Category Archives: Wildfires

Do wildfires contribute to ozone events in an urban area?

Do wildfires contribute to ozone pr?

Wildfires emit primary pollutants, including particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx [=NO+NO2]), and volatile organic compounds (VOCs) and contribute to the formation of secondary pollutants, such as ozone (O3) and peroxyacetyl nitrate (PAN). Wildfire emissions can enhance the production of O3 through the addition of NOx and VOCs. This paper investigated how wildfire emissions influenced the formation of ozone in an urban area.

In a recent Atmospheric Environment paper, Crystal McClure and Dan Jaffe investigated ozone (O3) enhancements during wildfire events in the Boise, Idaho, urban area over 2006–2017 and during a 2017 summer intensive campaign. They determined whether wildfire emissions are influencing the area by calculating a wildfire criterion based on NOAA’s Hazard Mapping System (HMS) smoke product and historically averaged fine particulate matter (diameter < 2.5 μm [PM2.5]) data. Using this criterion, they could categorize smoke vs. non-smoke events. They also used a Generalized Additive Model (GAM) to look at unusual sources of O3, such as wildfires. GAMs are useful in analyzing sources of O3 production by looking at meteorological and transport variables.

During the 2017 summer intensive campaign, they found that peroxyacetyl nitrate (PAN), reactive nitrogen (NOy), and maximum daily 8 hour average (MDA8) O3 showed significant enhancements during smoke events. These findings show that wildfire-influenced O3 enhancements are highly variable in urban areas—O3 enhancements generally increase up to around 60 μg/m3 of PM2.5 and then decrease at very high smoke concentrations.

This research suggests that measurements of multiple tracers are essential in order to fully describe wildfire plumes in urban areas. McClure and Jaffe conclude, “While we identify some effects on O3 due to wildfire emissions in an urban area, the need for improved classification of smoke versus non-smoke influenced days will likely become more important throughout the western U.S. as wildfire frequency and intensity are predicted to increase through the end of the century.”

Read the paper here

Wildfires and poor air quality—Is this the new normal?

When smoke gets in your eyes this summer, your thoughts are probably turning to wildfires. Wildfires are on nearly everyone’s mind these days in the Pacific Northwest because of the smoky haze and poor air quality that is blanketing our area. This August is similar to August 2017, and so you might wonder—why is this happening and is it going to continue? Those are the questions many reporters have been asking Dan Jaffe in the last few weeks.

A new paper by group members Crystal McClure and Dan Jaffe published in the Proceedings of the National Academy of Science addresses these questions. This research highlights the dramatic gains in air quality that have taken place in the last few decades around the country except in the Northwest. In this region, the 98th percentile of daily fine particulate matter (PM2.5), or in other words the seven worst air quality days each year, is getting worse. Around the US, there have been improvements in air quality from reduced power plant, industry, and automobile emissions, but in the Northwest, those reductions are outweighed by the emissions from wildfires. Learn more about this paper.

The indications are that the wildfire season will continue to get worse in the Northwest. Forest management practices and meteorological factors such as increased spring and summer temperatures, earlier snowmelt, and dryer forest conditions contribute to the current situation. “We want to be careful not to put it all on climate change, but climate change is clearly a contributing factor, and particularly in the size of these fires,” Dan Jaffe told E&E News. “A fire that used to become a small fire has now become a massive conflagration.” We will see more high fire years and, in general, longer fire seasons and bigger fires.

The increase in wildfires and smoky conditions causes adverse health effects. Wildfires are a major source of fine particulate matter, which is small enough to be inhaled deeply into the lungs. The health impacts of breathing smoke can be significant, especially for children, the elderly, and people with pulmonary, cardiovascular, and other chronic conditions.

To listen and watch interviews with Dan Jaffe about wildfires and air quality, visit:

To read more, see:

To see all news reports and articles about our research, see our In the News page.

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: