Glyoxal and Methylglyoxal Setschenow Salting Constants in Sulfate, Nitrate, and Chloride Solutions: Measurements and Gibbs Energies

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• 作者：Eleanor M. Waxman ; Jonas Elm ; Theo Kurt茅n ; Kurt V. Mikkelsen ; Paul J. Ziemann ; Rainer Volkamer
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：October 6, 2015
• 年：2015
• 卷：49
• 期：19
• 页码：11500-11508
• 全文大小：420K
• ISSN：1520-5851

文摘

Knowledge about Setschenow salting constants, K_S, the exponential dependence of Henry鈥檚 Law coefficients on salt concentration, is of particular importance to predict secondary organic aerosol (SOA) formation from soluble species in atmospheric waters with high salt concentrations, such as aerosols. We have measured K_S of glyoxal and methylglyoxal for the atmospherically relevant salts (NH₄)₂SO₄, NH₄NO₃, NaNO₃, and NaCl and find that glyoxal consistently 鈥渟alts-in鈥?(K_S of 鈭?.16, 鈭?.06, 鈭?.065, 鈭?.1 molality^鈥?, respectively) while methylglyoxal 鈥渟alts-out鈥?(K_S of +0.16, +0.075, +0.02, +0.06 molality^鈥?). We show that K_S values for different salts are additive and present an equation for use in atmospheric models. Additionally, we have performed a series of quantum chemical calculations to determine the interactions between glyoxal/methylglyoxal monohydrate with Cl^{鈥?/sup>, NO₃鈥?/sup>, SO₄2鈥?/sup>, Na+, and NH₄+ and find Gibbs free energies of water displacement of 鈭?0.9, 鈭?2.0, 鈭?2.9, 2.09, and 1.2 kJ/mol for glyoxal monohydrate and 鈭?.1, 鈭?0.3, 鈭?.91, 6.11, and 1.6 kJ/mol for methylglyoxal monohydrate with uncertainties of 8 kJ/mol. The quantum chemical calculations support that SO₄2鈥?/sup>, NO₃鈥?/sup>, and Cl鈥?/sup> modify partitioning, while cations do not. Other factors such as ion charge or partitioning volume effects likely need to be considered to fully explain salting effects.}