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

Monitoring

Looking upward into the trees. In the center is a pole with an assembly of passive samplers used for monitoring air quality.A passive sampler labeled with each of the air pollutant monitors labeled: ozone, nitric acid vapor, ammonia, and nitrogen oxide.
Left: Assembly of passive samplers used for air quality monitoring in the Athabasca Oil Sands Region, Alberta, Canada. (U.S. Forest Service/Andrzej Bytnerowicz)
Right: Devils Postpile National Monument, eastern Sierra Nevada. (U.S. Forest Service/Andrzej Bytnerowicz)

Monitoring of air pollution concentrations, atmospheric deposition, and their effects on forests has been conducted in forested areas of California, including vast areas of complex mountain terrain.

This research is needed to determine the extent and magnitude of potential pollutants impacts in areas at risk and to determine changes in forest structure, composition and health.

Our focus is on the Sierra Nevada Mountains and southern California Transverse Ranges, such as San Bernardino and San Gabriel Mountains (including the San Dimas Experimental Forest managed by PSW). In addition, we have been monitoring air pollution and atmospheric deposition in the western U.S. and in the Athabasca Oil Sands Region, Alberta, Canada.

We use passive samplers and portable active monitors for monitoring air pollutants such as ozone, nitric acid vapor, ammonia, and nitrogen oxides in forested and remote areas on a large scale. Using these low-cost monitoring devices on carefully designed monitoring networks allows for developing maps of spatial distribution of air pollutants concentrations.

A map shows the concentrations of ammonia in the central Sierra Nevada showing the highest concentrations on the coastal side of the mountains. A map shows the concentrations of nitric acid in the central Sierra Nevada showing the highest concentrations on the coastal side of the mountains.
Geostatistical maps of ammonia (left) and nitric acid (right) distribution in central Sierra Nevada based on the passive sampler results.

Ion Exchange Resin (IER) collectors

Looking upward into the trees. In the center is a pole with an assembly of passive samplers used for monitoring air quality.A passive sampler labeled with each of the air pollutant monitors labeled: ozone, nitric acid vapor, ammonia, and nitrogen oxide.
Left: IER collectors measure bulk deposition in a bog. (U.S. Forest Service/Mark Fenn)
Right: IER collectors measure throughfall in a jack pine stand in the Athabasca Oil Sands Region, Alberta, Canada. (Wood Buffalo Environmental Association/Natalie Bonnell)

A full evaluation of air pollution effects on ecosystems requires an estimate of total deposition fluxes. Collection of throughfall (rainfall in a forest area that is not intercepted by the crown canopy and reaches the forest floor) is widely acknowledged as a practical method of monitoring atmospheric deposition to forests. We have developed a "passive" throughfall collector in which the deposition is captured in ion exchange resin columns.

This method of throughfall collection is much less expensive than conventional methods and provides an opportunity to quantify nitrogen and sulfur deposition at a greater number of sites than previously possible. Using this method we are increasing our understanding of the levels of nitrogen deposition inputs that cause various effects on forests throughout California and in other western ecosystems. Description of IER methods

These remote boreal forest monitoring sites are accessible by helicopter only. Because of the remoteness of this area conventional event-based sampling is not feasible. On the other hand, these IER passive samplers require only two site visits per year, a highly cost-effective and practical approach for measuring atmospheric deposition inputs in remote areas. Monitored pollutants include nitrogen and sulfur compounds as well as major base cations, important for buffering the effects of acidic deposition on the sandy soils in this region. Notice the co-located passive samplers installed in the bog for measuring atmospheric gaseous pollutant concentrations.

Smoke obscures the sun across a mountainous landscape with vegetation  shadowed in the foreground.
Experimental setup for the Integrated Total Nitrogen Input (ITNI) study. (University of California, Riverside/Beatriz Vindiola)

Integrated Total Nitrogen Input (ITNI) study

This novel technique is based on isotope pool dilution, in which the plant/soil system is labeled with a known amount of stable isotope of N (15N). Then the total amount of atmospheric deposition in all forms is quantified as the 15N label is diluted by atmospheric nitrogen inputs to the plant/soil system.

Results from these experiments, when compared with standard deposition measurements indicate how well standard approaches are quantifying total nitrogen deposition. Because of the difficulties in quantifying atmospheric dry deposition, there is great benefit in using complementary empirical and modeling approaches.

Hybrid approach for annual measurements of pollution in Wilderness

An Ion Exchange Resin sampler used to measure summertime bulk deposition. A close up of a metal tool used to remove a sample of snow.
Left: An IER sampler used to measure summertime bulk deposition. (U.S. Forest Service/Drew Farr)
Right: Snowpack sampling is used to measure wet and dry deposition during winter. (University of California, Riverside/James Sickman)

National atmospheric deposition monitoring networks do not have adequate capacity to measure the important nitrogen (N) and sulfur (S) air pollutants that are deposited to high elevation Class I Wilderness areas. These networks include a limited number of sites on the one hand and furthermore, the monitoring approaches of the national networks cannot measure inputs in the deep snowpacks that are common in Class I areas of the West.

To remedy this problem, we have developed a practical hybrid approach for measuring annual N and S deposition to high elevation remote sites. This information is needed to evaluate ecosystem responses to air pollution and to determine areas at risk of acidification and eutrophication impacts as a result of chronic air pollution exposure.

This monitoring approach consists of measuring deposition from bulk precipitation during the summer season with ion exchange resin samplers (left photo) and wintertime deposition is measured by sampling and analyzing nitrogen and sulfur ions in the snowpack. Summing the results from the two sampling periods provides year-round atmospheric deposition measurements.

Studies
  • Distribution of ozone, ozone precursors and gaseous components of atmospheric nitrogen deposition in the Lake Tahoe Basin. A. Bytnerowicz, M. Fenn, A. Gertler, H. Preisler and B. Zielinska, 2010.
  • Secondary pollutant formation in the Lake Tahoe Basin. B. Zielinska, A. Bytnerowicz and A. Gertler, 2012.
  • Evaluation of nitric acid and ammonia air pollution in the Athabasca Oil Sands Region. A. Bytnerowicz, 2005-2014.
  • Nitrogenous air pollutants in the Bucegi National Park, Romania. A. Bytnerowicz, 2012-2014.
  • The effects of nitrogen deposition on coastal sage scrub invasion and reestablishment in the Santa Monica Mountains National Recreation Area. Justin Valliere, Edith Allen, Andrzej Bytnerowicz and Mark Fenn, 2012-2016.
  • Evaluation of atmospheric nitrogen deposition and effects in the Sierra Nevada and White Mountains subalpine zone. A. Bytnerowicz, C. Millar, M. Fenn and H. Preisler, 2014.
  • A stable isotope approach for determining total atmospheric nitrogen deposition from throughfall measurements. M. Fenn, J. Sickman, A. James. 2013-2016.
Publications
Last Modified: Nov 30, 2018 12:25:21 PM