Abstract. In this study we identify pyrolysis gases from prescribed burns conducted in
pine forests with a shrub understory captured using a manual extraction
device. The device selectively sampled emissions ahead of the flame front,
minimizing the collection of oxidized gases, with the captured gases analyzed in
the laboratory using infrared (IR) absorption spectroscopy. Results show
that emission ratios (ERs) relative to CO for ethene and acetylene were
significantly greater than in previous fire studies, suggesting that the sample
device was able to collect gases predominantly generated prior to ignition.
Further evidence that ignition had not begun was corroborated by novel IR
detections of several species, in particular naphthalene. With regards to
oxygenated species, several aldehydes (acrolein, furaldehyde, acetaldehyde,
formaldehyde) and carboxylic acids (formic, acetic) were all observed;
results show that ERs for acetaldehyde were noticeably greater, while ERs for
formaldehyde and acetic acid were lower compared to other studies. The
acetylene-to-furan ratio also suggests that high-temperature pyrolysis was
the dominant process generating the collected gases.
Abstract. Volatile organic compounds (VOCs) are emitted from many sources, including
wildland fire. VOCs have received heightened emphasis due to such gases'
influential role in the atmosphere, as well as possible health effects. We
have used extractive infrared (IR) spectroscopy on recent prescribed burns
in longleaf pine stands and herein report the first detection of five
compounds using this technique. The newly reported IR detections include
naphthalene, methyl nitrite, allene, acrolein and acetaldehyde. We discuss
the approaches used for detection, particularly the software methods needed
to fit the analyte and multiple (interfering) spectral components within the
selected spectral micro-window(s). We also discuss the method's detection
limits and related parameters such as spectral resolution.
Abstract. Pyrolysis is the first step in a series of chemical and physical processes that produce flammable organic gases from wildland fuels that can result in a wildland fire. We report results using a new time-resolved Fourier transform infrared (FTIR) method that correlates the measured FTIR spectrum with an infrared thermal image sequence, enabling the identification and quantification of gases within different phases of the fire process. The flame from burning fuel beds composed of pine needles (Pinus palustris) and mixtures of sparkleberry, fetterbush, and inkberry plants was the natural heat source for pyrolysis. Extractive gas samples were analyzed and identified in both static and dynamic modes synchronized to thermal infrared imaging: a total of 29 gases were identified including small alkanes, alkenes, aldehydes, nitrogen compounds, and aromatics, most previously measured by FTIR in wildland fires. This study presents one of the first identifications of phenol associated with both pre-combustion and combustion phases using ca. 1 Hz temporal resolution. Preliminary results indicate ∼2.5× greater phenol emissions from sparkleberry and inkberry compared to fetterbush, with differing temporal profiles.
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