Scientific Data 4:170003 doi: 10.1038/sdata.2017.3 (2018); Published 14 March 2017; Updated 8 May 2018 The affiliation of Cathrine Lund Myhre was incorrectly stated in the original publication. It ...is: 19 NILU -Norwegian Institute for Air Research, Instituttveien 18, Kjeller 2007, Norway.
Ye et al. have determined a maximum nitrous acid (HONO) yield of 3% for the reaction HO2·H2O + NO2, which is much lower than the yield used in our work. This finding, however, does not affect our ...main result that HONO in the investigated Po Valley region is mainly from a gas-phase source that consumes nitrogen oxides.
The temperature dependence of the kinetic isotope effect (KIE) of β-pinene ozonolysis was investigated experimentally at 258, 273 and 303 K in the AIDA atmospheric simulation chamber. Compound ...specific carbon isotopic analysis of gas phase samples was performed off-line with a Thermo Desorption-Gas Chromatography-Isotope Ratio Mass Spectrometry (TD-GC-IRMS) system. From the temporal behavior of the δ^sup 13^C of β-pinene a KIE of 1.00358 ± 0.00013 was derived at 303 K, in agreement with literature data. Furthermore, KIE values of 1.00380 ± 0.00014 at 273 K and 1.00539 ± 0.00012 at 258 K were determined, showing an increasing KIE with decreasing temperature. A parameterization of the observed KIE temperature dependence was deduced and used in a sensitivity study carried out with the global chemistry transport model MOZART-3. Two scenarios were compared, the first neglecting, the second implementing the KIE temperature dependence in the simulations. β-Pinene stable carbon isotope ratio and concentration were computed, with emphasis on boreal zones. For early spring it is shown that when neglecting the temperature dependence of KIE, the calculated average age of β-pinene in the atmosphere can be up to two times overor underestimated. The evolution of the isotopic composition of the major β-pinene oxidation product, nopinone, was examined using Master Chemical Mechanism (MCM) simulations. The tested hypothesis that formation of nopinone and its associated KIE are the determining factors for the observed δ^sup 13^C values of nopinone is supported at high β-pinene conversion levels.
The KIE of b-pinene ozonolysis increases with decreasing temperature Nopinone loss processes can be neglected for its isotopic evolution Temperature dependence of KIE should be implemented in global ...modeling The temperature dependence of the kinetic isotope effect (KIE) of -pinene ozonolysis was investigated experimentally at 258, 273 and 303 K in the AIDA atmospheric simulation chamber. Compound specific carbon isotopic analysis of gas phase samples was performed off-line with a Thermo Desorption-Gas Chromatography-Isotope Ratio Mass Spectrometry (TD-GC-IRMS) system. From the temporal behavior of the 13C of -pinene a KIE of 1.00358 ± 0.00013 was derived at 303 K, in agreement with literature data. Furthermore, KIE values of 1.00380 ± 0.00014 at 273 K and 1.00539 ± 0.00012 at 258 K were determined, showing an increasing KIE with decreasing temperature. A parameterization of the observed KIE temperature dependence was deduced and used in a sensitivity study carried out with the global chemistry transport model MOZART-3. Two scenarios were compared, the first neglecting, the second implementing the KIE temperature dependence in the simulations. -Pinene stable carbon isotope ratio and concentration were computed, with emphasis on boreal zones. For early spring it is shown that when neglecting the temperature dependence of KIE, the calculated average age of -pinene in the atmosphere can be up to two times over- or underestimated. The evolution of the isotopic composition of the major -pinene oxidation product, nopinone, was examined using Master Chemical Mechanism (MCM) simulations. The tested hypothesis that formation of nopinone and its associated KIE are the determining factors for the observed 13C values of nopinone is supported at high -pinene conversion levels.
A chamber study was carried out to investigate the stable carbon isotopic composition (13C) of secondary organic aerosol (SOA) formed from ozonolysis of -pinene. -Pinene (600 ppb) with a known 13C ...value (-30.1) and 500 ppb ozone were injected into the chamber in the absence of light and the resulting SOA was collected on preheated quartz fiber filters. Furthermore, 13C values of the gas-phase -pinene and one of its oxidation products, nopinone, were measured using a gas chromatograph coupled to an isotope ratio mass spectrometer (GC-IRMS). -Pinene was progressively enriched with the heavy carbon isotope due to the kinetic isotope effect (KIE). The KIE of the reaction of -pinene with ozone was measured to be 1.0026 (3 2.6 #+ 1.5). The 13C value of total secondary organic aerosol was very similar to that of its precursor (average = -29.6 #+ 0.2) independent of experiment time. Nopinone, one of the major oxidation products of -pinene, was found in both the gas and aerosol phases. The gas-phase nopinone was heavier than the initial -pinene by 1.3 but lighter than the corresponding aerosol-phase nopinone. On average, the gas-phase nopinone was lighter by 2.3 than the corresponding aerosol-phase nopinone. The second product found in the SOA was detected as acetone, but it desorbed from the filter at a higher temperature than nopinone, which indicates that it is a pyrolysis product. The acetone showed a much lower 13C (-36.6) compared to the initial -pinene 13C.
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