The gas and tar composition of a wildland fire diffusion flame from longleaf pine needles is currently relatively unmeasured and more data are needed to fill in the gap between pyrolysis data and smoke plume data, thus improving physical and chemical modeling of wildland smoke formation. A pilot experiment to measure light gas and tar composition of such a flame is described for three flame zones: persistent flame (flame base), intermittent flame, and smoke plume. Flame gases from 24 experimental fires were collected in canisters and analyzed for CO2, CO, H2, CH4, and C2 to C7 hydrocarbon gases. Other light gases were measured using FTIR spectroscopy. Condensed gas (tar) samples were collected and analyzed using GC/MS. Results from compositional data analysis suggest significant differences in (relative) concentration of compounds detected in the three zones. Statistical tests for differences in flame zones were performed using canister data. Concentration of hydrocarbons relative to CO and CO2 decreased from the persistent flame zone through the intermittent flame zone into the flame-free plume. This was likely due to oxidation reactions in the flame as well as entrainment of air into the flame/ plume. Partial agreement between persistent flame zone composition and pyrolysis data for a global kinetic model provided support for future use of the kinetics model in physically-based fire models. The identification of gases and tars in different flame zones supported a conceptual model of a wildland flame.

Background Fire models use pyrolysis data from ground samples and environments that differ from wildland conditions. Two analytical methods successfully measured oxidative pyrolysis gases in wind tunnel and field fires: Fourier transform infrared (FTIR) spectroscopy and gas chromatography with flame-ionisation detector (GC-FID). Compositional data require appropriate statistical analysis. Aims To determine if oxidative pyrolysis gas composition differed between analytical methods and locations (wind tunnel and field). Methods Oxidative pyrolysis gas sample composition collected in wind tunnel and prescribed fires was determined by FTIR and GC/FID. Proportionality between gases was tested. Analytical method and location effects on composition were tested using permutational multivariate analysis of variance and the Kruskal–Wallis test. Key results Gases proportional to each other were identified. The FTIR composition differed between locations. The subcomposition of common gases differed between analytical methods but not between locations. Relative amount of the primary fuel gases (CO, CH4) was not significantly affected by location. Conclusions Composition of trace gases differed between the analytical methods; however, each method yielded a comparable description of the primary fuel gases. Implications Both FTIR and GC/FID methods can be used to quantify primary pyrolysis fuel gases for physically-based fire models. Importance of the trace gases in combustion models remains to be determined.

Composition of pyrolysis gases for wildland fuels is often determined using ground samples heated in non-oxidising environments. Results are applied to wildland fires where fuels change spatially and temporally, resulting in variable fire behaviour with variable heating. Though historically used, applicability of traditional pyrolysis results to the wildland fire setting is unknown. Pyrolytic and flaming combustion gases measured in wind tunnel fires and prescribed burns were compared using compositional data techniques. CO2 was dominant in both. Other dominant gases included CO, H2 and CH4. Relative amounts of CO, CO2 and CH4 were similar between fire phases (pyrolysis, flaming combustion); relatively more H2 was observed in pyrolysis samples. All gas log-ratios with CO2 in pyrolysis samples were larger than in flaming combustion samples. Presence of live plants significantly affected gas composition. A logistic regression model correctly classified 76% of the wind tunnel samples as pyrolysis or flaming combustion based on gas composition. The model predicted 60% of the field samples originated from pyrolysis. Fire location (wind tunnel, field) and fire phase affected gas composition. The compositional approach enabled analysis and modelling of gas compositions, producing results consistent with the basic characteristics of the data.

Pyrolysis products from wildland fuels are typically measured under tightly controlled conditions using fuels which have been processed to remove water content and physical shape. Different instruments can be used to identify and quantify the composition of these gases. Measurement of pyrolysis gases under conditions typical of wildland fires has seldom occurred. We used FTIR spectroscopy and GC/FID analysis to measure pyrolysis gases produced in wind tunnel experiments and small prescribed burns in longleaf pine needle fuel beds with live shrubs. Use of compositional data techniques on the 8 common gases measured by both methods showed that the compositions were affected by the measurement method and interaction between method and location was significant.

