Speciation of gas-phase and fine particle emissions from burning of foliar fuels

Characterizing PM2.5 Emissions and Temporal Evolution of Organic Composition from Incense Burning in a California Residence

The chemical composition of incense-generated organic aerosol in residential indoor air has received limited attention in Western literature. In this study, we conducted incense burning experiments in a single-family California residence during vacancy. We report the chemical composition of organic fine particulate matter (PM2.5), associated emission factors (EFs), and gas-particle phase partitioning for indoor semivolatile organic compounds (SVOCs). Speciated organic PM2.5 measurements were made using two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HR-ToF-MS) and semivolatile thermal desorption aerosol gas chromatography (SV-TAG). Organic PM2.5 EFs ranged from 7 to 31 mg g-1 for burned incense and were largely comprised of polar and oxygenated species, with high abundance of biomass-burning tracers such as levoglucosan. Differences in PM2.5 EFs and chemical profiles were observed in relation to the type of incense burned. Nine indoor SVOCs considered to originate from sources other than incense combustion were enhanced during incense events. Time-resolved concentrations of these SVOCs correlated well with PM2.5 mass (R2 > 0.75), suggesting that low-volatility SVOCs such as bis(2-ethylhexyl)phthalate and butyl benzyl phthalate partitioned to incense-generated PM2.5. Both direct emissions and enhanced partitioning of low-volatility indoor SVOCs to incense-generated PM2.5 can influence inhalation exposures during and after indoor incense use.

Aerosolomics based approach to discover source molecular markers: A case study for discriminating residential wood heating vs garden green waste burning emission sources

Biomass burning is a significant source of particulate matter (PM) in ambient air and its accurate source apportionment is a major concern for air quality. The discrimination between residential wood heating (RWH) and garden green waste burning (GWB) particulate matter (PM) is rarely achieved. The objective of this work was to evaluate the potential of non-targeted screening (NTS) analyses using HRMS (high resolution mass spectrometry) data to reveal discriminating potential molecular markers of both sources. Two residential wood combustion appliances (wood log stove and fireplace) were tested under different output conditions and wood moisture content. GWB experiments were carried out using two burning materials (fallen leaves and hedge trimming). PM samples were characterized using NTS approaches with both LC- and GC-HRMS (liquid and gas chromatography-HRMS). The analytical procedures were optimized to detect as many species as possible. Chemical fingerprints obtained were compared combining several multivariate statistical analyses (PCA, HCA and PLS-DA). Results showed a strong impact of the fuel nature and the combustion quality on the chemical fingerprints. 31 and 4 possible markers were discovered as characteristic of GWB and RWH, respectively. Complementary work was attempted to identify potential molecular formulas of the different potential marker candidates. The combination of HRMS NTS chemical characterization with multivariate statistical analyses shows promise for uncovering organic aerosol fingerprinting and discovering potential PM source markers.

Emission characteristics of carbonyl compounds from open burning of typical subtropical biomass in South China

Open biomass burning (OBB) is one of the largest primary emission sources for atmospheric carbonyl compounds, key precursors for ozone and secondary organic aerosol pollution. To clarify the carbonyl emissions, the comprehensive characteristics of C1-C10 carbonyl compounds from open burning of seven typical subtropical biomass in China were investigated in this study, which included subtropical plants and agricultural residues. Total 27 carbonyl compounds were detected. The total EFs were 2824 mg kg-1 with 95% confidence interval (CI) [2418, 3322] for burning subtropical plants and 4080 mg kg-1 with 95% CI [3446, 4724] for burning agriculture residues, respectively. The EFs were 2-3 orders of magnitude larger than previous values in China. Aliphatic aldehydes were the largest group of carbonyl groups, with acetaldehyde, as the most abundant carbonyl species (about 30% contribution). Formaldehyde, acetone, acrolein, glyoxal, methylglyoxal, butanone, isovaleraldehyde, and m-tolualdehyde were also found to be abundant and varying with the types of biomass burnt. Formaldehyde emission ratios to acetonitrile and CO were lower than those in previous studies both for burning plants and agricultural residues. There were significant variabilities in the emission ratios and factors among different types of OBBs. Strong positive correlations were found between carbonyl emissions and CO emissions and water content in biomass; furthermore, total carbonyl concentrations measured in the flaming stage were higher than those in the smoldering one. This study provides important fundamental measurement data on carbonyl emissions from burning typical subtropical plants and agricultural residues, which will help improve the quality of emission inventories and better understand the potential impacts of OBB on regional air quality in southern China.

Theoretical study on the potential environmental and ecological risk of 4-ethylphenol induced by hydroxyl radical

This study closely examines the environmental fate of 4-ethylphenol (4-EP), a significant byproduct of biomass combustion. We employed quantum chemical calculations to investigate the reaction mechanism, kinetics, and ecotoxicity of 4-EP initiated by OH radicals in various environments (aqueous, atmospheric liquid, atmospheric and inhomogeneous phases). Our findings highlight that solvent effects contribute to a higher OH-addition reaction branching ratio (Γadd) of 0.68 for 4-EP in an aqueous solution, compared to 0.26 in the gas-phase environment and 0.22 in the inhomogeneous environment at 298 K. We determined the rate constants for the liquid-phase, gas-phase, and nonhomogeneous phase to be 1.14 × 109 s-1 M-1, 3.09 × 109 s-1 M-1, and 6.19 × 1014 s-1 M-1, respectively. Notably, the adsorption of mineral particles considerably enhances the reaction rate of 4-EP with OH radicals. 4-ethylbenzene-1,2-diol, 4-hydroxycyclohexa-3,5-diene-1,2-dione, 1-ethyl-6-methyl-6H-benzo(c)chromene-4,9-diol, 5-ethyl-6'-(1-hydroxyethyl)-(1,1'-biphenyl)-2,3,3'-triol and 2-ethyl-4,6,9-trimethyl-6H-benzo(c) chromene are major products in both gas-phase and liquid-phase reactions, and (2Z, 4Z)-4-ethyl-6-oxohexa-2,4-dienoic acid is also one of the major products in gas-phase reactions. Toxicological predictions indicate that the ecotoxicity of 4-ethyl-6-methyl-6H-benzo(c)chromene-1,9-diol, 2-ethyl-6-methyl-6H-benzo(c)chromene-3,9-diol, and 2-ethyl-4,6,9-trimethyl-6H-benzo(c) chromene surpassed that of 4-EP. However, the toxicity of the reaction products is reduced in the presence of NOx. This investigation provides an exhaustive theoretical foundation for comprehending the degradation behavior of 4-EP and underscores the need to consider various environmental factors in assessing the potential risk of biomass combustion by products.

Broadband Cavity-Enhanced Absorption Spectroscopy (BBCEAS) Coupled with an Interferometer for On-Band and Off-Band Detection of Glyoxal

Glyoxal (CHOCHO) is a trace gas in the atmosphere, often used as an indicator of biogenic emissions. It is frequently compared to formaldehyde concentrations, which serve as indicators of anthropogenic emissions, to gain insights into the characteristics of the environmental source. This study employed broadband cavity-enhanced absorption spectroscopy to detect gaseous CHOCHO, methylglyoxal, and NO2. Two different detection methods are compared. Spectrograph and CCD Detection: This approach involves coupling the system to a spectrograph with a charge-coupled device (CCD) detector. It achieved a 1 min 1-σ detection limit of 2.5 × 108 molecules/cm3, or 10 parts per trillion (ppt). Methylglyoxal and NO2 achieved 1 min 1-σ detection limits of 34 ppt and 22 ppt, respectively. Interferometer and PMT Detection: In this method, an interferometer is used in conjunction with a photomultiplier tube (PMT) detector. It resulted in a 2 min 1-σ detection limit of 1.5 × 1010 molecules/cm3, or 600 ppt. The NO2 2 min 1-σ detection limit was determined to be 900 ppt. Concentrations of methylglyoxal were difficult to determine using this method, as they appeared to be below the detection limit of the instrument. This study discusses the advantages and limitations of each of these detection methods.

Overview of PM2.5 and health outcomes: Focusing on components, sources, and pollutant mixture co-exposure

PM_2.5 varies in source and composition over time and space as a complicated mixture. Consequently, the health effects caused by PM_2.5 varies significantly over time and generally exhibit significant regional variations. According to numerous studies, a notable relationship exists between PM_2.5 and the occurrence of many diseases, such as respiratory, cardiovascular, and nervous system diseases, as well as cancer. Therefore, a comprehensive understanding of the effect of PM_2.5 on human health is critical. The toxic effects of various PM_2.5 components, as well as the overall toxicity of PM_2.5 are discussed in this review to provide a foundation for precise PM_2.5 emission control. Furthermore, this review summarizes the synergistic effect of PM_2.5 and other pollutants, which can be used to draft effective policies.

