Investigating acidification mechanisms of Saharan dust aerosols: Implications for Fe solubility and marine primary productivity
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Through collaboration with Jordi Dachs (IIQAB-CSIC, Barcelona) and Antonio Tovar (IMEDEA-CSIC, Mallorca), we are involved with the Spanish campaign RODA (English translation of the acronym RODA = Oceanic Eddies and Atmospheric Deposition in the Canary Current). The figure to the right shows cruise tracks from two cruises that took place during August 2006 (red line) and February 2007 (blue line) just off the coast of West Africa. Aerosol samples were collected during these cruises, and are being measured for sulfate D17O in our lab. |
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The figure to the left shows sulfate D17O (color scale) and concentration (size) of aerosol samples measured during both RODA cruises. The laboratory measurements were performed by our former graduate student, Dan Allman. These observations are being interpreted quantitatively in terms of the importance of different sulfate production pathways utilizing the GEOS-Chem global 3D chemical transport model. Helen Amos, an undergraduate researcher, is currently leading the global modeling effort. |
| The figure to the right shows a box model study of the sensitivity of sulfate D17O to the reaction probability (g) of SO2 on dust. The box model uses meteorological and chemical conditions of the subtropical North Atlantic marine boundary layer during the February 2007 cruise. The values of g reflect the range of g values used in various global modeling studies reported in the literature. The figure shows that when dust concentrations (represented by non-sea-salt Ca2+) are low, the value of sulfate D17O shows little sensitivity to g as expected. However, when dust concentrations are high, the value of sulfate D17O is very sensitive to the value of g, with D17O values ranging from ~1 - 5 ‰. The low and high values of nssCa2+ shown here are representative of the full range of nssCa2+ observations during the February 2007 cruise as measured via ICP in Ron Sletten's lab by Dan Allman. |
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| People: | |
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Becky Alexander, Daniel Allman, and Helen
Amos, University of Washington Jordi Dachs, Institute for Chemical and Environmental Research, IIQAB-CSIC, Barcelona, Spain Antonio Tovar, Mediterranean Institute for Advanced Studies, IMEDEA-CSIC, Mallorca, Spain Duncan Fairlie, Harvard University and NASA Langley |
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| References: | |
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Fairlie, T.D., D.J. Jacob, J.E. Dibb, B. Alexander, M.A.
Avery, A. van Donkelaar, and L. Zhang,
Impact of mineral dust on
nitrate, sulfate and ozone in transpacific Asian pollution plumes, Atmos. Chem. Phys.
Discuss, 9, 24477-24510, 2009. Allman, D.J., "Quantifying sulfate formation pathways downwind of the Sahara desert: Influence of dust aerosols on the marine boundary layer sulfur budget", M.S. Thesis, June 2009. Amos, H.M, D.J. Allman, B. Alexander (2009), "Investigating the influence of dust aerosol on the atmospheric sulfur budget in the marine boundary layer using oxygen isotope measurements of sulfate aerosol and a one-dimensional box model", UW Undergraduate Research Symposium, Seattle, WA, May 15, 2009. (Poster) Allman, D.J., H.M. Amos, B. Alexander (2008), "Quantifying sulfur acidification mechanisms of Saharan dust aerosols", EOS Trans, AGU, 89, Fall Meet. Suppl., Abstract A11C-0126. (Poster) | |
| Funding: | |
| NSF-ATM 0607846 | |
