environmental conditions; Exact sciences and technology; Geophysics; Mercury; Photochemicals; Speciation; Troposphere; wet deposition; Puerto Rico; United States; Antilles; Greater Antilles; West Indies; Eastern U.S; Caribbean region; USA; ASW, Caribbean Sea, Greater Antilles, Puerto Rico; depletion; models; boundary layer; mercury; Regional scope; fine-grained materials; oxidation; concentration; global; Deposition rate; troposphere; North America; Dry deposition; speciation; point sources; coastal zone; correlation; Dew; inclusions
• ISSN: 0148-0227; 2169-897X; 2156-2202; 2169-8996
• DOI: 10.1029/2010JD014064

This study presents >5 cumulative years of tropospheric mercury (Hg) speciation measurements, over the period of 2003–2009, for eight sites in the central and eastern United States and one site in coastal Puerto Rico. The purpose of this research was to identify local and regional processes that impact Hg speciation and deposition (wet + dry) across a large swath of North America. Sites sampled were selected to represent both a wide range of mercury exposure and environmental conditions. Seasonal mean concentrations of elemental Hg (1.27 ± 0.31 to 2.94 ± 1.57 ng m−3; ± σ), reactive gaseous mercury (RGM; 1.5 ± 1.6 to 63.3 ± 529 pg m−3), and fine particulate Hg (1.2 ± 1.4 to 37.9 ± 492 pg m−3) were greatest at sites impacted by Hg point sources. Diel bin plots of Hgo and RGM suggest control by a variety of local/regional processes including impacts from Hg point sources and boundary layer/free tropospheric interactions as well as from larger‐scale processes affecting Hg speciation (i.e., input of the global Hg pool, RGM formed from oxidation of Hgo by photochemical compounds at coastal sites, and elemental Hg depletion during periods of dew formation). Comparison of wet Hg deposition (measured), RGM and fine particulate Hg dry deposition (calculated using a multiple resistance model), and anthropogenic point source emissions varied significantly between sites. Significant correlation between emission sources and dry deposition was observed but was highly dependant upon inclusion of data from two sites with exceptionally high deposition. Findings from this study highlight the importance of environmental setting on atmospheric Hg cycling and deposition rates.