HR: 0830h
AN: B21F-0769    [PDF]
TI: Estimates of soluble iron from observations and a global mineral aerosol model
AU: * Hand, J L
EM: hand@cira.colostate.edu
AF: Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO 80523 United States
AU: Mahowald, N M
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 United States
AU: Chen, Y
AF: Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD 20688 United States
AU: Siefert, R L
AF: Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD 20688 United States
AU: Luo, C
AF: Bren School of Environmental Science and Management and Institute for Computational Earth System Science, University of California, Santa Barbara, Santa Barbara, CA 93106 United States
AB: Desert dust deposition to the ocean may be a significant source of biogeochemically important elements, specifically iron. The bioavailability of iron in the oceans requires it to be in a soluble form, and because atmospheric iron in desert dust is typically insoluble, understanding the atmospheric processes that convert insoluble iron to a more soluble form is essential. Understanding these relationships is especially important in remote ocean regions where iron may be the limiting nutrient. Observations of soluble iron from 2001 cruise-based aerosol measurements in the Atlantic and Pacific Oceans ranged from 0- 49.4% in fine mode ($<$ 3 micrometer in diameter) and 0-95.2% in the coarse mode. Correlations between percent soluble iron with other aerosol species were found for some of the cruises, suggesting iron processing in aerosol solutions may be important. We test two simple hypotheses of soluble iron enhancement using a global model of mineral aerosols. The first method assumes that iron solubility increases as iron is exposed to solar radiation, approximating photoreduction reactions that are important pathways for enhancement of soluble iron. The second process imitates cloud processing of iron by increasing the amount of soluble iron when the mineral aerosol comes into contact with a cloud. Both methods resulted in similar magnitudes of percent soluble iron compared to observations but did not capture specific events, perhaps because the model does not include aerosol interactions between species other than mineral dust.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2003 Fall Meeting