Burn pit-related smoke causes developmental and behavioral toxicity in zebrafish: Influence of material type and emissions chemistry

Combustion of mixed materials during open air burning of refuse or structural fires in the wildland urban interface produces emissions that worsen air quality, contaminate rivers and streams, and cause poor health outcomes including developmental effects. The zebrafish, a freshwater fish, is a useful model for quickly screening the toxicological and developmental effects of agents in such species and elicits biological responses that are often analogous and predictive of responses in mammals. The purpose of this study was to compare the developmental toxicity of smoke derived from the burning of 5 different burn pit-related material types (plywood, cardboard, plastic, a mixture of the three, and the mixture plus diesel fuel as an accelerant) in zebrafish larvae. Larvae were exposed to organic extracts of increasing concentrations of each smoke 6-to-8-hr post fertilization and assessed for morphological and behavioral toxicity at 5 days post fertilization. To examine chemical and biological determinants of toxicity, responses were related to emissions concentrations of polycyclic hydrocarbons (PAH). Emissions from plastic and the mixture containing plastic caused the most pronounced developmental effects, including mortality, impaired swim bladder inflation, pericardial edema, spinal curvature, tail kinks, and/or craniofacial deformities, although all extracts caused concentration-dependent effects. Plywood, by contrast, altered locomotor responsiveness to light changes to the greatest extent. Some morphological and behavioral responses correlated strongly with smoke extract levels of PAHs including 9-fluorenone. Overall, the findings suggest that material type and emissions chemistry impact the severity of zebrafish developmental toxicity responses to burn pit-related smoke.

Monitoring redox stress in human airway epithelial cells exposed to woodsmoke at an air-liquid interface

Wildland fires contribute significantly to the ambient air pollution burden worldwide, causing a range of adverse health effects in exposed populations. The toxicity of woodsmoke, a complex mixture of gases, volatile organic compounds, and particulate matter, is commonly studied in vitro using isolated exposures of conventionally cultured lung cells to either resuspended particulate matter or organic solvent extracts of smoke, leading to incomplete toxicity evaluations. This study aimed to improve our understanding of the effects of woodsmoke inhalation by building an advanced in vitro exposure system that emulates human exposure of the airway epithelium. We report the development and characterization of an innovative system that permits live-cell monitoring of the intracellular redox status of differentiated primary human bronchial epithelial cells cultured at an air-liquid interface (pHBEC-ALI) as they are exposed to unfractionated woodsmoke generated in a tube furnace in real time. pHBEC-ALI exposed to freshly generated woodsmoke showed oxidative changes that were dose-dependent and reversible, and not attributable to carbon monoxide exposure. These findings show the utility of this novel system for studying the molecular initiating events underlying woodsmoke-induced toxicity in a physiologically relevant in vitro model, and its potential to provide biological plausibility for risk assessment and public health measures.

Chemistry, lung toxicity and mutagenicity of burn pit smoke-related particulate matter

BACKGROUND

Open burning of anthropogenic sources can release hazardous emissions and has been associated with increased prevalence of cardiopulmonary health outcomes. Exposure to smoke emitted from burn pits in military bases has been linked with respiratory illness among military and civilian personnel returning from war zones. Although the composition of the materials being burned is well studied, the resulting chemistry and potential toxicity of the emissions are not.

METHODS

Smoke emission condensates from either flaming or smoldering combustion of five different types of burn pit-related waste: cardboard; plywood; plastic; mixture; and mixture/diesel, were obtained from a laboratory-scale furnace coupled to a multistage cryotrap system. The primary emissions and smoke condensates were analyzed for a standardized suite of chemical species, and the condensates were studied for pulmonary toxicity in female CD-1 mice and mutagenic activity in Salmonella (Ames) mutagenicity assay using the frameshift strain TA98 and the base-substitution strain TA100 with and without metabolic activation (S9 from rat liver).

RESULTS

Most of the particles in the smoke emitted from flaming and smoldering combustion were less than 2.5 µm in diameter. Burning of plastic containing wastes (plastic, mixture, or mixture/diesel) emitted larger amounts of particulate matter (PM) compared to other types of waste. On an equal mass basis, the smoke PM from flaming combustion of plastic containing wastes caused more inflammation and lung injury and was more mutagenic than other samples, and the biological responses were associated with elevated polycyclic aromatic hydrocarbon levels.

CONCLUSIONS

This study suggests that adverse health effects of burn pit smoke exposure vary depending on waste type and combustion temperature; however, burning plastic at high temperature was the most significant contributor to the toxicity outcomes. These findings will provide a better understanding of the complex chemical and combustion temperature factors that determine toxicity of burn pit smoke and its potential health risks at military bases.

Cookstove Emissions and Performance Evaluation Using a New ISO Protocol and Comparison of Results with Previous Test Protocols

In 2018, the International Organization for Standardization (ISO) 19867-1 "Harmonized laboratory test protocols" were released for establishing improved quality and comparability for data on cookstove air pollutant emissions, efficiency, safety, and durability. This is the first study that compares emissions [carbon dioxide, carbon monoxide, total hydrocarbons, methane, nitrogen oxides, fine particulate matter (PM_2.5), organic carbon, elemental carbon, and ultrafine particles] and efficiency data between the ISO protocol and the Water Boiling Test (WBT). The study examines six stove/fuel combinations [liquefied petroleum gas (LPG), pellet, wood fan, wood rocket, three stone fire, and charcoal] tested in the same US EPA laboratory. Evaluation of the ISO protocol shows improvements over previous test protocols and that results are relatively consistent with former WBT data in terms of tier ratings for emissions and efficiency, as defined by the ISO 19867-3 "Voluntary Performance Targets." Most stove types remain similarly ranked using ISO and WBT protocols, except charcoal and LPG are in higher PM_2.5 tiers with the ISO protocol. Additionally, emissions data including polycyclic aromatic hydrocarbons are utilized to compare between the ISO and Firepower Sweep Test (FST) protocols. Compared to the FST, the ISO protocol results in generally higher PM_2.5 tier ratings.

