Chemistry atmospheric aerosol particles

It follows from this discussion that the study of properties and effects of atmospheric aerosol particles exceeds the scope of air chemistry. Considering the complexity of the problem, we restrict our discussion in the following to the presentation of formation processes and principal physical and chemical properties of background aerosol in the troposphere and stratosphere. 

Hgure 6 Schematic diagram of aTOF-LMMS developed at the University of California, Ftiverside. (Adapted from Card E, Mayer JE, Morrical BD, et al. (1997) Real-time analysis of individual atmospheric aerosol particles design and performances of a portable aTOF-MS. Analytical Chemistry 69 4083-4091 American Chemical Society.)... 

As discussed in Section 6.5, water vapor and the heat released and absorbed by transitions of water between the vapor state and the liquid or solid state are strongly involved in atmospheric energy transfer. Condensed water vapor in the form of very small droplets is of considerable concern in atmospheric chemistry. The harmful effects of some air pollutants—for instance, the corrosion of metals by acid-forming gases—requires the presence of water, which may come from the atmosphere. Atmospheric water vapor has an important influence on pollution-induced fog formation under some circumstances. Water vapor interacting with pollutant particulate matter in the atmosphere may reduce visibility to undesirable levels through the formation of very small atmospheric aerosol particles. 

George, 1. J., and J.P.D. Abbatt, Heterogeneous Oxidation of Atmospheric Aerosol Particles by Gas-Phase Radicals, Nature Chemistry 2, 713-22 (2010). 

The Chemistry of Atmospheric Aerosol Particles in the Amazon Basin... 

Recently was estimated an expected impact on the global chemistry of the atmosphere of the indirect heterogeneous photocatalytic reactions under the much more abundant near ultraviolet, visible and near infrared solar light [2]. As photocatalysts may serve atmospheric aerosols, i.e. ultrasmall solid particles that sometimes are embedded into liquid droplets. Aerosols are known to contain Ti02, Fc203, ZnO and other natural oxides, as well as metal sulfides of volcanic or antropogenic origin, that may serve as semiconductor photocatalysts (see Fig.5). Aerosols are known to be concentrated mainly in the air layers near the surface of the Earth, i.e. in the troposphere, rather than stratosphere. 

The chemical characterization of aerosol particles currently is of great interest in the field of atmospheric chemistry. A major goal is the development of a method for continuous elemental analysis of aerosols, especially for the elements C, N, and S. Chemiluminescence reactions described in this chapter have adequate sensitivity and selectivity for such analyses. In fact, considering that a 1- j.m-diameter particle has a mass of =0.5-1.0 pg, online analysis of single aerosol particles should be achievable, especially for larger particles. 

Sander, R. Modeling atmospheric chemistry Interactions between gas-phase species and liquid cloud/aerosol particles, Surv. Geophys., 20, 1-31, 1999. 

This review of the chemistry and physics of microparticles and their characterization is by no means comprehensive, for the very large range of masses that can be studied with the electrodynamic balance makes it possible to explore the spectroscopy of atomic ions. This field is a large one, and Nobel laureates Hans Dehmelt and Wolfgang Paul have labored long in that fruitful scientific garden. The application of particle levitation to atmospheric aerosols, to studies of Knudsen aerosol phenomena, and to heat and mass transfer in the free-molecule regime would require as much space as this survey. 

The finding that the heterogeneous chemistry that occurs on polar stratospheric clouds also occurs in and on liquid solutions in the form of liquid aerosol particles and droplets in the atmosphere provided a key link in understanding the effects of volcanic eruptions on stratospheric ozone in both the polar regions and midlatitudes. As discussed herein, the liquid particles formed from volcanic emissions are typically 60-80 wt% H2S04-H20, and hence the chemistry discussed in the previous section can also occur in these particles (Hofmann and Solomon, 1989). We discuss briefly in this section the contribution of volcanic emissions to the chemistry of the stratosphere and to ozone depletion on a global scale. For a brief review of this area, see McCormick et al. (1995). 

Calhoun, J. A., T. S. Bates, and R. J. Charlson, Sulfur Isotope Measurements of Submicrometer Sulfate Aerosol Particles over the Pacific Ocean, Geophys. Res. Lett, 18, 1877-1880 (1991). Capaldo, K. P., and S. N. Pandis, Dimethylsulfide Chemistry in the Remote Marine Atmosphere Evaluation and Sensitivity Analysis of Available Mechanisms, J. Geophys. Res., 102, 23251-23267 (1997). 

Compositional analyses of size-segregated particles from ambient atmospheric aerosols are vital for understanding the sources and effects of these aerosols. Three challenges exist for analytical chemistry in the next decade ... 

The atmosphere is a complex medium in which several phases coexist gas, aerosol particles, condensed water, liquid, and ice particles. All of the interactions that may occur between these various phases are included in the term multiphase or heterogeneous chemistry. Clouds favor the development of atmospheric multiphase chemistry, as they are composed of all three atmospheric phases (i.e., gas, liquid, and solid phases that stimulate a full set of reactions). Moreover, clouds modify radiative properties by diffusion of short-wavelength radiation coming from... 

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