HR: 10:20h
AN: P22B-01    [Abstracts]
TI: Granulometry and geochemistry of aeolian dust during emission from Owens (dry) Lake, California
AU: Rojo, A
EM: arojo2@utep.edu
AF: Environmental Science and Engineering Program, University of Texas at El Paso, El Paso, TX 79968 United States
AU: * Gill, T E
EM: tegill@utep.edu
AF: Environmental Science and Engineering Program, University of Texas at El Paso, El Paso, TX 79968 United States
AU: * Gill, T E
EM: tegill@utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968 United States
AU: Gillette, D A
EM: gillette.dale@epamail.epa.gov
AF: NOAA Atmospheric Sciences Modeling Division / U.S. EPA, MD-81, ResearchTrianglePark, NC 27711 United States
AU: Emmert, S P
EM: semmert@utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968 United States
AU: Barnes, M A
EM: melanie.barnes@ttu.edu
AF: Department of Geosciences, Texas Tech University, Lubbock, TX 79409 United States
AB: We utilize a variety of methods to correlate particle size distributions (PSD) with the geochemistry of aeolian dusts being generated at Owens (dry) Lake, California. Elemental analysis of dust samples was performed via proton-induced X-ray emission (PIXE) and inductively coupled plasma - atomic emission spectrometry (ICP-AES). PSD (submicron through coarse sand) of dust (in air and water, dispersed and undispersed) were determined via laser diffraction to evaluate dust grain sizes (percent volume) as a function of time, height above the playa surface, and distance downwind of the initiation point of dust emission, as well as the effect of precipitation and soluble salts on overall dust loading. Aeolian sediments were collected at up to six heights up to 1m above the playa surface at up to seven sites along a 1.5 km long upwind-downwind transect during the Lake Owens Dust Experiment (LODE) I in March 1993. The initial dust event on March 11, 1993 was characterized by the wind erosion of an efflorescent playa surface rich in sodium sulfates and other evaporites deposited by saline groundwater discharge during late winter and early spring. Dust from this event was rich in clays as well as evaporites. The proportion of the finest (respirable) and coarsest (saltating) airborne particles decreased with distance downwind, while the proportion of mid-sized grains (silt) increased downwind. The proportion of clay and silt sized particles consistently increased with height and sand (saltating particle) content decreased with height above the playa at each site during LODE I. Percent volume of sand peaked in the fine sand (100-250 micrometers) range. The proportion of particles in any given size fraction had no clear pattern from one dust storm to another. PIXE analyses revealed the presence of at least 20 elements; several additional trace elements were detected at ppm levels by ICP-AES. Na, Si, and Ca were present at the highest concentrations (tens of weight percent) while several metals were present in trace concentrations (ppm). The concentrations of Na and S increased with height above the surface, suggesting emission of fine sodium sulfate aerosols during the initial storm in LODE I which deflated a surface layer of efflorescent salts. Na and S concentrations of the dust initially increased with distance downwind of the zero point and then decreased. As, Cu, Br, and Ni concentrations (up to tens of ppm) showed no preferential variation with height above the playa or distance downwind of the zero point, but clearly increased with time as dust events continued on March 11 -17 - 23, 1993 and the wind began to erode primarily clastic sediments. Fe, Al, and K concentrations decreased with distance and height, and increased from dust storm to dust storm. These preliminary results demonstrate the application of laser diffraction to determine the granulometry of aeolian dust in arid-land sediments and soils. The combined textural and geochemical analyses on aeolian dusts captured near their points of injection into the atmosphere will improve our understanding of the influence of saltating particles and fine-grained aeolian inputs on dust emissions and the potential risks to the public and environment.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 1029 Composition of aerosols and dust particles
DE: 1051 Sedimentary geochemistry
DE: 1065 Major and trace element geochemistry
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005