Non-invasive survey technology for estimating the distribution of oxidant solution: A pilot injection study.

In-situ chemical oxidation (ISCO) can remove pollutants efficiently. However, the most important key to successfully conducting ISCO on site is to place the oxidant in close contact with the contaminant. Therefore, monitoring tools that provide for enhanced tracking of the injectate offer considerable benefit to guide subsequent ISCO injections.

Assessing the rate and timing of leaf wax regeneration in Fraxinus americana using stable hydrogen isotope labeling.

Rationale: Understanding leaf wax regeneration and recycling is crucial for plant physiology and paleoclimate studies. However, our recent isotope labeling experiments on a grass species (Phleum pratense) yielded different conclusions from published data on a tree species (Populus trichocarpa), with the former showing rapid regeneration and the latter little regeneration in mature leaves. It is therefore important to determine if the discrepancies in published results were due to differing dynamics of leaf wax regeneration and/or caveats in experimental methods.

Thin layer chromatography in the separation of unsaturated organic compounds using silver-thiolate chromatographic material.

We report the use of silver-thiolate chromatographic material (AgTCM) as a stable material for use in TLC. The AgTCM stationary phase operates under the same principles as silver-ion chromatography, separating compounds by degree of unsaturation; however, the AgTCM stationary phase shows considerable advantages over Ag-TLC in terms of light stability and shelf lifetime. We demonstrate the light stability of the AgTCM-TLC and its application for separations based on the degrees of unsaturation using fatty acid methyl esters (FAMEs) and polycyclic aromatic hydrocarbons (PAHs).

Using tracer technique to study the flow behavior of surfactant foam.

Surfactant foam was used to remove absorbed hydrocarbons from soils. The nature and extent of the foam pathway decide the efficiency of this technology. The characteristics and behavior of foam flow are difficult to visually observe.

Coupled acidification and ultrasound with iron enhances nitrate reduction.

Contaminated soils, especially when pollutant concentrations are high, pose potentially serious threats to surface and groundwater quality, when there are spills, discharges, or leaking storage tanks. For in situ remediation of nitrate in groundwater, the use of zero-valent iron (Fe(0)) is suggested. The formation of passivating scales on Fe(0) over time may limit the long-term reduction potential of Fe(0).

Air distribution and size changes in the remediated zone after air sparging for soil particle movement.

In an unconsolidated porous medium, soil particles can be mobilized by physical perturbation. In model systems of fluids flowing over spherical particles attached to flat surfaces, the hydrodynamic shear force depends on the fluid viscosity, particle radius, and flow velocity. Soil particles can be reasonably expected to be transported by flowing water during air sparging when the particle-size distribution does not fit the densest possible particle arrangement.

Estimating the change of porosity in the saturated zone during air sparging.

Air sparging is a remedial method for groundwater. The remedial region is similar to the air flow region in the saturated zone. If soil particles are transported during air sparging, the porosity distributions in the saturated zone change, which may alter the flow path of the air.

Air flow paths and porosity/permeability change in a saturated zone during in situ air sparging.

This study develops methods to estimate the change in soil characteristics and associated air flow paths in a saturated zone during in situ air sparging. These objectives were achieved by performing combined in situ air sparging and tracer testing, and comparing the breakthrough curves obtained from the tracer gas with those obtained by a numerical simulation model that incorporates a predicted change in porosity that is proportional to the air saturation. The results reveal that revising the porosity and permeability according to the distribution of gas saturation is helpful in breakthrough curve fitting, however, these changes are unable to account for the effects of preferential air flow paths, especially in the zone closest to the points of air injection.

A new design of groundwater sampling device and its application.

Compounds in the atmosphere contaminate samples of groundwater. An inexpensive and simple method for collecting groundwater samples is developed to prevent contamination when the background concentration of contaminants is high. This new design of groundwater sampling device involves a glass sampling bottle with a Teflon-lined valve at each end.

Mobilizing particles in a saturated zone during air sparging.

The mobilization of soil particles changes the porosity of saturated zone during air sparging. Soil porosity is shown to be correlated with soil electrical resistivity. This study performs porosity-resistivity tests to establish the relationship between porosity and resistivity of quartz sand.