The surface water composition of Pinal Creek has been affected by input of a low-oxygen ground water plume with high metal concentrations, particularly manganese and copper, and low pH. The pH of the stream water increases from approximately 6.0 to 7.8 downstream of the point of entry, which may affect the rate of manganese oxide precipitation. The purpose of this study was to determine the role of gas exchange processes on the observed downstream increase in pH at Pinal Creek. A finite-difference model was developed to calculate downstream changes in concentration of volatile solutes in small streams. Gas exchange rate constants used in the model were estimated using propane tracer techniques. Modeled simulations of dissolved oxygen and dissolved inorganic carbon transport in a 2.6 km reach at Pinal Creek, Arizona closely matched field observations. Based on the carbon balance and alkalinity balances, it can be concluded that downstream changes in pH can be sufficiently explained by acid/base chemistry of carbonate and CO2 degassing. Laboratory batch studies conducted in the laboratory using Pinal Creek water indicated that biological activity may be an important control on the precipitation of the black manganese oxides that were observed to coat the sediments in Pinal Creek.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/278498 |
| Date | January 1995 |
| Creators | Hulseapple, Scott Michael, 1970- |
| Contributors | Conklin, Martha H., Harvey, Judson W. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Thesis-Reproduction (electronic) |
| 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. |
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