dc.contributor.advisor	Brooks, Bryan W.
dc.contributor.author	Valenti, Theodore Walter.
dc.contributor.department	Ecological, Earth, and Environmental Sciences.	en
dc.contributor.other	Baylor University. Institute of Ecological, Earth and Environmental Sciences.	en
dc.date.accessioned	2010-10-08T16:30:58Z
dc.date.available	2010-10-08T16:30:58Z
dc.date.copyright	2010
dc.date.issued	2010
dc.description.abstract	Freshwater is increasingly becoming a finite resource in many regions of the world. Gaps between estimated water supply and demand continue to narrow and the prospects of acquiring additional sources of freshwater remain limited. Furthermore, economically efficient water resource management practices are perplexed by increasing urbanization and changing land-use in semi-arid regions. Although repeated use of water is a practical and effective means for easing strain on water supplies, there is concern that unnecessary contamination may diminish future value of this important resource. Some surface waters in semi-arid regions of the U.S. are effluent-dominated as flow is comprised of >90% treated wastewater. Ionizable compounds are chemicals often associated with urban development and examples include pharmaceuticals, agrochemicals, natural toxins, and other common contaminants (e.g. ammonia). Because continued population growth and urbanization are likely to increase contaminant release and alter dilution capacity of receiving systems, it is important that best management approaches are developed at the watershed scale to limit water quality degradation associated with ionizable compounds. Current methods for prospective and retrospective ecological risk assessments of ionizable compounds seldom consider site-specific conditions during the analysis of effects of phase. Ionization state is largely controlled by the acid/base dissociation constant (pKa) and pH of the solution where a compound resides. Stream water quality can therefore influence ionization state, which is important because the unionized forms a more lipophilic and have a greater propensity to cross cellular membranes. Consequently, the unionized forms are hypothetically more toxic. I completed toxicity tests in the laboratory using various contaminants as model ionizable compounds over a gradient of environmentally-relevant surface water pH and then related measured toxicological endpoints to observed pH of surface waters using both discrete and probabilistic ecological risk assessment approaches. The result of my studies clearly demonstrated that site-specific pH may influence the toxicity of ionizable contaminants. Potential modifications to conceptual frameworks of ecological risk assessment for ionizable contaminants are suggested so that uncertainty can be reduced.	en
dc.description.degree	Ph.D.	en
dc.description.statementofresponsibility	by Theodore W. Valenti, Jr.	en
dc.format.extent	440484 bytes
dc.format.extent	443091 bytes
dc.format.extent	443088 bytes
dc.format.extent	71823 bytes
dc.format.extent	2188710 bytes
dc.format.mimetype	application/pdf
dc.format.mimetype	application/pdf
dc.format.mimetype	application/pdf
dc.format.mimetype	application/pdf
dc.format.mimetype	application/pdf
dc.identifier.citation	Valenti TW, James SV, Lahousse M, Schug KA, Roelke DL, Grover JP, Brooks BW. "A mechanistic explanation for pH-dependent ambient aquatic toxicity of Prymnesium parvum Carter." Toxicon 55, 5 (2010): 990-998.	en
dc.identifier.citation	Valenti TW, James SV, Lahousse M, Schug KA, Roelke DL, Grover JP, Brooks BW. "Influences of pH on amine toxicology and implications for harmful algal bloom ecology." Toxicon 55, 5 (2010): 1038-1043.	en
dc.identifier.citation	Valenti TW, Perez –Hurtado P, Chambliss CK, Brooks BW. "Acute and sublethal toxicity of sertraline to Pimephales promelas over a surface water pH gradient: Implications of ionization state for risk assessment." Environ Tox Chem 28 (2009): 2685-2694.	en
dc.identifier.uri	http://hdl.handle.net/2104/8063
dc.language.iso	en_US	en
dc.rights	Baylor University theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. Contact librarywebmaster@baylor.edu for inquiries about permission.	en
dc.rights.accessrights	Worldwide access.	en
dc.rights.accessrights	Access changed 9/4/2013.
dc.subject	Environmental risk assessment.	en
dc.subject	Aquatic ecotoxicology.	en
dc.subject	Ionizable contaminants.	en
dc.subject	Site-specific pH.	en
dc.subject	Emerging contaminants.	en
dc.title	Advancing an understanding of ecological risk assessment approaches for ionizable contaminants in aquatic systems.	en
dc.type	Thesis	en

Advancing an understanding of ecological risk assessment approaches for ionizable contaminants in aquatic systems.

Files

Original bundle

License bundle

Collections