Award Date

1-1-1996

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

Number of Pages

127

Abstract

Experiments were conducted to assess and model the effects of unsaturated zone soil moisture content on vapor-phase pollutant propagation in a controlled setting. A two-dimensional sandtank was utilized for controlled vapor-phase experiments, with pollutant vapors of octane and diesel fuel introduced through a finely slotted source tube. Soil moisture content was varied from 0% to 10% by weight for octane experiments, and from 0% to 5% by weight for diesel fuel. The effects of introduced soil moisture on the transport of each pollutant vapor were observed via soil-gas sampling from access ports. Soil-gas samples were analyzed with FID gas chromatography to determine a gross hydrocarbon concentration for discrete time intervals and distances from the vapor source; Analytical modeling methods based on Fickian diffusion, developed by Kreamer (1982), were used to estimate two primary diffusion parameters D{dollar}\sb{\rm e}{dollar}, the effective diffusion coefficient, and A*, the sorption corrected porosity. Estimations were carried out using a FORTRAN program with a non-linear subroutine. The estimated parameters were used to model concentration curves for each moisture content. The modeling indicated adverse effects on vapor propagation near 2% moisture content for octane and 2% moisture content for diesel fuel; A trend observed for the octane vapor modeling illustrates the relationship of D{dollar}\rm\sb{e},\ D\sb{k},{dollar} and A* to the tortuosity factor. Tortuosity was observed to decrease as moisture content increased up to 5% by mass. As moisture content increase beyond 5% gravimetrically, tortuosity began to increase as the porosity became occluded by water molecules.

Keywords

Content; Controlled; Effects; Experiments; Laboratory; Moisture; Phase; Pollutant; Propagation; Soil; Unsaturated; Vapor; Zone

Controlled Subject

Hydrology; Environmental sciences

File Format

pdf

File Size

2816 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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