Tropospheric Sulfate Aerosol Formation Via Ion-Ion Recombination

Abstract

We propose a source of aerosols in the lower atmosphere associated with the creation, growth, and recombination of ubiquitous cosmogenically generated ions. This particle source should be favorable in the relatively clean, stable marine boundary layer, providing a uniform, continuous fine particle generator in the presence of dimethylsulfide emissions. Through this mechanism, new sulfate aerosols can be formed at sulfuric acid vapor partial pressures well below the supersaturations required for homogeneous binary nucleation of sulfuric acid/water solutions, which is consistent with numerous observations of new particle formation under sub-saturated conditions. The evolving aerosols in turn control the acid vapor concentration and thus modulate the sizes of the precursor ions and the rate of new particle formation. A simple model representing this nonlinear coupled system predicts that the physical and chemical processes connecting ions, vapors, and aerosols effectively constrain the particle population to a relatively narrow range of values. This self-limiting behavior may explain in part the apparent stability of the marine sulfate aerosol, with mean concentrations of the order of several hundred per cubic centimeter. BACKGROUNDIt has been proposed 1 that dimethylsulfide (DMS), a natural biogenic byproduct of phytoplankton metabolism,

From molecular clusters to nanoparticles: Role of ambient ionization in tropospheric aerosol formation

“…To be sure, them are many other factors affecting aerosol formation and growth in addition to the ionization rate that have not been considered here, including the identities and abundances of precursor vapors, and the compositions and surface areas of background aerosols. Moreover, simplified analytical approaches to the problem [Turco et al, 2000], which seem to capture the strong nonlinear behavior of this coupled ion, aerosol, vapor system as seen in the present simulations, imply relatively low sensitivity of long-term aerosol populations to GCR variations.…”

A dynamic aerosol module for global chemical transport models: Model description

“…The flexible nature of this model makes it easy to consider other nucleation schemes that involve other gas and aerosol components, such as sulfate‐mediated organic components [ R. Zhang et al , 2004; Kulmala et al , 2004], ion‐mediated nucleation [ Laakso et al , 2002; Turco et al , 2000], the ternary nucleation of H 2 SO 4 , NH 3 and H 2 O [ Napari et al , 2002], and nucleation of biogenic iodide emissions [ O'Dowd et al , 2002]. In addition, consideration of secondary organic aerosols [ Chung and Seinfeld , 2002] and of NH 4 and HNO 3 partitioning into the aerosol phase [ Adams et al , 2001; Rodriguez and Dabdub , 2004] is straightforward.…”

The role of cosmic rays in the Earth’s atmospheric processes

“…Model calculations [10,45,49] showed that a 20% variation in the ionization rate in the lower atmosphere could lead to a change in concentration of 3 to 10 nm diameter aerosols of about 5 to 10% and some of them may contribute to the CCN population. However, the fraction of CCN originating from CR ionization will depend upon many factors including availability of condensable gas, direct source of CCN and cloud processing.…”

“…The observation of size and density distribution of aerosols in the region of low cloud formation indicates that participating aerosols are produced locally. In the troposphere ionization is the main source of ultra-fine aerosol particles (<20nm) formation, and the subsequent growth into the matured aerosol distributions which act as CCN [49].…”