Atmospheric Ions and Aerosol Formation

Abstract

This paper discusses atmospheric ions and their role in aerosol formation. Emphasis is placed upon the upper troposphere where very low temperatures tend to facilitate new particle formation by nucleation. New measurements addressed include: Laboratory measurements of cluster ions, aircraft measurements of ambient atmospheric ions, atmospheric measurements of the powerful nucleating gas H 2 SO 4 and its gaseous precursor SO 2 . The paper also discusses model simulations of aerosol formation and growth. It is concluded that in the upper troposphere new aerosol formation via ions is a frequent process with relatively large rates. However new particle formation by homogeneous nucleation which does not involve ions also seems to be efficient. The bottleneck in the formation of upper troposphere aerosol particles with sizes sufficiently large to be climate relevant is mostly not nucleation but sufficient growth of new and still very small particles. Our recent upper troposphere SO 2 measurements suggest that particle growth by gaseous sulphuric acid condensation can be efficient in certain circumstances. If so, cosmic ray mediated formation of CCN sized particles should at least occasionally be operative in the upper troposphere.

The role of highly oxygenated molecules (HOMs) in determining the composition of ambient ions in the boreal forest

“…It is well known that ambient ions are able to enhance the formation rate of new particles and the mechanism is known as ion-induced nucleation (Raes et al, 1986;Yu and Turco, 2001;Kirkby, 2007;Arnold, 2008;Hirsikko et al, 2011). Recent laboratory experiments performed in the European Centre for Nuclear Research (CERN; CLOUD experiment) have systematically explored the influence of ions on new particle formation (NPF) in several different chemical systems.…”

Infrared Photodissociation Spectroscopy of Microhydrated Nitrate–Nitric Acid Clusters NO3–(HNO3)m(H2O)n

“…1,2 Nitrate (NO 3 − ) and its clusters with nitric acid (HNO 3 ) and water are among the most abundant anions in the atmosphere. They were first measured in the stratosphere in 1978 3 and, five years later, in the troposphere by Arnold with a balloon-borne mass spectrometer.…”

“…6 A major source of these clusters is oxidation of NO x to HNO 3 and subsequent deprotonation via galactic cosmic rays, radioactivity, and electrical discharges. 1 The resulting NO 3 − reacts promptly with trace gases via ion−molecule reactions forming NO 3 − (HNO 3 ) m (H 2 O) n clusters. Understanding the structure, stability, reactivity, and growth rates of nitrate-containing clusters is crucial for improving atmospheric ion chemistry models.…”

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

“…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.…”