Urban-Scale Air Pollution

At the scale of an urban area, covering tens to hundreds of square kilometers, air quality is likely to be affected by chemicals emitted from many locations. 

Superposition of plumes, much as was done with perturbations to hydraulic head in Section 3.2.3, is a legitimate way to determine the chemical concentrations resulting from several sources, because in most cases the dispersal of one chemical has little effect on the behavior of other chemicals. 

To solve this problem, first estimate the mass of CO produced per mass of fuel consumed. Given mass balance constraints, the mass of exhaust products and H20 produced from combustion of 1 mol of octane must be 496 g (the 

Second, estimate the total CO release per square kilometer  

estimate the volume of air per square kilometer into which the mass of CO can mix  

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PEM (Pollution Episodic Model) is an urban scale air pollution model capable of predicting short-term average surface concentrations and deposition fluxes of two gaseous or particulate pollutants. 

Problems of air pollution exist on all scales from extremely local to global. These are divided in this chapter into five different scales local, urban, regional, continental, and global. The local scale includes up to about 5 km. The urban scale extends to the order of 50 km. The regional scale is from 50 to 500 km. Continental scales are from 500 to several thousand km. Of course, the global scale extends worldwide. 

At least three types of problems contribute to air pollution problems on the regional scale. One is the carryover of urban oxidant problems to the regional scale. With the existence of major metropolitan areas in close proximity, the air from one metropolitan area, containing both secondary pollutants formed through reactions and primary pollutants, flows on to the adjacent metropolitan area. The pollutants from the second area are then added on top of the "background" from the first. 

The other major aspect of air pollution reduction is the control of shortterm episodes on the urban scale. This aspect is called tactical because, prior to an episode, a scenario of tactical maneuvers must be developed... 

Certainly, photochemical air pollution is not merely a local problem. Indeed, spread of anthropogenic smog plumes away from urban centers results in regional scale oxidant problems, such as found in the NE United States and many southern States. Ozone production has also been connected with biomass burning in the tropics (79,80,81). Transport of large-scale tropospheric ozone plumes over large distances has been documented from satellite measurements of total atmospheric ozone (82,83,84), originally taken to study stratospheric ozone depletion. 

Road traffic is widely recognised to be a significant and increasing source of air pollutants in urban and industrial areas but also at a regional scale worldwide. Emissions from road traffic can be divided into three different components ... 

The on-line integration of meso-scale meteorological models and atmospheric aerosol and chemical transport models enables the utilization of all meteorological 3D fields in ACTMs at each time step and the consideration of the feedbacks of air pollution (e.g. urban aerosols) on meteorological processes and climate forcing. 

The model system is developed to simulate aerosols and gas-phase compounds from regional to urban scale of ground-level gas-phase air pollutants. It has been used for air quality forecasts of ground-level gas-phase air pollutants and modelling of historical data. 

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