Award Date

1-1-2007

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Water Resource Management

First Committee Member

Charalambos Papelis

Number of Pages

123

Abstract

The Las Vegas Wash (Wash) channels the Las Vegas Valley's (Valley) treated wastewater, shallow groundwater, urban runoff, and stormwater runoff before terminating in Lake Mead at Las Vegas Bay. The population increase in the Valley has caused a dramatic increase in the flow of the Wash due to urbanization and increased wastewater effluent. Erosion control structures have been constructed to reduce erosion. These structures affect the flow of sediment through the Wash and might affect the distribution of potential contaminants in a way that can negatively impact plant and animal life; The chemical constituents examined in this study are arsenic, boron, selenium and phosphorus. Sediment samples were collected from above and below each of the erosion control structures using appropriate sampling techniques to obtain representative samples. Physical characterization of the samples, including particle size distribution, surface area analysis particle morphology, and mineralogy, was performed. The elements of concern were extracted from the sediments and analyzed to determine concentrations. The physical characteristics of the samples were compared to the concentrations in order to determine the relationship between those characteristics and the distribution of the elements. In addition, elemental concentrations were compared to the location of the samples along the Wash to determine how the erosion control structures might affect elemental distribution. The results show that samples with the following characteristics are more likely to have higher than average concentrations of selenium, arsenic, boron, and phosphorus: (1) contain lower percentages of quartz, (2) contain higher percentages of calcite and dolomite, (3) are from locations immediately downstream of an erosion control structure, or (4) have an above average surface area. Additionally, restoration activities that disturb bank soils and sediments in the Wash may help to elevate levels of the elements of interest near those areas, at least temporarily. The age of the structure may also be a factor in higher than average accumulation of selenium, arsenic, boron, and phosphorus. Shallow groundwater might be an additional source of the elements considered; This study shows the significance of detailed sediment characterization in the interpretation of elemental distribution trends within the Wash. This approach will be useful in future studies within the Wash and in other urban watersheds in arid and semi-arid regions.

Keywords

Control; Distribution; Effects; Erosion; Las Vegas Metals; Nutrients; Sediments; Selected; Structures; Vegas; Wash

Controlled Subject

Environmental sciences; Geochemistry

File Format

pdf

File Size

3409.92 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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