Category Archives: Publications

New critical review of wildland fire impacts on air quality

Dr. Dan Jaffe is the lead author on a critical review that examines the processes that influence wildfires and prescribed fires and their effects on air quality in the U.S. This review, “Wildfire and prescribed burning impacts on air quality in the United States,” is published in the June issue of the Journal of the Air & Waste Management Association. This paper is the result of a collaboration between Dan Jaffe and Susan O’Neill, Narasimhan Larkin, Amara Holder, David Peterson, Jessica Halofsky, and Ana Rappold. These coauthors have brought their range of expertise to the issues related to wildland fires and have examined each of the processes influencing these fires and also the effects of the fires, “including the natural role of wildland fire, forest management, ignitions, emissions, transport, chemistry, and human health impacts.”

Large wildfires in the U.S. are becoming more common, and their emissions of particulate matter (PM) and gaseous compounds negatively impact air quality and human health. The air quality trend in the U.S. has been improving in the last decades. However, seasonal wildfires threaten to undermine this progress in parts of the country. The area burned by wildland fires has grown significantly in the last few decades due to “past forest management practices, climate change, and other human factors.” This has resulted in millions of people experiencing high levels of air pollution. As cities and towns have spread further into wildlands, costs for fire suppression (to protect human developments) and the consequences of fires have increased significantly.

U.S. wildire area burned and federal suppression costs for 1985-2018

Total U.S. wildfire area burned (ha) and federal suppression costs for 1985–2018 scaled to constant (2016) U.S. dollars. Trends for both wildfire area burned and suppression indicate about a four-fold increase over a 30-year period. Data source: National Interagency Fire Center, Fire Information Statistics, accessed December 2, 2019. https://www.nifc.gov/fireInfo/fireInfo_statistics.html.

In this review, Dr. Jaffe and his coauthors describe the current state of the research and identify key data gaps. Their goal is to identify areas that are well understood and areas that need more research. They recommend eight specific areas for future research.

Read the paper here

Free paper eprints available here

2 new papers explore methods for measuring biomass burning pollutants

Research by Jaffe Group postdoctoral scholars Dr. James Laing and Dr. Boggarapu Praphulla Chandra has resulted in two new peer-reviewed publications. Both papers examine methods used for measuring air pollutants from wildfires.

The first paper, “Comparison of filter-based absorption measurements of biomass burning aerosol and background aerosol at the Mt. Bachelor Observatory,” was recently published in Aerosol and Air Quality Research. The authors, Dr. James Laing, Dr. Daniel Jaffe, and Dr. Arthur Sedlacek, III, evaluated the upgraded aethalometer (AE33, Magee Scientific) and the new tricolor absorption photometer (TAP, Brechtel) to assess their effectiveness in measuring wildfire aerosol plumes. These instruments measure light-absorbing organic aerosols, which are emitted primarily in biomass burning. Both instruments were deployed at Mt. Bachelor Observatory (MBO) in central Oregon during the summer of 2016. Each instrument uses a similar methodology (“light extinction through an aerosol-laden filter”), but each has a unique set of corrections necessary to address filter-based bias and other issues. The coauthors found that when using the AE33 manufacturer’s recommended settings, correction factors that are larger than the manufacturer’s recommended factor are needed to calculate accurate absorption coefficients and equivalent black carbon.

Read the full paper.

In the second paper, coauthors Dr. Boggarapu Praphulla Chandra, Dr. Crystal McClure, JoAnne Mulligan, and Dr. Daniel Jaffe evaluated the use of dual-bed thermal desorption (TD) tubes with an auto-sampler to sample volatile organic compounds (VOCs). Their paper, “Optimization of a method for the detection of biomass-burning relevant VOCs in urban areas using thermal desorption gas chromatography mass spectrometry,” appeared in the journal Atmosphere in March. For this study, the authors utilized a portable, custom-made “suitcase” sampler, which they deployed in  Boise, ID, during the summer of 2019.

The sampler continuously collected samples of VOCs on the TD tubes for up to six days without the need for continuous on-site monitoring. The tubes were later transferred to the lab for analysis using thermal desorption gas chromatography mass spectrometry (TD-GC-MS) to detect VOCs.

Suitcase thermal desorption VOC auto-sampler 4-2020

(a) Internal view of the volatile organic compound (VOC) suitcase sampler; (b) Flow diagram of the VOC suitcase sampler; (c) Schematic diagram of the dual-bed TD tubes.

They found that “reactive and short-lived VOCs such as acetonitrile (a specific chemical tracer for biomass burning), acetone, n-pentane, isopentane, benzene, toluene, furan, acrolein, 2-butanone, 2,3-butanedione, methacrolein, 2,5- dimethylfuran, and furfural . . . can be quantified reproducibly with a total uncertainty of ≤30% between the collection and analysis, and with storage times of up to 15 days.”

