What question did this study set out to answer?

This research aims to quantify the role of wildfire emissions in influencing urban ozone levels in eastern Australia.

April 26, 2026

Quantifying Contributions of Wildfire to Urban Ozone in Eastern Australia via in Situ Observation and Machine Learning

YXYang XiaoClimate Central HZHongzhi ZhangQueensland University of Technology DGDaniel GuoQueensland University of Technology

Key Points

This research aims to quantify the role of wildfire emissions in influencing urban ozone levels in eastern Australia.
Analyzed long-term air quality data (2011–2020) for PM2.5, O3, HCHO, NO2, and VOCs
Utilized a machine learning model (XGBoost) to assess contributions of wildfires on O3 levels
Examined airmass trajectories and fire hotspots to determine wildfire impacts on air quality.
Mean increase of 0.3 ppb O3 at Memorial Park and 1.0 ppb at Springwood during wildfire periods
Significant increases of 5.1 ppb at Memorial Park and 6.8 ppb at Springwood during severe wildfire conditions (PM2.5 > 25 μg m–3)
Memorial Park showed greater sensitivity of O3 alterations to changes in HCHO and NO2 compared to Springwood.

Abstract

In the Southern Hemisphere, knowledge of the influence of wildfire emissions on urban air quality is limited. This study examines long-term air quality data sets of fine particulate matter (PM2.5), ozone (O3), formaldehyde (HCHO), nitrogen dioxide (NO2), and benzene, toluene, and xylene at Memorial Park and Springwood in eastern Australia in 2011–2020. Analyses of the airmass trajectories and fire hotspots suggest notable increases in trajectory-fire interceptions and wildfire-influenced hours since 2018. Compared with nonwildfire periods, concentrations of all measured air pollutants were generally higher during wildfire periods. A machine learning model based on eXtreme Gradient Boosting (XGBoost) algorithm was deployed to quantify the contribution of wildfires to O3, indicating mean increases of 0.3 and 1.0 ppb in the net O3 change (ΔO3) at Memorial Park and Springwood, respectively. Such increases in ΔO3 due to wildfires were statistically significant only at Springwood and not at Memorial Park. During severe wildfire periods, as indicated by PM2.5 > 25 μg m–3, statistically significant increases in ΔO3 were observed at the two sites, with 5.1 ppb at Memorial Park and 6.8 ppb at Springwood. Analyzing the sensitivity of ΔO3 to the proxies for the O3 precursors (i.e., HCHO, NO2), we found that Memorial Park exhibited higher degrees of daytime ΔO3 alteration than Springwood, under similar levels of changes in HCHO or NO2 concentrations.

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