Geoscience Reference
In-Depth Information
3.1
Introduction
The term “aerosol” is quite familiar to everyone. Every day we see dust particles
suspended in air, fumes from cigarettes, releases from transport, smoke from
chimneys, etc. And almost nobody suspects that most aerosol particles are simply
invisible. Despite this fact, these particles whose sizes do not exceed a fraction of
a micrometer are of great importance for the formation of the present-day state
of the atmosphere. It is these particles that serve as the condensation centers for
the formation of cloud particles which cannot otherwise form at low water vapor
supersaturation in the atmosphere (Charlson and Heitzenberg
1995
; Seinfeld and
Pandis
2006
; Lohman and Feichter
2005
; Friedlander
2000
). Meanwhile, little is
known about the nature of atmospheric aerosol particles or about the processes
leading to their production in the atmosphere. The reasons for this are clear: the
particles are so small that we are not able to distinguish them in optical microscopes.
Electron microscopes are also powerless because the particles are unstable under the
incident electron beam. Still, some speculations about the properties of the aerosol
particles are admissible, and we can formulate some theories allowing us to come
to conclusions concerning the consequences of the interactions of aerosol particles
with our instruments and the environment.
The tiniest aerosol particles are produced by a number of specific mechanisms.
All include spontaneous nucleation as the first stage; that is, the particles are
assumed to form from vapors of sufficiently low volatile substances produced in the
atmosphere from anthropogenic or natural organic releases. After chains of chemical
and photochemical intraatmospheric processes, these releases convert to aerosol
particles, which then grow by condensing other low volatile substances that are not
able to form particles by nucleation (for example, if their vapor concentrations are
not sufficient for initiating the nucleation process).
A huge amount of literature is devoted to atmospheric nanoaerosols. For
extensive citations of the work of the past century, see the topics of Seinfeld and
Pandis (
2006
) and of Friedlander (
2000
). The goal of this review is to direct the
attention of atmospheric scientists to some part of efforts that have remained beyond
the mainstream of current atmospheric studies.
3.1.1
Atmospheric Aerosol Processes
Although more than a century has passed since Aitken's discovery of the secondary
background aerosols, interest in these did not diminish until the present time.
Recently, the dynamics of particle formation has again received considerable
attention. Papers reporting on the results of field measurements continue to appear in
connection with climatological and ecological needs (Boy and Kulmala
2002
;Boy
et al.
2003
; Castelman
1982
; Kulmala et al.
2004
; Lyubovtseva et al.
2005
,
2010
;
Stolzenburg et al.
2005
;YuandTurko
2001
).