Zebrafish irritant responses to wildland fire-related biomass smoke are influenced by fuel type, combustion phase, and byproduct chemistry

Human exposure to wildfire-derived particulate matter (PM) is linked to adverse health outcomes; however, little is known regarding the influence of biomass fuel type and burn conditions on toxicity. The aim of this study was to assess the irritant potential of extractable organic material (EOM) of biomass smoke condensates from five fuels (eucalyptus, pine, pine needle, peat, or red oak), representing various fire-prone regions of the USA, burned at two temperatures each [flaming (approximately 640°C) or (smoldering approximately 500°C)] using a locomotor assay in zebrafish (Danio rerio) larvae. It was postulated that locomotor responses, as measures of irritant effects, might be dependent upon fuel type and burn conditions and that these differences relate to combustion byproduct chemistry. To test this, locomotor activity was tracked for 60 min in 6-day-old zebrafish larvae (25-32/group) immediately after exposure to 0.4% dimethyl sulfoxide (DMSO) vehicle or EOM from the biomass smoke condensates (0.3-30 µg EOM/ml; half-log intervals). All EOM samples produced concentration-dependent irritant responses. Linear regression analysis to derive rank-order potency indicated that on a µg PM basis, flaming pine and eucalyptus were the most irritating. In contrast, on an emission-factor basis, which normalizes responses to the amount of PM produced/kg of fuel burned, smoldering smoke condensates induced greater irritant responses (>100-fold) than flaming smoke condensates, with smoldering pine being the most potent. Importantly, irritant responses significantly correlated with polycyclic aromatic hydrocarbon (PAH) content, but not with organic carbon or methoxyphenols. Data indicate that fuel type and burn condition influence the quantity and chemical composition of PM as well as toxicity.

Censoring Trace-Level Environmental Data: Statistical Analysis Considerations to Limit Bias

Trace-level environmental data typically include values near or below detection and quantitation thresholds where health effects may result from low-concentration exposures to one chemical over time or to multiple chemicals. In a cook stove case study, bias in dibenzo[a,h]anthracene concentration means and standard deviations (SDs) was assessed following censoring at thresholds for selected analysis approaches: substituting threshold/2, maximum likelihood estimation, robust regression on order statistics, Kaplan-Meier, and omitting censored observations. Means and SDs for gas chromatography-mass spectrometry-determined concentrations were calculated after censoring at detection and calibration thresholds, 17% and 55% of the data, respectively. Threshold/2 substitution was the least biased. Measurement values were subsequently simulated from two log-normal distributions at two sample sizes. Means and SDs were calculated for 30%, 50%, and 80% censoring levels and compared to known distribution counterparts. Simulation results illustrated (1) threshold/2 substitution to be inferior to modern after-censoring statistical approaches and (2) all after-censoring approaches to be inferior to including all measurement data in analysis. Additionally, differences in stove-specific group means were tested for uncensored samples and after censoring. Group differences of means tests varied depending on censoring and distributional decisions. Investigators should guard against censoring-related bias from (explicit or implicit) distributional and analysis approach decisions.

Chemical composition, structures, and light absorption of N-containing aromatic compounds emitted from burning wood and charcoal in household cookstoves

N-containing aromatic compounds (NACs) are an important group of light-absorbing molecules in the atmosphere. They are often observed in combustion emissions, but their chemical formulas and structural characteristics remain uncertain. In this study, red oak wood and charcoal fuels were burned in cookstoves using the standard water boiling test (WBT) procedure. Submicron aerosol particles in the cookstove emissions were collected using quartz (Q _f ) and polytetrafluoroethylene (PTFE) filter membranes positioned in parallel. A back-up quartz filter (Q _b ) was also installed downstream of the PTFE filter to evaluate the effect of sampling artifact on NACs measurements. Liquid chromatography-mass spectroscopy (LC-MS) techniques identified seventeen NAC chemical formulas in the cookstove emissions. The average concentrations of total NACs in Q _b samples (0.37 ± 0.31 - 1.79 ± 0.77 μg m^-3) were greater than 50% of those observed in the Q _f samples (0.51 ± 0.43 - 3.91 ± 2.06 μg m^-3), and the Q _b to Q _f mass ratios of individual NACs had a range of 0.02 - 2.71, indicating that the identified NACs might have substantial fractions remaining in the gas-phase. In comparison to other sources, cookstove emissions from red oak or charcoal fuels did not exhibit unique NAC structural features, but had distinct NACs composition. However, before identifying NACs sources by combining their structural and compositional information, the gas-particle partitioning behaviors of NACs should be further investigated. The average contributions of total NACs to the light absorption of organic matter at λ = 365 nm (1.10 - 2.57%) in Q _f and Q _b samples (10.7 - 21.0%) are up to 10 times larger than their mass contributions (Q _f 0.31 - 1.01%, Q _b 1.08 - 3.31%), so the identified NACs are mostly strong light absorbers. To explain more sample extracts absorption, future research is needed to understand the chemical and optical properties of high molecular weight (e.g., MW > 500 Da) entities in particulate matter.

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.