The deployment of advanced nuclear technologies is anticipated to be part of the actions required to mitigate global climate change. The successful deployment of these new technologies, like all new infrastructure projects, will be more successful if the projects have strong public support. Successful deployment of energy infrastructure correlates with thoughtful approaches to equitable energy transitions. This work recalls the history of recent energy infrastructure deployments, shows where the inclusion of social scientists has improved the possibility of success and proposes specific steps to make future deployments of advanced nuclear technologies successful.

Radiological release incidents can potentially contaminate widespread areas with radioactive materials and decontamination efforts are typically focused on populated areas, which means radionuclides may be left in forested areas for long periods of time. Large wildfires in contaminated forested areas have the potential to reintroduce these radionuclides into the atmosphere and cause exposure to first responders and downwind communities. One important radionuclide contaminant released from radiological incidents is radiocesium (137Cs) due to high yields and its long half-life of 30.2 years. An Eulerian 3D photochemical transport model was used to estimate potential ambient impacts of 137Cs re-emission due to wildfire following hypothetical radiological release scenarios. The Community Multiscale Air Quality (CMAQ) model did well at predicting levels and periods of increased PM2.5 carbon due to wildfire smoke at routine surface monitors in California during the summer of 2016. The model also did well at capturing the extent of the surface mixing layer compared to aerosol lidar measurements. Emissions from a large hypothetical wildfire were introduced into the wildland-urban interface (WUI) impacted by a hypothetical radiological release event. While ambient concentrations tended to be highest near the fire, the highest population committed effective dose equivalent by inhalation to an adult from 137Cs over an hour was downwind where wind flows moved smoke to high population areas. Seasonal variations in meteorology (wind flows) can result in differential population impacts even in the same metropolitan area. Modeled post-incident ambient levels of 137Cs both near these wildfires and further downwind in nearby urban areas were well below levels that would necessitate population evacuation or warrant other protective action recommendations such as shelter-in-place. These results suggest that 1) the modeling system captures local to regional scale transport and levels of PM2.5 from wildfire and 2) first responders and downwind population would not be expected to be at elevated risk from the initial inhalathion exposure of 137Cs re-emission.

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.

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.

Recent studies have shown that organic aerosol (OA) could have a nontrivial role in atmospheric light absorption at shorter visible wavelengths. Good estimates of OA light absorption are therefore necessary to better estimate radiative forcing due to these aerosols in climate models. One of the common techniques used to measure OA light absorption is the solvent extraction technique from filter samples which involves the use of a spectrophotometer to measure bulk absorbance by the solvent-soluble organic fraction of particulate matter. Measured solvent-phase absorbance is subsequently converted to particle-phase absorption coefficient using scaling factors. The conventional view is to apply a correction factor of 2 to absorption coefficients obtained from solvent-extracted OA based on Mie calculations. The appropriate scaling factors are a function of biases due to incomplete extraction of organic carbon (OC) by solvents and size-dependent absorption properties of OA. The range for these biases along with their potential dependence on burn conditions is an unexplored area of research. Here, we performed a comprehensive laboratory study involving three solvents (water, methanol, and acetone) to investigate the bias in absorption coefficients obtained from solvent-extraction-based photometry techniques as compared to in situ particle-phase absorption for freshly emitted OA from biomass burning. We correlated the bias with OC∕TC (total carbon) mass ratio and single scattering albedo (SSA) and observed that the conventionally used correction factor of 2 for water and methanol-extracted OA might not be extensible to all systems, and we suggest caution while using such correction factors to estimate particle-phase OA absorption coefficients. Furthermore, a linear correlation between SSA and the OC∕TC ratio was also established. Finally, from the spectroscopic data, we analyzed the differences in absorption Ångström exponents (AÅE) obtained from solution- and particulate-phase measurements. We noted that AÅE from solvent-phase measurements could deviate significantly from their OA counterparts.

