Thursday, November 16, 2006 - 10:25 AM

Field and Laboratory Evaluation of a Soil-Applied, Organic Emulsion.

Michael Young, Darren Meadows, Todd Caldwell, David Shafer, Julie Miller, Steve Zitzer, Eric McDonald, and John Goreham. Desert Research Institute, 755 E. Flamingo Rd., Las Vegas, NV 89119

In this study, the ability of an organic-based emulsion—a blend of organic esters, surfactants, water, and a proprietary chelating agent—was examined to stabilize depleted uranium (DU). Potential impacts to hydrologic and ecosystem processes from topical application were also investigated. Two overriding hypotheses were tested: (1) the emulsion would reduce DU solubility on desert soils, and (2) the emulsion would alter infiltration and surface runoff potential, potentially influencing germination of native seeds. Field and laboratory experiments were run at the Yuma Proving Ground (YPG), Yuma, AZ and near Las Vegas, NV to test these hypotheses. At YPG, triplicate tension infiltrometer measurements and rainfall simulation experiments were conducted to examine the temporal dynamics (~0 mo, 3 mo, 6 mo, 12 mo), dilution ratio (control, 4:1, 6:1), geomorphic effects (young vs. old soils), and surface disturbance (raked vs. natural) impact to the hydrologic properties of the soil. After approximately 13 months of exposure to atmospheric conditions, the topical application of emulsion tended to mobilize DU versus untreated DU-containing soils. One explanation for this result may be that the low-pH emulsion increased DU solubility before the chelating agent could fully react with it. Results showed that the emulsion significantly reduced (~1 order of magnitude) the saturated hydraulic conductivity of the soil and decreased the time to ponding immediately following application. However, six months after treatment, few plots differed statistically from the pretreatment values, indicating a relatively short-lived hydrologic effect, and no differences were found between emulsion concentrations. The emulsion also appeared to have a larger impact on the younger soil, perhaps because the older, finer-grained surface is naturally less permeable. In summary, no long-term (6-months) hydrologic or ecosystem impacts were observed from application of the emulsion, but the chelating ability of the emulsion also was shown to have limited effectiveness.