The role of fuel type and combustion phase on the toxicity of biomass smoke following inhalation exposure in mice

The characteristics of wildland fire smoke exposures which initiate or exacerbate cardiopulmonary conditions are unclear. We previously reported that, on a mass basis, lung toxicity associated with particulate matter (PM) from flaming smoke aspirated into mouse lungs is greater than smoldering PM. In this study, we developed a computer-controlled inhalation system which can precisely control complex biomass smoke emissions from different combustion conditions. This system was used to examine the toxicity of inhaled biomass smoke from peat, eucalyptus, and oak fuels generated under smoldering and flaming phases with emissions set to the same approximate concentration of carbon monoxide (CO) for each exposure (60-110 ppm), resulting in PM levels of ~ 4 mg/m³ for flaming and ~ 40 mg/m³ for smoldering conditions. Mice were exposed by inhalation 1 h/day for 2 days, and assessed for lung toxicity at 4 and 24 h after the final exposure. Peat (flaming and smoldering) and eucalyptus (smoldering) smoke elicited significant inflammation (neutrophil influx) in mouse lungs at 4 h with the peat (flaming) smoke causing even greater lung inflammation at 24-h post-exposure. A significant alteration in ventilatory timing was also observed in mice exposed to the peat (flaming) and eucalyptus (flaming and smoldering) smoke immediately after each day of exposure. No responses were seen for exposures to similar concentrations of flaming or smoldering oak smoke. The lung toxicity potencies (neutrophil influx per PM mass) agreed well between the inhalation and previously reported aspiration studies, demonstrating that although flaming smoke contains much less PM mass than smoldering smoke, it is more toxic on a mass basis than smoldering smoke exposure, and that fuel type is also a controlling factor.

High-Throughput Video Processing of Heart Rate Responses in Multiple Wild-type Embryonic Zebrafish per Imaging Field

Heart rate assays in wild-type zebrafish embryos have been limited to analysis of one embryo per video/imaging field. Here we present for the first time a platform for high-throughput derivation of heart rate from multiple zebrafish (Danio rerio) embryos per imaging field, which is capable of quickly processing thousands of videos and ideal for multi-well platforms with multiple fish/well. This approach relies on use of 2-day post fertilization wild-type embryos, and uses only bright-field imaging, circumventing requirement for anesthesia or restraint, costly software/hardware, or fluorescently-labeled animals. Our original scripts (1) locate the heart and record pixel intensity fluctuations generated by each cardiac cycle using a robust image processing routine, and (2) process intensity data to derive heart rate. To demonstrate assay utility, we exposed embryos to the drugs epinephrine and clonidine, which increased or decreased heart rate, respectively. Exposure to organic extracts of air pollution-derived particulate matter, including diesel or biodiesel exhausts, or wood smoke, all complex environmental mixtures, decreased heart rate to varying degrees. Comparison against an established lower-throughput method indicated robust assay fidelity. As all code and executable files are publicly available, this approach may expedite cardiotoxicity screening of compounds as diverse as small molecule drugs and complex chemical mixtures.

Light absorption of organic carbon and its sources at a southeastern U.S. location in summer

Light-absorbing organic carbon (OC), also referred to as "brown carbon" (BrC), has been intensively investigated in atmospheres impacted by biomass burning. However, other BrC sources (e.g., secondary formation in the atmosphere) are rarely studied in ambient aerosols. In the current work, forty-five PM_2.5 filter samples were collected in Research Triangle Park (RTP), NC, USA from June 1st to July 15th, 2013. The bulk carbonaceous components, including OC, elemental carbon (EC), water soluble OC (WSOC), and an array of organic molecular markers were measured; an ultraviolet/visible spectrometer was used to measure the light absorption of methanol extractable OC and WSOC. The average light absorption per OC and WSOC mass of PM_2.5 samples in summer RTP are 0.36 ± 0.16 m² gC^-1 and 0.29 ± 0.13 m² gC^-1, respectively, lower than the ambient aerosol samples impacted by biomass burning and/or fossil fuel combustion (0.7-1.6 m² gC^-1) from other places. Less than 1% of the aqueous extracts absorption is attributed to the light-absorbing chromophores (nitroaromatic compounds) identified in this work. To identify the major sources of BrC absorption in RTP in the summer, Positive Matrix Factorization (PMF) was applied to a dataset containing optical properties and chemical compositions of carbonaceous components in PM_2.5. The results suggest that the formation of biogenic secondary organic aerosol (SOA) containing organosulfates is an important BrC source, contributing up to half of the BrC absorption in RTP during the summertime.

Composition and light absorption of N-containing aromatic compounds in organic aerosols from laboratory biomass burning

This study seeks to understand the compositional details of N-containing aromatic compounds (NACs) emitted during biomass burning (BB) and their contribution to light-absorbing organic carbon (OC), also termed brown carbon (BrC). Three laboratory BB experiments were conducted with two U.S. pine forest understory fuels typical of those consumed during prescribed fires. During the experiments, submicron aerosol particles were collected on filter media and subsequently extracted with methanol and examined for their optical and chemical properties. Significant correlations (p < 0.05) were observed between BrC absorption and elemental carbon (EC)/OC ratios for individual burns data. However, the pooled experimental data indicated that the BB BrC absorption depends on more than the BB fire conditions as represented by the EC/OC ratio. Fourteen NAC formulas were identified in the BB samples, most of which were also observed in simulated secondary organic aerosol (SOA) from photo-oxidation of aromatic VOCs with NO_X. However, the molecular structures associated with the identical NAC formula from BB and SOA are different. In this work, the identified NACs from BB are featured by methoxy and cyanate groups, and are predominately generated during the flaming phase. The mass concentrations of identified NACs were quantified using authentic and surrogate standards, and their contributions to bulk light absorption of solvent extractable OC were also calculated. The contributions of identified NACs to organic matter (OM) and BrC absorption were significantly higher in flaming-phase samples than those in smoldering-phase samples, and correlated with EC/OC ratio (p < 0.05) for both individual burns and pooled experimental data, indicating that the formation of NACs from BB largely depends on burn conditions. The average contributions of identified NACs to overall BrC absorption at 365 nm ranged from 0.087 ± 0.024 to 1.22 ± 0.54%, 3 - 10 times higher than their mass contributions to OM (0.023 ± 0.0089 to 0.18 ± 0.067%), so the NACs with light absorption identified in this work from BB are likely strong BrC chromophores. Further studies are warranted to identify more light-absorbing compounds to explain the unknown fraction (> 98%) of BB BrC absorption.

