Persistent Link:
http://hdl.handle.net/10150/282136
Title:
Transport of gas-phase contaminants in the unsaturated zone
Author:
Popovicova, Jarmila, 1968-
Issue Date:
1996
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The goal of this dissertation was to examine transport of gas-phase contaminants and the processes causing nonideal transport. With one exception, all experimental work was performed with synthetic porous media (glass beads). I performed experiments with methane, trichloroethene, benzene, and toluene. Transport experiments for gas-phase contaminants in dry homogeneous and heterogeneous porous media were performed to study dispersion of gases during transport. Axial diffusion was found to be a primary contributor to dispersion at gas velocities < 20 cm min⁻¹. Conversely, mechanical mixing was the main contributor to total dispersion at gas velocities > 50 cm min⁻¹. Dispersion of gas-phase contaminants during transport through dry heterogeneous (macroporous) medium was caused by three processes: axial diffusion, which was predominant at gas velocity < 20 cm min⁻¹ and negligible at gas velocity > 100 cm min⁻¹; mechanical mixing, predominant at gas velocities ranging from 30 to 120 cm min⁻¹; and diffusion between macropore and micropore domains, the main contribution to total dispersion at gas velocities above 160 cm min⁻¹. The latter process was responsible for rate-limited transport of gas-phase contaminants (methane, trichloroethene, benzene) through heterogeneous porous medium causing increased dispersion, early breakthrough, and tailing of breakthrough curves. Transport of gas-phase contaminants through the unsaturated heterogeneous porous medium showed a similar trends. The presence of heterogeneity and immobile water caused nonequilibrium transport of methane and trichloroethene. Predictions of breakthrough curves, which fit the experimental data well, were estimated independently and demonstrated that diffusion between macropore and micropore domains have a more pronounced effect on transport nonequilibrium than diffusion in immobile water. Retention of gas-phase contaminants in the unsaturated porous media was also examined. Solid-phase sorption of gas-phase contaminants was minimal and thus not responsible for delay during the transport. The major contribution to total retention was due to accumulation at the gas-water interface. For example, 62-73% and 30-50% total trichloroethene mass was retained at the interface during transport through the glass beads and aquifer material, respectively. Accumulation of benzene at the interface contributed to total benzene retention by 53-61% of total mass.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Environmental.; Environmental Sciences.; Engineering, Environmental.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Soil, Water and Environmental Science
Degree Grantor:
University of Arizona
Advisor:
Brusseau, Mark

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleTransport of gas-phase contaminants in the unsaturated zoneen_US
dc.creatorPopovicova, Jarmila, 1968-en_US
dc.contributor.authorPopovicova, Jarmila, 1968-en_US
dc.date.issued1996en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe goal of this dissertation was to examine transport of gas-phase contaminants and the processes causing nonideal transport. With one exception, all experimental work was performed with synthetic porous media (glass beads). I performed experiments with methane, trichloroethene, benzene, and toluene. Transport experiments for gas-phase contaminants in dry homogeneous and heterogeneous porous media were performed to study dispersion of gases during transport. Axial diffusion was found to be a primary contributor to dispersion at gas velocities < 20 cm min⁻¹. Conversely, mechanical mixing was the main contributor to total dispersion at gas velocities > 50 cm min⁻¹. Dispersion of gas-phase contaminants during transport through dry heterogeneous (macroporous) medium was caused by three processes: axial diffusion, which was predominant at gas velocity < 20 cm min⁻¹ and negligible at gas velocity > 100 cm min⁻¹; mechanical mixing, predominant at gas velocities ranging from 30 to 120 cm min⁻¹; and diffusion between macropore and micropore domains, the main contribution to total dispersion at gas velocities above 160 cm min⁻¹. The latter process was responsible for rate-limited transport of gas-phase contaminants (methane, trichloroethene, benzene) through heterogeneous porous medium causing increased dispersion, early breakthrough, and tailing of breakthrough curves. Transport of gas-phase contaminants through the unsaturated heterogeneous porous medium showed a similar trends. The presence of heterogeneity and immobile water caused nonequilibrium transport of methane and trichloroethene. Predictions of breakthrough curves, which fit the experimental data well, were estimated independently and demonstrated that diffusion between macropore and micropore domains have a more pronounced effect on transport nonequilibrium than diffusion in immobile water. Retention of gas-phase contaminants in the unsaturated porous media was also examined. Solid-phase sorption of gas-phase contaminants was minimal and thus not responsible for delay during the transport. The major contribution to total retention was due to accumulation at the gas-water interface. For example, 62-73% and 30-50% total trichloroethene mass was retained at the interface during transport through the glass beads and aquifer material, respectively. Accumulation of benzene at the interface contributed to total benzene retention by 53-61% of total mass.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Environmental.en_US
dc.subjectEnvironmental Sciences.en_US
dc.subjectEngineering, Environmental.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineSoil, Water and Environmental Scienceen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBrusseau, Marken_US
dc.identifier.proquest9706690en_US
dc.identifier.bibrecord.b34303285en_US
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