Direct emissions of particulate glyoxal and methylglyoxal from biomass burning and coal combustion

Glyoxal (Gly) and methylglyoxal (Mgly) are key precursors globally for secondary organic aerosol (SOA) formation. These two species were often thought to be formed in the atmosphere via photochemical oxidation of organics from biogenic and anthropogenic origins, although few studies have shown their direct emissions. In this study, we report direct emissions of particulate Gly and Mgly from different residential fuels typically used in north China. The emission ratios (ERs) and emission factors (EFs) of particulate Gly and Mgly for biomass burning were approximate 5-fold and 7-fold higher than those for coal combustion, respectively. The large variances in emissions of Gly and Mgly could be attributed to the different combustion processes, which influenced by the fuel types and combustion conditions. The averaged ERs and EFs of particulate Gly and Mgly were about one order of magnitude lower than their gaseous counterparts due to the low Henry's law constant, which was also consistent with the low particle-to-gas ratio of Gly (0.04) and Mgly (0.02). Our results suggest that the direct emissions of Gly and Mgly from emission sources should be considered when estimating the formation of SOA from Gly and Mgly.

Development of Volatility Distributions for Organic Matter in Biomass Burning Emissions

The volatility distribution of organic emissions from biomass burning and other combustion sources can determine their atmospheric evolution due to partitioning/aging. The gap between measurements and models predicting secondary organic aerosol has been partially attributed to the absence of semi- and intermediate volatility organic compounds (S/I-VOC) in models and measurements. However, S/I-VOCs emitted from these sources and typically quantified using the volatility basis framework (VBS) are not well understood. For example, the amount and composition of S/I-VOCs and their variability across different biomass burning sources such as residential woodstoves, open field burns, and laboratory simulated open burning are uncertain. To address this, a novel filter-in-tube sorbent tube sampling method collected S/I-VOC samples from biomass burning experiments for a range of fuels and combustion conditions. Filter-in-tube samples were analyzed using thermal desorption-gas chromatography-mass spectrometry (TD/GC/MS) for compounds across a wide range of volatilities (saturation concentrations; -2 ≤ logC* ≤ 6). The S/I-VOC measurements were used to calculate volatility distributions for each emissions source. The distributions were broadly consistent across the sources with IVOCs accounting for 75% - 90% of the total captured organic matter, while SVOCs and LVOCs were responsible for 6% - 13% and 1% - 12%, respectively. The distributions and predicted partitioning were generally consistent with literature. Particulate matter emission factors spanned two orders of magnitude across the sources. This work highlights the potential of inferring gas-particle partitioning behavior of biomass burning emissions using filter-in-tube sorbent samples analyzed offline. This simplifies both sampling and analysis of S/I-VOCs for studies focused on capturing the full range of organics emitted.

Mechanisms of Lung Damage and Development of COPD Due to Household Biomass-Smoke Exposure: Inflammation, Oxidative Stress, MicroRNAs, and Gene Polymorphisms

Chronic exposure to indoor biomass smoke from the combustion of solid organic fuels is a major cause of disease burden worldwide. Almost 3 billion people use solid fuels such as wood, charcoal, and crop residues for indoor cooking and heating, accounting for approximately 50% of all households and 90% of rural households globally. Biomass smoke contains many hazardous pollutants, resulting in household air pollution (HAP) exposure that often exceeds international standards. Long-term biomass-smoke exposure is associated with Chronic Obstructive Pulmonary Disease (COPD) in adults, a leading cause of morbidity and mortality worldwide, chronic bronchitis, and other lung conditions. Biomass smoke-associated COPD differs from the best-known cigarette smoke-induced COPD in several aspects, such as a slower decline in lung function, greater airway involvement, and less emphysema, which suggests a different phenotype and pathophysiology. Despite the high burden of biomass-associated COPD, the molecular, genetic, and epigenetic mechanisms underlying its pathogenesis are poorly understood. This review describes the pathogenic mechanisms potentially involved in lung damage, the development of COPD associated with wood-derived smoke exposure, and the influence of genetic and epigenetic factors on the development of this disease.

The Fate of Protonated Guaiacol and Its Derivatives in the Gas Phase

Guaiacol (2-methoxyphenol) and its derivatives are a class of semivolatile polar organic molecules possessing low molecular weights. Owing to their volatility, guaiacol and its derivatives can interact with atmospheric water and form protonated methoxyphenols through proton transfer. The aim of the present work is to study the dissociation of these protonated ions and hence, potentially, their atmospheric fate. Tandem mass spectrometry was employed to analyze the unimolecular dissociation of the protonated forms of guaiacol (2-methoxyphenol, 1), creosol (2-methoxy-4-methylphenol, 2), 4-ethylguaiacol (4-ethyl-2-methoxyphenol, 3), 4-vinylguaiacol (2-methoxy-4-vinylphenol, 4), eugenol (2-methoxy-4-prop-2-enylphenol, 5), and vanillin (4-hydroxy-3-methoxybenzaldehyde, 6). Density functional theory at the B3LYP/6-31G(d) (1-5) and B3LYP/6-311+G(d,p) (6) levels of theory were applied to determine the observed minimum energy reaction pathways, and reliable energetics were acquired using CBS-QB3 single-point energy calculations. All the protonated ions, with the exception of 6, exhibit the loss of CH₃OH via a series of hydrogen transfers, followed by ring contraction to lose CO. This common dissociation pathway leads to the formation of a cyclopentadienyl ion as the main dissociation product. Conversely, 6 first exhibits the loss of CO, followed by sequential losses of CH₃OH and CO to generate a cyclopentadienyl ion. Additionally, minor fragmentation channels are also observed for the different protonated ions: CH₂ loss in 1; CH₄ and H₂O losses in 3; CH₃ loss in 4, 5, and 6; C₂H₄ and CH₂CHCH₂ losses in 5; H loss in 6. Altogether, the protonated ions primarily lose CH₃OH and CO as neutral molecules and generate a cyclopentadienyl ion as a dissociation product.

Seasonal variations and potential sources of biomass burning tracers in particulate matter in Nanjing aerosols during 2017-2018

Biomass burning (BB) is an important source of atmospheric particulate matter and can adversely affect air quality, visibility, human health, and climate change. To study the characteristics and potential source regions of BB tracers in PM_2.5, a liquid chromatography-mass spectrometry instrument (HPLC-MS/MS) is applied in this study to develop and validate a method to determine organic tracers of BB in 397 aerosol samples. The total mean concentrations of 17 tracers measured in 2017 and 2018 were 333.32 ng m^-3 and 243.45 ng m^-3, respectively. Among them, the concentration of levoglucosan was the highest among all the tracers, with 325.63 ng m^-3 in 2017 and 237.47 ng m^-3 in 2018. The BB tracers showed obvious seasonal variations characteristics, most of which were abundant in winter. However, the concentrations of 3,4-dimethoxyacetic acid and sinapinic acid were higher in summer and spring than that in the other seasons. There were obvious differences in the Potential Source Contribution Factor (PSCF) model results of the BB's potential source area annually and in different seasons. The results of the potential source analysis showed that Beijing-Tianjin-Hebei had a great impact on the Nanjing air quality in 2017. Finally, five source factors for BB were identified based on the Positive Matrix Factor (PMF) model, and these were cellulose, hardwood, softwood, grass, and secondary formed. During the 2 years, cellulose was the largest contributor to biomass burning. Owing to the different fire conditions each year, the contribution of the five factors to the BB tracers was also different. For example, the contribution of softwood to the BB tracers was greater in 2018 (8.4%) than in 2017 (5.2%), while the contributions of hardwood and cellulose did not change significantly.

Rapid increase in atmospheric glyoxal and methylglyoxal concentrations in Lhasa, Tibetan Plateau: Potential sources and implications

Glyoxal (Gly) and methylglyoxal (Mgly) are the intermediate products of several volatile organic compounds (VOCs) as well as the precursors of brown carbon and may play key roles in photochemical pollution and regional climate change in the Tibetan Plateau (TP). However, their sources and atmospheric behaviors in the TP remain unclear. During the second Tibetan Plateau Scientific Expedition and Research in the summer of 2020, the concentrations of Gly (0.40 ± 0.30 ppbv) and Mgly (0.57 ± 0.16 ppbv) observed in Lhasa, the most densely populated city in the TP, had increased by 20 and 15 times, respectively, compared to those measured a decade previously. Owing to the strong solar radiation, secondary formations are the dominant sources of both Gly (71%) and Mgly (62%) in Lhasa. In addition, primary anthropogenic sources also play important roles by emitting Gly and Mgly directly and providing abundant precursors (e.g., aromatics). During ozone pollution episodes, local anthropogenic sources (industries, vehicles, solvent usage, and combustion activities) contributed up to 41% and 45% in Gly and Mgly levels, respectively. During non-episode periods, anthropogenic emissions originating from the south of Himalayas also have non-negligible contributions. Our results suggest that in the previous decade, anthropogenic emissions have elevated the levels of Gly and Mgly in the TP dramatically. This study has important implications for understanding the impact of human activities on air quality and climate change in this ecologically fragile area.

