HR: 17:15h
AN: B34B-06 INVITED     [Abstracts]
TI: Effects of Desert Dust on Nutrient Cycling in the San Juan Mountains, Colorado
AU: * Neff, J C
EM: neffjc@colorado.edu
AF: Geological Sciences Department, University of Colorado CB 399, Boulder, CO 80309 United States
AU: Farmer, L
B34B-06 AF: Geological Sciences Department, University of Colorado CB 399, Boulder, CO 80309 United States
AU: Farmer, L
B34B-06 AF: National Snow and Ice Data Center Center for the Study of Earth from Space , University of Colorado at Boulder 449 UCB, Boulder, CO 80309 United States
AU: Painter, T H
EM: tpainter@nsidc.org
AF: National Snow and Ice Data Center Center for the Study of Earth from Space , University of Colorado at Boulder 449 UCB, Boulder, CO 80309 United States
AU: Landry, C
EM: clandry@snowstudies.org
AF: Center for Snow and Avalanche Studies , PO Box 190 , Silverton, CO 81433 United States
AU: Reynolds, R
EM: rreynolds@usgs.gov
AF: Earth Surface Processes Team, US Geological Survey MS 980, Denver Federal Center, Denver, CO 80225 United States
AB: The San Juan Mountains of southwestern Colorado lie downwind from several major deserts and experience several dust-deposition events each year. These events appear related to storms that erode soils in the deserts of the western US and then deposit atmospheric dust from these soils during or after snowfall during large late winter and spring deposition events. To evaluate the biogeochemical implications of eolian deposition, we collected dust from distinct layers deposited into the seasonal snowpack. We also sampled soils and lake sediments in a high-elevation catchment in the San Juan Mountains. Atmospheric dust was characterized by measurements of chemical composition, Sr isotopic content and analysis of the organic and inorganic constituents of deposited eolian material. The origins of snowpack dust in the San Juans were analyzed using atmospheric tracer transport modeling. These analyses suggest that many dust events originate in southern Utah and northern Arizona, areas that have undergone substantial land use change through the 20^th century and that experience severe wind erosion of soils during periodic severe droughts. Analyses of ⁸⁷Sr/⁸⁶Sr isotope ratios dust, soils, bedrock, and sediments suggest that eolian dust may compose as much as 90% of the near-surface soil (top 5 cm). In alpine lake sediments, Sr isotopes suggest a relatively recent (20^th century) increase in the fraction of sediments derived from dust (relative to bedrock) and a similarly large contribution of dust to surface sediments. Sediment chemistry in two small alpine tarns show changes in Ca, Mg, Al, and Fe concentrations that imply increasing dust (vs. bedrock) contributions to lake sediments over the past 100-200 years. Increasing loading of Ca, Mg and P to alpine basins may have implications for alpine and sub-alpine biogeochemical cycling including water quality and plant nutrient use.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: Fall Meeting 2005