Thermodynamics of the formation of sulfuric acid dimers in the binary (H<sub>2</sub>SO<sub>4</sub>–H<sub>2</sub>O) and ternary (H<sub>2</sub>SO<sub>4</sub>–H<sub>2</sub>O–NH<sub>3</sub>) system

Abstract

Abstract. Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF). Both the binary (H 2 SO 4 -H 2 O) system and the ternary system involving ammonia (H 2 SO 4 -H 2 O-NH 3 ) may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a chemical ionization mass spectrometer (CIMS). From these measurements, dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of Published by Copernicus Publications on behalf of the European Geosciences Union. A. Kürten et al.: Thermodynamics of the formation of sulfuric acid dimersH 2 SO 4 q NH 3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248 K. We estimate the thermodynamic properties (dH and dS) of the H 2 SO 4 q NH 3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using chemical ionization-atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry.

New Particle Formation in the Atmosphere: From Molecular Clusters to Global Climate

“…As nucleation is a nonlinear process and the J are extremely sensitive to the temperature, RH, and concentrations of nucleation precursors, it is difficult to obtain consistent data from different experimental setups. The chamber experiment results are also difficult to interpret, because wall loss of nucleation vapors Zhang et al, 2014), clusters (Ehrhart & Curtius, 2013;Kürten et al, 2015;McMurry & Li, 2017), and particles must be accounted for the accurate calculation of J and GR. Nucleation studies have been made with fast flow reactors (Ball et al, 1999;Benson et al, 2011;Berndt et al, 2010;Brus et al, 2010;Hanson & Lovejoy, 2006;Lovejoy et al, 2004;Young et al, 2008;Zhang et al, 2004), expansion cloud chambers (Katz, 1970), environmental smog chambers (Metzger et al, 2010;Riccobono et al, 2012), real plant chambers (Hao et al, 2009;Joutsensaari et al, 2005;Mentel et al, 2009), and recently at CERN in the large environmental chamber CLOUD (Almeida et al, 2013;Kirkby et al, 2016;Kürten et al, 2014;Lehtipalo et al, 2016;Tröstl et al, 2016).…”

“…Ammonia and amines have been observed in small sulfuric acid clusters in both the laboratory and the atmosphere (Almeida et al, 2013;Bianchi et al, 2014;Hanson & Eisele, 2002;Kirkby et al, 2011;Kürten et al, 2014;Schobesberger et al, 2015;Yao et al, 2018;Yu, McGraw, & Lee, 2012). Figure 4 shows an approximate 1:1 molar ratio of sulfuric acid and ammonia (or DMA) in newly formed clusters at the atmospherically relevant gaseous [NH 3 ]/[H 2 SO 4 ] concentration ratios of 10-500 Schobesberger et al, 2015).…”

“…Field measurements showed that gaseous sulfuric acid in concentrations of greater than approximately 10 5 molecules/cm 3 is necessary for observable NPF in the atmosphere (Erupe et al, 2010;McMurry et al, 2005;Nieminen et al, 2009). In addition, several other nucleating precursors have been implicated for NPF under diverse environments, including ions (Kirkby et al, 2011;Kirkby et al, 2016), ammonia/amines (Almeida et al, 2013;Glasoe et al, 2015;Kirkby et al, 2011;Kürten et al, 2014;Yao et al, 2018;Yu & Luo, 2014a;Yu, McGraw, & Lee, 2012), HOMs Jokinen et al, 2015;Tröstl et al, 2016), other organic compounds (Metzger et al, 2010;Zhang et al, 2004), and iodine oxides (O'Dowd et al, 2002;Sipilä et al, 2016).…”

“…Figure 4 shows an approximate 1:1 molar ratio of sulfuric acid and ammonia (or DMA) in newly formed clusters at the atmospherically relevant gaseous [NH 3 ]/[H 2 SO 4 ] concentration ratios of 10-500 Schobesberger et al, 2015). While amines can strongly enhance the J ( Almeida et al, 2013;Glasoe et al, 2015), studies show there is a saturation effect of J or dimer concentrations with a further increase in DMA concentrations, for example, when exceeding 5 pptv DMA at temperatures between 278 and 300 K (Almeida et al, 2013;Chen et al, 2012;Jen et al, 2014;Kürten et al, 2014). With 5-32 pptv or higher concentrations of DMA, formation of neutral sulfuric acid dimers reaches the kinetic limit with a power dependence of J on [H 2 SO 4 ] of 2, indicating highly stable clusters with negligible evaporation (Almeida et al, 2013;Kürten et al, 2014).…”

Experimental particle formation rates spanning tropospheric sulfuric acid and ammonia abundances, ion production rates, and temperatures

“…The concentration of H 2 SO 4 has been measured with a calibrated Chemical Ionization Mass Spectrometer at concentrations between~5 × 10 5 and~1 × 10 9 cm À3 [Kürten et al, 2011. The measurement of sulfuric acid monomers and neutral dimers at low temperatures during CLOUD5 is described elsewhere [Kürten et al, 2015]. For experiments where ammonia was intentionally added to the chamber, a gas bottle of NH 3 diluted in nitrogen (1% of NH 3 in N 2 , Carbagas) was used.…”