Light absorption of organic carbon emitted from burning wood, charcoal, and kerosene in household cookstoves

Household cookstove emissions are an important source of carbonaceous aerosols globally. The light-absorbing organic carbon (OC), also termed brown carbon (BrC), from cookstove emissions can impact the Earth's radiative balance, but is rarely investigated. In this work, PM_2.5 filter samples were collected during combustion experiments with red oak wood, charcoal, and kerosene in a variety of cookstoves mainly at two water boiling test phases (cold start CS, hot start HS). Samples were extracted in methanol and extracts were examined using spectrophotometry. The mass absorption coefficients (MAC_λ, m² g^-1) at five wavelengths (365, 400, 450, 500, and 550 nm) were mostly inter-correlated and were used as a measurement proxy for BrC. The MAC₃₆₅ for red oak combustion during the CS phase correlated strongly to the elemental carbon (EC)/OC mass ratio, indicating a dependency of BrC absorption on burn conditions. The emissions from cookstoves burning red oak have an average MAC_λ 2-6 times greater than those burning charcoal and kerosene, and around 3-4 times greater than that from biomass burning measured in previous studies. These results suggest that residential cookstove emissions could contribute largely to ambient BrC, and the simulation of BrC radiative forcing in climate models for biofuel combustion in cookstoves should be treated specifically and separated from open biomass burning.

Characterization of organic nitrogen in aerosols at a forest site in the southern Appalachian Mountains

This study investigates the composition of organic particulate matter in PM2.5 in a remote montane forest in the southeastern US, focusing on the role of organic nitrogen (N) in sulfur-containing secondary organic aerosol (nitrooxy-organosulfates) and aerosols associated with biomass burning (nitro-aromatics). Bulk water-soluble organic N (WSON) represented ~ 14% w/w of water-soluble total N (WSTN) in PM2.5 on average across seasonal measurement campaigns conducted in the spring, summer, and fall of 2015. The largest contributions of WSON to WSTN were observed in spring (~ 18% w/w) and the lowest in the fall (~ 10% w/w). On average, identified nitro-aromatic and nitrooxy-organosulfate compounds accounted for a small fraction of WSON, ranging from ~ 1% in spring to ~ 4% in fall, though were observed to contribute as much as 28% w/w of WSON in individual samples that were impacted by local biomass burning. The highest concentrations of oxidized organic N species occurred during summer (average of 0.65 ng N m-3) along with a greater relative abundance of higher-generation oxygenated terpenoic acids, indicating an association with more aged aerosol. The highest concentrations of nitro-aromatics (e.g., nitrocatechol and methyl-nitrocatechol), levoglucosan, and aged SOA tracers were observed during fall, associated with aged biomass burning plumes. Nighttime nitrate radical chemistry is the most likely formation pathway for nitrooxy-organosulfates observed at this low NO x site (generally < 1 ppb). Isoprene-derived organosulfate (MW216, 2-methyltetrol derived), which is formed from isoprene epoxydiols (IEPOX) under low NO x conditions, was the most abundant individual organosulfate. Concentration-weighted average WSON / WSOC ratios for nitro-aromatics + organosulfates + terpenoic acids were 1 order of magnitude lower than the overall aerosol WSON / WSOC ratio, indicating the presence of other uncharacterized higher-N-content species. Although nitrooxy-organosulfates and nitro-aromatics contributed a small fraction of WSON, our results provide new insight into the atmospheric formation processes and sources of these largely uncharacterized components of atmospheric organic N, which also helps to advance the atmospheric models to better understand the chemistry and deposition of reactive N.

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.

Evaluating the Performance of Household Liquefied Petroleum Gas Cookstoves

Liquefied petroleum gas (LPG) cookstoves are considered to be an important solution for mitigating household air pollution; however, their performance has rarely been evaluated. To fill the data and knowledge gaps in this important area, 89 laboratory tests were conducted to quantify efficiencies and pollutant emissions from five commercially available household LPG stoves under different burning conditions. The mean thermal efficiency (±standard deviation) for the tested LPG cookstoves was 51 ± 6%, meeting guidelines for the highest tier level (Tier 4) under the International Organization for Standardization, International Workshop Agreement 11. Emission factors of CO₂, CO, THC, CH₄, and NO_x on the basis of useful energy delivered (MJ_d) were 142 ± 17, 0.77 ± 0.55, 130 ± 196, 5.6 ± 8.2, and 46 ± 9 mg/MJ_d, respectively. Approximately 90% of the PM_2.5 data were below the detection limit, corresponding to an emission rate below 0.11 mg/min. For those data above the detection limit, the average emission factor was 2.4 ± 1.6 mg/MJ_d, with a mean emission rate of 0.20 ± 0.16 mg/min. Under the specified gas pressure (2.8 kPa), but with the burner control set to minimum air flow rate, less complete combustion resulted in a visually yellow flame, and CO, PM_2.5, EC, and BC emissions all increased. LPG cookstoves met guidelines for Tier 4 for both CO and PM_2.5 emissions and mostly met the World Health Organization Emission Rate Targets set to protect human health.

