Award Date

1-1-2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Science

First Committee Member

Spencer M. Steinberg

Number of Pages

199

Abstract

Lake Mead is located in the Mojave Desert and provides water for several states in the southwestern U.S. Although most of the water in Lake Mead originates from the Colorado River, there are several minor sources of water, such as the Virgin River, the Muddy River, and the Las Vegas Wash, that could impact water quality. The principal objective of this study was to obtain new and fundamental information about dissolved organic carbon (DOC) in the Lake. This study focuses on the development of concentration methods for aquatic humic substances (HS, major components of DOC), and the characterization of HS using various analytical methods that are capable of elucidating their unique molecular signatures that indicate their sources. Both evaporative concentration and solid phase extraction (using DiscoveryRTM DPA-6S resin) methods have been utilized to obtain HS from the Lake. The limitations of both approaches are elucidated. Characterization methods include fluorescence (synchronous and excitation-emission matrix), UV-Visible, and IR spectroscopy, high-performance size exclusion chromatography (HPSEC), tetramethylammonium hydroxide (TMAH) thermochemolysis GC-MS and pyrolysis GC-MS. To better reveal characteristics of HS in the Lake, site profiles, depth profiles, and seasonal variations are investigated. Finally correlation analyses among the different parameters have also been examined. Overall, the HS samples from the four sources (especially the Las Vegas Wash), near the confluence of the Las Vegas Wash in Las Vegas Bay, and close to the lakeshore have been found to have different properties compared with those toward the center of the Lake.

Keywords

Carbon; Characterization; Dissolved; Dissolved Organic Carbon; Humic; Lake; Lake Mead; Mead; Organic

Controlled Subject

Environmental sciences; Chemistry, Analytic; Environmental engineering; Limnology

File Format

pdf

File Size

4403.2 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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