Dynamics, atmospheric aerosols

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

Dragoescu, C., Friedlander, S. (1989) Dynamics of the aerosol products of incomplete combustion in urban atmospheres. Aerosol... 

Meng, Z., D. Dabdub, and J. H. Seinfeld, Size-Resolved and Chemically Resolved Model of Atmospheric Aerosol Dynamics, J. Geophys. Res., 103, 3419-3435 (1998). 

The arsenal of aerosol measurement methods has expanded dramatically over recent years, but a number of needs for fundamental research into the nature and origins of the atmospheric aerosol cannot be met by the current instrumentation. Instrumentation that has proven most valuable in the chemical characterization of the atmospheric aerosol is woefully inadequate either for following the chemical dynamics of aerosols because of the rapid changes that occur in homogeneous reacting systems or for unraveling the complexity of the aerosol products. 

Rimnacova D, Zdimal V, Schwarz J, Smolik J, Rimnac M (2011) Atmospheric aerosols in suburb of Prague the dynamics of particle size distributions. Atmos Res 101 539-552... 

However, the thermal fluctuations are not the only process that could perturb the propagation of ultrashort laser pulses through the atmosphere. Aerosol particles, like water droplets or dust, can have dimensions of several tens of microns, comparable with the filament diameter they could seriously harm the delicate dynamical balance required to propagate filaments. 

In this section we focus on four specific environmental problems coal combustion aerosol formation, dynamics of atmospheric aerosols, the chemical characterization of particles, and the role of aerosols in clean room technology or so-called microcontamination control. For the reader interested in an introduction to aerosol science, we recommend three texts [6-8]. 

An important current problem is attaining sufficient understanding of atmospheric aerosol dynamics to develop mathematical models capable of relating emission reductions of primary gaseous and particulate pollutants to changes in ambient aerosol loadings and thereby to improvements in visibility and health effects. These models involve thermodynamics, transport phenomena, and chemical kinetics in an intricate equilibrium and... 

The variety of reactions which have been described indicate the large number of chemical species which enter in the troposphere and which may have an impact upon the environment. It is necessary to emphasize that all species are in a dynamic equilibrium for the meteorological turbulence so that in some cases redox and acid-base reactions occur with the formation of stable compounds with high formation constants but nevertheless the reagent species are detectable in the atmosphere. A typical example is the evaluation of the atmospheric aerosol where besides the presence of ammonium sulphates, free ammonia and sulphuric acid may coexist. 

Meng Z., Dabdub D., and Seinfeld J. H. (1998) Size-resolved and chemically resolved model of atmospheric aerosol dynamics. J. Geophys. Res. 103, 3419- 3435. 

The atmospheric aerosol has profound effects on the nature of the air environment. Effects on human health have led to the establishment of ambient air qualtiy standards by the United States and other industrial nations. The optical properties of the aerosol alTect local and regional visibility and Earth s radiation balance, hence global climate. There is evidence that reactions that take place on the surface of the stratospheric aerosol play a major role in the destruction of the stratospheric ozone layer. Particularly complex (and poorly understood) arc the indirect effects of the aerosol serving as condensation nuclei for the formation of clouds which in turn affect the radiation balance. For an extensive review of the properties of the atmospheric aerosol and its effects, especially health related, the reader is referred to the document prepared by the U.S. EPA (1996) for use in setting the ambient air quality standard for particulate matter. Atmospheric aerosol properties and dynamics are reviewed in detail by Seinfeld and Pandis (1998). 

In this section, basic concepts from aerosol dynamics and the general dynamic equation (GDE) are employed to explain important features of atmospheric size di.stribiition functions. The goal is to provide physical insight into these features. For the application of numerical methods to modeling atmospheric aerosol dynamics, the reader is referred to Wexler et al. (1994) and Jacobson (1997). 

Further in.sighl into atmospheric aerosol dynamics can be obtained by analyzing variations in aerosol chemical composition with lime at a given sampling site. Many long-time... 

Variations in atmospheric aerosol compositions can be linked to aerosol dynamics through 1------ -----i- conservation of. species for the chemical components in the submicron... 

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