Transport modeling of metal contaminants in a stream-aquifer system

Persistent Link:
http://hdl.handle.net/10150/288879
Title:
Transport modeling of metal contaminants in a stream-aquifer system
Author:
Choi, Jung-Yill, 1963-
Issue Date:
1998
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:
Pinal Creek, Arizona has been contaminated by discharge of acidic (pH = 5.8-6.3) and metal-rich ground water that was released from mining activities. In the stream, pH increases from approximately 6.0 to 7.8, while dissolved Mn(II) decreases from approximately 70.0 to 50.0 mg/L over 3 km downstream of the point of groundwater discharge. It was hypothesized that the spatial variation of in-stream pH is controlled by CO₂ gas-exchange and affects transport of dissolved Mn(II) through pH-dependent microbial oxidation in hyporheic zones. An existing transport model was extended to include carbonate equilibria, CO₂ degassing and pH-dependent Mn(II) removal processes and applied to predict the alkalinity-inorganic carbon (Cτ)-pH balance and transport of Mn(II) in natural stream based on field and laboratory experiments. The simulation results reproduced the overall trends of alkalinity, Cτ, and pH, and were in good agreement with dissolved Mn(II) in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivity of predictions to physical and chemical parameters used in the extended transport model. MPSA results imply that CO₂ degassing and pH-dependent microbial oxidation are the most important factors controlling the spatial variation in pH and reactive uptake of dissolved Mn(II) in the stream system. Using stream tracer injections, streambed sediments and aquatic vegetation areas were identified as physical-storage zones within the stream where biogeochemical reactions were enhanced. The traditional one-storage transport model was extended to describe the hyporheic processes associated with two independent transient storage zones. The extended model was used to evaluate the applicability and accuracy of one-storage transport model to two-storage stream system. One-storage transport model has very strict limitation in its application for the two-storage stream system and is only valid if two retention times of transported solutes are very close (Tr₁/Tr2 1.0). The presented field and modeling approaches, which include model extension for the processes of CO₂ degassing and pH-dependent biogeochemical reactions, and generalized sensitivity analysis can improve our understanding of transport of metal contaminants in natural stream-aquifer system.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Hydrology.; Environmental Sciences.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Hydrology and Water Resources
Degree Grantor:
University of Arizona
Advisor:
Conklin, Martha

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleTransport modeling of metal contaminants in a stream-aquifer systemen_US
dc.creatorChoi, Jung-Yill, 1963-en_US
dc.contributor.authorChoi, Jung-Yill, 1963-en_US
dc.date.issued1998en_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.abstractPinal Creek, Arizona has been contaminated by discharge of acidic (pH = 5.8-6.3) and metal-rich ground water that was released from mining activities. In the stream, pH increases from approximately 6.0 to 7.8, while dissolved Mn(II) decreases from approximately 70.0 to 50.0 mg/L over 3 km downstream of the point of groundwater discharge. It was hypothesized that the spatial variation of in-stream pH is controlled by CO₂ gas-exchange and affects transport of dissolved Mn(II) through pH-dependent microbial oxidation in hyporheic zones. An existing transport model was extended to include carbonate equilibria, CO₂ degassing and pH-dependent Mn(II) removal processes and applied to predict the alkalinity-inorganic carbon (Cτ)-pH balance and transport of Mn(II) in natural stream based on field and laboratory experiments. The simulation results reproduced the overall trends of alkalinity, Cτ, and pH, and were in good agreement with dissolved Mn(II) in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivity of predictions to physical and chemical parameters used in the extended transport model. MPSA results imply that CO₂ degassing and pH-dependent microbial oxidation are the most important factors controlling the spatial variation in pH and reactive uptake of dissolved Mn(II) in the stream system. Using stream tracer injections, streambed sediments and aquatic vegetation areas were identified as physical-storage zones within the stream where biogeochemical reactions were enhanced. The traditional one-storage transport model was extended to describe the hyporheic processes associated with two independent transient storage zones. The extended model was used to evaluate the applicability and accuracy of one-storage transport model to two-storage stream system. One-storage transport model has very strict limitation in its application for the two-storage stream system and is only valid if two retention times of transported solutes are very close (Tr₁/Tr2 1.0). The presented field and modeling approaches, which include model extension for the processes of CO₂ degassing and pH-dependent biogeochemical reactions, and generalized sensitivity analysis can improve our understanding of transport of metal contaminants in natural stream-aquifer system.en_US
dc.description.noteDigitization note: p. 87 and p. 156 missing from paper original.-
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectHydrology.en_US
dc.subjectEnvironmental Sciences.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineHydrology and Water Resourcesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorConklin, Marthaen_US
dc.identifier.proquest9901705en_US
dc.identifier.bibrecord.b38830279en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.