Quantifying the air-surface exchange of Hg-o from soils is critical to understanding the cycling of mercury in different environmental compartments. Dynamic flux chambers (DFCs) have been widely employed for Hg-o flux measurement over soils. However, DFCs of different sizes, shapes, and sampling flow rates yield distinct measured fluxes for a soil substrate under identical environmental conditions. In this study, we performed an integrated modeling, laboratory and field study to design a DFC capable of producing a steady and uniform air flow over a flat surface. The new DFC was fabricated using polycarbonate sheets. The internal velocity field was experimentally verified against model predictions using both theoretical and computational fluid dynamics techniques, suggesting fully developed flow with velocity profiles in excellent agreement with model results. Laboratory flux measurements demonstrated that the new design improves data reproducibility as compared to a conventional DFC, and reproduces the model-predicted flux trend with increasing sampling flow. A mathematical relationship between the sampling flow rate and surface friction velocity, a variable commonly parametrized in atmospheric models, was developed for field application. For the first time, the internal shear property of a DFC can be precisely controlled using the sampling flow rate, and the flux under atmospheric condition can be inferred from the measured flux and surface shear property. The demonstrated methodology potentially bridges the gap in measured fluxes obtained by the DFC method and the micrometeorological methods.

Publication name	ENVIRONMENTAL SCIENCE & TECHNOLOGY　Volume: 46 　Issue: 16 　Pages: 8910-8920　 Published: AUG 21 2012
Author(s)	Lin, Che-Jen; Zhu, Wei; Li, Xianchang; Feng, Xinbin; Sommar, Jonas;Shang, Lihai
Corresponding author	LIN Chejen  Jerry.Lin@lamar.edu  1. Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang 550002, Peoples R China   2. Lamar Univ, Dept Civil Engn, Beaumont, TX 77710 USA  3. S China Univ Technol, Coll Environm Sci & Engn, Guangzhou 510006, Guangdong, Peoples R China

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