Numerical evaluation of static-chamber measurements of soil-atmosphere gas exchange: Identification of physical processes

Journal Article · Wed May 01 04:00:00 EDT 1996 · Soil Science Society of America Journal

DOI:https://doi.org/10.2136/sssaj1996.03615995006000030009x· OSTI ID:263227

Healy, R W; Striegl, R G ^[1]; Russell, T F ^[2]; Hutchinson, G L ^[3]; Livingston, G P ^[4]

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1. Geological Survey, Lakewood, CO (United States)
2. Univ. of Colorado, Denver, CO (United States)
3. USDA-ARS-NPA, Ft. Collins, CO (United States)
4. NASA Ames Research Center, Moffett Field, CA (United States)

The exchange of gases between soil and atmosphere is an important process that affects atmospheric chemistry and therefore climate. The static-chamber method is the most commonly used technique for estimating the rate of that exchange. We examined the method under hypothetical field conditions where diffusion was the only mechanism for gas transport and the atmosphere outside the chamber was maintained at a fixed concentration. Analytical and numerical solutions to the soil gas diffusion equation in one and there dimensions demonstrated that gas flux density to a static chamber deployed on the soil surface was less in magnitude than the ambient exchange rate in the absence of the chamber. This discrepancy, which increased with chamber deployment time and air-filled porosity of soil, is attributed to two physical factors: distortion of the soil gas concentration gradient (the magnitude was decreased in the vertical component and increased in the radial component) and the slow transport rate of diffusion relative to mixing within the chamber. Instantaneous flux density to a chamber decreased continuously with time; steepest decreases occurred so quickly following deployment and in response to such slight changes in mean chamber headspace concentration that they would likely go undetected by most field procedures. Adverse influences of these factors were reduced by mixing the chamber headspace, minimizing deployment time, maximizing the height and radius of the chamber, and pushing the rim of the chamber into the soil. 29 refs., 8 figs., 1 tab.

• Sponsoring Organization: USDOE
• OSTI ID: 263227
• Journal Information: Soil Science Society of America Journal, Journal Name: Soil Science Society of America Journal Journal Issue: 3 Vol. 60; ISSN 0361-5995; ISSN SSSJD4
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ATMOSPHERES
CARBON DIOXIDE
DIFFUSION
EXPOSURE CHAMBERS
FLUX DENSITY
GASES
KINETICS
MASS TRANSFER
NUMERICAL SOLUTION
SOILS