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Open AccessArticle

Air/Surface Exchange of Gaseous Elemental Mercury at Different Landscapes in Mississippi, USA

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Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
2
Department of Biology, University of Mississippi, University, MS 38677, USA
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(9), 538; https://doi.org/10.3390/atmos10090538
Received: 8 August 2019 / Revised: 5 September 2019 / Accepted: 6 September 2019 / Published: 11 September 2019
(This article belongs to the Special Issue Atmospheric Mercury: Sources, Sinks, and Transformations)
Mercury (Hg) is a global pollutant with human health and ecological impacts. Gas exchange between terrestrial surfaces and the atmosphere is an important route for Hg to enter and exit ecosystems. Here, we used a dynamic flux chamber to measure gaseous elemental Hg (GEM) exchange over different landscapes in Mississippi, including in situ measurements for a wetland (soil and water), forest floor, pond, mowed field and grass-covered lawn, as well as mesocosm experiments for three different agricultural soils. Fluxes were measured during both the summer and winter. Mean ambient levels of GEM ranged between 0.93–1.57 ng m−3. GEM emission fluxes varied diurnally with higher daytime fluxes, driven primarily by solar radiation, and lower and more stable nighttime fluxes, dependent mostly on temperature. GEM fluxes (ng m−2 h−1) were seasonally dependent with net emission during the summer (mean 2.15, range 0.32 to 4.92) and net deposition during the winter (−0.12, range −0.32 to 0.12). Total Hg concentrations in the soil ranged from 17.1 ng g−1 to 127 ng g−1 but were not a good predictor of GEM emissions. GEM flux and soil temperature were correlated over the forest floor, and the corresponding activation energy for Hg emission was ~31 kcal mol−1 using the Arrhenius equation. There were significant differences in GEM fluxes between the habitats with emissions for grass > wetland soil > mowed field > pond > wetland water ≈ forest ≈ agriculture soils. Overall, we demonstrate that these diverse landscapes serve as both sources and sinks for airborne Hg depending on the season and meteorological factors. View Full-Text
Keywords: mercury; air-surface exchange; dynamic flux chamber; soils; wetland; forest floor; pond mercury; air-surface exchange; dynamic flux chamber; soils; wetland; forest floor; pond
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Cizdziel, J.V.; Zhang, Y.; Nallamothu, D.; Brewer, J.S.; Gao, Z. Air/Surface Exchange of Gaseous Elemental Mercury at Different Landscapes in Mississippi, USA. Atmosphere 2019, 10, 538.

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