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particles, foreign aerosols, or atmospheric ions. The production of nonvolatile
substances, in turn, demands some special conditions to be fulfilled imposed on the
emission rates of volatile organics from vegetation, the current chemical content of
the atmosphere, rates of stirring and exchange processes between lower and upper
atmospheric layers, and the presence of foreign aerosols (accumulation fraction,
first of all) serving as the condensational sinks for trace gases and the coagulation
sinks for the particles of nucleation mode, the interactions with air masses from
contaminated or clean regions (Boy and Kulmala 2002 ; Boy et al. 2003 ;Kulmala
et al. 2004 ;Kerminenetal. 2004 ; Dal Maso et al. 2005 ; Aalto et al. 2001 ;Areyetal.
1990 ; Juozaitis et al. 1996 ). Such a plethora of very diverse factors, most of which
have a stochastic nature, prevents direct attacks of this effect. A very large number of
field measurements of the nucleation bursts dynamics appeared during the past two
decades (see a review article Kulmala et al. 2004 and references Boy and Kulmala
2002 ; Boy et al. 2003 ; Lyubovtseva et al. 2010 ; Stolzenburg et al. 2005 ;Kerminen
et al. 2004 ;Areyetal. 1990 ; Juozaitis et al. 1996 ). The attempts at modeling this
important and still enigmatic process also appeared rather long ago. Here we avoid
the long history of this problem and cite only the models that appeared in the
twenty-first century (Stolzenburg et al. 2005 ; Anttila et al. 2004 ; Korhonen et al.
2003 , 2004 ; Grini et al. 2005 ). The earlier citations can be found in these works. All
models (without exception) started from the commonly accepted point of view that
the chemical reactions of trace gases are responsible for the formation of nonvolatile
precursors, which then give the life to subnano- and nanoparticles in the atmosphere.
In their turn, these particles are considered as active participants of the atmospheric
chemical cycles leading to particle formation (Janson et al. 2001 ). Hence, any model
of nucleation bursts included (and includes) coupled chemical and aerosol blocks.
This coupling leads to strong nonlinearities whose appearance, on the other hand,
is not surprising. Indeed, all intra-atmospheric chemical processes are described by
a set of nonlinear equations, not all of which are, in addition, firmly established,
and there is no assurance that we know all the participants of the chemical cycles
leading to the production of low volatile gas constituents which then convert to the
tiniest aerosol particles.
3.1.2
Models of Aerosol Processes
Our main idea is to decouple the aerosol and chemical parts of the particle formation
process and to consider only the aerosol part of the problem. We thus introduce
the concentrations of nonvolatile substances responsible for particle growth and the
rate of embryo production as external parameters whose values can be found either
from measurements or calculated independently, once the input concentrations of
reactants and the pathways leading to the formation of these nonvolatile substances
are known. Next, introducing the embryo production rate allows us to avoid the
rather slippery problem of the mechanisms responsible for embryo formation.
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