USDA Forest Service
 

Pacific Southwest Research Station

 
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Research Topics Air Quality

Smoke Effects

Smoke obscures the sun across a mountainous landscape with vegetation  shadowed in the foreground.
The plume from the Lake Fire is observed from Menifee, Calif., about 60 km south of the fire. (U.S. Forest Service/Andrzej Bytnerowicz)

Smoke emission impacts on particulate matter and ozone

Prior to employing land management practices such as prescribed burns, it is important to evaluate the potential spread of resulting smoke emissions and their impact on ecosystems and agricultural systems. Fire emissions combine with urban pollution, causing elevated levels of gaseous and aerosol air pollutants in areas distant from fires. Smoke from wildfires promotes the formation of particulate matter, which impacts visibility and causes regional haze. In addition, fire emissions may also increase concentrations of ozone affecting human and ecosystem health.

Prescribed fire is an important land management tool for National Forest managers. The U.S. Forest Service air resources managers and local air quality management districts (such as the San Joaquin Valley Air Pollution Control District) protect good air quality based on the regulations set by the U.S. Environmental Protection Agency and the California Air Resources Board.

Existing models of smoke chemistry, transport and dispersion need to be tested under local and regional conditions. Controlled (prescribed) fires should be considered as an effective fuel management tool in California forests. However, during their use attention should be paid to the national and California ambient air quality standards (AAQS) for particulate matter1 and ozone2.

Our research conducted in collaboration with the USDA Forest Service Region 5, National Park Service, University of California, Merced, St. Mary’s College and Desert Research Institute has been focused on impacts of wildland fires on ambient air quality. It has been done from a perspective of fire emission effects on selected receptor sites such as the Santa Margarita Reserve in southern California or Devils Postpile National Monument in eastern Sierra Nevada. By using various monitoring methodologies (including passive samplers and real-time electronic instruments), as well as analysis of air masses movement (HYSPLIT backward and forward trajectories) and meteorological conditions, we evaluate impacts of fires emissions on ambient air quality with emphasis on ozone and PM2.5.

Smoke obscures the sun across a mountainous landscape with vegetation  shadowed in the foreground.

One - and three- hour rolling averages of PM2.5 measured at Devils Postpile National Monument in summer 2013.

Note elevated to “unhealthy” PM2.5 levels during the Aspen Fire and levels classified as “unhealthy to sensitive people” during the Rim Fire. (University of California, Merced/Donald Schweizer, unpublished)

Results of our monitoring efforts show that long-range transport of polluted air masses from the source areas (such as the San Joaquin Valley in California) may increase O3 levels of the remote receptor sites of the Sierra Nevada during both the absence and the presence of wildland fires. Contribution of fire emissions to increased O3 depend on their chemical composition, meteorological conditions, distance and intensity of photochemical reactions.  

1Particulate matter is monitored as fine particles of diameter <2.5 mm (PM2.5) and coarse particles of diameter <10 mm (PM10). Violation of the California AAQS for PM10 occurs when 24 hour average concentration is >50 µg m-3 or annual mean is >20 µg m-3; violation of the federal AAQS occurs at >150 µg m-3 and >50 µg m-3, respectively. Violation of the California AAQS for PM2.5 occurs when annual mean is >12 µg m-3; violation of the federal standard occurs when 24 hour value is >65 µg m-3 or annual value is >15 µg m-3.   

2Violation of the California ozone standard occurs when 1 hour average is >0.09 ppm or 8 hour average is >0.07 ppm; violation of the federal standard occurs when 8 hour average is >0.08 ppm as the 4th highest value averages over 3 years.   

Smoke emissions, nitric acid vapor, and N deposition

Smoke obscures the sun across a mountainous landscape with vegetation  shadowed in the foreground.Smoke obscures the sun across a mountainous landscape with vegetation  shadowed in the foreground.
Increased nitric acid concentrations in in the Athabasca Oil Sands Region in summer 2011 caused by expansive wildland fires (left), compared with the low-fire summer of 2012 (right).

Concentrations of nitric (HNO3) and nitrous (HONO) acid vapors, similar to those of ozone, increase downwind from forest fires during their flaming phase. In addition, elevated levels of ammonia (NH3) have been found downwind of fires during their smoldering phase. Nitric and nitrous acids, as well as ammonia, are important components of dry deposition of nitrogen (N) to forests.

Because of the widespread and largely detrimental effects of elevated atmospheric N deposition, quantification of ecosystem N inputs from air pollution is needed. This has been done with the use of passive samplers for nitric and nitrous acids, ammonia and nitrogen oxides (NOx). Throughfall collection and analysis using ion exchange resin (IER) has been extensively used in various field monitoring campaigns in California and Canada.


Studies
  • Monitoring of ozone ambient air pollution at Devils Postpile National Monument, eastern Sierra Nevada. Andrzej Bytnerowicz and Joel Burley, 2007-2008.
  • Evaluation of air quality at Devils Postpile National Monument, eastern Sierra Nevada Mountains. Andrzej Bytnerowicz, Joel Burley, Monica Buhler, Ricardo Cisneros, Don Schweizer and Barbara Zielinska, 2013-2014.
  • Monitoring nitric and ammonia air pollution in the Athabasca Oil Sands Region, Alberta, Canada. Andrzej Bytnerowicz, 2005–2013.
Publications
Last Modified: Nov 30, 2018 12:25:15 PM