Contemporary geochemical composition and flux of aeolian dust to the San Juan Mountains, Colorado, United States

Abstract

, with individual deposition events reaching as high as 2 g m −2 . Dust deposited in the San Juan Mountains was primarily composed of silt-and clay-sized particles, indicating a regional source area. The concentrations of most major and minor elements in this dust were similar to or less than average upper continental crustal concentrations, whereas trace element concentrations were often enriched. In particular, dust collected from the San Juan Mountain snowpack was characterized by enrichments of heavy metals including As, Cu, Cd, Mo, Pb, and Zn. The mineral composition of dust partially explained dust geochemistry; however, based on results of a sequential leaching procedure it appeared that trace element enrichments were associated with the organic-, and not the mineral-, fraction of dust. Our observations show that the dust-derived fluxes of several nutrients and trace metals are substantial and, because many elements are deposited in a mobile form, could be important controls of vegetation, soil, or surface water chemistry. The flux measurements reported here are useful benchmarks for the characterization of ecosystem biogeochemical cycling in the Rocky Mountains.

Atmospheric deposition as a source of carbon and nutrients to an alpine catchment of the Colorado Rocky Mountains

“…Precipitation has been shown to be an important C input for carbon-poor environments, such as coastal areas (Kieber et al, 2006(Kieber et al, , 2007 and the open ocean (Willey et al, 2000, Economu and Mihalopoulos, 2002, Jurado et al, 2008. For alpine environments, Litaor (1987) and Ley et al (2004) in the Colorado Rocky Mountains and more recently Mladenov et al (2009Mladenov et al ( , 2010 in the Sierra Nevada of Spain reported that aeolian deposition comprised about 10 % to 20 % organic C. Lawrence et al (2010) also found surprisingly high organic C content in dust deposition. Mladenov et al (2009) used spectroscopic techniques (UV-vis absorbance and fluorescence) in combination with air mass backward trajectories to demonstrate that water soluble organic carbon (WSOC) from dust emitted in Africa and deposited at an alpine site in Spain contained substantial amounts of humic-like fluorescent compounds.…”

“…High Ca 2+ and DOP content is characteristic of dust deposition to the Colorado Rocky Mountains from the Colorado Plateau and Mojave Desert (Lawrence et al, 2010), which is most pronounced during the spring. Three high Ca 2+ precipitation events measured in 2010 (4, 11, and 18 May) had backward trajectories showing a Colorado Plateau air mass source (Supplement Fig.…”

“…The dry deposition input of Ca was not measured, but this input should be substantial because Ca is an important component of dust deposition in the Rocky Mountains (Lawrence et al, 2010). Indeed Clow et al (1997) found that atmospheric wet and dry deposition inputs of Ca represented > 25 % of the Ca export from a similar alpine/subalpine watershed in Loch Vale, Colorado, based on strontium tracer results.…”

Combined impacts of current and future dust deposition and regional warming on Colorado River Basin snow dynamics and hydrology

“…This sustained level of increased dust production and deposition appears to have been increasing further over recent decades (Brahney et al, 2013), and recent hydrologic studies show it has been affecting snowmelt rates and runoff timing and volume from the Colorado River Basin Skiles et al, 2012). Though some global dust sources exceed the intensity of dust emission in the southwestern US (e.g., Yu et al, 2012), multiple lines of evidence, including backtrajectory analysis, dust particle sizes, and synoptic event drivers, demonstrate the primarily regional provenance of dust deposited on UCRB snowpacks Neff et al, 2008;Lawrence and Neff, 2009;Lawrence et al, 2010;Steenburgh et al, 2012).…”

Effect of Atmospheric Deposition and Weathering on Trace Element Concentrations in Glacial Meltwater at Grand Teton National Park, Wyoming, U.S.A.

“…Dust contributes substantial loading of soluble salts, metals, and metalloids to snowpack (Turk et al, 2001;Clow et al, 2002;Ingersoll et al, 2008;Lawrence et al, 2010;Rhoades et al, 2010;Carling et al, 2012). Trace metal concentrations in dust (e.g., As, Cd, Cu, Mo, Pb, and Zn) are enriched relative to average upper continental crust, and dust-derived trace metals are more available and mobile relative to other sources (Lawrence and Neff, 2009;Lawrence et al, 2010Lawrence et al, , 2013. Dust sources impacting the Teton Range include the Snake River Plain agricultural area to the west and oil and gas extraction to the south and east (Spaulding et al, 2015).…”