From: Roger Greenway, ENN
Published June 5, 2013 07:28 AM

Good News about Los Angeles Air Pollution

The emission reduction requirements on automobiles and trucks are resulting in improving air quality in the Los Angeles area. They have significantly reduced Ozone concentrations, a principal component of the smog that has been so common in the area.

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Another benefit is that these reductions have altered the pollution chemistry in the atmosphere, making the eye-stinging "organic nitrate" component of air pollution plummet, according to a new study led by a scientist from NOAA's Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder.

For the study, being published online in the Journal of Geophysical Research-Atmospheres, the scientists analyzed new data from research aircraft along with archived data going back a half-century to produce a comprehensive study of air pollution in the Los Angeles region.

"This is good news: LA's air has lost a lot of its 'sting,' " said lead author Ilana Pollack, a CIRES scientist who works at NOAA's Earth System Research Laboratory in Boulder. "Our study shows exactly how that happened, and confirms that California's policies to control emissions have worked as intended."

Scientists have studied the origins and levels of air pollutants in the South Coast Air Basin — a region encompassing the Los Angeles urban area — for a long time. Since the 1960s, they have measured levels of ozone and other air pollutants that are formed in the atmosphere (so-called "secondary" pollutants) and the ingredients, or "precursors," that form them: volatile organic compounds (VOCs) and nitrogen oxides (NOx). These precursors are directly emitted from various sources, primarily vehicle exhaust in LA but also from power-generating facilities, industry, and natural sources such as vegetation.

As studies began to identify the high levels of air pollution and its causes, policies and controls were implemented to restrict emissions of the NOx and VOC ingredients that result in ozone and other secondary air pollutants. Although the population in the Southern California region has tripled between 1960 and 2010, and the number of vehicles has increased by a similar factor, research studies have indicated that air pollution in the region has decreased — as a result of these policies.

To pin down the exact nature of the downward trends and the related changes in the chemistry causing the declining levels of pollutants, Pollack and her team examined new data from research aircraft and archived data from roadside monitors and ground-based instruments. In doing so, they generated a synthesis of information on ozone, other secondary pollutants and pollutant precursors from 1960 to 2010. This work included measurements of ozone and nitrogen oxides collected by Pollack and her colleagues over the South Coast Air Basin using instruments aboard NOAA's P-3 research aircraft during a California-based mission in 2010.

Los Angeles skyline image via Shutterstock.

Read more at University of Colorado.

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