Embedded Files
Wildfires are a substantial source of atmospheric pollutants. The number and size of wildfires are predicted to increase as a result of historical fire suppression practices and ongoing climate change. This threatens to offset some of the improvements in air quality in the United States over the past few decades, particularly during fire season. However, the poorly characterized emissions and complex chemistry in wildfire plumes hinder our ability to accurately predict the impacts of wildfires on air quality.
Brown carbon evolution in wildfire plumes
Brown carbon evolution in wildfire plumes
We compiled measurements from five field campaigns (SEAC4RS 2013, FireLab 2016, WE-CAN 2018, FIREX-AQ 2019, and AEROMMA 2023) to investigate the evolution of brown carbon from emission source to thousands of kilometers downwind.
To account for the variability in emission ratios, we developed a novel parameterization. The parameterization uses the ratio of CH3CN/HCN as the basis.
The evolution of brown carbon absorption in the free troposphere is characterized as a function of hydroxyl radical (OH) exposure, yielding an effective photochemical rate constant of 9.7 × 10–12 cm3 molecule–1 s–1. The lifetime of brown carbon absorption is about 23 hr.
Related Publications:
Chen et al., Atmospheric Evolution of Brown Carbon from Wildfires in North American. EST 2025
Ozone chemistry in wildfire plumes
Ozone chemistry in wildfire plumes
Here we introduce a novel analysis (i.e., single transect analysis) of the evolving chemistry of wildfires, and quantitatively diagnose the key variables that control ozone formation, including oxidant sources, volatile organic compounds (VOCs) emissions, the chemistry of nitrogen oxides (NOx) and peroxy radicals (RO2).
We find that in the near field, OH produced via photolysis of HONO initiates VOCs oxidation, which proceeds in the presence of NOx and leads to efficient O3 formation. After a few hours, the HONO has been consumed and NOx has been both diluted sufficiently and converted to PANs and nitrate such that the O3 formation slows by several orders of magnitude.
Further, we derive a simple parameterization to predict ozone formation in temperate wildfires and estimate that wildfire emissions can produce a 3 ppb enhancement over the western U.S. during the fire season.
Related Publications:
Xu et al., Ozone chemistry in western U.S. wildfire plumes. Science Advances 2021, 7 (50), eabl3648.
Figure source: Xu et al. 2021 Science Advances.
Caltech CIMS on NASA DC-8 aircraft. Photo source: a professional photographer
Page updated
Google Sites
Report abuse