Hydration of the Bisulfate Ion: Atmospheric Implications

Abstract

Using molecular dynamics configurational sampling combined with ab initio energy calculations, we determined the low energy isomers of the bisulfate hydrates. We calculated the CCSD(T) complete basis set (CBS) binding electronic and Gibbs free energies for 53 low energy isomers of HSO(4)(-)(H(2)O)(n=1-6) and derived the thermodynamics of adding waters sequentially to the bisulfate ion and its hydrates. Comparing the HSO(4)(-)/H(2)O system to the neutral H(2)SO(4)/H(2)O cluster, water binds more strongly to the anion than it does to the neutral molecules. The difference in the binding thermodynamics of HSO(4)(-)/H(2)O and H(2)SO(4)/H(2)O systems decreases with increasing number of waters. The thermodynamics for the formation of HSO(4)(-)(H(2)O)(n=1-5) is favorable at 298.15 K, and that of HSO(4)(-)(H(2)O)(n=1-6) is favorable for T < 273.15 K. The HSO(4)(-) ion is almost always hydrated at temperatures and relative humidity values encountered in the troposphere. Because the bisulfate ion binds more strongly to sulfuric acid than it does to water, it is expected to play a role in ion-induced nucleation by forming a strong complex with sulfuric acid and water, thus facilitating the formation of a critical nucleus.

Experimental investigation of ion–ion recombination under atmospheric conditions

“…The change in ion mobility is plausible, as we know that aerosol particles with a diameter larger than 10 nm tend to be hygroscopic, changing their diameter according to the RH (Onasch et al, 1999;Keskinen et al, 2013). We also know, from quantum chemistry calculations, that ions form clusters with water and that the amount of water attached is dependent on RH (Kurtén et al, 2007;Husar et al, 2012;Henschel et al, 2014;Olenius et al, 2014). This explanation matches the observed data qualitatively.…”

Estimating the Lower Limit of the Impact of Amines on Nucleation in the Earth’s Atmosphere

“…The number of initial/guess geometries ranged from fewer than 10-15 in the case when H2O was not involved in cluster formation to more than 70 in the case when high (k > 3) hydrates are formed. The performance of the PW91PW91/6-311++G (3df, 3pd) method has been systematically validated against experimental Gibbs free energies for clusters relevant to the Earth's atmosphere [6,22,25,[52][53][54] and has shown a very good agreement with all the currently available experiments and higher level ab initio studies [55][56][57][58][59]. The method has been successfully applied to a wide range of nucleation problems including the classical problem Wilson's of the sign preference [52], stability and dipole moment of sulfuric acid hydrates, atmospheric nucleation of H2SO4-H2O ions of different sign and composition [53], temperature and concentration dependencies of the H2O nucleation rates [54], and impact of ammonia and organic acids on the stability of neutral and charged binary H2SO4-H2O clusters.…”

Mechanism of the Gaseous Hydrolysis Reaction of SO2: Effects of NH3 versus H2O

“…The MD sampling scheme has been successfully applied to hydrated sulfuric acid 47 and other hydrated clusters. 48,49 We ran a two-step MD simulation, as described in refs 47−49, first a simulation of heating processes from 0 K to the final temperature T f for 1 ns, followed by a production run at T f for 10 ns. The T f was 200 and 210 K for as well as the corresponding pathways for the hydrolysis of SO 2 in the clusters were examined.…”