California air pollution creeps into remote Sierra monument

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Air pollution is a growing concern at Devils Postpile National Monument, near Mammoth Lakes, California. Photo courtesy National Park Service.

Wildfires, industrial sources contribute to ozone problems in the Eastern Sierra Nevada

By Summit Voice

SUMMIT COUNTY — Devils Postpile National Monument in the eastern Sierra Nevada is about as far as you can get from California’s industrial urban centers, yet air quality at the site has suffered in recent years as pollution blows in from other parts of the state, according to a new U.S. Forest Service-led study.

The monument, near the resort town of Mammoth Lakes, features one of the best examples of columnar basalt formations and is also a gateway to High Sierra wilderness areas bordering on Yosemite National Park.

Ozone precursors (nitrogen oxides and volatile organic compounds) from wildland fires, as well as ozone from the Bay Area and Central Valley resulted in exceedances of federal air quality standards, as well as state air quality standards during the 2007-2008 study period, at levels that pose a risk to sensitive individuals and indicate a need for long-term ozone monitoring.

“These findings are important for Sierra Nevada air and land managers and indicate that even at remote eastern Sierra locations, ozone air pollution may be a problem for human and ecosystem health,” said Dr. Andrzej Bytnerowicz, a research ecologist from the U.S. Forest Service’s Pacific Southwest Research Station.

There is also a need for evaluation of ozone effects on forest health since this pollutant may weaken trees, making them more sensitive to drought and bark beetle attacks, and consequently resulting in premature death and higher susceptibility to wildland fires, Bytnerowicz explained.

“Due to these potential risks, there is a need for long-term ozone monitoring in the Sierra Nevada in general, but especially in the areas with high local population and many summer recreational visitors,” said Bytnerowicz, lead author of the study that was recently published in in the journal Atmospheric Environment.

Key findings include:

  • Higher ozone peak concentrations in the high-fire year were attributed to emissions of ozone precursors (nitrogen oxides and volatile organic compounds) from wildland fires upwind of Devils Postpile in addition to polluted air traveling from the California Central Valley and the San Francisco Bay Area.
  • The highest ozone levels occurred when air masses swept through the San Francisco Bay Area and the California Central Valley in a northwest to southeasterly direction before reaching Devils Postpile at low altitudes. Both local generation of ozone and long-range transport of polluted air from the Central Valley occasionally caused increased air pollution at Devils Postpile.
  • The lowest ozone pollution occurred when air masses traveling over the Pacific Ocean passed from west to east at high altitudes, sweeping above the polluted air masses of the Central Valley.

The full report is available at: http://treesearch.fs.fed.us/pubs/43284.

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