Light Absorption of Secondary Organic Aerosol: Composition and Contribution of Nitroaromatic Compounds

Secondary organic aerosol (SOA) can affect the atmospheric radiation balance through absorbing light at shorter visible and UV wavelengths. However, the composition and optical properties of light-absorbing SOA is poorly understood. In this work, SOA filter samples were collected during individual chamber experiments conducted with three biogenic and eight aromatic volatile organic compound (VOC) precursors in the presence of NO_X and H₂O₂. Compared with the SOA generated using the aromatic precursors, biogenic SOA generally exhibits negligible light absorption above 350 nm; the aromatic SOA generated in the presence of NO_X shows stronger light absorption than that generated with H₂O₂. Fifteen nitroaromatic compound (NAC) chemical formulas were identified and quantified in SOA samples. Their contributions to the light absorption of sample extracts were also estimated. On average, the m-cresol/NO_X SOA sample has the highest mass contribution from NACs (10.4 ± 6.74%, w/w), followed by naphthalene/NO_X (6.41 ± 2.08%) and benzene/NO_X (5.81 ± 3.82%) SOA. The average contributions of NACs to total light absorption were at least two times greater than their average mass contributions at 365 and 400 nm, revealing the potential use of chromophoric NACs as brown carbon (BrC) tracers in source apportionment and air quality modeling studies.

Temperature and Driving Cycle Significantly Affect Carbonaceous Gas and Particle Matter Emissions from Diesel Trucks

The present study examines the effects of fuel [an ultralow sulfur diesel (ULSD) versus a 20% v/v soy-based biodiesel-80% v/v petroleum blend (B20)], temperature, load, vehicle, driving cycle, and active regeneration technology on gas- and particle-phase carbon emissions from light and medium heavy-duty diesel vehicles (L/MHDDV). The study is performed using chassis dynamometer facilities that support low-temperature operation (-6.7 °C versus 21.7 °C) and heavy loads up to 12 000 kg. Organic and elemental carbon (OC-EC) composition of aerosol particles is determined using a thermal-optical technique. Gas- and particle-phase semivolatile organic compound (SVOC) emissions collected using traditional filter and polyurethane foam sampling media are analyzed using advanced gas chromatograpy/mass spectrometry methods. Study-wide OC and EC emissions are 0.735 and 0.733 mg/km, on average. The emissions factors for diesel vehicles vary widely, and use of a catalyzed diesel particle filter (CDPF) device generally mutes the carbon particle emissions in the exhaust, which contains ~90% w/w gas-phase matter. Interestingly, replacing ULSD with B20 did not significantly influence SVOC emissions, for which sums range from 0.030 to 9.4 mg/km for the L/MHDDVs. However, both low temperature and vehicle cold-starts significantly increase SVOCs in the exhaust. Real-time particle measurements indicate vehicle regeneration technology did influence emissions, although regeneration effects went unresolved using bulk chemistry techniques. A multistudy comparison of the toxic particle-phase polycyclic aromatic hydrocarbons (PAHs; molecular weight (MW) ≥ 252 amu) in diesel exhaust indicates emission factors that span up to 8 orders of magnitude over the past several decades. This study observes conditions under which PAH compounds with MW ≥ 252 amu appear in diesel particles downstream of the CDPF and can even reach low-end concentrations reported earlier for much larger HDDVs with poorly controlled exhaust streams. This rare observation suggests that analysis of PAHs in particles emitted from modern L/MHDDVs may be more complex than recognized previously.

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%.

Mutagenicity and oxidative damage induced by an organic extract of the particulate emissions from a simulation of the deepwater horizon surface oil burns

Emissions from oil fires associated with the "Deepwater Horizon" explosion and oil discharge that began on April 20, 2010 in the Gulf of Mexico were analyzed chemically to only a limited extent at the time but were shown to induce oxidative damage in vitro and in mice. To extend this work, we burned oil floating on sea water and performed extensive chemical analyses of the emissions (Gullett et al., Marine Pollut Bull, in press, ). Here, we examine the ability of a dichloromethane extract of the particulate material with an aerodynamic size ≤ 2.5 µm (PM2.5 ) from those emissions to induce oxidative damage in human lung cells in vitro and mutagenicity in 6 strains of Salmonella. The extract had a percentage of extractable organic material (EOM) of 7.0% and increased expression of the heme oxygenase (HMOX1) gene in BEAS-2B cells after exposure for 4 hr at 20 µg of EOM/ml. However, the extract did not alter mitochondrial respiration rate as measured by extracellular flux analysis. The extract was most mutagenic in TA100 +S9, indicative of a role for polycyclic aromatic hydrocarbons (PAHs), reflective of the high concentrations of PAHs in the emissions (1 g/kg of oil consumed). The extract had a mutagenicity emission factor of 1.8 ± 0.1 × 105 revertants/megajoulethermal in TA98 +S9, which was greater than that of diesel exhaust and within an order of magnitude of open burning of wood and plastic. Thus, organics from PM2.5 of burning oil can induce oxidative responses in human airway epithelial cells and are highly mutagenic. Environ. Mol. Mutagen. 58:162-171, 2017. © 2017 Wiley Periodicals, Inc.

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.

Characterization of the particulate emissions from the BP Deepwater Horizon surface oil burns

Sampling of the smoke plumes from the BP Deepwater Horizon surface oil burns led to the unintentional collection of soot particles on the sail of an instrument-bearing, tethered aerostat. This first-ever plume sampling from oil burned at an actual spill provided an opportunistic sample from which to characterize the particles' chemical properties for polycyclic aromatic hydrocarbons (PAHs), organic carbon, elemental carbon, metals, and polychlorinated dibenzodioxins/dibenzofurans (PCDDs/PCDFs) and physical properties for size and nanostructure. Thermal-optical analyses indicated that the particulate matter was 93% carbon with 82% being refractory elemental carbon. PAHs accounted for roughly 68μg/g of the PM filter mass and 5mg/kg oil burned, much lower than earlier laboratory based studies. Microscopy indicated that the soot is distinct from more common soot by its aggregate size, primary particle size, and nanostructure. PM-bound metals were largely unremarkable but PCDD/PCDF formation was observed, contrary to other's findings. Levels of lighter PCDD/PCDF and PAH compounds were reduced compared to historical samples, possibly due to volatilization or photo-oxidation.

