The role of atmospheric ions in aerosol nucleation – a review

Abstract

Abstract. Atmospheric aerosols affect climate and yet the reason for many observed events of new aerosol formation is not understood. One of the theories put forward to explain these events is that the presence of ions can enhance the formation of aerosols. The theory is called Ion Induced Nucleation and in this paper the state of observations, theory and experiments within the field will be reviewed. While evidence for Ion Induced Nucleation is accumulating the exact mechanism is still not known and more research is required to understand and quantify the effect.

Vibrational Spectroscopy of Bisulfate/Sulfuric Acid/Water Clusters: Structure, Stability, and Infrared Multiple-Photon Dissociation Intensities

“…In addition to the field studies that measure atomic masses and relative abundances of HSO 4 − (H 2 SO 4 ) m (H 2 O) n species, 1,7−10 a number of kinetics studies have investigated small ionic clusters of strong acids. 11−14 These studies have yielded rate constants for the reaction of the clusters with sulfuric acid and other molecular acids like HNO 3 .…”

“…The barrier to transfer of a single proton, that is, IRPD spectroscopy is a powerful structural probe of these and other small atmospherically relevant clusters. 22 The hydrated bisulfate and sulfate systems HSO 4 − (H 2 O) n and SO 4 2− (H 2 O) n have been studied previously using this method. 23−25 The bisulfate system showed the formation of extensive H-bonding networks starting at n = 3, while spectra of the hydrated sulfate dianions indicated more ligand-like binding to the sulfate core, confirmed by recent high-level calculations up to n = 6.…”

“…6 In this paper, the structure and stability of HSO 4 − (H 2 SO 4 ) m (H 2 O) n clusters are studied using infrared photodissociation (IRPD) spectroscopy in combination with electronic structure calculations. Moreover, infrared multiple-photon dissociation (IRMPD) spectra of HSO 4 − (H 2 SO 4 ) m are compared to single-photon IRPD spectra of the corresponding H 2 -tagged species in order to shed light on the nature of "IRMPD-transparent" vibrational modes.…”

“…1 Charged species are important in the early stages of atmospheric aerosol growth through the process of ion-induced nucleation, 2,3 with negative ions serving as more effective nucleation sites than positive ions. 4 Experimental aerosol growth studies for ionic clusters of sulfuric acid and water (charge carrier HSO 4 − or H + ) have been completed under a variety of conditions. These studies find that at room temperature, the uptake of sulfuric acid by negative ions is preferred to the uptake of water, as explained by the ability of H 2 SO 4 to make stronger H-bonds to the negative HSO 4 − core.…”

“…4 Experimental aerosol growth studies for ionic clusters of sulfuric acid and water (charge carrier HSO 4 − or H + ) have been completed under a variety of conditions. These studies find that at room temperature, the uptake of sulfuric acid by negative ions is preferred to the uptake of water, as explained by the ability of H 2 SO 4 to make stronger H-bonds to the negative HSO 4 − core. 5 At temperatures representative of the midtroposphere (248 K), ions of the type HSO 4 − (H 2 SO 4 ) m (H 2 O) n are the dominant nucleating cluster.…”