Indexes of tobacco smoke contribution to environmental particulates based on molecular fingerprints of alkanes

Tobacco smoke (TS) is the source of a number of toxicants affecting the atmosphere and poses a threat to smokers and the whole community. Chemical, physical, and toxicological features of smoking products (vapors as well as mainstream, side stream, and third-hand smoke) have been investigated extensively. Special attention is paid to organic compounds (individually or in combination giving rise to peculiar molecular fingerprints), potentially able to act as "chemical signature" of TS. In this regard, the percent distribution of long-chainnormal, iso, and anteiso alkanes was ascertained as typical of TS. Nevertheless, until now no indexes have been identified as suitable for assessing the global TS contribution to environmental pollution, e.g., the TS percentage in carbonaceous aerosol and in deposited dusts, the only exception consisting in the use of nicotelline as tracer. This paper describes the results of an extensive study aimed at chemically characterizing the nonpolar lipid fraction associated to suspended particulates (PMs) and deposition dusts (DDs) collected at indoor and outdoor locations. Based on the iso, anteiso, and normal C₂₉-C₃₄ alkane profile in the samples as well in tobacco smoke- and no-TS-related emissions (literature data), various parameters describing the distribution of compounds were investigated. Finally, a cumulative variable was identified as the tobacco smoke impact index (TS%) suitable for estimating the TS percentage occurring in the particulate matter. The TS% rates were plotted vs. the exceedance of normal C₃₁ alkane with respect to the average of C₂₉ and C₃₃ homologs, which results higher in TS than in most other emissions, revealing a link in the case of suspended particulates but not of deposited dusts. According to back analysis carried out on all particulate matter sets, it was found that traces of TS affect even remote areas, while inside the smokers' homes the contributions of TS to PM could account for up to ~61% and ~10%, respectively, in PM and DD. This confirms the need of valuing the health risk posed by TS to humans, by means of tools easy to apply in extensive investigations.

Emission factors and chemical characterization of particulate emissions from garden green waste burning

This work provides an evaluation of the emission factors (EFs) of typical garden waste burning (fallen leaves and hedge trimming) in terms of particulate matter (PM), elemental and organic carbon (EC-OC) together with a detailed chemical characterization of 88 particle-bound organic species including polycyclic aromatic hydrocarbons (PAHs), levoglucosan and its isomers, lignin breakdown products (methoxyphenols), cholesterol, alkanes, polyols and sugars. Furthermore, wood-log based burning experiments have been performed to highlight key indicators or chemical patterns of both, green waste and wood burning (residential heating) sources, that may be used for PM source apportionment purposes. Two residential log wood combustion appliances, wood stove (RWS) and fireplace, under different output conditions (nominal and reduced) and wood log moisture content (mix of beech, oak and hornbeam), have been tested. Open wood burning experiments using wood logs were also performed. Green waste burning EFs obtained were comparable to the available literature data for open-air biomass burning. For PM and for most of the organic species studied, they were about 2 to 30 times higher than those observed for wood log combustion experiments. Though, poor performance wood combustions (open-air wood log burning, fireplace and RWS in reduced output) showed comparable EFs for levoglucosan and its isomers, methoxyphenols, polyols, PAHs and sugars. Toxic PAH equivalent benzo[a]pyrene EFs were even 3-10 times higher for the fireplace and open-air wood log burning. These results highlighted the impact of the nature of the fuel burnt and the combustion performances on the emissions. Different chemical fingerprints between both biomass burning sources were highlighted with notably a predominance of odd high-molecular weight n-alkanes (higher carbon preference index, CPI), lower levoglucosan/mannosan ratio and lower sinapylaldehyde abundance for green waste burning. However, the use of such indicators seems limited, especially if applied alone, for a clear discrimination of both sources in ambient air.

Comparison of physical and chemical characteristics and oxidative potential of fine particles emitted from rice straw and pine stem burning

Agricultural burning and forest fires are common in Northeast Asia and contribute to the elevation of fine particulate pollution, which greatly affects air quality. In this study, chemical and physical attributes, as well as the oxidative potential of fine particles produced from rice straw and pine stem burning in a laboratory-scale chamber were determined. The burning of rice straw generated notably lower emissions of fine particles and elemental carbon (EC) than did the burning of pine stems. The longer retention of ultrafine particles was observed for rice straw burning likely caused by this material's longer period of initial flaming combustion. Organic carbon (OC), OC/EC, K⁺/OC, K⁺/EC, Zn, and alkanoic acid were higher in the fine particles of rice straw burning, while EC, K⁺/Cl^-, Fe, Cr, Al, Cu, and levoglucosan were higher for pine stem burning particles. Chemical data were consistent with a higher hygroscopic growth factor and cloud formation potential and lower amount of agglomerated soot for rice straw burning particles. Rice straw burning particles displayed an oxidative potential seven times higher than that of pine stems.

Importance of Wintertime Anthropogenic Glyoxal and Methylglyoxal Emissions in Beijing and Implications for Secondary Organic Aerosol Formation in Megacities

Atmospheric glyoxal (GLY) and methylglyoxal (MGLY) are key precursors of secondary organic aerosol (SOA). However, anthropogenic emissions of GLY and MGLY and their contribution to surface GLY and MGLY concentrations, as well as the secondary organic aerosol (SOA) formation, are not well quantified. By developing an emission inventory of anthropogenic GLY and MGLY and improving the Community Multiscale Air Quality Model (CMAQ) with SOA formation from irreversible surface uptake of GLY and MGLY, as well as a precursor-origin resolved technique, we quantified the source contributions of GLY and MGLY and their impact on wintertime SOA formation in Beijing, China. The total emissions of GLY and MGLY in Beijing in 2017 are 1.1 × 10⁴ kmol and 7.0 × 10³ kmol, respectively. Anthropogenic primary emissions are found to be the dominant contributor to wintertime GLY and MGLY concentrations (∼74% for GLY and ∼63% for MGLY). Anthropogenic primary emissions of GLY and MGLY contributes to 30% of GLY/MGLY SOA daily average concentration and accounts for up to 45% of nighttime GLY/MGLY SOA in winter. The study suggests that the anthropogenic GLY and MGLY emissions, mainly from gasoline vehicles and cooking, are important for SOA formation and shall be strictly controlled in Chinese megacities.

Comparative study on respiratory function among rural women using biomass fuel and non-biomass fuel: evidence of a cross-sectional survey in Bangladesh

Respiratory diseases' mortality and morbidity have been a major public health burden primarily attributed to widespread exposure to indoor and outdoor pollutants in the environment. The study conducted among 510 Bangladeshi women residing in the northeastern zone of the Sylhet division from semi-urban and rural settings to compare the biomass fuel users (N = 255) with the non-biomass users (N = 255). It has been observed that all the symptoms had a higher prevalence among the women who were exposed to biomass fuel compared with those exposed to clean gas fuel. Women exposed to biomass group reported frequent cough and phlegm production episodes during a 3-month timeline before the survey period which was found statistically higher (p < 0.001) compared with that of the clean gas fuel group. Moreover, the use of biomass fuel has been associated with a significant decrease in forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and peak expiratory flow rate (PEFR). Appropriate strategies from stakeholders and government authorities in disseminating health hazards from biomass fuel along with supporting the community by providing alternative energy sources for cooking can largely impact people's lives.

Significant ultrafine particle emissions from residential solid fuel combustion

When addressing particulate matter (PM) emissions from residential solid fuel combustion, ultrafine particles are usually merged into PM_2.5, while whose mass concentration is applied as the index in evaluating PM pollution as well as assessing PM-induced health risk. This may not effectively represent the risk from ultrafine particles. In this study, we explored ultrafine particle emissions during residential combustion under both laboratory-controlled and real-world rural household conditions. Significant ultrafine particle emissions (i.e. with emission factors between 2 × 10¹⁵ to 2 × 10¹⁶ particles per kg of fuel) are found for both coal and biomass. High emissions of particle mass concentration often occur at the beginning of the combustion (i.e. the first 30 min after fire start) while high emissions of particle number concentration occur in a later combustion period (60-150 min). Ultrafine particles account for over 90% of the emitted total particle number concentration from 3 nm to 10 μm. These emissions elevate ultrafine particle number concentration by more than a decade in indoor environment under which household residents are directly exposed. In addition, we show that there is notable inconsistency between reducing PM_2.5 mass based emissions and reducing ultrafine particle number based emissions among various control strategies that were proposed for reducing pollution from residential combustion. Both "cleaner" fuels and stoves that are designed to reduce PM_2.5 emissions are found to be not necessarily effective in reducing ultrafine particle emissions, even increase their emissions in some cases. These findings indicate that the overlook of ultrafine particle emissions from residential solid fuel combustion can lead to potential health risk to household residents, especially to those vulnerable ones (e.g., the elderly and children) who are more sensitive to indoor air pollution. More attentions are needed on ultrafine particle pollution and its potential health risk in comparison to using the PM mass concentration index alone.

