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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
Author(s) -
Krueger B. J.,
Grassian V. H.,
Laskin A.,
Cowin J. P.
Publication year - 2003
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2002gl016563
Subject(s) - calcium carbonate , nitric acid , calcium , chemistry , calcium nitrate , relative humidity , chemical engineering , scanning electron microscope , aerosol , carbonate , reactivity (psychology) , mineralogy , inorganic chemistry , materials science , organic chemistry , meteorology , medicine , physics , alternative medicine , pathology , engineering , composite material
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.