HR: 14:25h
AN: A23D-04 [Abstracts]
TI: Heterogeneous Chemistry of Individual Mineral Dust Particles with Nitric Acid. Laboratory and Field
Observations.
AU: * Laskin, A
EM: Alexander.Laskin@pnl.gov
AF: Pacific Northwest National Laboratory, POB 999, K8-88, Richland, WA 99352
AU: Grassian, V H
EM: vicki-grassian@uiowa.edu
AF: Department of Chemistry and the Center for Global and Regional Environmental Research, University of
Iowa, Iowa city, IA 52242
AU: Rudich, Y
EM: yinon.rudich@weizmann.ac.il
AF: Department of Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100
Israel
AB:
This study presents laboratory and field evidence of complete, irreversible processing of solid calcium carbonate
(calcite)-containing particles and quantitative formation of liquid calcium nitrate particles apparently as result of
heterogeneous reaction of calcite with nitric acid. The heterogeneous chemistry of individual dust particles from four
authentic dust samples with gas-phase nitric acid is presented. Morphology and compositional changes of individual particles
as they react with nitric acid were observed using conventional scanning electron microscopy with energy dispersive analysis
of X-rays (SEM/EDX) and computer controlled SEM/EDX. Environmental Scanning Electron Microscopy (ESEM) was utilized to
investigate the hygroscopic behavior of mineral dust particles reacted with nitric acid. Differences in the reactivity of
mineral dust particles from these four different dust source regions with nitric acid were observed. Mineral dust from
source regions containing high levels of calcium, namely China loess dust and Saudi coastal dust, were found to react to the
greatest extent. Formation of nitrates from individual calcite particles was also followed as a function of time in field
aerosol samples collected at Shoresh, Israel. We show that calcium carbonate rich dust aerosols may exhibit continuous,
extensive reactivity with nitric acid resulting in formation of highly hygroscopic calcium nitrate particles. Transformation
of hygroscopically inert dry mineral dust particles into hygroscopic wet aerosol may have substantial impacts on the light
scattering properties, the ability to modify clouds and heterogeneous chemistry.
DE: 4801 Aerosols (0305)
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting