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From page 72... ... The impacts of fire emissions from human-made materials and firefighting activities on the chemistry and fate of WUI fire plumes is not well understood. Relative to wildland fire emissions, WUI emissions have increased levels of several types of compounds, including reactive halogenated compounds (HCl, HBr, HF) Read the entire page →
From page 73... ... CO in the troposphere is slowly transported to the mesosphere and stratosphere. Primary degradation pathway of tropospheric CO is via its reaction with photochemically produced hydroxyl radicals, resulting in formation of CO2.a In the stratosphere, it reacts with atomic oxygen generated by the photodissociation of O2 to form CO2.a Formaldehyde Released to the atmosphere in large amounts and is Breaks down in the gas phase to formic acid and CO. Read the entire page →
From page 74... ... Oxidized rapidly in atmospheric waters and Oxidized by OH radicals in the gas phase and Depending on the hydroxyl removed from the atmosphere by precipitation or in clouds/fogs by peroxides, NO2, and transition radical concentration, sulfur dioxide dry deposition, mainly as sulfuric acid (acid rain) Read the entire page →
From page 75... ... The half-life for HBr in the atmosphere (HBr) is estimated to be a few hours; however, Likely to be removed by both wet and dry Can react with hydroxyl radicals to form bromide it will dynamically partition very deposition. Read the entire page →
From page 76... ... and vegetation. reaction with the hydroxyl radical in surfaces and oxidant gases like NO2, O3, and relatively clean air, are about 6 hours Partitioning of PAHs between the gas and the SO3, and and 10 hours, respectively; PAHs may condensed phases depends on their volatility, the (2) Read the entire page →
From page 77... ... HCl, HBr, HF, PFASs, PCBs, PCDDs, PDBEs, and phosphate ester flame retardants are expected to be found in higher concentrations in WUI fires than in wildland fires. aUS Agency for Toxic Substances and Disease Registry. Read the entire page →
From page 78... ... 78 THE CHEMISTRY OF FIRES AT THE WILDLAND-URBAN INTERFACE Atmospheric Transport and Chemical Transformations Plume Rise Plume Dilution & Dispersion Wet & dry deposition Gas phase, aqueous, catalytic & multiphase chemistry Near-field exposure Local exposure to Regional exposure to fresh emissions fresh emissions to the transformed WUI plume SPATIAL 1–10 KM 10–100 KM >100 KM SCALE TEMPORAL MINUTES HOURS DAYS SCALE FIGURE 4-1 The movement and changes of WUI emissions over space and time. The processes, shown in the top half above the structures, are discussed in this chapter. Read the entire page →
From page 79... ... . • Chlorinated and oxygenated aromatics are likely to form in WUI fire plumes, since aromatic compounds are substantial components of wildland fire plumes, chlorine radicals and hydroxyl radicals are expected to be present in WUI fire plumes, and chlorinated aromatics and oxygenated aromatics are known to form in the atmosphere (e.g., from gas-phase chlorine radical reaction with PAHs; Ohura et al., 2005; Riva et al., 2015) Read the entire page →
From page 80... ... . Much is left to learn about the formation of secondary species with toxic potential downwind of WUI fires. Read the entire page →
From page 81... ... . Nitrate radical, produced from the oxidation of NO2 by O3, is a major nighttime oxidant in wildland fire plumes and may be enhanced in WUI fires due to high emissions of oxides of nitrogen formed as a result of nitrogen in the fire's fuel (fuel NOx) Read the entire page →
From page 82... ... . Finding: The increase in reactive nitrogen and halogen emissions in WUI fires relative to wildland fires, and the VOC-to-NOx ratios of WUI fire emissions, are not well characterized; this information could improve prediction of ozone from WUI fires. Read the entire page →
From page 83... ... However, model prediction of the magnitude of SOA formation downwind of wildland fires (Theodoritsi et al., 2021) and WUI fires remains uncertain due in part to inadequate chemical characterization of IVOCs and other precursor emissions, the partial understanding of oxidation mechanisms, and a lack of thermodynamic data for the oxidation products. Read the entire page →
From page 84... ... Many of the most important processes are controlled by radical chemistry. Because WUI fires have the potential to have significantly different radical reactivities than wildland fires, due to the increased presence of halogen radicals, metals, and other species, critical chemical pathways have the potential to have different rates and to be qualitatively different than in wildland fires. Read the entire page →
From page 85... ... Different types of models are used to characterize chemical transformations in wildland fire and WUI plumes over local, regional, and continental scales. The complex gas-phase chemical transformations, particle-phase chemical transformations, and gas-to-particle partitioning associated with wildland fires and WUI fires, outlined in this chapter, are tracked using computationally intensive models that couple chemical transport and transformation. Read the entire page →
From page 86... ... 86 THE CHEMISTRY OF FIRES AT THE WILDLAND-URBAN INTERFACE FIGURE 4-2 Example of daily fire locations (top) and fire plume projections (bottom) Read the entire page →
From page 87... ... . Chemical transport models have generally not been optimized to address the unique chemistries and transport characteristics of wildland fire plumes. Read the entire page →
From page 88... ... Finding: Current models lack the chemical specificity needed to track in detail the types of toxicants associ ated with wildland fires and WUI fires. Research need: Development of condensed chemical mechanisms is needed for use in applying chemical transport models to WUI fires. Read the entire page →
From page 89... ... • Development of sub-grid-cell models that could be used to model the mixing of fire plumes with ambient air and the structure of single-structure or neighborhood-scale plumes • Development of chemical transport models that could be used in prognostic mode to facilitate first-responder activity during environmental crises, and communication/decision-making coordination (a technology link to communicate predictions at the different scales of responders) Research need: A combination of research approaches is needed to understand and predict toxicant concen trations downwind of WUI fires and ultimately mitigate their health risks. Read the entire page →
From page 90... ... 2000. "Secondary Organic Aerosol Formation in Cloud and Fog Droplets: A Literature Evalu ation of Plausibility." Atmospheric Environment 34(10) Read the entire page →
From page 91... ... 2019. "Nighttime Chemical Transformation in Biomass Burning Plumes: A Box Model Analysis Initialized with Aircraft Observations." Environmental Science & Technology 53(5) Read the entire page →
From page 92... ... 2017. "Multi-instrument Comparison and Compilation of Non-methane Organic Gas Emissions from Biomass Burning and Impli cations for Smoke-Derived Secondary Organic Aerosol Precursors." Atmospheric Chemistry and Physics 17(2) Read the entire page →
From page 93... ... 2013. "Chemical Insights, Explicit Chemistry, and Yields of Secondary Organic Aerosol from OH Radical Oxidation of Methylglyoxal and Glyoxal in the Aqueous Phase." Atmospheric Chemistry and Physics 13(17) Read the entire page →
From page 94... ... 2019. "Simulation of Fresh and Chemically-Aged Biomass Burning Organic Aerosol." Atmospheric Environment 196:27–37. Read the entire page →
From page 95... ... 2010. "Insights into Secondary Organic Aerosol Formed via Aqueous-Phase Reactions of Phenolic Compounds Based on High Resolution Mass Spectrometry." Atmospheric Chemistry and Physics 10(10) Read the entire page →
From page 96... ... 2012. "Secondary Organic Aerosol Formation from Inter mediate-Volatility Organic Compounds: Cyclic, Linear, and Branched Alkanes." Environmental Science & Technology 46(16) Read the entire page →
From page 97... ... 2013. "Secondary Organic Aerosol Formation from Biomass Burning Intermediates: Phenol and Methoxyphenols." Atmospheric Chemistry and Physics 13(16) Read the entire page →
From page 99... ... Additionally, reports of data from WUI fires in California document levels of metals measured in ash samples collected in impacted neighborhoods, with elevated levels of antimony and other species (TetraTech Inc., 2019) Read the entire page →
From page 100... ... . Therefore, the discussion cites studies that provide information originally collected for wildland fires, which can be extrapolated to WUI fires. Read the entire page →
From page 101... ... . A WUI fire can potentially impact the operations of a CWS in both the short and long term. Read the entire page →
From page 102... ... Limited work exists on the characterization of these particles after wildland fires, and to the best of the committee's knowledge, no work has been done on any particles emanating from urban fires or WUI fires. Ultimately, the particles that mobilize in water serve as a substrate from which the water can leach off other potential pollutants. Read the entire page →
From page 103... ... Chapter 3 describes in general terms the complexity that is expected from combustion during WUI fires. These compounds may form in the gas phase and then partition to water or into ashes. Read the entire page →
From page 104... ... 104 THE CHEMISTRY OF FIRES AT THE WILDLAND-URBAN INTERFACE TABLE 5-2 Identifications of Compound Classes Found in Ash Leachates and Water Samples from Wildland Fires Compound Chemical Structure Quinoline monocarboxylic acids Quinoline dicarboxylic acids Naphthoic acid Naphthalene dicarboxylic acids Naphthalene tricarboxylic acids Benzofuran monocarboxylates Benzofuran dicarboxylates Benzofuran tricarboxylates SOURCE: Adapted from Ferrer et al. Read the entire page →

From page 72...

... The impacts of fire emissions from human-made materials and firefighting activities on the chemistry and fate of WUI fire plumes is not well understood. Relative to wildland fire emissions, WUI emissions have increased levels of several types of compounds, including reactive halogenated compounds (HCl, HBr, HF)