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Composition of Dust

Dust in the western US ; a history of mineral aerosol deposition to Colorado Jason Neff CU Boulder, Geological Sciences & Environmental Studies With many contributions from Rich Reynolds, Lang Farmer, Tom Painter, Ashley Ballantyne, Dan Fernandez, Corey Lawrence & Chris Landry.

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Composition of Dust

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  1. Dust in the western US; a history of mineral aerosol deposition to Colorado Jason NeffCU Boulder, Geological Sciences & Environmental StudiesWith many contributions from Rich Reynolds,Lang Farmer, Tom Painter, Ashley Ballantyne,Dan Fernandez, Corey Lawrence & Chris Landry

  2. Composition of Dust Mineral material (variable in composition – benign to not so benign…) Industrial/combustion byproducts – soot, sulfate aerosols, others… Agricultural materials – minerals with other compounds also present Organic material – bacteria, viruses, soils, anthropogenic organic material

  3. Dust Transport to the SW US Dust storm forming over the Gobi April 16, 1998 Dust arriving at North America April 25, 1998

  4. US Sources Owens (dry) Lake --a major source of SW mineral dust (~7 % of PM10 in US) enriched in alkaline salts and trace metals Current conditions caused by water diversion beginning 1913 Two common dust sources in the Mojave Desert Photo by W. Cox, GBUAPCD Feb. 21, 1985 Dust from Ft. Irwin overrides mountains on eastern edge of base

  5. Dust over the Colorado Plateau

  6. Wilson Peak before and after April, 2006 dust storm. Photos by J. Overpeck, U of Arizona.

  7. San Juan Mountains, 5-21-2004

  8. Local vs. Far-Traveled Sources Dust and Lake Sediments

  9. Dust Deposition in San Juan Mountains 2003 1999 2004

  10. Finding Dust…

  11. Local Material Dust and sediments Dust, Sediments and Bedrock

  12. ~2000 years Sediment Age Model 210Pb for past ~150 years 14C of Terrestrial macrofossils for older material

  13. ~1920 ~1920 ~1860 ~1850 ~1000 BC ~1000 BC ~3000 BC Pacific Railway Act – 1862 Taylor Grazing Act - 1934

  14. Red Snows of the San Juans

  15. Taylor Grazing Districts in 1937 (Bureau of Land Management) Land Use Change in the Western US 1870 – 4.1 million beef cattle and 4.8 million sheep 1900 – 19.6 million beef cattle and 25.1 million sheep 1920s/1930s – severely degraded rangelands over large parts of the Western US 1934 Taylor Grazing Act passed by congress

  16. Implications 1 • Large potential increases in element deposition rates Mineral Soils Organic Matter Industrial contaminants (atmospheric N) Agricultural contaminants (pesticides)

  17. 1950 1950 1920 1920

  18. Dust deposition, composition and human health implications Particle size Particle composition (this can change)

  19. Regional Dust Fluxes are Large!

  20. N – Combustion and Agricultural Sources P – Agricultural Sources Organic Compounds – multiple human sources

  21. Supported by the A.W. Mellon Foundation & the US Geologic Survey

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