Effects of Cold Temperature and Ethanol Content on VOC Emissions from Light-Duty Gasoline Vehicles

Emissions of speciated volatile organic compounds (VOCs), including mobile source air toxics (MSATs), were measured in vehicle exhaust from three light-duty spark ignition vehicles operating on summer and winter grade gasoline (E0) and ethanol blended (E10 and E85) fuels. Vehicle testing was conducted using a three-phase LA92 driving cycle in a temperature-controlled chassis dynamometer at two ambient temperatures (-7 and 24 °C). The cold start driving phase and cold ambient temperature increased VOC and MSAT emissions up to several orders of magnitude compared to emissions during other vehicle operation phases and warm ambient temperature testing, respectively. As a result, calculated ozone formation potentials (OFPs) were 7 to 21 times greater for the cold starts during cold temperature tests than comparable warm temperature tests. The use of E85 fuel generally led to substantial reductions in hydrocarbons and increases in oxygenates such as ethanol and acetaldehyde compared to E0 and E10 fuels. However, at the same ambient temperature, the VOC emissions from the E0 and E10 fuels and OFPs from all fuels were not significantly different. Cold temperature effects on cold start MSAT emissions varied by individual MSAT compound, but were consistent over a range of modern spark ignition vehicles.

Cold temperature and biodiesel fuel effects on speciated emissions of volatile organic compounds from diesel trucks

Speciated volatile organic compounds (VOCs) were measured in diesel exhaust from three heavy-duty trucks equipped with modern aftertreatment technologies. Emissions testing was conducted on a chassis dynamometer at two ambient temperatures (-7 and 22 °C) operating on two fuels (ultra low sulfur diesel and 20% soy biodiesel blend) over three driving cycles: cold start, warm start and heavy-duty urban dynamometer driving cycle. VOCs were measured separately for each drive cycle. Carbonyls such as formaldehyde and acetaldehyde dominated VOC emissions, making up ∼ 72% of the sum of the speciated VOC emissions (∑VOCs) overall. Biodiesel use led to minor reductions in aromatics and variable changes in carbonyls. Cold temperature and cold start conditions caused dramatic enhancements in VOC emissions, mostly carbonyls, compared to the warmer temperature and other drive cycles, respectively. Different 2007+ aftertreatment technologies involving catalyst regeneration led to significant modifications of VOC emissions that were compound-specific and highly dependent on test conditions. A comparison of this work with emission rates from different diesel engines under various test conditions showed that these newer technologies resulted in lower emission rates of aromatic compounds. However, emissions of other toxic partial combustion products such as carbonyls were not reduced in the modern diesel vehicles tested.

Carbonaceous aerosols emitted from light-duty vehicles operating on gasoline and ethanol fuel blends

This study examines the chemical properties of carbonaceous aerosols emitted from three light-duty gasoline vehicles (LDVs) operating on gasoline (e0) and ethanol-gasoline fuel blends (e10 and e85). Vehicle road load simulations were performed on a chassis dynamometer using the three-phase LA-92 unified driving cycle (UDC). Effects of LDV operating conditions and ambient temperature (-7 and 24 °C) on particle-phase semivolatile organic compounds (SVOCs) and organic and elemental carbon (OC and EC) emissions were investigated. SVOC concentrations and OC and EC fractions were determined with thermal extraction-gas chromatography-mass spectrometry (TE-GC-MS) and thermal-optical analysis (TOA), respectively. LDV aerosol emissions were predominantly carbonaceous, and EC/PM (w/w) decreased linearly with increasing fuel ethanol content. TE-GC-MS analysis accounted for up to 4% of the fine particle (PM2.5) mass, showing the UDC phase-integrated sum of identified SVOC emissions ranging from 0.703 μg km(-1) to 18.8 μg km(-1). Generally, higher SVOC emissions were associated with low temperature (-7 °C) and engine ignition; mixed regression models suggest these emissions rate differences are significant. Use of e85 significantly reduced the emissions of lower molecular weight PAH. However, a reduction in higher molecular weight PAH entities in PM was not observed. Individual SVOC emissions from the Tier 2 LDVs and fuel technologies tested are substantially lower and distributed differently than those values populating the United States emissions inventories currently. Hence, this study is likely to influence future apportionment, climate, and air quality model predictions that rely on source combustion measurements of SVOCs in PM.

Pollutant emissions and energy efficiency under controlled conditions for household biomass cookstoves and implications for metrics useful in setting international test standards

Realistic metrics and methods for testing household biomass cookstoves are required to develop standards needed by international policy makers, donors, and investors. Application of consistent test practices allows emissions and energy efficiency performance to be benchmarked and enables meaningful comparisons among traditional and advanced stove types. In this study, 22 cookstoves burning six fuel types (wood, charcoal, pellets, corn cobs, rice hulls, and plant oil) at two fuel moisture levels were examined under laboratory-controlled operating conditions as outlined in the Water Boiling Test (WBT) protocol, Version 4. Pollutant emissions (carbon dioxide, carbon monoxide, methane, total hydrocarbons, and ultrafine particles) were continuously monitored. Fine particle mass was measured gravimetrically for each WBT phase. Additional measurements included cookstove power, energy efficiency, and fuel use. Emission factors are given on the basis of fuel energy, cooking energy, fuel mass, time, and cooking task or activity. The lowest PM(2.5) emissions were 74 mg MJ(delivered)(-1) from a technologically advanced cookstove compared with 700-1400 mg MJ(delivered)(-1) from the base-case open 3-stone cookfire. The highest thermal efficiency was 53% compared with 14-15% for the 3-stone cookfire. Based on these laboratory-controlled test results and observations, recommendations for developing potentially useful metrics for setting international standards are suggested.