Composition and source apportionment of saccharides in aerosol particles from an agro-industrial zone in the Indo-Gangetic Plain

The characterization of saccharidic compounds in atmospheric aerosols is important in order to retrieve information about organic carbon sources and their transport pathways through the atmosphere. In this study, composition and sources of saccharides in PM₁₀ were determined in a South Asian megacity (Faisalabad) during the year 2015 - 2016. PM₁₀ sampled on quartz filters was analyzed by anion exchange chromatography for the selected saccharidic compounds. The average PM₁₀ concentration was found to be 744 ± 392 μg m^-3, exceeding the daily limits proposed by Pak-EPA (150 μg m^-3), US-EPA (150 μg m^-3), and WHO (50 μg m^-3). The average total saccharidic concentration was found to be 2820 ± 2247 ng m^-3. Among the different saccharidic categories, anhydrosugars were the most abundant in concentration followed by primary sugars and sugar alcohols. The correlation and principal component analysis indicated emissions from biomass combustion, soil suspensions from areas such as farmlands having high microorganism activity, and biogenic emissions such as airborne fungal spores and vegetation detritus as major sources of saccharides in the aerosol samples.

Emission characteristics of size distribution, chemical composition and light absorption of particles from field-scale crop residue burning in Northeast China

Crop residue burning in China increased significantly in the last decade, especially it took up a majority in Northeast China, which plays an important role of severe haze pollution. Hence, two main types of crop residues (corn and rice straw) were chosen to characterize the particle number concentration, chemical components of fine particulate matter and optical properties of carbonaceous aerosols by a suite of fast-response online portable instruments, together with offline sampling and analysis, during the field-based combustion experiments in Northeast China. For the range of 250 and 2500 nm, more particles were emitted from rice straw burning than those from corn straw burning, and the time-averaged number concentration of particles during the flaming process was approximately 2 times higher than that during the smoldering process for these two straws. Organic carbon (OC), elemental carbon (EC) and water-soluble ions were the most abundant components and accounted for 42.5 ± 7.5%, 7.7 ± 1.7% and 18.0 ± 3.4% of the PM_2.5, respectively. Furthermore, rice straw burning emitted higher OC and lower Cl^- and K⁺ than those from corn straw burning. The average absorption Ångström exponent (AAE) of carbonaceous aerosols was 2.1 ± 0.3, while the AAE of brown carbon (BrC) was 4.7 ± 0.4 during the whole burning process. On average, BrC contributed to 63% and 20% of the total light absorption at 375 nm and 625 nm, respectively. Parameterization of BrC absorption revealed that the fraction of absorption from BrC has a reasonably good correlation with EC/OC (-0.84) and AAE (0.94) at 375 nm. Generally, combustion conditions can affect the optical properties of carbonaceous aerosols, and a negative correlation (-0.77) was observed between the AAE and modified combustion efficiency; in addition, the percentage of absorption due to BrC were lower at the flaming phase.

Molecular characteristics and stable carbon isotope compositions of dicarboxylic acids and related compounds in the urban atmosphere of the North China Plain: Implications for aqueous phase formation of SOA during the haze periods

In the past five years, Chinese government has promulgated stringent measures to mitigate air pollution. However, PM_2.5 levels in the China North Plain (NCP), which is one of the regions with the heaviest air pollution in the world, are still far beyond the World Health Organization (WHO) standard. To improve our understanding on the sources and formation mechanisms of haze in the NCP, PM_2.5 samples were collected during the winter of 2017 on a day/night basis at the urban site of Liaocheng, which is one of the most polluted cities in the NCP. The samples were determined for molecular distributions and stable carbon isotope compositions of dicarboxylic acids and their precursors (ketocarboxylic acids and α-dicarbonyls), levoglucosan, elemental carbon (EC), organic carbon (OC) and water-soluble organic carbon (WSOC). Our results showed that oxalic acid (C₂) is the dominant dicarboxylic acid, followed by succinic acid (C₄) and malonic acid (C₃), and glyoxylic acid (ωC₂) is the most abundant ketocarboxylic acids. Concentrations of C₂, glyoxal (Gly) and methylglyoxal (mGly) presented robust correlations with levoglucosan, suggesting that biomass burning is a significant source of PM_2.5 in the NCP. Moreover, C₂ and Gly and mGly linearly correlated with SO₄^2-, relative humidity (RH), aerosol liquid water content (LWC) as well as particle in-situ pH (pH_is), indicating that aqueous-phase oxidation is the major formation pathway of these SOA, and is driven by acid-catalyzed oxidation. Concentrations and relative abundances of secondary species including SNA (SO₄^2-, NO₃^- and NH₄⁺), dicarboxylic acids, and aerosol LWC in PM_2.5 are much higher in the haze periods than in the clean periods, suggesting that aqueous reaction is a vital role in the haze formation. In comparison with those in the clean periods, stable carbon isotopic compositions (δ¹³C) of major dicarboxylic acids and related SOA and the mass ratios of C₂/diacids, C₂/Gly and C₂/mGly are higher in the haze periods, indicating that haze particles were more aged and enriched in secondary species.

Theoretical study on the mechanisms, kinetics and ecotoxicity assessment of OH-initiated reactions of guaiacol in atmosphere and wastewater

The OH-initiated transformation mechanisms, kinetics and ecotoxicity assessment of guaiacol (2-methoxyphenol) in the presence of O₂/NO_x were investigated both in atmosphere and wastewater. The solvent effect lowers the energy barriers of initial OH-addition reactions more than H-abstraction reactions, leading to much higher addition branching ratio (Γ_add) of 0.92 in aqueous solution than that of 0.42 in gas-phase. At 298 K, the overall rate constants of the title reactions in atmosphere and wastewater are 5.56 × 10^-12 and 1.41 × 10^-11 cm³ molecule^-1 s^-1 with corresponding half-lives of 34.6 h and 0.82 s, respectively. In atmosphere, all the proposed favorable products including nitroguaiacols, methoxybenzoquinone, 2-hydroxyphenyl formate, 2-methoxybenzene-1, 3-diol and dialdehyde could contribute to secondary organic aerosols (SOAs). In wastewater, NO₂ addition reactions lead to higher toxicity of products (nitroguaiacols and 2-methoxybenzene-1, 4-diol) than that of parental guaiacol. However, O₂/NO addition pathways may generate less harmful products except for methoxybenzoquinone (P3) which is with higher toxicity than guaiacol. Therefore, more attention should be focused on the products formed from OH-initiated reactions of guaiacol both in atmosphere and wastewater.

Carbonaceous Particulate Matter Emitted from a Pellet-Fired Biomass Boiler

Biomass pellets are a source of renewable energy; although, the air pollution and exposure risks posed by the emissions from burning pellets in biomass boilers (BBs) are uncertain. The present study examines the organic species in fine particle matter (PM) emissions from an BB firing switchgrass (SwG) and hardwood (HW) biomass pellets using different test cycles. The organic and elemental carbon (OC and EC) content and select semivolatile organic compounds (SVOCs) in filter-collected PM were identified and quantified using thermal-optical analysis and gas chromatography–mass spectrometry (GC–MS), respectively. Fine PM emissions from the BB ranged from 0.4 g/kg to 2.91 g/kg of pellets burned of which 40% ± 17% w/w was carbon. The sum of GC–MS quantified SVOCs in the PM emissions varied from 0.13 to 0.41 g/g OC. Relatively high levels of oxygenated compounds were observed in the PM emissions, and the most predominant individual SVOC constituent was levoglucosan (12.5–320 mg/g OC). The effect of boiler test cycle on emissions was generally greater than the effect due to pellet fuel type. Organic matter emissions increased at lower loads, owing to less than optimal combustion performance. Compared with other types of residential wood combustion studies, pellet burning in the current BB lowered PM emissions by nearly an order of magnitude. PM emitted from burning pellets in boilers tested across multiple studies also contains comparatively less carbon; however, the toxic polycyclic aromatic hydrocarbons (PAH) in the PM tested across these pellet-burning studies varied substantially, and produced 2–10 times more benzo[k]fluoranthene, dibenz[a,h]anthracene and indeno[1,2,3-c,d]pyrene on average. These results suggest that further toxicological evaluation of biomass pellet burning emissions is required to properly understand the risks posed.

Elevated levels of glyoxal and methylglyoxal at a remote mountain site in southern China: Prompt in-situ formation combined with strong regional transport

The dicarbonyls glyoxal (Gly) and methylglyoxal (Mgly) are key tracers for the oxidation of volatile organic compounds (VOCs) in the atmosphere, but their atmospheric chemistry in remote forest environments is not well understood. A study was carried out during Jul. 31-Nov. 5 of 2016 at the summit of Mt. Tianjing (1690 m.a.s.l.), a remote mountaintop site in southern China, to measure the levels of Gly and Mgly and explore their sources and fate. During the study period, the average mixing ratios of Gly and Mgly were 509 ± 31 pptv and 340 ± 32 pptv, respectively, with the Gly/Mgly ratios averaging 1.8 ± 0.2. Both the dicarbonyl concentrations and the Gly/Mgly ratios were significantly higher than those observed in other background sites. Production yield calculations and meteorological data analysis indicate that high levels of Gly and Mgly observed at the study site were largely a combined result of rapid in-situ formation and regional transport by prevailing winds. On average, in-situ formation from precursors is estimated to account for 67% of the observed Mgly and about 9% of the observed Gly. There were significant changes in Gly and Mgly mixing ratios among different time periods when air masses from different source regions dominated, indicating contribution of regional transport to the observed dicarbonyl mixing ratios at the study site. Biogenic emissions in eastern China and anthropogenic emissions in the Pearl River Delta region were the two main sources responsible for the dicarbonyls observed at the site during most of the sampling period, but large-scale biomass burning in central China was also important in the late autumn, as supported by a backward trajectory analysis of fire spot data and the identification of biomass burning tracers. This study provides insights into the background atmospheric chemistry and the impact of biogenic and anthropogenic sources on the dicarbonyls speciation.

