Evidence for multi-decadal fuel buildup in a large California wildfire from smoke radiocarbon measurements

Bibliographic Data

ID15550322
AuthorsA Odwuor (0000-0001-9104-5025, University of California, Irvine, corresponding author), Cindy C Yañez (0000-0003-1521-2906, University of California, Irvine), Yang Chen (0000-0001-5943-3247, University of California, Irvine), F M Hopkins (0000-0002-6110-7675, University of California, Riverside), A Moreno (0009-0009-6027-5966, California Air Resources Board), Xiaomei Xu (0000-0001-5677-2497, University of California, Irvine), C I Czimczik (0000-0002-8251-6603, University of California, Irvine), James T Randerson (0000-0001-6559-7387, University of California, Irvine)
Year2023
Volume18
Issue9
Pages094030-094030
Publication date2023-08-03
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueEnvironmental Research Letters (JOURNAL)
Journal identifiersISSN: 1748-9326 • E-ISSN: 1748-9326
PublisherIOP Publishing (PUBLISHER • GB)
DOI10.1088/1748-9326/aced17
OpenAlexW4385519763
LanguageEN
Citations received2
References cited53

In recent decades, there has been a significant increase in annual area burned in California’s Sierra Nevada mountains. This rise in fire activity has prompted the need to understand how historical forest management practices affect fuel composition and emissions. Here we examined the total carbon (TC) concentration and radiocarbon abundance (Δ 14 C) of particulate matter (PM) emitted by the KNP Complex Fire, which occurred during California’s 2021 wildfire season and affected several groves of giant sequoia trees in the southern Sierra Nevada. During a 26 h sampling period, we measured concentrations of fine airborne PM (PM 2.5 ), as well as dry air mole fractions of carbon monoxide (CO) and methane (CH 4 ), using a ground-based mobile laboratory. We also collected filter samples of PM 2.5 for analysis of TC concentration and Δ 14 C. High correlation among PM 2.5 , CO, and CH 4 time series confirmed that our PM 2.5 measurements captured variability in wildfire emissions. Using a Keeling plot approach, we determined that the mean Δ 14 C of PM 2.5 was 111.6 ± 7.7‰ ( n = 12), which was considerably enriched relative to atmospheric carbon dioxide in the northern hemisphere in 2021 (−3.2 ± 1.4‰). Combining these Δ 14 C data with a steady-state one-box ecosystem model, we estimated that the mean age of fuels combusted in the KNP Complex Fire was 40 years, with a range of 29–57 years. These results provide evidence for emissions originating from woody biomass, larger-diameter fine fuels, and coarse woody debris that have accumulated over multiple decades. This is consistent with independent field observations that indicate high fire intensity contributed to widespread giant sequoia mortality. With the expanded use of prescribed fires planned over the next decade in California to mitigate wildfire impacts, our measurement approach has the potential to provide regionally-integrated estimates of the effectiveness of fuel treatment programs

Air pollution · Archaeology · Atmospheric sciences · Geography · Meteorology · Northern Hemisphere · Particulates · Physical geography · Radiocarbon dating · Smoke · Atmospheric and Environmental Gas Dynamics · Atmospheric chemistry and aerosols · Chemistry · Environmental Science · Fire effects on ecosystems · Environmental Chemistry · Geology

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