If a radiological incident such as a nuclear power plant accident, a radiological dispersal device, or detonation of an improvised nuclear device occurs, significant areas may be contaminated. Initial cleanup priorities would likely focus on populated areas, leaving the forested areas to pass several seasons where the overhead canopy materials would fall to the forest floor. In the event of a wildfire in a radionuclide-contaminated forest, some radionuclides would be emitted in the air while the rest would remain in the ash. This paper reports on a laboratory simulation study that examines the partitioning of cesium-133 (a nonradioactive isotope of cesium) between airborne particulate matter and residual nonentrained ash when pine needles and peat are doped with cesium. Only 1-2.5% of the doped cesium in pine needles was emitted as particulate matter, and most of the cesium was concentrated in the particulate fraction greater than 10 mu m in aerodynamic diameter. For peat fires, virtually all of the cesium remained in the ash. The results from this study will be used for modeling efforts to assess potential exposure risks to firefighters and the surrounding public. Implications: There is a potential for emissions of radionuclides such as cesium-137 from a wildfire over a radionuclide-contaminated forest. This paper reports on a laboratory simulation study of a wildfire with two types of biomass doped with nonradioactive cesium. This simulation suggests that only 1-2.5% of the cesium in the biomass will be emitted from the wildfire, while the rest will reside in the residual ash. In this study, pine needles were the only contributor to the air emissions of cesium; duff was not a source of cesium emissions. In this study, cesium emitted from the simulated wildfire was concentrated in the particle sizes larger than 10 mu m.

Abstract. Recent studies have shown that organic aerosol (OA) could have a non-trivial role in atmospheric light absorption at shorter visible wavelengths. Good estimates of OA absorption are therefore necessary to accurately calculate radiative forcing due to these aerosols in climate models. One of the common techniques used to measure OA light absorption is the solvent extraction technique from filter samples which involves the use of a spectrophotometer to measure bulk absorbance of the solvent-soluble organic fraction of particulate matter. Measured bulk absorbance is subsequently converted to particle-phase absorption coefficient using correction factors. The appropriate correction factors to use for performing this conversion under varying scenarios of organic carbon (OC) to total carbon (TC) mass ratios has been an unexplored area of research. The conventional view is to apply a correction factor of 2 for water-extracted OA based on Mie calculations. Here, we performed a comprehensive laboratory study involving three solvents (water, methanol, and acetone) to investigate the corrections factors for converting from bulk-to-particle phase absorption coefficients (babs,OA/babs,bulk) for primary OA emitted from biomass burning. We parametrized these correction factors as a function of OC / TC mass ratio and single scattering albedo (SSA). We observed these correction factors to be a function of the OC / TC ratio of the aerosol, and that the conventionally used correction factor of 2 for water-extracted OA could severely underpredict OA absorption at high EC mass fractions. We recommend using babs,OA/babs,bulk values between 2 and 11 for water extracts and values between 1 and 4 for methanol extracts based on OC / TC ratios, for EC mass fractions less than 0.25. Furthermore, a linear correlation between SSA and OC / TC ratio was also established. Finally, from the spectroscopic data, we analyzed the differences in Absorption Ångström Exponents (AÅE) obtained from bulk- and particulate-phase measurements. We noted that AÅE from bulk measurements deviate significantly from their OA counterparts.

Pyrolysis of intact wildland fuels in the southern United States is being measured at bench, wind tunnel, and field scales as part of a larger research project to measure and model pyrolysis of wildland fuels to improve models used to predict prescribed fire behavior.Traditional pyrolysis experiments typically use dried, ground samples in either an inert or oxidizing environment subject to uniform heating and heat transfer.Fletcher and others are presenting results of pyrolysis experiments using a flat-flame burner to heat intact foliage from 14 species of plants native to the southern U.S. at this conference.The fuel beds in prescribed burns in southern pine forests are composed of a mixture of dead pine needles and a large variety of herbaceous and woody plants.We have burned 73 fuel beds composed of Pinus palustris needles and mixtures of Lyonia lucida, Ilex glabra, and Vaccinium darrowii plants in a wind tunnel facility with and without a moderate wind speed of ~ 1 m s-1.The flame from the spreading fire is the heat source for the pyrolysis experiment.Canister samples of pyrolysis and flaming combustion gases within the fuel bed have been collected for offline analysis.Open path spectrometers nonintrusively measured composition of pyrolysis gases in real-time.Thermocouples, a Schmidt-Boelter heat flux sensor, a nadir thermal IR camera, and background-oriented Schlieren photography estimated heat transfer and air flow around the plants.This presentation will present results of this ongoing work.

Constraining the complex refractive indices, optical properties and size of brown carbon (BrC) aerosols is a vital endeavor for improving climate models and satellite retrieval algorithms. Smoldering wildfires are the largest source of primary BrC, and fuel parameters such as moisture content, source depth, geographic origin, and fuel packing density could influence the properties of the emitted aerosol. We measured in situ spectral (375-1047 nm) optical properties of BrC aerosols emitted from smoldering combustion of Boreal and Indonesian peatlands across a range of these fuel parameters. Inverse Lorenz-Mie algorithms used these optical measurements along with simultaneously measured particle size distributions to retrieve the aerosol complex refractive indices (m=n+ix). Our results show that the real part n is constrained between 1.5 and 1.7 with no obvious functionality in wavelength (lambda), moisture content, source depth, or geographic origin. With increasing X from 375 to 532 nm, k decreased from 0.014 to 0.003, with corresponding increase in single scattering albedo (SSA) from 0.93 to 0.99. The spectral variability of K follows the Kramers-Kronig dispersion relation for a damped harmonic oscillator. For lambda >= 532 nm, both K and SSA showed no spectral dependency. We discuss differences between this study and previous work. The imaginary part K was sensitive to changes in FPD, and we hypothesize mechanisms that might help explain this observation. (C) 2017 Elsevier Ltd. All rights reserved.

Fire frequency in low-elevation coniferous forests in western North America has greatly declined since the late 1800s. In many areas, this has increased tree density and the proportion of shade-tolerant species, reduced resource availability, and increased forest susceptibility to forest insect pests and high-severity wildfire. In response, treatments are often implemented with the goal of increasing ecosystem resilience by increasing resistance to disturbance. We capitalized on an existing replicated study of fire and stand density treatments in a ponderosa pine (Pinus ponderosa)-Douglas-fir (Pseudotsuga menziesii) forest in western Montana, USA, that experienced a naturally occurring mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak 5 yr after implementation of fuels treatments. We explored whether treatment effects on tree-level defense and stand structure affected resistance to MPB. Mortality from MPB was highest in the denser, untreated control and burn-only treatments, with approximately 50% and 39%, respectively, of ponderosa pine killed during the outbreak, compared to almost no mortality in the thin-only and thin-burn treatments. Thinning treatments, with or without fire, dramatically increased tree growth and resin ducts relative to control and burn-only treatments. Prescribed burning did not increase resin ducts but did cause changes in resin chemistry that may have affected MPB communication and lowered attack success. While ponderosa pine remained dominant in the thin and thin-burn treatments after the outbreak, the high pine mortality in the control and burn-only treatment caused a shift in species dominance to Douglas-fir. The high Douglas-fir component in the control and burn-only treatments due to 20th century fire exclusion, coupled with high pine mortality from MPB, has likely reduced resilience of this forest beyond the ability to return to a ponderosa pine-dominated system in the absence of further fire or mechanical treatment. Our results show treatments designed to increase resistance to high-severity fire in ponderosa pine-dominated forests in the Northern Rockies can also increase resistance to MPB, even during an outbreak. This study suggests that fuel and restoration treatments in fire-dependent ponderosa pine forests that reduce tree density increase ecosystem resilience in the short term, while the reintroduction of fire is important for long-term resilience.

As an alternative to open pile burning, use of forest wastes from fuel hazard reduction projects at Blodgett Forest Research Station for electricity production was shown to produce energy and emission benefits: energy (diesel fuel) expended for processing and transport was 2.5% of the biomass fuel (energy equivalent); based on measurements from a large pile burn, air emissions reductions were 98%-99% for PM2.5, CO (carbon monoxide), NMOC (nonmethane organic compounds), CH4 (methane) and BC (black carbon), and 20% for NOx and CO2-equivalent greenhouse gases. Due to transport challenges and delays, delivered cost was $70 per bone dry ton (BDT) - comprised of collection and processing ($34/BDT) and transport ($36/BDT) for 79 miles one way - which exceeded the biomass plant gate price of $45/BDT. Under typical conditions, the break-even haul distance would be approximately 30 miles one way, with a collection and processing cost of $30/BDT and a transport cost of $16/BDT. Revenue generated from monetization of the reductions in air emissions has the potential to make forest fuel reduction projects more economically viable.

