Measurement of Air and
VOC Vapor Fluxes during Gas-Driven Soil Remediation: Bench-Scale Experiments
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Abstract
In this laboratory study, an experimental method was
developed for the quantitative analyses of gas fluxes in soil during
advective air flow. One-dimensional column and two- and three-dimensional
flow chamber models were used in this study. For the air flux measurement, <i>n</i>-octane vapor was used as a tracer, and it was introduced
in the air flow entering the physical models. The tracer (<i>n</i>-octane) in the gas effluent from the models was captured
for a finite period of time using a pack of activated carbon, which
then was analyzed for the mass of <i>n</i>-octane. The air
flux was calculated based on the mass of <i>n</i>-octane
captured by the activated carbon and the inflow concentration. The
measured air fluxes are in good agreement with the actual values for
one- and two-dimensional model experiments. Using both the two- and
three-dimensional models, the distribution of the air flux at the
soil surface was measured. The distribution of the air flux was found
to be affected by the depth of the saturated zone. The flux and flux
distribution of a volatile contaminant (perchloroethene) was also
measured by using the two-dimensional model. Quantitative information
of both air and contaminant flux may be very beneficial for analyzing
the performance of gas-driven subsurface remediation processes including
soil vapor extraction and air sparging