HR: 1330h
AN: A12B-0081    [PDF]
TI: Microscopic Structure of an Individual Sea Salt Particle: How Does It Look Like?
AU: * Laskin, A
EM: Alexander.Laskin@pnl.gov
AF: W.R.Willey Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O.Box 999 K8-88, Richland, WA 99352
AB: Over the last few decades much attention has been given to the physical and chemical properties of sea salt aerosol, which is considerably one of the most abundant aerosols emitted naturally in marine and coastal areas. Previous studies of different research groups have clearly demonstrated that variety of atmospheric heterogeneous processes of sea salt particles are effectively controlled by particle-absorbed water. Specifically, there is increasing evidence that heterogeneous chemistry of deliquesced sea salt particles can lead to the formation of photochemically active gas-phase halogen products. Sea salt particle is a diverse mixture of mineral salts. Consequently, understanding of the gas-particle reaction mechanisms requires detailed account of its internal composition together with knowledge of origin and location of particle-absorbed water. In this work we present solid evidence based on electron microscopy observations that: (1) when sea salt particle dries out it ousts highly soluble magnesium salts toward particle surface forming a natural thick coating that surrounds NaCl crystals located in the core, (2) the magnesium salts coating remain deliquesced at relative humidity as low as RH=15% revealing the fact that the water absorbed by sea salt particle is largely a solvent water of the magnesium salts brine. With the exception of extremely low relative humidity it is evident that in the real environment of the lower atmosphere a sea salt particle is either a liquid microdroplet or at least it has liquid outer shell of deliquesced magnesium salts. The implications of this fact to heterogeneous chemistry of sea salt particles, their optical properties, hygroscopicity and phase transitions are highlighted and discussed.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 4801 Aerosols (0305)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting