Using Magnetism to Identify Wetland Soils

By measuring concentrations of magnetic minerals in soils, ISGS researchers have enhanced existing methods used to legally define wetlands and to assess potential wetland mitigation and restoration sites.

ISGS geologists use a highly sensitive magnetic probe to quickly classify wetland soils, identify hydric soil boundaries, study soil drainage, and map soil types. The ISGS technique gathers data faster than the more labor-intensive methods scientists have traditionally used to obtain U.S. Department of Agriculture field indicators for hydric soils typical of wetlands. Knowing where hydric and nonhydric soils occur can aid scientific studies and can help the Illinois Department of Transportation meet regulatory requirements for constructing or restoring wetlands as part of the state’s road construction program.

ISGS researchers evaluated the use of magnetic susceptibility measurements to identify soil types at eight test sites in Illinois in 2001–2002. They used a special probe, which is similar to a highly sensitive metal detector but gives readings in numbers instead of audible tones. Hydric soils produce lower numbers on the probe's readout than do nonhydric soils because the saturated conditions typical of wetlands cause the submicroscopic magnetic minerals present in soil to dissolve.

Geologists can use the probe to take readings more quickly over a larger area than is possible with other methods, and the findings can be interpreted in the field. The method is nondestructive and noninvasive.

The study was funded by a grant from the University of Illinois Research Board. This research was also a part of an Illinois Natural Resources Environmental Science Department master's thesis.

Updated 05/18/2011 SLD