Soil vapor extraction (SVE) is a technique that is frequently used to remediate unsaturated soils in the vadose zone that are contaminated with volatile organic compounds. Laboratory research and field experience have demonstrated that rate-limited mass transfer of a contaminant from aquifer solids and soil water to the gas phase significantly impacts the efficacy and speed of the remediation. An exact analytical solution to equations describing SVE controlled by rate-limited mass transfer is presented. Processes modeled include contaminant advective-dispersive transport in a gas phase converging on an extraction well and rate-limited mass transfer of dissolved and sorbed contaminants into the gas phase, with the rate limitation modeled assuming first-order kinetics. In addition to the exact solution an approximate solution, as well as an exact solution for plug flow (no dispersion), is presented. These analytical solutions may be useful in verifying numerical codes that are being developed to model SVE of volatile organic compounds. |