Uptake of SO₂ to Aqueous Formaldehyde Surfaces

Abstract

Aqueous surfaces act as a gateway to absorption and aqueous-phase reaction of gases in the atmosphere. The composition of aerosols varies greatly and is expected to influence the structure of the interface. For example, aldehydes comprise a significant fraction of atmospheric organics and are likely to accumulate at aqueous surfaces. But it is difficult to anticipate their effect on the migration of gaseous species through the interfacial region. Surface organics may act as a barrier to absorption, or they may facilitate uptake via cooperative interactions with absorbing compounds. The surface spectroscopic studies presented here examine the nature of the vapor/water interface during uptake of SO(2) to aqueous formaldehyde solutions, elucidating the role of surface species in a multicomponent interfacial system. The results show that the product of the reaction between SO(2) and formaldehyde, hydroxymethanesulfonate, shows a surface affinity that is enhanced in the presence of SO(2).

Interaction of SO2 with the Surface of a Water Nanodroplet

“…Sulfur dioxide (SO 2 ) in the atmosphere largely stems from fossil fuel combustion at power plants, − industrial facilities, − and anthropogenic activities. , Sulfur dioxide from these sources can accumulate in fogwater and cloud droplets, thereby playing an important role in many atmospheric processes such as radiation trapping and scattering, − and the formation of secondary pollutants including sulfates, organosulfate aerosols, and acid rain. − …”

Photochemistry of HOSO radical in the gas phase

“…8,9 Recent studies show that HOSO and OH radicals may be produced through the reaction of H 2 O and excited SO 2 [Eqs. (1) and (2)], 10,11 SO 2 + hν → 3 SO 2 ,…”

Computational Vibrational Sum Frequency Spectra of Formaldehyde and Hydroxymethanesulfonate at Aqueous Interfaces

“…30 The experimental VSF studies of formaldehyde surfaces could not determine the interfacial hydrated:unhydrated ratio explicitly. 5 Comparison of experimental and calculated spectra are used to verify that the hydrated form of formaldehyde is still the dominant species at the interface. Calculated VSF spectra in both SSP and SPS polarization schemes for formaldehyde and methylene glycol are shown in Figure 2 with experimental spectra of aqueous formaldehyde shown for comparison.…”

“…Examining the complicated chemistry between formaldehyde and SO 2 will elucidate changes in surface composition, gas uptake, and surface to bulk partitioning in this atmospherically realistic system. Previous work in the Richmond laboratory has used vibrational sum frequency spectroscopy to examine the behavior of aqueous formaldehyde interfaces in the presence of flowing SO 2 gas, 5 laying the groundwork for the work presented here. The previous formaldehyde-SO 2 studies in the Richmond laboratory performed by Ota et al 5 had three major conclusions.…”

“…Previous work in the Richmond laboratory has used vibrational sum frequency spectroscopy to examine the behavior of aqueous formaldehyde interfaces in the presence of flowing SO 2 gas, 5 laying the groundwork for the work presented here. The previous formaldehyde-SO 2 studies in the Richmond laboratory performed by Ota et al 5 had three major conclusions. First, in accord with bulk thermodynamics, 13−15 at the aqueous interface, formaldehyde exists in its hydrated form, methylene glycol.…”