An assessment of important SPECIATE profiles in the EPA emissions modeling platform and current data gaps

The United States (US) Environmental Protection Agency (EPA)'s SPECIATE database contains speciated particulate matter (PM) and volatile organic compound (VOC) emissions profiles. Emissions profiles from anthropogenic combustion, industry, wildfires, and agricultural sources among others are key inputs for creating chemically-resolved emissions inventories for air quality modeling. While the database and its use for air quality modeling are routinely updated and evaluated, this work sets out to systematically prioritize future improvements and communicate speciation data needs to the research community. We first identify the most prominent profiles (PM and VOC) used in the EPA's 2014 emissions modeling platform based on PM mass and VOC mass and reactivity. It is important to note that the on-road profiles were excluded from this analysis since speciation for these profiles is computed internally in the MOVES model. We then investigate these profiles further for quality and to determine whether they were being appropriately matched to source types while also considering regional variability of speciated pollutants. We then applied a quantitative needs assessment ranking system which rates the profile based on age, appropriateness (i.e. is the profile being used appropriately), prevalence in the EPA modeling platform and the quality of the reference. Our analysis shows that the highest ranked profiles (e.g. profile assignments with the highest priority for updates) include PM_2.5 profiles for fires (prescribed, agricultural and wild) and VOC profiles for crude oil storage tanks and residential wood combustion of pine wood. Top ranked profiles may indicate either that there are problems with the currently available source testing or that current mappings of profiles to source categories within EPA's modeling platform need improvement. Through this process, we have identified 29 emissions sourcecategories that would benefit from updated mapping. Many of these mapping mismatches are due to lack of emissions testing for appropriate source categories. In addition, we conclude that new source emissions testing would be especially beneficial for residential wood combustion, nonroad gasoline exhaust and nonroad diesel equipment.

Aromatic acids as biomass-burning tracers in atmospheric aerosols and ice cores: A review

Biomass burning (BB) is one of the largest sources of carbonaceous aerosols with adverse impacts on air quality, visibility, health and climate. BB emits a few specific aromatic acids (p-hydroxybenzoic, vanillic, syringic and dehydroabietic acids) which have been widely used as key indicators for source identification of BB-derived carbonaceous aerosols in various environmental matrices. In addition, measurement of p-hydroxybenzoic and vanillic acids in snow and ice cores have revealed the historical records of the fire emissions. Despite their uniqueness and importance as tracers, our current understanding of analytical methods, concentrations, diagnostic ratios and degradation processes are rather limited and scattered in literature. In this review paper, firstly we have summarized the most established methods and protocols for the measurement of these aromatic acids in aerosols and ice cores. Secondly, we have highlighted the geographical variability in the abundances of these acids, their diagnostic ratios and degradation processes in the environments. The review of the existing data indicates that the concentrations of aromatic acids in aerosols vary greatly with locations worldwide, typically more abundant in urban atmosphere where biomass fuels are commonly used for residential heating and/or cooking purposes. In contrast, their concentrations are lowest in the polar regions which are avoid of localized emissions and largely influenced by long-range transport. The diagnostic ratios among aromatic acids can be used as good indicators for the relative amounts and types of biomass (e.g. hardwood, softwood and herbaceous plants) as well as photochemical oxidation processes. Although studies suggest that the degradation processes of the aromatic acids may be controlled by light, pH and hygroscopicity, a more careful investigation, including closed chamber studies, is highly appreciated.

Characterization of the chemical components and bioreactivity of fine particulate matter produced during crop-residue burning in China

Five types of crop residue (rice, wheat, corn, sorghum, and sugarcane) collected from different provinces in China were used to characterize the chemical components and bioreactivity properties of fine particulate matter (PM_2.5) emissions during open-burning scenarios. Organic carbon (OC) and elemental carbon (EC) were the most abundant components, contributing 41.7%-54.9% of PM_2.5 emissions. The OC/EC ratio ranged from 8.8 to 31.2, indicating that organic matter was the dominant component of emissions. Potassium and chloride were the most abundant components in the portion of PM_2.5 composed of water-soluble ions. The coefficient of divergence ranged from 0.27 to 0.51 among various emissions profiles. All samples exposed to a high PM_2.5 concentration (150 μg/mL) exhibited a significant reduction in cell viability (A549 lung alveolar epithelial cells) and increase in lactic dehydrogenase (LDH) and interleukin 6 levels compared with those exposed to 20 or 0 μg/mL. Higher bioreactivity (determined according to LDH and interleukin 6 level) was observed for the rice, wheat, and corn samples than for the sorghum straw samples. Pearson's correlation analysis suggested that OC, heavy metals (chromium, manganese, iron, nickel, copper, zinc, tin, and barium), and water-soluble ions (fluoride, calcium, and sulfate) are the components potentially associated with LDH production.

Effects of wood moisture on emission factors for PM2.5, particle numbers and particulate-phase PAHs from Eucalyptus globulus combustion using a controlled combustion chamber for emissions

Polycyclic aromatic hydrocarbons, PM_2.5 and micrometer-sized particles are mainly emitted by residential wood combustion, affecting air pollution in the cities of Chile. Eucalyptus globulus (EG) at 0% and 25% wood moisture was burning using a new controlled combustion chamber for emissions (3CE) to determine the emission factors of PM_2.5, micrometer-sized particle numbers (0.265μm to 34.00μm) and 16 EPA-PAHs plus retene adsorbed on PM_2.5 quartz filters. A method using accelerated solvent extraction, concentration, clean-up and GC-MS is proposed for determining emission factors for 16 EPA-PAHs for the concentration from biomass combustion. Chromatographic conditions and analytical steps were optimized in terms of linearity, selectivity, limits of detection and quantification, precision and accuracy. The recovery obtained from urban dust SRM 1649A (NIST reference material) analyses was between 63% (benzo[b]fluoranthene) and 102% (benzo[k]fluoranthene). In this investigation, it was shown that increasing the wood moisture in combustion tests decreased combustion efficiency (93% to 49%) and increased the emission factors of total PAHs (5215.47ngg^-1 to 7644.48ngg^-1), the gravimetric PM2.5 (2.01g kg^-1 to 22.90gkg^-1) and the total number of measured micrometer-sized particles (3.15×1012 particles kg^-1 to 1.33×1013 particles kg^-1) due to incomplete combustion. The PM_2.5 emission rates (ERs) were estimated using EG at 0% WM (2.39g^-1 to 3.15gh^-1) and 25% WM (27.32gh^-1 to 35.77gh^-1) for three regions of Chile. In almost all regions, the Chilean emission regulations were exceeded for PM_2.5 from wood combustion in the heater (stove with thermal power ≤8kW and emission limit of 2.5gh^-1). Finally, when using wet wood for residential combustion, the amount of PAHs on the PM_2.5 increased, presenting a potential hazard to population health. Therefore, improvements are necessary in the current regulation of PM emissions.

Assessing PM2.5 Model Performance for the Conterminous U.S. with Comparison to Model Performance Statistics from 2007-2015

Previous studies have proposed that model performance statistics from earlier photochemical grid model (PGM) applications can be used to benchmark performance in new PGM applications. A challenge in implementing this approach is that limited information is available on consistently calculated model performance statistics that vary spatially and temporally over the U.S. Here, a consistent set of model performance statistics are calculated by year, season, region, and monitoring network for PM2.5 and its major components using simulations from versions 4.7.1-5.2.1 of the Community Multiscale Air Quality (CMAQ) model for years 2007-2015. The multi-year set of statistics is then used to provide quantitative context for model performance results from the 2015 simulation. Model performance for PM2.5 organic carbon in the 2015 simulation ranked high (i.e., favorable performance) in the multi-year dataset, due to factors including recent improvements in biogenic secondary organic aerosol and atmospheric mixing parameterizations in CMAQ. Model performance statistics for the Northwest region in 2015 ranked low (i.e., unfavorable performance) for many species in comparison to the 2007-2015 dataset. This finding motivated additional investigation that suggests a need for improved speciation of wildfire PM2.5emissions and modeling of boundary layer dynamics near water bodies. Several limitations were identified in the approach of benchmarking new model performance results with previous results. Since performance statistics vary widely by region and season, a simple set of national performance benchmarks (e.g., one or two targets per species and statistic) as proposed previously are inadequate to assess model performance throughout the U.S. Also, trends in model performance statistics for sulfate over the 2007 to 2015 period suggest that model performance for earlier years may not be a useful reference for assessing model performance for recent years in some cases. Comparisons of results from the 2015 base case with results from five sensitivity simulations demonstrated the importance of parameterizations of NH3 surface exchange, organic aerosol volatility and production, and emissions of crustal cations for predicting PM2.5 species concentrations.

