Volatile organic vapor diffusion and adsorption in soils

Journal Article · Fri Jul 01 04:00:00 EDT 1994 · Journal of Environmental Quality

DOI:https://doi.org/10.2134/jeq1994.00472425002300040026x· OSTI ID:263107

Petersen, L W; Moldrup, P ^[1]; Rolston, D E ^[2]; Yamaguchi, T ^[3]

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1. Aalborg Univ. (Denmark)
2. Univ. of California, Davis, CA (United States)
3. Hiroshima Univ., Kagamiyama, Higashi-Hiroshima (Japan)

Knowledge of the relationship between D{sub p}/D{sub o} (diffusion coefficient in soil divided by diffusion coefficient in free air) and the volumetric soil-air content, {epsilon}, is important when modeling gaseous movement of volatile organic compounds (VOCs) in soils. The effective diffusion of trichloroethylene (TCE), toluene and freon in Yolo silt loam (fine-silty, mixed, nonacid, thermic Typic Xerorthent) were measured in a two-chamber diffusion apparatus. The experiments were conducted on packed soil cores over a range of water contents. It was found that for water contents higher than four molecular layers of water surface coverage, solid/vapor partition coefficients, K{sub D}; were consistent with values predicted by Henry`s Law constants (K{sub H}), and aqueous/solid partition coefficients, K{sub D}. For less than four molecular layers of water, sorption increased by orders of magnitude. The vapor retardation factors, along with the measured effective diffusion, allowed a calculation of diffusion coefficients (D{sub P}) for the investigated species by using the analytical solution to diffusion in a two-chamber apparatus. Values of the ratio D{sub P}/D{sub O} were generally higher than the values predicted by the Millington-Quirk equation, and lower than the values predicted by the Penman equation. Compared with the nonreactive tracer freon, D{sub P}/D{sub O} values for TCE and toluene agreed very well for higher water contents. Values obtained for air-dry soil, however, were under-predicted. The experimental work for determination of the effective diffusion of reactive tracers can, therefore, for sufficiently high water contents be limited to the determination of D{sub P}/D{sub O-{epsilon}} relations for a nonreactive tracer and measurement of K{sub D}, K{sub D}{sup {prime}}, and K{sub H} values for the reactive tracers. 36 refs., 6 figs.

• Sponsoring Organization: USDOE
• OSTI ID: 263107
• Report Number(s): CONF-9101175--
• Journal Information: Journal of Environmental Quality, Journal Name: Journal of Environmental Quality Journal Issue: 4 Vol. 23; ISSN JEVQAA; ISSN 0047-2425
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ADSORPTION
CONTAMINATION
DIFFUSION
ENVIRONMENTAL TRANSPORT
ORGANIC COMPOUNDS
SOILS
VOLATILE MATTER