A USGS scientist used an all-terrain vehicle to tow a device to measure the electrical resistivity of the subsurface. The system consists of five receivers that measure resistivity and one transmitter that sends an electrical signal into the ground (photo taken from Lucius and others, 2008).

USGS scientists collecting gas samples from the unsaturated zone. Subsurface gases are drawn through a small glass tube filled with an adsorbing material, which traps mercury or volatile organic compounds for later analysis.

Modeled tritium migration in unsaturated-zone sediments from an idealized representation of a radioactive-waste disposal trench. Contours (wavy blue lines) show concentrations in tritium units after 40 years of coupled gas-phase and liquid-phase transport. The new model accounts for waste heating by decay of radioisotopes and organic matter, pressurization by gas generation, and sediment properties that account for preferential transport parallel to sedimentary layering.

Map of tritium concentrations in soil-water vapor at a depth of 0.5 meter, Soil-water concentrations are inferred from measured plant-water concentrations and predictive relations between plant-water and soil-water-vapor concentrations. Concentrations are given in bequerels per liter (Bq/L). One Bq/L (one decay per second) equals approximately 8.47 tritium units.

Collection of soil-water vapor samples for tritium determination. The collection is part is part of a long-term monitoring program on the transport of tritium in the unsaturated zone.

USGS scientist sampling plants for tritium analysis. The plants act as "detectors" for the presence of tritium in the soil's water vapor.

On-site facility for collection of soil-water vapor and unsaturated-zone gas from a deep borehole for tritium and volatile-organic compound analyses. USGS scientists are conducting research on the transport and fate of tritium and other contaminants in desert environments with thick unsaturated zones.

Collection of soil-gas samples for volatile-organic compound analysis. USGS scientists are studying the transport and fate of volatile-organic compounds in the unsaturated zone.

Soil sampling for naturally occurring perchlorate in Amargosa Desert soils.

Inspecting a pit wall for evidence of a geologic fault. Faults can form pathways or barriers to the transport of contaminants in the unsaturated zone.

Belowground and aboveground features and processes being evaluated at the Amargosa Desert Research Site—soil properties, root distribution, transpiration, and evaporation. USGS scientists are quantifying the movement of soil moisture and tritium from the shallow unsaturated zone to the atmosphere.

Eddy covariance station used to measure continuous evapotranspiration from desert soil and plants. The station non-invasively collects atmospheric data that are analyzed to calculate continuous water-vapor flux values.