Emissions of particulate matter, carbon monoxide and nitrogen oxides from the residential burning of waste paper briquettes and other fuels

Using waste paper as fuel for domestic heating is a beneficial recycling option for small island developing states where there are lacks of resources for energy and waste treatment. However, there are concerns about the impact of air pollutants emitted from the burning of the self-made paper briquettes as household air pollution is recognised as the greatest environmental risk for human. In this study, combustion tests were carried out for paper briquettes made in one Pacific island and three commercial fuels in Australia including wood briquettes, kindling firewood and coal briquettes in order to: 1) characterise the emissions of three criteria air pollutants including particulate matters, CO and NO_x including their emission factors (EF) from the tested fuels; and 2) compare the EFs among the tested fuels and with others reported in the literature. The results showed that waste paper briquettes burned quickly and generated high temperature but the heat value is relatively low. Paper briquettes and coal briquettes produced higher CO concentration than the others while paper briquettes generated the highest NO_x level. Only PM_2.5 concentration emitted from paper briquettes was similar to kindling firewood and lower than wood briquettes. Burning of paper briquettes and wood briquettes produced particulate matter with large average count median diameter (72 and 68 nm) than coal briquette and kindling firewood (45 and 51 nm). The EFs for CO, NO_x and PM_2.5 of paper briquettes were within the range of EFs reported in this study as well as in the literature. Overall, the results suggested that using paper briquettes as fuel for domestic heating will not likely to generate higher level of three major air pollutants compared to other traditional fuels.

Emission Characteristics of Particulate Matter, Volatile Organic Compounds, and Trace Elements from the Combustion of Coals in Mongolia

This study characterized emissions of particulate matter (PM), volatile organic compounds (VOCs), heavy metals, and anions from Mongolian bituminous coals in a controlled heating experiment. Three coal samples from Alag Tolgoi (coal 1), Baganuur (coal 2), and Nalaikh (coal 3) were combusted at a constant heat flux of 50 kW/m² using a dual-cone calorimeter. The coal samples were commonly used in ger district of Ulaanbaatar, Mongolia. PM10 emission factors were 1122.9 ± 526.2, 958.1 ± 584.0, and 472.0 ± 57.1 mg/kg for coal samples 1, 2, and 3, respectively. PM with a diameter of 0.35⁻0.45 µm was dominant and accounted for 41, 34, and 48% of the total PM for coal samples 1, 2, and 3, respectively. The emissions of PM and VOC from coals commonly used in Ulaanbaatar, Mongolia were significant enough to cause extremely high levels of indoor and outdoor air pollution.

Distribution of coal and coal combustion related organic pollutants in the environment of the Upper Silesian Industrial Region

In this study, a large sample set (276) was separated into up to 15 groups, including coal, fly ash, total particulate matter, coal wastes, river sediments, and different water types. Grouping the sample set into these categories helped to identify the typical features of combustion or water-washing and compare them using newly developed polycyclic aromatic hydrocarbon diagnostic ratios. A wide range of organic pollutants were identified in samples, including aromatic and polycyclic hydrocarbons, nitrogen-heterocycles, sulphur-heterocycles + trithiolane, and polycyclic aromatic hydrocarbons substituted with oxygen functional groups. The distribution of compounds was significantly influenced by water washing or combustion. During the self-heating of coal wastes, secondary compounds such as chlorinated aromatics (chlorobenzene, chloroanthracene, etc.) or light sulphur compounds (e.g. benzenethiol and benzo[b]thiophene) were formed (synthesised). Since these compounds are generally absent in sedimentary organic matter, their origin may be connected with high-temperature formation in burning coal dumps. These compounds should be identified as persistent organic pollutants (POPs) in the environment. The newly defined diagnostic ratios have worked well in separating samples (petrogenic and pyrogenic) and have pointed out the effect of incomplete combustion on self-heated coal waste, ash from domestic furnaces, or water washing and biodegradation of the studied compounds.

Mutagenicity and Lung Toxicity of Smoldering vs. Flaming Emissions from Various Biomass Fuels: Implications for Health Effects from Wildland Fires

BACKGROUND

The increasing size and frequency of wildland fires are leading to greater potential for cardiopulmonary disease and cancer in exposed populations; however, little is known about how the types of fuel and combustion phases affect these adverse outcomes.

OBJECTIVES

We evaluated the mutagenicity and lung toxicity of particulate matter (PM) from flaming vs. smoldering phases of five biomass fuels, and compared results by equal mass or emission factors (EFs) derived from amount of fuel consumed.

METHODS

A quartz-tube furnace coupled to a multistage cryotrap was employed to collect smoke condensate from flaming and smoldering combustion of red oak, peat, pine needles, pine, and eucalyptus. Samples were analyzed chemically and assessed for acute lung toxicity in mice and mutagenicity in Salmonella.

RESULTS

The average combustion efficiency was 73 and 98% for the smoldering and flaming phases, respectively. On an equal mass basis, PM from eucalyptus and peat burned under flaming conditions induced significant lung toxicity potencies (neutrophil/mass of PM) compared to smoldering PM, whereas high levels of mutagenicity potencies were observed for flaming pine and peat PM compared to smoldering PM. When effects were adjusted for EF, the smoldering eucalyptus PM had the highest lung toxicity EF (neutrophil/mass of fuel burned), whereas smoldering pine and pine needles had the highest mutagenicity EF. These latter values were approximately 5, 10, and 30 times greater than those reported for open burning of agricultural plastic, woodburning cookstoves, and some municipal waste combustors, respectively.

CONCLUSIONS

PM from different fuels and combustion phases have appreciable differences in lung toxic and mutagenic potency, and on a mass basis, flaming samples are more active, whereas smoldering samples have greater effect when EFs are taken into account. Knowledge of the differential toxicity of biomass emissions will contribute to more accurate hazard assessment of biomass smoke exposures. https://doi.org/10.1289/EHP2200.

Production of N2O5 and ClNO2 through Nocturnal Processing of Biomass-Burning Aerosol

Biomass burning is a source of both particulate chloride and nitrogen oxides, two important precursors for the formation of nitryl chloride (ClNO₂), a source of atmospheric oxidants that is poorly prescribed in atmospheric models. We investigated the ability of biomass burning to produce N₂O₅(g) and ClNO₂(g) through nocturnal chemistry using authentic biomass-burning emissions in a smog chamber. There was a positive relationship between the amount of ClNO₂ formed and the total amount of particulate chloride emitted and with the chloride fraction of nonrefractory particle mass. In every fuel tested, dinitrogen pentoxide (N₂O₅) formed quickly, following the addition of ozone to the smoke aerosol, and ClNO₂(g) production promptly followed. At atmospherically relevant relative humidities, the particulate chloride in the biomass-burning aerosol was rapidly but incompletely displaced, likely by the nitric acid produced largely by the heterogeneous uptake of N₂O₅(g). Despite this chloride acid displacement, the biomass-burning aerosol still converted on the order of 10% of reacted N₂O₅(g) into ClNO₂(g). These experiments directly confirm that biomass burning is a potentially significant source of atmospheric N₂O₅ and ClNO₂ to the atmosphere.

Emission factors from different burning stages of agriculture wastes in Mexico

Open-air burning of agricultural wastes from crops like corn, rice, sorghum, sugar cane, and wheat is common practice in Mexico, which in spite limiting regulations, is the method to eliminate such wastes, to clear the land for further harvesting, to control grasses, weeds, insects, and pests, and to facilitate nutrient absorption. However, this practice generates air pollution and contributes to the greenhouse effect. Burning of straws derived from the said crops was emulated in a controlled combustion chamber, hence determining emission factors for particles, black carbon, carbon dioxide, carbon monoxide, and nitric oxide throughout the process, which comprised three apparent stages: pre-ignition, flaming, and smoldering. In all cases, maximum particle concentrations were observed during the flaming stage, although the maximum final contributions to the particle emission factors corresponded to the smoldering stage. The comparison between particle size distributions (from laser spectrometer) and black carbon (from an aethalometer) confirmed that finest particles were emitted mainly during the flaming stage. Carbon dioxide emissions were also highest during the flaming stage whereas those of carbon monoxide were highest during the smoldering stage. Comparing the emission factors for each straw type with their chemical analyses (elemental, proximate, and biochemical), some correlations were found between lignin content and particle emissions and either particle emissions or duration of the pre-ignition stage. High ash or lignin containing-straw slowed down the pre-ignition and flaming stages, thus favoring CO oxidation to CO₂.

