Larry D. Stetler

Microbial Diversity in Uranium Mining-Impacted Soils as Revealed by High-Density 16S Microarray and Clone Library

Microbial diversity was characterized in mining-impacted soils collected from two abandoned uranium mine sites, the Edgemont and the North Cave Hills, South Dakota, using a high-density 16S microarray (PhyloChip) and clone libraries. Characterization of the elemental compositions of soils by X-ray fluorescence spectroscopy revealed higher metal contamination including uranium at the Edgemont than at the North Cave Hills mine site. Microarray data demonstrated extensive phylogenetic diversity in soils and confirmed nearly all clone-detected taxonomic levels. Additionally, the microarray exhibited greater diversity than clone libraries at each taxonomic level at both the mine sites. Interestingly, the PhyloChip detected the largest number of taxa in Proteobacteria phylum for both the mine sites. However, clone libraries detected Acidobacteria and Bacteroidetes as the most numerically abundant phyla in the Edgemont and North Cave Hills mine sites, respectively. Several 16S rDNA signatures found in both the microarrays and clone libraries displayed sequence similarities with yet-uncultured bacteria representing a hitherto unidentified diversity. Results from this study demonstrated that highly diverse microbial populations were present in these uranium mine sites. Diversity indices indicated that microbial communities at the North Cave Hills mine site were much more diverse than those at the Edgemont mine site.

Environmental Impacts from Wind Erosion of Abandoned Mine Lands

Sampling and analysis of aeolian dust originating from abandoned uranium mine lands in northwestern South Dakota has been used to map concentration and extent of heavy metals contamination on dust. Analytes of concern were uranium, uranium isotopes, and arsenic and to a lesser extent thorium, copper, and molybdenum. Sampling methodologies included using a portable wind tunnel, passive and aspirated aerosol samplers, and skimming dust from the surface soil. The study area consisted of numerous and small abandoned uranium mine site that extended over approximately 1000 km2 and were never remediated, leaving them exposed to often sever environmental degradation leading to potential offsite contamination. Climatic analysis indicated an entrainment wind speed of 21 km/h for the average soil conditions surrounding the abandoned mine sites. Wind speeds in excess of this threshold value occurred 23.2% of the time, but occurred 60% of the time the wind was from the dominant NW direction. Thus, sampling for determining aeolian signatures was concentrated in the NW-SE direction. Analytical techniques included ICP-MS performed at university and commercial laboratories, XRD, and SEM. Results were evaluated against an established background concentration value for each analyte derived from known non-impacted areas. Aeolian analytical results were plotted as functions of the dominant NW wind direction and topography and were compared to a larger, regional-scale database that included surface soil, surface water, and groundwater samples. Additionally, a proof-of-concept study was performed that evaluated the validity of using alternative dust sampling techniques including skimming surface soil from both within and outside of a wind tunnel trackway, and sieving a bulk soil sample using a 400 mesh sieve. These results showed that for the analytes of concern, no significant differences in concentrations were detected between the wind tunnel results and those from the alternate sampling methods. This allowed a greater flexibility in available sampling methods and provided a valid means for sample collection in areas the wind tunnel could not reach. Results from the aeolian-portion of the study indicated extremely low concentrations of metals existed in the soil dust with a background uranium concentration of 0.74 mg/kg, a value 30 times less than background uranium concentration in soil. Overall, metals concentrations in the soil dust were most likely natural constituents of in-situ soil-forming processes and not derived from aeolian processes originating from the abandoned mine sites.

Environmental Impacts from the North Cave Hills Abandoned Uranium Mines, South Dakota

This study evaluated environmental impacts from historical uranium mining to soil, water, and air resources occurring on private lands surrounding the North Cave Hills complex within Custer National Forest, northwest South Dakota. Surface water concentrations of As, Cu, Mo, U, and V exceeded established background concentrations within approximately 27 km of stream length flowing below abandoned mines. Uranium concentrations in soils were mostly below the background value of 22 mg/kg and had a generally decreasing trend with increasing distance from the source areas, with higher values were associated with washover deposits and channeling of sediments.

Technology enabled curriculum for a first-year engineering program

For the past three years, all first year engineering students at the South Dakota School of Mines & Technology have enrolled in a common introduction to engineering course. The course features a common curriculum contained on a course CD, utilization of technology tools, an engineering design project, and introduction to technical writing. All sections of the course are taught in a single classroom that is set up with tables and equipped with wireless notebook PCs. Technology tools are focused on collection, manipulation, and presentation of data using electronic portfolios, a permanent digital archive, spreadsheet tools, and data loggers. The use of spreadsheets for solving engineering problems is illustrated through example problems and several tutorial exercises that are both contained on the curricular CD. Portable data loggers are utilized in lab projects for collecting data that is then manipulated and analyzed on a spreadsheet. The design project requires students teams to function within specified design parameters, construct a simple device that is then used to collect data, analyze the data, and present the results both in an oral presentation and a formal technical document. In this paper, examples of technology uses in the curricular materials, engineering problems, and design projects used will be illustrated and discussed.