tailieunhanh - Air Pollution: A Half Century of ProgressINGANNIVERSARY ARTICLE Air Pollution: A Half Century of ProgressJohn H. SeinfeldDept. of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 DOI 10.1002/aic.10102 Published online in Wiley Inte

The larger, so-called "coarse" particles are mostly produced by mechanical processes, such as automobile tire wear on the road, industrial cutting, grinding and pulverizing processes and re-suspension of particles from the ground or other surfaces by wind and human activities. The chemical composition of coarse particles may be somewhat similar to the chemical composition of soil in that area, along with industrial compounds from activities such as mining or smelting operations. The coarse fraction of urban aerosols also contains bits of plants, molds, spores and some bacteria. Thus the characteristics of the coarse particles may vary greatly. | ENVIRONMENTAL AND ENERGY ENGINEERING ANNIVERSARY ARTICLE Air Pollution A Half Century of Progress John H. Seinfeld Dept. of Chemical Engineering California Institute of Technology Pasadena CA 91125 DOI Published online in Wiley InterScience . In the 50 years since the air pollution episodes of Donora PA and London . a great deal of progress has been made in understanding the nature and sources of air pollution and the atmospheric transport and transformation of pollutants. Also many significant technological advances in air pollution control equipment such as the automobile exhaust gas catalytic converter have led to effective reduction of emissions from a variety of major pollution sources. Finally remarkable developments in instrumentation for sampling the trace species in the atmosphere have been and continue to be made. Relatively less progress has been made in understanding the biological mechanisms by which pollutants lead to human injury and mortality. In this review the focus is on the extraordinary progress that has been made over the last half century in understanding the atmospheric nature and behavior of pollutants both gaseous and particulate. A major breakthrough was the determination of the gas-phase chemistry of both the natural and polluted atmosphere chemistry that leads to the formation of ozone and a vast array of oxidized molecules. The mechanisms of the oxidation of atmospheric sulfur dioxide one of the main primary pollutants were elucidated. Finally the chemistry physics and optics of atmospheric particulate matter aerosols have been laid open by many stunning research achievements. Whereas 50 years ago air pollution was thought to be confined to the area around a city it is now recognized that species emitted on one continent frequently find their way to other continents. Strategies for dealing with a truly global atmospheric backyard now represent a major challenge. 2004 American Institute of