Clair JM, Wolfe GM, Hanisco TF, Keutsch FN, Ryerson TB, Brown SS. Emissions of Glyoxal and Other Carbonyl Compounds from Agricultural Biomass Burning Plumes Sampled by Aircraft

We report enhancements of glyoxal and methylglyoxal relative to carbon monoxide and formaldehyde in agricultural biomass burning plumes intercepted by the NOAA WP-3D aircraft during the 2013 Southeast Nexus and 2015 Shale Oil and Natural Gas Nexus campaigns. Glyoxal and methylglyoxal were measured using broadband cavity enhanced spectroscopy, which for glyoxal provides a highly selective and sensitive measurement. While enhancement ratios of other species such as methane and formaldehyde were consistent with previous measurements, glyoxal enhancements relative to carbon monoxide averaged 0.0016 ± 0.0009, a factor of 4 lower than values used in global models. Glyoxal enhancements relative to formaldehyde were 30 times lower than previously reported, averaging 0.038 ± 0.02. Several glyoxal loss processes such as photolysis, reactions with hydroxyl radicals, and aerosol uptake were found to be insufficient to explain the lower measured values of glyoxal relative to other biomass burning trace gases, indicating that glyoxal emissions from agricultural biomass burning may be significantly overestimated. Methylglyoxal enhancements were three to six times higher than reported in other recent studies, but spectral interferences from other substituted dicarbyonyls introduce an estimated correction factor of 2 and at least a 25% uncertainty, such that accurate measurements of the enhancements are difficult.

Occupational Tasks Influencing Lung Function and Respiratory Symptoms Among Charcoal-Production Workers: A Time-Series Study

Background

Tasks involved in traditional charcoal production expose workers to various levels of charcoal dust and wood smoke. This study aimed to identify specific tasks influencing lung function and respiratory symptoms.

Methods

Interviews, direct observation, and task/symptom checklists were used to collect data from 50 charcoal-production workers on 3 nonwork days followed by 11 workdays. The peak expiratory flow rate (PEFR) was measured four times per day.

Results

The PEFR was reduced and the prevalence of respiratory symptoms increased over the first 6–7 workdays. The PEFR increased until evening on nonwork days but not on workdays. Loading the kiln and collecting charcoal from within the kiln markedly reduced the PEFR and increased the odds of respiratory symptoms.

Conclusion

Tasks involving entry into the kiln were strongly associated with a short-term drop in the PEFR and the occurrence of respiratory symptoms, suggesting a need for the use of protective equipment and/or the operation of an effective kiln ventilation system.

Analysis of aerosol composition data for western United States wildfires between 2005 and 2015: Dust emissions, chloride depletion, and most enhanced aerosol constituents

This study examines major wildfires in the western United States between 2005 and 2015 to determine which species exhibit the highest percent change in mass concentration on day of peak fire influence relative to preceding nonfire days. Forty-one fires were examined using the Environmental Protection Agency (EPA) Interagency Monitoring of Protected Visual Environments (IMPROVE) data set. Organic carbon (OC) and elemental carbon (EC) constituents exhibited the highest percent change increase. The sharpest enhancements were for the volatile (OC1) and semivolatile (OC2) OC fractions, suggestive of secondary organic aerosol formation during plume transport. Of the noncarbonaceous constituents, Cl, P, K, NO3-, and Zn levels exhibited the highest percent change. Dust was significantly enhanced in wildfire plumes, based on significant enhancements in fine soil components (i.e., Si, Ca, Al, Fe, and Ti) and PMcoarse (i.e., PM10-PM2.5). A case study emphasized how transport of wildfire plumes significantly impacted downwind states, with higher levels of fine soil and PMcoarse at the downwind state (Arizona) as compared to the source of the fires (California). A global model (Navy Aerosol Analysis and Prediction System, NAAPS) did not capture the dust influence over California or Arizona during this case event because it is not designed to resolve dust dynamics in fires, which motivates improved treatment of such processes. Significant chloride depletion was observed on the peak EC day for almost a half of the fires examined. Size-resolved measurements during two specific fires at a coastal California site revealed significant chloride reductions for particle aerodynamic diameters between 1 and 10 μm.

A Laboratory Comparison of Emission Factors, Number Size Distributions, and Morphology of Ultrafine Particles from 11 Different Household Cookstove-Fuel Systems

Ultrafine particle (UFP) emissions and particle number size distributions (PNSD) are critical in the evaluation of air pollution impacts; however, data on UFP number emissions from cookstoves, which are a major source of many pollutants, are limited. In this study, 11 fuel-stove combinations covering a variety of fuels and different stoves are investigated for UFP emissions and PNSD. The combustion of LPG and alcohol (∼10¹¹ particles per useful energy delivered, particles/MJ_d), and kerosene (∼10¹³ particles/MJ_d), produced emissions that were lower by 2-3 orders of magnitude than solid fuels (10¹⁴-10¹⁵ particles/MJ_d). Three different PNSD types-unimodal distributions with peaks ∼30-40 nm, unimodal distributions with peaks <30 nm, and bimodal distributions-were observed as the result of both fuel and stove effects. The fractions of particles smaller than 30 nm (F₃₀) varied among the tested systems, ranging from 13% to 88%. The burning of LPG and alcohol had the lowest PM_2.5 mass emissions, UFP number emissions, and F₃₀ (13-21% for LPG and 35-41% for alcohol). Emissions of PM_2.5 and UFP from kerosene were also low compared with solid fuel burning but had a relatively high F₃₀ value of approximately 73-80%.

Characterization of emissions and residues from simulations of the Deepwater Horizon surface oil burns

The surface oil burns conducted by the U.S. Coast Guard from April to July 2010 during the Deepwater Horizon disaster in the Gulf of Mexico were simulated by small scale burns to characterize the pollutants, determine emission factors, and gather particulate matter for subsequent toxicity testing. A representative crude oil was burned in ocean-salinity seawater, and emissions were collected from the plume by means of a crane-suspended sampling platform. Emissions included particulate matter, aromatic hydrocarbons, polychlorinated dibenzodioxins/dibenzofurans, elements, and others, the sum of which accounted for over 92% by mass of the combustion products. The unburned oil mass was 29% of the original crude oil mass, significantly higher than typically reported. Analysis of alkanes, elements, and PAHs in the floating residual oil and water accounted for over 51% of the gathered mass. These emission factors, along with toxicity data, will be important toward examining impacts of future spill burning operations.

Emission factors for PM2.5, CO, CO2, NOx, SO2 and particle size distributions from the combustion of wood species using a new controlled combustion chamber 3CE

The objective of this research was to determine emission factors (EF) for particulate matter (PM_2.5), combustion gases and particle size distribution generated by the combustion of Eucalyptus globulus (EG), Nothofagus obliqua (NO), both hardwoods, and Pinus radiata (PR), softwood, using a controlled combustion chamber (3CE). Additionally, the contribution of the different emissions stages associated with the combustion of these wood samples was also determined. Combustion experiments were performed using shaving size dried wood (0% humidity). The emission samples were collected with a tedlar bag and sampling cartridges containing quartz fiber filters. High reproducibility was achieved between experiment repetitions (CV<10%, n=3). The EF for PM_2.5 was 1.06gkg^-1 for EG, 1.33gkg^-1 for NO, and 0.84gkg^-1 for PR. Using a laser aerosol spectrometer (0.25-34μm), the contribution of particle emissions (PM_2.5) in each stage of emission process (SEP) was sampled in real time. Particle size of 0.265μm were predominant during all stages, and the percentages emitted were PR (33%), EG (29%), and NO (21%). The distributions of EF for PM_2.5 in pre-ignition, flame and smoldering stage varied from predominance of the flame stage for PR (77%) to predominance of the smoldering stage for NO (60%). These results prove that flame phase is not the only stage contributing to emissions and on the contrary, pre-ignition and in especial post-combustion smoldering have also very significant contributions. This demonstrates that particle concentrations measured only in stationary state during flame stage may cause underestimation of emissions.

Infrared spectroscopy of secondary organic aerosol precursors and investigation of the hygroscopicity of SOA formed from the OH reaction with guaiacol and syringol

Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) synchrotron analyses supplemented by density functional theory (DFT) anharmonic calculations have been undertaken to study the fundamental vibrational signatures of guaiacol and syringol, two methoxyphenol compounds found at the highest concentrations in fresh wood smoke and precursors of secondary organic aerosols (SOA) affecting the radiative balance and chemistry of the atmosphere. Nitroderivatives of these two compounds have also been studied experimentally for nitroguaiacol and theoretically for nitrosyringol. All the active fundamental vibrational bands have been assigned and compared to available gas phase measurements, providing a vibrational database of the main precursors for the analysis of SOA produced by atmospheric oxidation of methoxyphenols. In addition, the SOA formed in an atmospheric simulation chamber from the OH reaction with guaiacol and syringol were analyzed using the ATR-FTIR synchrotron spectroscopy and their hygroscopic properties were also investigated. The vibrational study confirms that nitroguaiacol and nitrosyringol are the main oxidation products of methoxyphenols by OH and are key intermediates in SOA production. The hydration experiments highlight the hydrophilic and hydrophobic characters of nitrosyringol and nitroguaiacol, respectively.

