Air Quality Manual: Analysis of Ambient Air Quality for Highway Projects.

摘要

Air pollution generally results from the interaction between pollutant sources and meteorological conditions. Sources of air pollutants within a highway corridor normally include stationary and mobile sources. Stationary sources may include domestic heaters, industrial installations, and power plants. Mobile sources include the motor vehicle traffic on freeways and local roads and streets. All sources contribute to the ambient air quality of a community. The primary pollutants emitted from motor vehicles are carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and particulates (mainly lead). Hydrocarbons and oxides of nitrogen combine in a photochemical process to form smog. The formation of photochemical smog is extremely complex and is related to the amount of ultraviolet radiation present, the relative concentrations of each primary pollutant, and the time for this reaction to take place. Carbon monoxide is a stable gas and does not take part in the photochemical process. The California Air Resources Board (ARB) made studies of the percentages of pollutant loads attributed to stationary and mobile sources for the Los Angeles Basin, San Diego, and the San Francisco Bay area. The average percentages of pollutant loads for these areas indicate that about 90%, 61%, and 64%, respectively, of CO, HC, and NOx are attributed to motor vehicles.