ANALYSIS OF REGIONAL AEOLIAN TRANSPORT OF HEAVY METALS IN HARDING COUNTY, SOUTH DAKOTA

This project integrates research objectives, sample collection, and evaluation of regional aeolian transport trends using laboratory and geospatial analysis methods. The study site for this project is in Harding County, South Dakota and consists of several of the approximately 103 abandoned open-pit uranium mines at North and South Cave Hills, and at Slim Buttes. Most of the mines are on U.S. Forest Service land and have received no capping or other remediation efforts for the past 50 years.

More recently, US-EPA CERCLA funds and a $179 million settlement have provided funding for the investigation and clean-up of these mine sites. Past studies have indicated the presence of heavy metals and other elements such as arsenic, uranium, radium, and thorium at various locations throughout the region.

Geospatial analysis of trends from all three sites will provide a better understanding of regional aeolian transport patterns. Recommendations can then be shared with the U.S. Forest Service in order to separate those areas in critical need of remediation from areas where little or no remediation may be needed.

Field samples from all three sites were analyzed for the presence of heavy metals. Samples were then sieved in order to separate fine to very-fine soil fraction to determine the percentage of material that could be subjected to aeolian transport in the study area. Directionality components of ambient, wind, and bulk sampling were analyzed geospatially using ArcGIS 10.3. This paper answers two important questions. First, radionuclide concentrations tend to decrease moving away from the mine sites. Second, the wind trends have a regional direction of northwest to southeast. The completed map of the project area can provide insight to the U.S. Forest Service and local stakeholders (such as ranchers), to determine areas in critical need of remediation efforts.