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Total Sulfate vs. Sulfuric Acid Monomer Concenterations in Nucleation Studies.

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    0473037 - ÚCHP 2017 RIV DE eng J - Journal Article
    Neitola, K. - Brus, David - Makkonen, U. - Sipilä, M. - Mauldin III, R.L. - Sarnela, N. - Jokinen, T. - Lihavainen, H. - Kulmala, M.
    Total Sulfate vs. Sulfuric Acid Monomer Concenterations in Nucleation Studies.
    Atmospheric Chemistry and Physics. Roč. 15, č. 6 (2015), s. 3429-3443. ISSN 1680-7316
    Grant - others:AFCE(FI) 1118615
    Institutional support: RVO:67985858
    Keywords : ion-induced nucleation * particle formation * experimental setup
    Subject RIV: CF - Physical ; Theoretical Chemistry
    Impact factor: 5.114, year: 2015

    Sulfuric acid is known to be a key component for atmospheric nucleation. Precise determination of sulfuric-acid concentration is a crucial factor for prediction of nucleation rates and subsequent growth. In our study, we have noticed a substantial discrepancy between sulfuric-acid monomer concentrations and total-sulfate concentrations measured from the same source of sulfuric-acid vapor. The discrepancy of about 1-2 orders of magnitude was found with similar particle-formation rates. To investigate this discrepancy, and its effect on nucleation, a method of thermally controlled saturator filled with pure sulfuric acid (97% wt.) for production of sulfuric-acid vapor is applied and rigorously tested. The saturator provided an independent vapor-production method, compared to our previous method of the furnace (Brus et al., 2010, 2011), to find out if the discrepancy is caused by the production method itself. The saturator was used in a H2SO4-H2O nucleation experiment, using a laminar flow tube to check reproducibility of the nucleation results with the saturator method, compared to the furnace. Two independent methods of mass spectrometry and online ion chromatography were used for detecting sulfuric-acid or sulfate concentrations. Measured sulfuric-acid or total-sulfate concentrations are compared to theoretical predictions calculated using vapor pressure and a mixing law. The calculated prediction of sulfuric-acid concentrations agrees very well with the measured values when total sulfate is considered. Sulfuric-acid monomer concentration was found to be about 2 orders of magnitude lower than theoretical predictions, but with a temperature dependency similar to the predictions and the results obtained with the ion-chromatograph method. Formation rates are reproducible when compared to our previous results with both sulfuric-acid or total-sulfate detection and sulfuric-acid production methods separately, removing any doubts that the vapor-production method would cause the discrepancy.
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