Chemistry of wildfire smoke

This exercise is a part of Educator Guide: Wildfires May Boost Urban Ozone Levels / View Guide

Directions for teachers: Ask students to read the online Science News article “Wildfire smoke may ramp up toxic ozone production in cities,” which explores new research into the interactions between wildfire smoke and air pollution in cities, and answer the following questions. A version of the article, “Wildfires may boost urban ozone levels,” appears in the January 15, 2022 issue of Science News.

1. Wildfire smoke contains a dizzying array of organic compounds and nitrogen oxides among other molecules. How did the scientists described in the article study the chemistry of wildfire smoke in action?   

Scientists flew a jet in and out of smoke as the plumes drifted downwind of wildfires. The team collected air samples and recorded the kinds and amounts of each molecule detected in the smoky air. That let the team see how the smoke’s chemical composition changed over time.

2. Ozone can form as ingredients in wildfire smoke interact. How did scientists calculate the amount of ozone produced by wildfire emissions? What did the calculations show?

The researchers used the air measurements along with wind patterns and fuel from sampled wildfires to create an equation that estimates ozone production. The scientists found that the concentrations of nitrogen oxides in wildfire smoke decline as the plumes move downwind, so ozone production slows over time.

3. Based on the scientists’ findings, what can happen when wildfire smoke drifts into urban areas?

When wildfire smoke blows over cities, the smoke could get an infusion of nitrogen oxides — toxic gases found in car exhaust. When nitrogen oxides in city air mix with the wildfire smoke, ozone production could ramp up again.

4. What are the possible implications for urban air quality and human health?

Ozone levels could increase by as much as 3 parts per billion in the U.S. West during a typical fire season, worsening air quality. Though that increase is small, the researchers say it still could pose a health risk for people who are regularly exposed to smoke.

5. How might climate change make the situation worse?

Climate change is fueling more frequent and intense wildfires. More smoke means more ozone production. In addition to the health risks, the changes could complicate efforts to set meaningful air quality standards.

6. Choose a word from the story that you don’t use all the time and write a dictionary definition for the word using only context clues from the article. Don’t forget to include the word’s part of speech.

Student answers will vary. Noxious is an adjective. It means harmful or poisonous. Ozone is a noxious gas when people inhale it.