Ion-beam thermography analysis of the H2SO4-(NH4)(2)SO4 system in aerosol samples

Ion-beam thermography (IBT) is used to determine the chemical composition o f atmospheric aerosols. The aerosols are analysed by a combination of four ion-beam techniques PIXE, PESA, pNRA and cPESA during thermography. These t echniques monitor the concentrations of the available elements during the s tepwise heating of the sample. For each element a thermogram, i.e,, the con centration vs. temperature, is obtained. Vaporisation of chemical compounds generated during heating will result in a decrease in concentration in the thermograms at temperatures that are characteristic for the compounds. The compounds are identified by the stoichiometric ratios and the characterist ic vayorisation temperatures (CVT), This payer deals with the analysis of f ive different laboratory-produced aerosols with the following compositions: (NH4)(2)SO4, (NH4)(15)H0.5SO4, NH4HSO4, (NH4)(0.5)H1SO4 and H2SO4. All com pounds were readily separated with respect to response in IBT analysis and the amount of water bound to the two most acidic compounds could be quantif ied. (C) 2000 Elsevier Science B.V. All rights reserved.