The potential to detect wildfire-related species in the infrared
Résumé
Wildfires are a cause for growing concern for air quality and the climate. They represent a large source of emissions of gas-phase and particulate species. As a consequence of global warming, the spatial extent, severity and duration of wildfires is likely to increase, with current indications suggesting that this may already be happening. Wildfires are a truly global phenomenon, with largescale occurrences on each continent besides Antarctica. As an emission source, wildfires are highly complex, with a large variety of primary and secondary particulates and gases. Particulates are not expected to be long-lived, and so have an important, yet mostly short-term impact on climate and air quality. Conversely, the gas-phase species exhibit a range of lifetimes. Some are very short-lived such as furans, polyenes and other unsaturated species, which possess lifetimes of less than a day. Others could be long-lived, such as hydrogen cyanide (HCN), isocyanic acid (HNCO) and acetonitrile (CH3CN), which can persist for several years. Some species, such as the peroxyacyl nitrates, possess short lifetimes in the boundary layer, but may become long-lived as they are lofted. The main factors that govern the persistence of these chemicals are their reaction rates with atmospheric oxidants, their photolysis rates and their wet deposition rates. The detection and quantification of these molecules using remote sensing techniques will depend on their spectral characteristics and the availability of absorption cross sections. In each case, it is therefore necessary to obtain high-quality laboratory data on the chemical behaviour and spectroscopy of wildfire-related chemicals. Such data are not currently available in some cases, and the purpose of this presentation will be to assess the extent to which major classes of wildfire chemicals are covered by existing laboratory data, and where important gaps remain.
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