Seasonal variability in gaseous mercury fluxes measured in a high-elevation meadow |
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| Authors: | AD Converse AL Riscassi TM Scanlon |
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| Institution: | 1. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No. 18 Shuangqing Road, Beijing 100085, China;2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China;1. Department of Atmospheric Sciences, National Central University, Jhongli, 320, Taiwan;2. Environment and Climate Change Canada, Toronto, Ontario, Canada;1. Laboratoire Chrono-Environnement, UMR CNRS 6249, Université de Bourgogne Franche-Comté, Pôle Universitaire du Pays de Montbéliard, 4 Place Tharradin, BP 71427, 25211 Montbéliard, France;2. Laboratoire Chrono-Environnement, UMR CNRS 6249, Université de Bourgogne Franche-Comté, 16 Route de Gray, Besançon Cedex, 25030 France;3. Solvay Electrolyse France, Tavaux Cedex, 39500 France;4. Université de Lorraine, Faculté des Sciences et Technologies, BP 70239, Vandoeuvre-les-Nancy, 54506 France;1. DiSTeM, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy;2. IAMC-CNR, Capo Granitola, Via del Mare 3, 91021 Torretta Granitola, Trapani, Italy;3. IAMC-CNR, Naples, Calata Porta di Massa, Naples, Italy |
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| Abstract: | Seasonal patterns of atmospheric mercury (Hg) fluxes measured over vegetated terrestrial systems can provide insight into the underlying process controlling emission and deposition of Hg to vegetated surfaces. Gaseous elemental Hg fluxes were measured for week-long periods in each season (spring, summer, fall, and winter) over an uncontaminated high-elevation wetland meadow in Shenandoah National Park, Virginia using micrometeorological methods. Mean net deposition was observed in the spring (?4.8 ng m?2 h?1), emission in the summer (2.5 ng m?2 h?1), near zero flux in the fall (0.3 ng m?2 h?1), and emission in the winter (4.1 ng m?2 h?1). Nighttime deposition (when stomata are closed) and the poor correlation between Hg fluxes and canopy conductance during periods of active vegetation growth suggest that stomatal processes are not the dominant mechanism for ecosystem-level GEM exchange at this site. The strong springtime deposition relative to summer implies that young vegetation is better at scavenging Hg, with the highest deposition occurring at night possibly via a cuticular pathway. These results suggest that spring is a period of GEM deposition while other seasons exhibit net emission, emphasizing the importance of capturing GEM flux seasonality when determining total Hg budgets. |
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