Thermochemical biomass conversion systems have the potential to produce heat, power, fuels and other products from forest biomass at distributed scales that meet the needs of some forest industry facilities. However, many of these systems have not been deployed in this sector and the products they produce from forest biomass have not been adequately described or characterized with regards to chemical properties, possible uses, and markets. This paper characterizes the producer gas, biochar, and activated carbon of a 700 kg h −1 prototype gasification system and a 225 kg h −1 pyrolysis system used to process coniferous sawmill and forest residues. Producer gas from sawmill residues processed with the gasifier had higher energy content than gas from forest residues, with averages of 12.4 MJ m −3 and 9.8 MJ m −3 , respectively. Gases from the pyrolysis system averaged 1.3 MJ m −3 for mill residues and 2.5 MJ m −3 for forest residues. Biochars produced have

Wildland fires are major sources of trace gases and aerosol, and these emissions are believed to significantly influence the chemical composition of the atmosphere and the earth's climate system. The wide variety of pollutants released by wildland fire include greenhouse gases, photochemically reactive compounds, and fine and coarse particulate matter. Through direct emissions and secondary chemical and physical processes, wildland fire can have a significant impact on tropospheric chemistry and serve as a major source of air pollution. We provide a synthesis of emission factor data from the literature and previously unpublished research for use in global, continental and regional scale studies investigating the role of wildland fire emissions in atmospheric chemistry and climate. The emission factor data is presented by geographic zones (boreal, temperate, and tropical) and vegetation group (forest and savanna/rangeland), allowing researchers to account for the different emission characteristics exhibited by biomass burning in these disparate regions. A brief overview of the wildland fuel combustion process as related to emissions production is also provided. The atmospheric fate of wildland fire emissions is briefly discussed and related to the production of secondary air pollutants. Previously unpublished results from a series of fire emission studies in the United States and Canada are presented in an appendix.

We characterized the gas‐ and speciated aerosol‐phase emissions from the open combustion of 33 different plant species during a series of 255 controlled laboratory burns during the Fire Laboratory at Missoula Experiments (FLAME). The plant species we tested were chosen to improve the existing database for U.S. domestic fuels: laboratory‐based emission factors have not previously been reported for many commonly burned species that are frequently consumed by fires near populated regions and protected scenic areas. The plants we tested included the chaparral species chamise, manzanita, and ceanothus, and species common to the southeastern United States (common reed, hickory, kudzu, needlegrass rush, rhododendron, cord grass, sawgrass, titi, and wax myrtle). Fire‐integrated emission factors for gas‐phase CO2, CO, CH4, C2–4hydrocarbons, NH3, SO2, NO, NO2, HNO3, and particle‐phase organic carbon (OC), elemental carbon (EC), SO42−, NO3−, Cl−, Na+, K+, and NH4+generally varied with both fuel type and with the fire‐integrated modified combustion efficiency (MCE), a measure of the relative importance of flaming‐ and smoldering‐phase combustion to the total emissions during the burn. Chaparral fuels tended to emit less particulate OC per unit mass of dry fuel than did other fuel types, whereas southeastern species had some of the largest observed emission factors for total fine particulate matter. Our measurements spanned a larger range of MCE than prior studies, and thus help to improve estimates of the variation of emissions with combustion conditions for individual fuels.

Fuel biomass samples from southern Africa and the United States were burned in a laboratory combustion chamber while measuring the biomass consumption rate, the fire radiative energy (FRE) release rate (Rfre), and the smoke concentrations of carbon monoxide (CO), carbon dioxide (CO2), and particulate matter (PM). The PM mass emission rate (RPM) was quantified from aerosol optical thickness (AOT) derived from smoke extinction measurements using a custom‐made laser transmissometer. TheRPMandRfretime series for each fire were integrated to total PM mass and FRE, respectively, the ratio of which represents its FRE‐based PM emission coefficient (CePM). A strong correlation (r2= 0.82) was found between the total FRE and total PM mass, from which an averageCePMvalue of 0.03 kg MJ−1was calculated. This value agrees with those derived similarly from satellite‐borne measurements ofRfreand AOT acquired over large‐scale wildfires.