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  • DMS oxidation  (1)
  • methacrolein  (1)
  • 1
    ISSN: 1573-0662
    Schlagwort(e): DMS oxidation ; NO3 radical ; MSA-H2SO4 aerosol ; peroxy-nitrate intermediate ; sulphur cycle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract The reaction between dimethyl sulphide (DMS) and the nitrate radical NO3 in dark air was studied in a Teflon bag, monitoring products formed in the gas phase together with aerosol composition and size distributions in the course of the experiment. The formation of the condensable products methane sulphonic acid (MSA) and sulphuric acid (H2SO4) was found to happen via a gaseous, relatively stable PAN-like peroxynitrate intermediate (CH3S(O)O2NO2 or CH3S(O)2O2NO2, called MSPN) which can build up to concentrations in the gas phase that are a multiple of MSA and H2SO4. A coupled gas chemistry-aerosol dynamics model was fitted to the experimental data and led to a consistent description of the partitioning of the S-containing products (SO2, MSPN, MSA and H2SO4) over gas and aerosol phase. The optimized chemical model reproduces adequately the observed strong NO dependence of the MSPN-to-(MSA+H2SO4) conversion rate by gas-phase reactions. The fitted loss rate for MSPN via pathways not included in the gas-phase mechanisms (e.g. reaction on aerosol particles or on the wall) is 100–500 times smaller than for N2O5. The model predicts further that about 50% of the initial DMS is transformed to SO2. Fitting the aerosol dynamics model to the observed aerosol growth rate, led to an estimate for the MSA condensation accommodation coefficient (αMSA〉0.1) and for the MSA/H2SO4 formation ratio (1.2–3). The chemical model predicts that MSPN might be an important reservoir species for nitrogen, sulphur, and for aerosol formation in marine regions that are impacted by NO x -rich air masses.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of atmospheric chemistry 31 (1998), S. 247-267 
    ISSN: 1573-0662
    Schlagwort(e): isoprene ; methacrolein ; methyl vinyl ketone ; methyl butenol ; toluene ; chlorine atoms ; gas-phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract The reactions of isoprene, MBO (2-methyl-3-buten-2-ol) and toluene with chlorine atoms have been studied at 298 ± 5 K and 740 ± 5 Torr with the use of FTIR spectroscopy. Major products of the isoprene-Cl reaction and of the MBO-Cl reaction have been identified and quantified, and reaction mechanisms have been tentatively proposed in order to explain the products formed. The reaction between isoprene and Cl atoms yields mainly HCl, formyl chloride, formic acid, methylglyoxal (pyruvic aldehyde), CO and CO2, while the MBO-Cl reaction forms acetone, HCl, formyl chloride, formic acid, CO, CO2. As products from the reaction between toluene and Cl we identified and quantified HCl and benzaldehyde. The rate constants for the reactions of isoprene and toluene with Cl atoms have also been determined using a relative rate method. The measured values are: kisoprene = (5.5 ± 1.0) × 10−10 cm3 molecule−1 s−1 and ktoluene = (5.6 ± 1.3) × 10−11 cm3 molecule−1 s−1. Atmospheric lifetimes have been estimated from these values.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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