HR: 12:05h
AN: B11F-07    [PDF]
TI: Detection of the geographic distribution of source soil mineralogy in long range transported aerosol from {Ca} measurements and simulations in the {Dust Entrainment And Deposition (DEAD)} model
AU: * Zender, C S
EM: zender@uci.edu
AF: University of California at Irvine, Department of Earth System Science, Irvine, CA 92697 United States
AU: Bian, H
EM: bian@rondo.gsfc.nasa.gov
AF: NASA/GSFC, Code 916, Greenbelt, MD 20771 United States
AB: Calcium carbonate plays important indirect forcing roles in the chemical and biogeochemical system. Dust-borne CaCO$_{3}$ determines whether dust forms Ca(NO$_{3}$)$_{2}$ and deliquesces at ambient relative humidity, helps determine aerosol~pH, and limits uptake of reactive species such as HNO$_{3}$ and SO$_{2}$. We compare simulations with the Dust Entrainment and Deposition Model (DEAD) to observed climatologies of CaCO$_{3}$ at stations worldwide. Simulations employing realistic spatially heterogeneous CaCO$_{3}$ content in source soils perform better than simulations which assume the same global-mean CaCO$_{3}$ content is homogeneously distributed in Earth's soils. The signature of soil CaCO$_{3}$ heterogeneity is detected in mineral dust deposition at remote downwind stations in the Atlantic and Pacific. Examining the CaCO$_{3}$ deposition flux normalized by the annual dust deposition flux, we find that North Atlantic deposition is relatively poor in CaCO$_{3}$ due to lower-than-average content in African source regions. In contrast, Asian deposition is relatively high in CaCO$_{3}$ due to alkaline Central Asian soils. This regional CaCO$_{3}$ abundance amplifies the role of dust in heterogeneous chemistry in Asian regions. Summertime Asian dust reduces tropospheric O$_{3}$ more strongly than African dust to Asian dust encountering more ozone precursors (e.g., NO$_{x}$) and having greater CaCO$_{3}$ abundance. Our simulations show that assuming soil composition is globally uniform leads to detectable biases. This has important implications not only for CaCO$_{3}$, but for other biogeochemically significant mineral carried in dust such as Iron and Phosphate.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0322 Constituent sources and sinks
DE: 0368 Troposphere--constituent transport and chemistry
SC: Biogeosciences [B]
MN: 2003 Fall Meeting