The transformation of solid atmospheric particles into liquid droplets through heterogeneous chemistry: Laboratory insights into the processing of calcium containing mineral dust aerosol in the troposphere

[1] Individual calcium carbonate particles reacted with gas-phase nitric acid at 293 K have been followed using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX) analysis as a function of time and relative humidity (RH). The rate of calcium carbonate to calcium nitrate conversion is significantly enhanced in the presence of water vapor. The SEM images clearly show that solid CaCO 3 particles are converted to spherical droplets as the reaction proceeds. The process occurs through a two-step mechanism involving the conversion of calcium carbonate into calcium nitrate followed by the deliquescence of the calcium nitrate product. The change in phase of the particles and the significant reactivity of nitric acid and CaCO 3 at low RH are a direct result of the deliquescence of the product at low RH. This is the first laboratory study to show the phase transformation of solid particles into liquid droplets through heterogeneous chemistry.

[1]  P. Midgley,et al.  Transport and Chemical Transformation in the Troposphere , 2001 .

[2]  Fate of products of degradation processes: consequences for climatic change. , 1999, Chemosphere.

[3]  Irina N. Sokolik,et al.  Incorporation of mineralogical composition into models of the radiative properties of mineral aerosol from UV to IR wavelengths , 1999 .

[4]  D. Jacob.  Heterogeneous chemistry and tropospheric ozone , 2000 .

[5]  A. Laskin,et al.  Quantitative time-resolved monitoring of nitrate formation in sea salt particles using a CCSEM/EDX single particle analysis. , 2002, Environmental science & technology.

[6]  Robert Frouin,et al.  April 1998 Asian dust event: A southern California perspective , 2001 .

[7]  T. Gill,et al.  Long‐range transport of North African dust to the eastern United States , 1997 .

[8]  K. H. Fung,et al.  Hydration and Raman scattering studies of levitated microparticles: Ba(NO3)2, Sr(NO3)2, and Ca(NO3)2 , 1997 .

[9]  S. Martin,et al.  The size effect of hematite and corundum inclusions on the efflorescence relative humidities of aqueous ammonium sulfate particles , 2001 .

[10]  J. Lelieveld,et al.  Role of mineral aerosol as a reactive surface in the global troposphere , 1996 .

[11]  Joshua P. Hacker,et al.  Long‐range transport of Asian dust to the Lower Fraser Valley, British Columbia, Canada , 2001 .

[12]  H. Brink.  Reactive uptake of HNO3 and H2SO4 in sea-salt (NaCl) particles , 1998 .

[13]  A. Goodman,et al.  A laboratory study of the heterogeneous reaction of nitric acid on calcium carbonate particles , 2000 .

[14]  G. Carmichael,et al.  Gas-Particle Partitioning of Nitric Acid Modulated by Alkaline Aerosol , 2001 .

[15]  S. Martin,et al.  Size effect of hematite and corundum inclusions on the efflorescence relative humidities of aqueous ammonium nitrate particles , 2002 .

[16]  Gunnar Myhre,et al.  Global sensitivity experiments of the radiative forcing due to mineral aerosols , 2001 .