Tuesday, 11 July 2006 - 4:40 PM

Impacts of Applying an Organic Emulsion on Soil Hydrology and Dust Emissions from an Arid Soil.

Michael H. Young, Todd Caldwell, Darren Meadows, Vic Etyemezian, George Nikolic, David Shafer, Eric McDonald, Julie Miller, and John Goreham. Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119

The stabilization of environmental contaminants near the soil surface may produce undesired impacts on local ecosystems if the stabilizing agent alters the natural behavior of the soil. In this study, we investigated the potential hydrologic impacts of an organic-based emulsion, which was designed to stabilize disturbed and undisturbed desert soils, as well as its impact on dust emission potential. The “Encapco” emulsion used in this study is a blend of organic esters, surfactants, water, and a proprietary chelating agent. A primary benefit is its ability to chelate and stabilize metals found on soil surfaces, but a secondary benefit is the reduction of dust emission potential. The emulsion was tested on desert alluvial soils at the Yuma Proving Ground (YPG), Yuma, AZ, USA, and on controlled soil materials near Las Vegas, NV, USA. 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 soil's hydrologic properties. Results at YPG 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. The concentration of the applied emulsion did not affect the results, at least for the two test dilutions used. The emulsion also appeared to have a larger impact on the younger soil, perhaps because the older surface is naturally less permeable due to a fine-grained surface horizon. To better isolate the effect of soil texture on emulsion effectiveness, air quality experiments examined the dust emission potential for soils of four different particle size distributions. Experiments were conducted using the Portable In-situ Wind Erosion Laboratory (PI-SWERL) to quantify fugitive dust emissions and a tension infiltrometer to measure hydraulic properties. Experiments were performed on four plots treated with a single dilution and four untreated plots for each soil type (40 plots total). Preliminary results show that the emulsion significantly reduced the dust emission for all soils. At both field sites, the effects of emulsion on hydrology and dust emission tend to diminish with time. Controlled laboratory tests were conducted in tandem to evaluate breakdown mechanisms; those results indicate that the breakdown of the emulsion is dependent upon ultraviolet exposure. Thus, in warm desert climates with high incoming solar radiation, intermittent reapplication may be necessary. These experiments provide insight on secondary environmental effects of the emulsion, which could potentially impact local ecosystems and air quality. In addition, the results will help guide future field applications and develop more efficient application and re-application strategies.

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