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Vapor Transport in the Unsaturated Zone

Ground Water Hydrology

  1. Fred D. Tillman1,
  2. James A. Smith2

Published Online: 15 JUL 2005

DOI: 10.1002/047147844X.gw1226

Water Encyclopedia

Water Encyclopedia

How to Cite

Tillman, F. D. and Smith, J. A. 2005. Vapor Transport in the Unsaturated Zone. Water Encyclopedia. 5:543–548.

Author Information

  1. 1

    U.S. Environmental Protection Agency, Athens, Georgia

  2. 2

    University of Virginia, Charlottesville, Virginia

Publication History

  1. Published Online: 15 JUL 2005


In this section, we focus our attention primarily on the fate and transport of volatile organic vapors in the unsaturated zone. Organic vapors can arise from soil and groundwater contaminated with fuel hydrocarbons, organic solvents, pesticides, or other organic pollutants. Transport of these vapors occurs primarily by some combination of gas-phase Fickian diffusion (driven by organic vapor concentration gradients) and advection (driven by air pressure gradients). Other processes such as sorption to soil surfaces and air–water interfaces and biodegradation by soil microorganisms can further influence the fate and transport of organic vapors. We review these processes along with organic vapor sampling methodologies and chamber devices used to quantify organic vapor fluxes from the subsurface to the atmosphere.


  • vadose zone;
  • organic vapor;
  • diffusion;
  • advection;
  • barometric pumping;
  • flux chamber;
  • air pressure;
  • indoor air;
  • volatile organic compounds;
  • soil gas;
  • sorption;
  • biodegradation