Identification of subsurface features that affect offsite movement of waterborne contaminants through the use of soil classification/mapping techniques, electromagnetic inductance (EM), and ground-penetrating radar (GPR)

Concerns regarding the quality of our water resources and how to protect them are more evident today than ever before. Many every day human activities affect the quality of this finite resource. Agricultural activity can negatively impact water supplies. By confining large-scale agriculture onto more confined plots of land, inputs are maximized and the consequences are often detrimental to the environment. Specifically, groundwater is often affected by overuse of lands that are not suitable for the production pressures put on them.

This study utilized soil classification and characterization techniques as well as mapping techniques to identify and research features known to contribute to lateral subsurface movement of water within soil bodies. In addition to this, electromagnetic inductance (EM) and ground-penetrating radar (GPR) were used to aid in the identification of such features non-intrusively. The study was conducted on sites located on Major Land Resource Area (MLRA) 134, the Southern Mississippi Valley Silty Uplands. Eight pedons were described and sampled at sites near Lynville, Kentucky and Holly Springs, Mississippi. Both EM and GPR were used at these sites in order to identify locales of subsurface features thought to contribute to lateral subsurface movement of water.

The specific objectives of this study were: 1) Complete soil morphological, chemical, and physical characterization of landforms on MLRA 134 sites near Lynville, Kentucky and Holly Springs, Mississippi. 2) Classification of these soils to the family level of Soil Taxonomy 3) Conduct non-intrusive soil investigations using both EM and GPR 4) Assess how well this protocol works at the selected sites.

The soils encountered at the Lynville, Kentucky site consisted of fine-silty, mixed, active, thermic Typic Fragiudalfs and fine-silty, mixed, active, thermic Fragic Hapludalfs. The soils encountered at the Holly Springs, Mississippi site consisted of fine-silty, mixed, active, thermic Ultic Hapludalfs, fine-loamy, mixed, active, thermic Typic Fragiudalfs, and fine-loamy, mixed, active, thermic Typic Hapludults. The parent material sequence encountered at each of the sites consisted of loess, alluvium, and Tertiary aged coastal plain material. Loess had been eroded from two of the pedons characterized at the Holly Springs, Mississippi site.

Electromagnetic inductance provided a very useful depiction of the conductivity encountered at each of the study sites. Generally, soils at each site that contained fragipans were located in regions of higher conductivities in the resulting EM scans. The resulting ground-penetrating radar data collected at each of the sites were classified using a beta version fuzzy neural network classification program. The graphical representation of the GPR data collected at the Lynville, Kentucky site was similar to both the EM and soil maps generated for this site. The classification of GPR data taken at the Holly Springs, Mississippi Site was not as clear.