Urban-scale transformation

Ebel, A., R. Friedrich and H. Rodhe, Eds. (1997) Transport and chemical transformation of pollutants in the troposphere. Vol. 7 Tropospheric modelling and emission estimation. Chemical transport and emission modelling on regional, global and urban scales. Springer-Verlag, Berlin, 440 pp. 

The atmospheric chemical processes undergone by most pollutants are not readily describable by first-order kinetics. Hence, the simple Gaussian plume solution in Equation 5-3 is inapplicable in most cases where physiochemical transformations significantly alter concentrations on a time scale or space scale appropriate to an urban airshed. 

Table II gives typical ozone and oxides of nitrogen levels in these four regions. Urban- and regional-scale atmospheric chemistry is characterized by the definitive influence of anthropogenic emissions. The goals of a study of urban- and regional-scale atmospheric chemistry are to understand the atmospheric transformations of emitted species to be able to predict the formation of ozone and other pollutants, and to predict the pathways of removal of emitted species and their transformation products from the atmosphere.

Spatial scales characteristic of various atmospheric chemical phenomena are given in Table 1.1. Many of the phenomena in Table 1.1 overlap for example, there is more or less of a continuum between (1) urban and regional air pollution, (2) the aerosol haze associated with regional air pollution and aerosol-climate interactions, (3) greenhouse gas increases and stratospheric ozone depletion, and (4) tropospheric oxidative capacity and stratospheric ozone depletion. The lifetime of a species is the average time that a molecule of that species resides in the atmosphere before removal (chemical transformation to another species counts as removal). Atmospheric lifetimes vary from less than a second for... 

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