New Mexico Geological Society Annual Spring Meeting — Abstracts

Closed mines pose significant risks to the environment and human health. Uranium mine contamination of surface water, groundwater and soil have received moderate attention, but few studies have investigated dust transport of uranium. The latter has immediate implications for remediation efforts and environmental/human health regulators. Frequent dust storms intensify aeolian transport of uranium in arid settings. At the Jackpile Mine in Laguna Pueblo, New Mexico, 15 sets of dust traps have been installed at heights of 0.25 m, 0.5 m, 1.0 m and 1.5 m above the soil surface. Some of these traps are within the mine pit, while others are up to 4 km away; dust from these sites was collected every two months. In addition, soil samples from each site were collected and sieved into eight size classes. All samples were acid digested and the uranium content analyzed using Inductively Coupled Plasma Mass Spectrometry. We investigated whether uranium has an affinity for a particular particle-size class, with interest centered on particles small enough to be completely inhaled by humans. Results show that surface concentrations of uranium vary substantially across the landscape. Distance from the pit shows no correlation with uranium in the upper 5 cm of soil. Other factors appear to control accumulation, such as vegetation height and density and topographic relief, which are known to have a significant impact on wind speeds, soil erosion and dust deposition. Our study site has over 150 m of relief and intricate topography that lead to a range of wind speeds between sites. The soil uranium content determined at 15 sites has been compared to site elevation and vegetation height. Preliminary analysis suggests that elevation and vegetation height may impact local erosion and deposition of uranium. Dust mass was collected at each height and converted into a flux (g/d). The relationship between mass flux and height above ground followed a power-law relationship as supported by previous research (Zingg, 1953; Butterfield, 1999; Dong et al., 2003; Dong et al., 2004a, 2004b). Particle size fractionation during aeolian transport of the dust increased metal concentrations in four of six metals of concern.