Award Date

1-1-2002

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Committee Member

Moses Karakouzian

Number of Pages

170

Abstract

This study investigated the effect of vegetation on gradation of surficial soils and airborne concentrations of particulate matter at a site in the mesquite sand dunes within the Jornada Experimental Range, a research ranch near Las Cruces, New Mexico. Particles less than 10 microns in diameter were of particular interest. This study site was chosen because it had been in used in previous studies, and meteorological instruments and dust collectors were already installed. Aerodynamic size distributions for soil and airborne particulate matter samples collected at different positions near and on the dunes were determined using a laboratory settling tube apparatus. In addition, 6 continuous aerosol monitors were operated at locations upwind, downwind and on top of a sand dune during two dust storms; Locations of vegetation determined using aerial photographs with 1-m resolution compared well with manually-determined vegetation locations with 0.5-m resolution. Soil sample analysis showed significant differences in the particle size distributions for the samples collected from the streets, dune tops, and dune sides. Fine sand comprised a much larger component of the dune top samples (60%) compared to the street samples (48%), and soil particles less than 16 microns in diameter comprised 0.1% of the dune top samples compared to 0.0% for dune sides. Dust collector samples showed that amounts collected increased with the length of bare area, or "street," in front of the sampler along the predominant wind direction. A threshold velocity for fine particle emissions was identified at approximately 65 to 80 cm s -1. A flux model was based on continuous measurements along a mesquite dune centerline and wind data from nearby sensors for 10-minute periods when wind flow aligned with the dune. Wind data were borrowed from a collocated study, and thus were not positioned directly in line with the dune. Two combinations of wind sensors were chosen to estimate flow in front of, on top of, and behind the dune. Comparing the outcomes based on the DustTrak(TM) data and the two combinations of sensors revealed that the selection of the wind speed information was critical to the overall model results.

Keywords

Airborne; Airborne Particles; Dunes; Effects; Gradation; Mesquite; Mesquite Dunes; New Mexico; Particles; Soil; Soil Gradation; Vegetation

Controlled Subject

Environmental engineering; Environmental sciences

File Format

pdf

File Size

3901.44 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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