Atmos. Chem. Phys., 13, 5325-5336, 2013
www.atmos-chem-phys.net/13/5325/2013/
doi:10.5194/acp-13-5325-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Air-surface exchange measurements of gaseous elemental mercury over naturally enriched and background terrestrial landscapes in Australia
G. C. Edwards and D. A. Howard
Department of Environment and Geography, Macquarie University, North Ryde, NSW, 2109, Australia

Abstract. This paper presents the first gaseous elemental mercury (GEM) air-surface exchange measurements obtained over naturally enriched and background (<0.1 μg g−1 Hg) terrestrial landscapes in Australia. Two pilot field studies were carried out during the Australian autumn and winter periods at a copper-gold-cobalt-arsenic-mercury mineral field near Pulganbar, NSW. GEM fluxes using a dynamic flux chamber approach were measured, along with controlling environmental parameters over three naturally enriched and three background substrates. The enriched sites results showed net emission to the atmosphere and a strong correlation between flux and substrate Hg concentration, with average fluxes ranging from 14 ± 1 ng m−2 h−1 to 113 ± 6 ng m−2 h−1. Measurements at background sites showed both emission and deposition. The average Hg flux from all background sites showed an overall net emission of 0.36 ± 0.06 ng m−2 h−1. Fluxes show strong relationships with temperature, radiation, and substrate parameters. A compensation point of 2.48, representative of bare soils was determined. For periods of deposition, dry deposition velocities ranged from 0.00025 cm s−1 to 0.0083 cm s−1 with an average of 0.0041 ± 0.00018 cm s−1, representing bare soil, nighttime conditions. Comparison of the Australian data to North American data suggests the need for Australian-specific mercury air-surface exchange data representative of Australia's unique climatic conditions, vegetation types, land use patterns and soils.

Citation: Edwards, G. C. and Howard, D. A.: Air-surface exchange measurements of gaseous elemental mercury over naturally enriched and background terrestrial landscapes in Australia, Atmos. Chem. Phys., 13, 5325-5336, doi:10.5194/acp-13-5325-2013, 2013.
 
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