title: Dry deposition of gaseous oxidized mercury in Western Maryland.
abstract: The purpose of this study was to directly measure the dry deposition of gaseous oxidized mercury (GOM) in western Maryland. Annual estimates were made using passive ion-exchange surrogate surfaces and a resistance model. Surrogate surfaces were deployed for seventeen weekly sampling periods between September 2009 and October 2010. Dry deposition rates from surrogate surfaces ranged from 80 to 1512 pgm(-2)h(-1). GOM dry deposition rates were strongly correlated (r(2)=0.75) with the weekly average atmospheric GOM concentrations, which ranged from 2.3 to 34.1 pgm(-3). Dry deposition of GOM could be predicted from the ambient air concentrations of GOM using this equation: GOM dry deposition (pgm(-2)h(-1))=43.2 × GOM concentration-80.3. Dry deposition velocities computed using GOM concentrations and surrogate surface GOM dry deposition rates, ranged from 0.2 to 1.7 cms(-1). Modeled dry deposition rates were highly correlated (r(2)=0.80) with surrogate surface dry deposition rates. Using the overall weekly average surrogate surface dry deposition rate (369 ± 340 pg m(-2)h(-1)), we estimated an annual GOM dry deposition rate of 3.2 μg m(-2)year(-1). Using the resistance model, we estimated an annual GOM dry deposition rate of 3.5 μg m(-2)year(-1). Our annual GOM dry deposition rates were similar to the dry deposition (3.3 μg m(-2)h(-1)) of gaseous elemental mercury (GEM) at our site. In addition, annual GOM dry deposition was approximately 1/2 of the average annual wet deposition of total mercury (7.7 ± 1.9 μg m(-2)year(-1)) at our site. Total annual mercury deposition from dry deposition of GOM and GEM and wet deposition was approximately 14.4 μg m(-2)year(-1), which was similar to the average annual litterfall deposition (15 ± 2.1 μg m(-2)year(-1)) of mercury, which was also measured at our site.
authors.affiliation: Appalachian Laboratory, University of Maryland Center for Environmental Science, 301 Braddock Road, Frostburg, MD 21532, United States. mcastro@umces.edu
authors.forename: Mark S
authors.initials: MS
authors.lastname: Castro
authors.forename: Chris
authors.initials: C
authors.lastname: Moore
authors.forename: John
authors.initials: J
authors.lastname: Sherwell
authors.forename: Steve B
authors.initials: SB
authors.lastname: Brooks
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods*; D005740:Gases / Q000032:analysis / Q000737:chemistry; D008396:Maryland; D008628:Mercury / Q000032:analysis / Q000737:chemistry*; D017669:Mercury Compounds / Q000032:analysis / Q000737:chemistry*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010087:Oxides / Q000032:analysis / Q000737:chemistry*
chemical_list: D000393:Air Pollutants; D005740:Gases; D017669:Mercury Compounds; D010087:Oxides; D008628:Mercury