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The chemical composition of aerosols from wildland fire:Current state of the science and possible new directions.
Citation:
Hays, M., A. Holder, B. Gullett, Chris Geron, AND B. Hemming. The chemical composition of aerosols from wildland fire:Current state of the science and possible new directions. International Smoke Symposim, Hyattsville, MD, October 21 - 25, 2013.
Impact/Purpose:
Capturing and projecting the climate and health effects of fire-produced brown carbon, especially in the context of climate change, depends on our ability to estimate wildland fire emissions. The fire sciences community continually strives to advance our capability for anticipating fire and its characteristics. What is needed, now, is increased sophistication in our ability to use these fire characteristics, along with our knowledge of chemical kinetics and biomass fuel composition, to produce a more complete description of the organic pollutants emitted. This talk addresses some of the questions that must be considered in the effort to inventory BrC emissions, and the particular impacts such an inventory can be used to quantify.
Description:
Abundant evidence of the existence of a light-absorbing component of organic particles emitted by biomass combustion now exists in the scientific literature. The light absorbing properties of this material, commonly called "brown" carbon (BrC), make it a matter of interest to the climate and atmospheric chemistry community. Climate modeling calculations in combination with remote sensing observations suggest that, depending on the source, BrC can play a meaningful role in regional-scale biomass burning-induced positive climate forcing. This warming impact adds to existing concerns about the air quality effects of present and future wildfire. However, further consideration of the chemistry of light-absorbing organic compounds points up the relevance of these materials to human health and ecosystems toxicity. Molecular structures and chemical substituents necessary for light absorption in the UV/Vis range are commonly found among those compounds known to be toxic. Furthermore, while organic compounds of the right structure and composition can absorb light and add to the toxicity of solid fuel combustion particles, the addition of transition metals ubiquitous in biomass materials and entrained from soil during landscape fires may be amplifying these effects. Iron and several other transition metals are known to bind with derivatives of lignin, the primary structural material in biomass, to form electochemically-active complexes that both absorb solar radiation in the UV/visible portion of the solar spectrum, and participate in oxidation reactions that may play a role in the particular respiratory effects associated with smoke inhalation.