Emissions of Selected Semivolatile Organic Chemicals from Forest and Savannah Fires

The emission factors (EFs) for a broad range of semivolatile organic chemicals (SVOCs) from subtropical eucalypt forest and tropical savannah fires were determined for the first time from in situ investigations. Significantly higher (t test, P < 0.01) EFs (μg kg^-1 dry fuel, gas + particle-associated) for polycyclic aromatic hydrocarbons (∑₁₃ PAHs) were determined from the subtropical forest fire (7,000 ± 170) compared to the tropical savannah fires (1,600 ± 110), due to the approximately 60-fold higher EFs for 3-ring PAHs from the former. EF data for many PAHs from the eucalypt forest fire were comparable with those previously reported from pine and fir forest combustion events. EFs for other SVOCs including polychlorinated biphenyl (PCB), polychlorinated naphthalene (PCN), and polybrominated diphenyl ether (PBDE) congeners as well as some pesticides (e.g., permethrin) were determined from the subtropical eucalypt forest fire. The highest concentrations of total suspended particles, PAHs, PCBs, PCNs, and PBDEs, were typically observed in the flaming phase of combustion. However, concentrations of levoglucosan and some pesticides such as permethrin peaked during the smoldering phase. Along a transect (10-150-350 m) from the forest fire, concentration decrease for PCBs during flaming was faster compared to PAHs, while levoglucosan concentrations increased.

A review of biomass burning: Emissions and impacts on air quality, health and climate in China

Biomass burning (BB) is a significant air pollution source, with global, regional and local impacts on air quality, public health and climate. Worldwide an extensive range of studies has been conducted on almost all the aspects of BB, including its specific types, on quantification of emissions and on assessing its various impacts. China is one of the countries where the significance of BB has been recognized, and a lot of research efforts devoted to investigate it, however, so far no systematic reviews were conducted to synthesize the information which has been emerging. Therefore the aim of this work was to comprehensively review most of the studies published on this topic in China, including literature concerning field measurements, laboratory studies and the impacts of BB indoors and outdoors in China. In addition, this review provides insights into the role of wildfire and anthropogenic BB on air quality and health globally. Further, we attempted to provide a basis for formulation of policies and regulations by policy makers in China.

Polycyclic Aromatic Hydrocarbons in Fine Particulate Matter Emitted from Burning Kerosene, Liquid Petroleum Gas, and Wood Fuels in Household Cookstoves

This study measures polycyclic aromatic hydrocarbon (PAH) compositions in particulate matter emissions from residential cookstoves. A variety of fuel and cookstove combinations are investigated, including: (i) liquid petroleum gas (LPG), (ii) kerosene in a wick stove, (iii) wood (10 and 30% moisture content on a wet basis) in a forced-draft fan stove, and (iv) wood in a natural-draft rocket cookstove. The wood burning in the natural-draft stove had the highest PAH emissions followed by the wood combustion in the forced-draft stove and kerosene burning. LPG combustion has the highest thermal efficiency (∼57%) and the lowest PAH emissions per unit fuel energy, resulting in the lowest PAH emissions per useful energy delivered (in the unit of megajoule delivered, MJd). Compared with the wood combustion emissions, LPG burning also emits a lower fraction of higher molecular weight PAHs. In rural regions where LPG and kerosene are unavailable or unaffordable, the forced-draft fan stove is expected to be an alternative because its benzo[a]pyrene (B[a]P) emission factor (5.17-8.24 μg B[a]P/MJd) and emission rate (0.522-0.583 μg B[a]P/min) are similar to those of kerosene burning (5.36 μg B[a]P/MJd and 0.452 μg B[a]P/min). Relatively large PAH emission variability for LPG suggests a need for additional future tests to identify the major factors influencing these combustion emissions. These future tests should also account for different LPG fuel formulations and stove burner types.

Efficacy of interventions targeting household air pollution from residential wood stoves

Wood is commonly used for residential heating, but there are limited evidence-based interventions for reducing wood smoke exposures in the indoor environment. The Asthma Randomized Trial of Indoor Wood Smoke (ARTIS) study was designed to assess the efficacy of residential interventions to reduce indoor PM exposure from wood stoves. As part of a three-arm randomized placebo-controlled trial, two household-level interventions were evaluated: wood stove changeouts and air filtration units. Exposure outcomes included indoor measures such as continuous PM_2.5, particle counts, and carbon monoxide. Median indoor PM_2.5 concentration was 17.5 μg/m³ in wood-burning homes prior to interventions. No significant reductions in PM_2.5 concentrations were observed in the 40 homes receiving the placebo filter intervention. Sixteen homes received the wood stove changeout and showed no significant changes in PM_2.5 or particle counts. PM_2.5 concentrations were reduced by 68% in the filter intervention homes. Relative to placebo, air filtration unit homes had an overall PM_2.5 reduction of 63% (95% CI: 47-75%). Relative to the wood stove changeout, the filtration unit intervention was more efficacious and less expensive, yet compliance issues indicated a need for the evaluation of additional strategies for improving indoor air quality in homes using wood stoves.

Glyoxal measurement with a proton transfer reaction time of flight mass spectrometer (PTR-TOF-MS): characterization and calibration

We examine the potential for PTR-TOF-MS systems to quantitatively measure glyoxal in ambient air by characterizing the response of the instrument to a dilute glyoxal sample, calibrating the system as a function of humidity. The concentration of glyoxal in a sample air-stream was measured with an UV absorption spectrometer in parallel to a PTR-TOF-MS. This calibration demonstrated that the PTR-TOF-MS has a relatively low sensitivity to glyoxal particularly at high humidity. Extensive fragmentation of glyoxal to formaldehyde was observed. This behaviour not only desensitizes PTR-MS system to glyoxal; it may also pose a problem to the quantification of formaldehyde. © 2016 The Authors. Journal of Mass Spectrometry Published by John Wiley & Sons Ltd.

Ground-level air pollution changes during a boreal wildland mega-fire

The 2011 Richardson wildland mega-fire in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada had large effects on air quality. At a receptor site in the center of the AOSR ambient PM_2.5, O₃, NO, NO₂, SO₂, NH₃, HONO, HNO₃, NH₄⁺ and NO₃^- were measured during the April-August 2011 period. Concentrations of NH₃, HNO₃, NO₂, SO₂ and O₃ were also monitored across the AOSR with passive samplers, providing monthly summer and bi-monthly winter average values in 2010, 2011 and 2012. During the fire, hourly PM_2.5 concentrations >450μgm^-3 were measured at the AMS 1 receptor site. The 24-h National Ambient Air Quality Standard (NAAQS) of 35μgm^-3 and the Canada Wide Standard (CWS) of 30μgm^-3 were exceeded on 13days in May and 7days in June. During the fire emission periods, sharp increases in NH₃, HONO, HNO₃, NH₄⁺, NO₃^- and total inorganic reactive N concentrations occurred, all closely correlated with the PM_2.5 changes. There were large differences in the relative contribution of various N compounds to total inorganic N between the no-fire emission and fire emission periods. While in the absence of fires NO and NO₂ dominated, their relative contribution during the fires was ~2 fold smaller, mainly due to increased NH₃, NH₄⁺ and NO₃^-. Concentrations of HONO and HNO₃ also greatly increased during the fires, but their contribution to the total inorganic N pool was relatively small. Elevated NH₃ and HNO₃ concentrations affected large areas of northern Alberta during the Richardson Fire. While NH₃ and HNO₃ concentrations were not at levels considered toxic to plants, these gases contributed significantly to atmospheric N deposition. Generally, no significant changes in O₃ and SO₂ concentrations were detected and their ambient concentrations were below levels harmful to human health or sensitive vegetation.

Dicarboxylic acids, ω-oxocarboxylic acids, α-dicarbonyls, WSOC, OC, EC, and inorganic ions in wintertime size-segregated aerosols from central India: Sources and formation processes

The size distributions of aerosols can provide evidences for their sources and formation processes in the atmosphere. Size-segregated aerosols (9-sizes) were collected in urban site (Raipur: 21.2°N and 82.3°E) in central India during winter of 2012-2013. The samples were analyzed for dicarboxylic acids (C2-C12), ω-oxocarboxylic acids (ωC2-ωC9), pyruvic acid and α-dicarbonyls (C2-C3) as well as elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC) and inorganic ions. Diacids showed a predominance of oxalic acid (C2) followed by succinic and azelaic acid whereas ω-oxoacids exhibited a predominance of glyoxylic acid and glyoxal was more abundant than methylglyoxal in all the sizes. Diacids, ω-oxoacids and α-dicarbonyls showed bimodal size distribution with peaks in fine and coarse modes. High correlations of fine mode diacids and related compounds with potassium and levoglucosan suggest that they were presumably due to a substantial contribution of primary emission from biomass burning and secondary production from biomass burning derived precursors. High correlations of C2 with higher carbon number diacids (C3-C9) suggest that they have similar sources and C2 may be produced via the decay of its higher homologous diacids in fine mode. Considerable portions of diacids and related compounds in coarse mode suggest that they were associated with mineral dust particles by their adsorption and photooxidation of anthropogenic and biogenic precursors via heterogeneous reaction on dust surface. This study demonstrates that biomass burning and dust particles are two major factors to control the size distribution of diacids and related compounds in the urban aerosols from central India.