| Title: | In situ method to measure effective and sorption-affected gas-phase diffusion coefficients in soils |
| Address: | "Swiss Federal Institute of Technology (EPFL), ENAC-ISTE-LPE, CH-1015 Lausanne, Switzerland" |
| ISSN/ISBN: | 0013-936X (Print) 0013-936X (Linking) |
| Abstract: | "Transport modeling, risk assessment, and the evaluation of remediation strategies at contaminated sites require the knowledge of gas diffusivities in soil. A field method is presented, which determines the tortuosity factor and the mass fraction in the air phase of a volatile compound in situ. The compound is injected into the unsaturated zone together with a conservative gaseous tracer to form a point source. Concentrations are monitored at the injection point during 8 h and evaluated with an analytical equation for reactive transport. The air-filled porosity is determined independently. From these data, both the effective and the sorption-affected diffusion coefficients are obtained. Results are reported for volatile organic pollutants in both a lysimeter and a sandy soil. The measurements show good reproducibility. Batch experiments suggest that tracers were not truly conservative at subsurface temperatures. This may lead to a systematic underestimation of the effective diffusion coefficient by less than 10%, but the sorption-affected diffusion coefficients were probably overestimated by 15-20%. Nevertheless, the in situ method can avoid considerable uncertainties associated with choosing appropriate empirical relationships for the tortuosity factor or deviations from natural soil conditions in laboratory experiments" |
| Keywords: | "Adsorption Diffusion Environmental Monitoring/*methods Forecasting Gases *Models, Theoretical Risk Assessment *Soil Pollutants;" |
| Notes: | "MedlineWerner, David Hohener, Patrick eng Research Support, Non-U.S. Gov't 2003/07/02 Environ Sci Technol. 2003 Jun 1; 37(11):2502-10. doi: 10.1021/es020101s" |