Iron solubility related to particle sulfur content in source emission and ambient fine particles

The chemical factors influencing iron solubility (soluble iron/total iron) were investigated in source emission (e.g., biomass burning, coal fly ash, mineral dust, and mobile exhaust) and ambient (Atlanta, GA) fine particles (PM2.5). Chemical properties (speciation and mixing state) of iron-containing particles were characterized using X-ray absorption near edge structure (XANES) spectroscopy and micro-X-ray fluorescence measurements. Bulk iron solubility (soluble iron/total iron) of the samples was quantified by leaching experiments. Major differences were observed in iron solubility in source emission samples, ranging from low solubility (<1%, mineral dust and coal fly ash) up to 75% (mobile exhaust and biomass burning emissions). Differences in iron solubility did not correspond to silicon content or Fe(II) content. However, source emission and ambient samples with high iron solubility corresponded to the sulfur content observed in single particles. A similar correspondence between bulk iron solubility and bulk sulfate content in a series of Atlanta PM2.5 fine particle samples (N = 358) further supported this trend. In addition, results of linear combination fitting experiments show the presence of iron sulfates in several high iron solubility source emission and ambient PM2.5 samples. These results suggest that the sulfate content (related to the presence of iron sulfates and/or acid-processing mechanisms by H(2)SO(4)) of iron-containing particles is an important proxy for iron solubility.

Chemical characterization of the fine particle emissions from commercial aircraft engines during the Aircraft Particle Emissions eXperiment (APEX) 1 to 3

This paper addresses the need for detailed chemical information on the fine particulate matter (PM) generated by commercial aviation engines. The exhaust plumes of seven turbofan engine models were sampled as part of the three test campaigns of the Aircraft Particle Emissions eXperiment (APEX). In these experiments, continuous measurements of black carbon (BC) and particle surface-bound polycyclic aromatic compounds (PAHs) were conducted. In addition, time-integrated sampling was performed for bulk elemental composition, water-soluble ions, organic and elemental carbon (OC and EC), and trace semivolatile organic compounds (SVOCs). The continuous BC and PAH monitoring showed a characteristic U-shaped curve of the emission index (EI or mass of pollutant/mass of fuel burned) vs fuel flow for the turbofan engines tested. The time-integrated EIs for both elemental composition and water-soluble ions were heavily dominated by sulfur and SO(4)(2-), respectively, with a ∼2.4% median conversion of fuel S(IV) to particle S(VI). The corrected OC and EC emission indices obtained in this study ranged from 37 to 83 mg/kg and 21 to 275 mg/kg, respectively, with the EC/OC ratio ranging from ∼0.3 to 7 depending on engine type and test conditions. Finally, the particle SVOC EIs varied by as much as 2 orders of magnitude with distinct variations in chemical composition observed for different engine types and operating conditions.

Chemical characterization of the fine particle emissions from commercial aircraft engines during the Aircraft Particle Emissions eXperiment (APEX) 1 to 3

This paper addresses the need for detailed chemical information on the fine particulate matter (PM) generated by commercial aviation engines. The exhaust plumes of seven turbofan engine models were sampled as part of the three test campaigns of the Aircraft Particle Emissions eXperiment (APEX). In these experiments, continuous measurements of black carbon (BC) and particle surface-bound polycyclic aromatic compounds (PAHs) were conducted. In addition, time-integrated sampling was performed for bulk elemental composition, water-soluble ions, organic and elemental carbon (OC and EC), and trace semivolatile organic compounds (SVOCs). The continuous BC and PAH monitoring showed a characteristic U-shaped curve of the emission index (EI or mass of pollutant/mass of fuel burned) vs fuel flow for the turbofan engines tested. The time-integrated EIs for both elemental composition and water-soluble ions were heavily dominated by sulfur and SO(4)(2-), respectively, with a ∼2.4% median conversion of fuel S(IV) to particle S(VI). The corrected OC and EC emission indices obtained in this study ranged from 37 to 83 mg/kg and 21 to 275 mg/kg, respectively, with the EC/OC ratio ranging from ∼0.3 to 7 depending on engine type and test conditions. Finally, the particle SVOC EIs varied by as much as 2 orders of magnitude with distinct variations in chemical composition observed for different engine types and operating conditions.

Quantitative assessment of elemental carbon in the lungs of never smokers, cigarette smokers, and coal miners

Inhalation exposure to particulates such as cigarette smoke and coal dust is known to contribute to the development of chronic lung disease. The purpose of this study was to estimate the amount of elemental carbon (EC) deposits from autopsied lung samples from cigarette smokers, miners, and control subjects and explore the relationship between EC level, exposure history, and the extent of chronic lung disease. The samples comprised three subgroups representing never smokers (8), chronic cigarette smokers (26), and coal miners (6). Following the dissolution of lung tissue, the extracted EC residue was quantified using a thermal-optical transmission (TOT) carbon analyzer. Mean EC levels in the lungs of the control group were 56.68 ± 24.86 (SD) μg/g dry lung weight. Respective mean EC values in lung samples from the smokers and coal miners were 449.56 ± 320.3 μg/g and 6678.2 ± 6162 μg/g. These values were significantly higher than those obtained from the never-smoker group. EC levels in the lung and pack-years of cigarette smoking correlated significantly, as did EC levels and the severity of small airway disease. This study provides one of the first quantitative assessments of EC in human lungs from populations at high relative risk for the development of chronic lung disease.

