T133 Mineralogy, Geochemistry, and Physical Properties of Atmospheric Mineral Dust: Influences on the Atmosphere, the Cryosphere, Ecosystems, and Humans

Monday, 10 October 2011
1:30 PM - 5:30 PM
Room L100DE

MINERALOGY AND GEOCHEMISTRY OF VESICULAR SOILS AS AN ARCHIVE OF DUST DEPOSITION AND PROXY FOR A REGIONAL DUST SOURCE, CENTRAL UTAH, U.S.A

Paper number: T133-3
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM

Authors

Abstract

The Sevier Desert of central Utah is one of several known regional dust sources providing sediment for storms that affect Salt Lake City and adjacent Wasatch Mountains, northern Utah. Dust is a health concern in the Wasatch Front Megapolitan Region, and dust deposition in the Wasatch Mountains affects the albedo of the snowpack while simultaneously introducing anthropogenically derived trace elements into the closed Great Salt Lake drainage basin. The vesicular A (Av) horizon of soils developed on shoreline features of the latest Pleistocene Lake Bonneville provide an integrated record of dust deposition in central Utah since shoreline abandonment, 18–10 ka. Additionally, these Av soils characterize a regional signal for dust originating in the Sevier Desert, which may be compared to Holocene and Anthropocene dust deposition in northern Utah.

Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN) analysis and optical microscopy were used to study the mineralogy of Av horizons, and their chemistry was determined by ICP-MS analysis of major, minor, and trace elements in 24 hour nitric acid leachates. These data identified depositional contributions from the host lithology, as well as near- and far-field eolian sources. Consequently, many minerals and elements show strong concentration gradients at the <10 km scale. No strong evidence was found that the Sevier (Dry) Lake bed is a disproportionately important dust source within the Sevier Desert. Vertical and horizontal sampling profiles within Av horizons did not demonstrate a high potential for recovering temporally resolved variations in dust composition. Lead was an exception; samples from the upper 2 cm contain approximately twice the concentration of lower samples. Some elemental concentrations, including Li, Mn, Ce, and Nd, were found to be less variable and might provide a proxy for dust sourced in Sevier Desert.