Modern dust samples are useful for many types of studies, including eolian processes, human disturbances in the desert, soil genesis, ecosystem function, and groundwater chemistry.

Modern dust is collected in three ways:

1. Annual collection and analysis from passive-type pan samplers at numerous sites in southern Nevada and California since 1984 (see map). Information from these sites combined with soil and weather data sheds light on:

• Genesis of aridic soils. At sites with stars and dots (see map), accumulation of desert dust accounts for the most of the pedogenic material in the soils.
• Dust storms and climate. Most undisturbed areas do not produce much dust under normal conditions. Rather, high dust flux follows periods of high precipitation, which produce floods that deposit fine-grained sediment susceptible to deflation.
• Natural dust sources. Much more dust is derived from lightly vegetated alluvial fans and plains than from playas (unless heavy storms have flooded playa surfaces with fresh sediment). The Death Valley transect shows that the modern playa contributes salt and a carbonate-rich dust, but the wide plain of the Amargosa is a more important source of silt and clay (fines).



(click for larger image- 11K) Death Valley Transect

(click for larger image-9.4K) Antimony vs. distance from Owens Lake

• Owens (dry) Lake as a dust source. The bed of Owens Lake, desiccated by water diversions in the early 1900's, is the single largest source of PM-10 dust in the United States. Trace-element contents (see plot of antimony, Sb, versus distance from the lake bed) suggest that dust from Owens Valley is a significant part of deposited dust as much as 400 km downwind.
• Human disturbances in the desert. Dust deposition is significantly higher downwind of the few intensively farmed areas. Additions of construction dust are found near urbanizing areas like Las Vegas.

2. Dust is trapped on passive, air-foil collectors installed at each CLIM-MET station (beginning in 1998). Analysis by microbeam methods for particle morphology and chemical composition (from sticky carbon tape), as well as for flux and bulk chemistry (from a greased plate).

3. Dust in snow pack, analyzed for trace elements by ICP-MS and for flux.

• We are monitoring flux as a function of seasonal climatic variables and are comparing fluxes determined from the different sampling strategies.

• Analyses of dust from snow pack and air-foil collectors reveal that many are strongly enriched in trace elements relative to an average crustal rock composition.