As part of its Clean Thinking collection, Taylor & Francis is providing free access to a collection of articles on clean thinking for climate change. Included in the collection is the critical review “Wildfire and prescribed burning impacts on air quality in the United States,” published in the Journal of the Air & Waste Management Association in June 2020. Access is free until April 30, 2022.
“The impact of wildfire smoke on ozone production in an urban area: Insights from field observations and photochemical box modeling”
In this recently published paper, postdoctoral research associate Matt Ninneman and Dan Jaffe examined the effect of wildfire smoke on ozone (O3) production at an urban site in Bakersfield, CA. They used data from smoky and non-smoky weekdays in summer 2018. During this period, there were several active wildfires in northern California. The authors utilized a photochemical box model to analyze the data. The box model simulations indicate that maximum O3 production rates were about two times faster on smoky weekdays compared to non-smoky weekdays. Model sensitivity tests for smoky weekdays showed that (1) O3 was sensitive to both oxides of nitrogen (NOx) and volatile organic compounds (VOCs) and (2) aldehydes significantly affected O3 formation. Their results suggest that “a combination of anthropogenic VOC and NOx reductions will be the most effective strategy for decreasing O3 on typical non-smoky days.” However, only reductions in NOx are expected to have a significant impact on lowering O3 concentrations on typical smoky days, since VOC levels in smoke plumes are high.
“Observed relationship between ozone and temperature for urban nonattainment areas in the United States”
In a second recently published paper, Matt Ninneman and Dan Jaffe investigated the observed relationship between ground-level ozone (O3) and temperature from 1995 to 2020 at 20 U.S. cities that violate regulatory requirements for ground-level O3. They found that the median slope of the ground-level O3 versus temperature relationship declined in all regions, and the correlation between ground-level O3 and temperature weakened over time in the eastern and midwestern U.S. In the western U.S., ground-level O3 has declined more slowly and the correlation between ground-level O3 and temperature has changed negligibly due to the combined influence of high background O3 and wildfire smoke. This suggests that meeting regulatory requirements for ground-level O3 in the western U.S. will be more challenging than in other parts of the country.
A new paper by group members Dr. Nate May, Clara Dixon, and Dr. Dan Jaffe evaluates the effectiveness of low-cost air filter units during wildfire smoke events. The increased wildland fire activity in the western US in recent years produces high concentrations of fine particulate matter (PM2.5), which negatively affects the health of millions of people. During wildfire smoke events, staying indoors is often recommended. However, how good is indoor air quality during smoke events? The authors looked at PM2.5 measurements from the PurpleAir sensor network, a publicly available network of low-cost air quality sensors located indoors and outdoors. They also analyzed the effectiveness of residential filter units in reducing indoor PM2.5. One low-cost DIY filtration method consists of attaching a Minimum Efficiency Rating Value-13 (MERV-13) fan filter to a standard box fan. This method was found to be highly effective at reducing indoor PM2.5 when recirculating air in a single room.
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.
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.
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.
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.
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.