The Toxic Substances Hydrology (Toxics) Program is investigating factors and processes that control the transport and fate of contaminants in unsaturated zones (the zone in the subsurface between the land surface and underlying aquifers). Toxics Program scientists are developing methods for measuring and modeling the transport and fate of many different types of contaminants in the unsaturated zone. Such measurement tools, interpretive approaches, and modeling packages are needed for the design and management of waste-disposal facilities, to understand how nonpoint-source contaminants are transported to ground water, the cleanup of contaminated sites, and the monitoring of remediation systems. The unsaturated zone is particularly important at sites in the arid western United States that are being relied upon to isolate a significant portion of the Nation's radioactive and other hazardous wastes for periods up to thousands of years. The information presented on this page cuts across lines drawn by individual investigations and projects so that information on contaminant transport in surface-water can be presented in one place.
Investigations and Research Activities
Fact Sheets
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![Thermocouple psychrometer installation for evaluating an evapotranspiration landfill cover at Fort Carson, Colorado](https://webarchive.library.unt.edu/web/20090506164059im_/http://toxics.usgs.gov/photo_gallery/photos/adrs/carson5_s.jpg)
Thermocouple psychrometer installation for evaluating an evapotranspiration landfill cover at Fort Carson, Colorado
(Click on Image for a Larger Version)
Headlines
Bibliography
New Publications
Upcoming Publications
- Soil-CO2 flux in an arid environment--A multiple year study: Riggs, A.C., Stannard, D.I., Maestas, F., Karlinger, M., and Striegl, R.G., U.S. Geological Survey Scientific Investigations Report (IN PRESS).
- Transport of tritium contamination from the shallow unsaturated zone to the atmosphere in an arid environment: Garcia, C.A., Andraski, B.J., Stonestrom, D.A., Cooper, C.A., Johnson, M.J., Michel, R.L., and Wheatcraft, S.W., Vadose Zone Journal, v. 8, no. 2 (IN PRESS).
Newly Published
- Assessing recharge across the southwest: Stonestrom, D.A., 2009, Southwest Hydrology, v. 8, no. 1, p. 10-11.
- Effect of grain-coating mineralogy on nitrate and sulfate storage in the unsaturated zone: Reilly, T.J., Fishman, N.S., and Baehr, A.L., 2009, Vadose Zone Journal, v. 8, no. 1, p. 75-85, doi:10.2136/vzj2008.0053.
![Soil moisture probes and tensiometers installed in the side of a pit for monitoring a tracer test in the unsaturated zone at the Bemidji Crude Oil Spill Research Site, Minnesota. Note black oil-contaminated sand on pit walls.](https://webarchive.library.unt.edu/web/20090506164059im_/http://toxics.usgs.gov/photo_gallery/photos/bimidji/installed_probs_s.jpg)
Soil moisture probes and tensiometers installed in the side of a pit for monitoring a tracer test in the unsaturated zone at the Bemidji Crude Oil Spill Research Site, Minnesota. Note black oil-contaminated sand on pit walls.
(Click on Image for a Larger Version)
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