All posts tagged soil

Investigating the Effect of Texture on the Relative Benefit of Electroosmosis in Soil Remediation

The purpose of this experiment was to determine the influence of texture on the effect of electroosmosis (EO) on a hydraulic gradient imposed flow of an ionic solution through soil. It was hoped that by determining this, it would be possible to determine the effect of texture on the remedial potential of electroosmosis in a particular soil. A number of soil samples were gathered to provide a variety of attributes for a basis of comparison and analysis of trends. Soil samples were characterized for texture, pore space, particle density, and organic matter.

Using PVC pipe, a test chamber was designed to maintain an open-flow arrangement with a bottle used at the side of the anode to maintain a constant and relatively small external hydraulic gradient. The ionic solution used was a sodium chloride solution (3g/L).

For each test, an air-dried sample was loaded into the test chamber and the hydraulic gradient applied. Measurements of flow output were taken at ten-minute intervals for a total of four hours. Electroosmosis tests were run with a direct current of eight volts applied and control tests were run in the absence of electric current.

Of all variables, texture was found to be most directly related to the efficacy electroosmosis, with clay influencing EO negatively; the relationship identified substantiated the trend identified by the previous year’s study and contradicted the theoretical basis for electroosmotic efficacy.

Establishing a Correlation Between Texture and the Efficacy of Electroosmosis in Effecting the Removal of Organic Contaminants from Soil

The purpose of this experiment was to determine whether texture plays a significant role in determining the efficacy of electroosmosis in effecting the removal of organic, water-soluble contaminants from soil. Soil samples were collected which provided a wide assortment of attributes for a basis of comparison and analysis. The soil samples were oven-dried to assure the equal saturation of all the soil samples by equal concentrations of tannic acid.

A test chamber was constructed from a fluorescent tube protective cover and the end contacts of a fluorescent lamp. Three holes equidistant from one another were drilled in the tube in order to allow a measurement of tannic acid at regular intervals along the chamber. The test solution of tannic acid was 100 mg/L.

Each sample was saturated with tannic acid solution to the point that all pores were occupied. The test chamber was then filled with the saturated soil and the end caps sealed. An initial sample was taken from the test chamber in order to substantiate the initial concentration. A direct current of eight volts was then applied to the test chamber across the end contacts by means of a power supply. Every two hours for a total of six hours water samples were taken from each of the testing ports by means of pipettes. Each water sample was tested for tannic acid concentration.

The data collected show a tentative relationship of texture to electroosmotic efficacy and a distinct correlation between pore space and electroosmotic efficacy.

Establishing a Relationship of Texture to the Thermal Conductivity of Soil

The purpose of this experiment was to ascertain whether texture has a significant role in determining the thermal conductivity of soil. An attempt was made to collect samples which would be good representatives of each of the three soil textural classes. To eliminate moisture as a variable, all samples were oven-dried, and to eliminate color as a variable, all samples were heated from below.

A test chamber was constructed to keep the heating of the soil samples uniform by keeping the samples a constant distance from the heat lamp. Additionally, the test chamber’s sides were enclosed with aluminum sheets to minimize the influence of the air in the room on soil samples being tested.

Each sample was first placed in a freezer to lower its temperature and allow a greater increase in temperature to occur during heating. Exact starting and ending temperatures were not a concern, since it was the slope of the increase that was the focus of the investigation. The warming of each sample over the heat source was measured for twenty minutes, enough time to establish a distinct trend. Soil from each collection site was divided into two testing samples, which were each tested five times.

The data collected showed a direct relationship between thermal conductivity and texture as well as an indirect relationship through the variables influenced by texture, such as pore space and particle density. The direct relationship of texture to thermal conductivity shown was that as particle size decreased, thermal conductivity increased. The indirect relationship shown was that as particle density increases, thermal conductivity increases, and as pore space increases, thermal conductivity decreases. Another conclusion that can be drawn from the data is that in nature, it may ultimately be the water capacity of a soil (which is itself influenced by texture) which determines its thermal conductivity.