, Volume 56, Issue 1, pp 577-594

Atmospheric concentrations and deposition of Hg to A deciduous forest atwalker branch watershed, Tennessee, USA

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Abstract

Aerosol and total vapor-phase Hg concentrations in air have been measured at Walker Branch Watershed, Tennessee for ≈ 2 yr. Airborne Hg at this site is dominated by vapor forms which exhibit a strong seasonal cycle, with summer maxima that correspond to elevated air temperature. Concentrations in this forest are near background levels; however, concentrations at a site within 3 km are significantly elevated due to emissions from Hg-contaminated soils. The concentration data have been combined with a recently modified dry deposition model to estimate dry deposition fluxes to the deciduous forest at Walker Branch. Weekly mean modeled Vd values for Hg° ranged from <0.01 (winter) to > 0.1 (summer) cm s1. Weekly dry deposition fluxes ranged from <0.1 µg m−2 during winter to > 1.0 µgg m−2 in the summer. Our dry deposition estimates plus limited measurements of wet deposition in this area indicate that dry deposition may be the dominant input process in this forest, at least during the summer.

Research sponsored by the Atmosphere and Climate Research Division, U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. Environmental Sciences Division Publication No. 3595, ORNL.