Their research demonstrates the applicability of this flexible method for ambient VOC speciation and determining the influence of forest fire smoke. This sampling method offers a practical alternative for urban air quality monitoring sites because its portability does not require the installation of a complex and expensive instrument and its auto-sampling technique does not require continuous on-site monitoring.

Read the full paper.

Wildfires are causing extreme PM in the western US

Wildfire smoke on 9/6/2017

Wildfire smoke covering the Pacific Northwest and British Columbia on September 6, 2017, from MODIS true color reflectance image. Red dots represent fire locations. Source: https://worldview.earthdata.nasa.gov.

New research by James Laing and Dan Jaffe shows how increases in wildfire smoke have impacted air quality in the western US. Their recent paper, published in the June 2019 issue of EM—The Magazine for Environmental Managers, describes the changing air quality picture for western states. Even though air quality in most of the US has improved in the last four decades, due in large part to the US Clean Air Act regulations, it is not improving in much of the western US. The reason for the decrease in air quality in western states is wildfire smoke.

In 2017 and 2018, wildfires caused the largest daily mean concentrations of fine particulate matter (PM2.5; particles with diameter less than 2.5 μm) ever measured at monitoring sites in the US. Some of the extreme PM2.5 events of 2017–2018 include the following:

  • Seeley Lake, Montana, September 6, 2017—Highest daily PM2.5 on record (642 μg/m3). In August-September 2017, there were 35 days with PM2.5 > 150 μg/m3 and 18 with PM2.5 > 250 μg/m3.
  • Ventura, California, December 6, 2017—PM2.5 of 557 μg/m3, with a two-week average concentration of 165 μg/m3.
  • Seattle, Washington, August 21, 2018—Highest daily PM2.5 ever recorded in Seattle (110 μg/m3).
  • Medford, Oregon, September 6, 2017—Highest daily PM2.5 ever recorded in Medford (268 μg/m3), and eight days over 100 μg/m3 in 2017.

To put these measurements in context, the US Environmental Protection Agency (EPA) has set the daily PM2.5 standard at 35 μg/m3 (98th percentile < 35 μg/m3, averaged over 3 years). The EPA has also defined PM2.5 > 150 μg/m3 as very unhealthy and PM2.5 > 250 μg/m3 as hazardous. PM2.5 is such a health hazard because it can travel deep into the respiratory system due to its small size. Despite the gains in air quality in the US, about 30 million people live where the PM2.5 standard is not being met.

The estimated increase in the number and size of wildfires in the future raises issues for public officials and environmental managers. Complying with air quality standards and reducing human exposure to PM2.5 are causes for concern in the western US now and going forward.

Read the full paper here

Background ozone and implications for air quality management

In a new paper published in Elementa, Dan Jaffe and his coauthors look at background ozone in the US and how it influences whether states can meet air quality standards. Background ozone (O3) includes “contributions from natural and foreign sources of O3 that cannot be controlled by precursor emissions reductions solely within the US.” Understanding background O3 is necessary for air quality management overall and for states and municipalities to meet national air quality standards.

They examined over 100 published studies in order to assess what is the current knowledge about the distribution, trends, and sources of background ozone in the continental US. They found that “noncontrollable O3 sources, such as stratospheric intrusions or precursors from wildfires, can make significant contributions to O3 on some days, but it is challenging to quantify accurately these contributions.” In order to address this shortcoming, they recommend a more coordinated and focused approach to understanding background ozone in the US: improvements in the monitoring network, large-scale field experiments, more accurate and consistent chemical transport models, and more detailed observations of wildfires.

Read the paper here

US particulate matter air quality improves except in wildfire-prone areas—See our new group paper!

A new paper authored by Crystal McClure and Dan Jaffe describes the increasing  particulate matter (PM2.5) pollution over the last few decades in the Northwest. This research, published Monday in Proceedings of the National Academy of Sciences, analyzed PM2.5 data from rural monitoring (IMPROVE) sites across the contiguous US for 1988–2016. They found a decreasing trend  in PM2.5, and cleaner air, around the country except for in the Northwest, where there is a positive trend in PM2.5. This positive trend is associated with total carbon, a marker for wildfires.

The figure below shows trends in PM2.5 for 1988–2016 for the 98th quantile, that is, the seven highest days. In most of the Northwest (red and orange areas), these days are getting worse, while most of the country has improving air quality trends (purple, blue, and green areas).

Figure 1 in PNAS paper US particulate matter air quality improves except in wildfire-prone areas

The 98th Quantile Regression of PM2.5 trends. Observed PM trends for 1988–2016 (calculated using QR methods) from IMPROVE sites are shown by black dots with corresponding values in µg·m−3·y−1. Krige-interpolated values (calculated from observed data) are shown by the color ramp. Solid black lines with arrows (indicating direction) show the boundary where the Krige-interpolated PM2.5 trends within have a 90% probability of being positive or negative. Of the 157 sites, 92 show statistical significance (8 positive/84 negative).

Read the abstract on the PNAS website

This new research has been garnering a lot of press since its publication: