Solubility of Acetic Acid and Trifluoroacetic Acid in Low-Temperature (207鈭?45 K) Sulfuric Acid Solutions: Implications for the Upper Troposphere and Lower Stratosphere

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• 作者：Mads P. Sulbaek Andersen ; Jessica L. Axson ; Rebecca R. H. Michelsen ; Ole John Nielsen ; Laura T. Iraci
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：May 5, 2011
• 年：2011
• 卷：115
• 期：17
• 页码：4388-4396
• 全文大小：934K
• 年卷期：v.115,no.17(May 5, 2011)
• ISSN：1520-5215

文摘

The solubility of gas-phase acetic acid (CH₃COOH, HAc) and trifluoroacetic acid (CF₃COOH, TFA) in aqueous sulfuric acid solutions was measured in a Knudsen cell reactor over ranges of temperature (207鈭?45 K) and acid composition (40鈭?5 wt %, H₂SO₄). For both HAc and TFA, the effective Henry鈥檚 law coefficient, H*, is inversely dependent on temperature. Measured values of H* for TFA range from 1.7 脳 10³ M atm^鈭? in 75.0 wt % H₂SO₄ at 242.5 K to 3.6 脳 10⁸ M atm^鈭? in 40.7 wt % H₂SO₄ at 207.8 K. Measured values of H* for HAc range from 2.2 脳 10⁵ M atm^鈭? in 57.8 wt % H₂SO₄ at 245.0 K to 3.8 脳 10⁸ M atm^鈭? in 74.4 wt % H₂SO₄ at 219.6 K. The solubility of HAc increases with increasing H₂SO₄ concentration and is higher in strong sulfuric acid than in water. In contrast, the solubility of TFA decreases with increasing sulfuric acid concentration. The equilibrium concentration of HAc in UT/LS aerosol particles is estimated from our measurements and is found to be up to several orders of magnitude higher than those determined for common alcohols and small carbonyl compounds. On the basis of our measured solubility, we determine that HAc in the upper troposphere undergoes aerosol partitioning, though the role of H₂SO₄ aerosol particles as a sink for HAc in the upper troposphere and lower stratosphere will only be discernible under high atmospheric sulfate perturbations.