Source apportionment of fine (PM1.8) and ultrafine (PM0.1) airborne particulate matter during a severe winter pollution episode

Size-resolved samples of airborne particulate matter (PM) collected during a severe winter pollution episode at three sites in the San Joaquin Valley of California were extracted with organic solvents and analyzed for detailed organic compounds using GC-MS. Six particle size fractions were characterized with diameter (Dp) < 1.8 microm; the smallest size fraction was 0.056 < Dp < 0.1 microm which accounts for the majority of the mass in the ultrafine (PM0.1) size range. Source profiles for ultrafine particles developed during previous studies were applied to the measurements at each sampling site to calculate source contributions to organic carbon (OC) and elemental carbon (EC) concentrations. Ultrafine EC concentrations ranged from 0.03 microg m(-3) during the daytime to 0.18 microg m(-3) during the nighttime. Gasoline fuel, diesel fuel, and lubricating oil combustion products accounted for the majority of the ultrafine EC concentrations, with relatively minor contributions from biomass combustion and meat cooking. Ultrafine OC concentrations ranged from 0.2 microg m(-3) during the daytime to 0.8 microg m(-3) during the nighttime. Wood combustion was found to be the largest source of ultrafine OC. Meat cooking was also identified as a significant potential source of PM0.1 mass but further study is required to verify the contributions from this source. Gasoline fuel, diesel fuel, and lubricating oil combustion products made minor contributions to PM0.1 OC mass. Total ultrafine particulate matter concentrations were dominated by contributions from wood combustion and meat cooking during the current study. Future inhalation exposure studies may wish to target these sources as potential causes of adverse health effects.

Physical and chemical characterization of residential oil boiler emissions

The toxicity of emissions from the combustion of home heating oil coupled with the regional proximity and seasonal use of residential oil boilers (ROB) is an important public health concern. Yet scant physical and chemical information about the emissions from this source is available for climate and air quality modeling and for improving our understanding of aerosol-related human health effects. The gas- and particle-phase emissions from an active ROB firing distillate fuel oil (commonly known as diesel fuel) were evaluated to address this deficiency. Ion chromatography of impactor samples showed that the ultrafine ROB aerosol emissions were approximately 45% (w/w) sulfate. Gas chromatography-mass spectrometry detected various n-alkanes at trace levels, sometimes in accumulation mode particles, and out of phase with the size distributions of aerosol mass and sulfate. The carbonaceous matter in the ROB aerosol was primarily light-adsorbing elemental carbon. Gas chromatography-atomic emission spectroscopy measured a previously unrecognized organosulfur compound group in the ROB aerosol emissions. High-resolution transmission electron microscopy of ROB soot indicated the presence of a highly ordered primary particle nanostructure embedded in larger aggregates. Organic gas emissions were measured using EPA Methods TO-15 and TO-11A. The ROB emitted volatile oxygenates (8 mg/(kg of oil burned)) and olefins (5 mg/(kg of oil burned)) mostly unrelated to the base fuel composition. In the final analysis, the ROB tested was a source of numerous hazardous air pollutants as defined in the Clean Air Act Amendments. Approximations conducted using emissions data from the ROB tests show relatively low contributions to a regional-level anthropogenic emissions inventory for volitile organic compounds, PM2.5, and SO2 mass.

The application of thermal methods for determining chemical composition of carbonaceous aerosols: a review

Thermal methods of various forms have been used to quantify carbonaceous materials. Thermal/optical carbon analysis provides measurements of organic and elemental carbon concentrations as well as fractions evolving at specific temperatures in ambient and source aerosols. Detection of thermally desorbed organic compounds with thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) identifies and quantifies over 100 individual organic compounds in particulate matter (PM) samples. The resulting mass spectra contain information that is consistent among, but different between, source emissions even in the absence of association with specific organic compounds. TD-GC/MS is a demonstrated alternative to solvent extraction for many organic compounds and can be applied to samples from existing networks. It is amenable to field-deployable instruments capable of measuring organic aerosol composition in near real-time. In this review, thermal stability of organic compounds is related to chemical structures, providing a basis for understanding thermochemical properties of carbonaceous aerosols. Recent advances in thermal methods applied to determine aerosol chemical compositions are summarized and their potential for uncovering aerosol chemistry are evaluated. Current limitations and future research needs of the thermal methods are included.

Validation Studies of Thermal Extraction-GC/MS Applied to Source Emissions Aerosols. 1. Semivolatile Analyte−Nonvolatile Matrix Interactions

In this work, we develop a novel validation approach for studying how nonvolatile aerosol matrixes of considerably different chemical composition potentially affect the thermal extraction (TE)-GC/MS quantification of a wide range of trace semivolatile organic markers. The nonvolatile matrixes of a set of source emissions aerosols are first operationally isolated by thermally clearing the aerosols of their native semivolatile organic matter. TE-GC/MS analysis is then performed in triplicate on matrixes refortified with multilevel organic compound standard suites. The spiking of empty thermal extraction tubes and blank quartz filters is introduced as experimental control and also allows for the calculation of method detection limits. For the vast majority of organic compounds fortifying the matrixes (e.g., the alkane, alkene, cycloalkane, sterane, and phthalate classes), the analytical bias observed was classified as either minor or nonexistent. Furthermore, compound recoveries were generally highly reproducible, demonstrating relative standard deviations of less than 20%. For a diesel engine exhaust sample, significant matrix effects for the six- and seven-ring polycyclic aromatic hydrocarbons (PAHs) are observed and ascribed to the high proportion of elemental carbon in the sample. Our results suggest that TE-GC/MS may underestimate inhalation exposures to PAHs (with 5 rings or more) in atmospheric aerosols replete with diesel engine exhaust (e.g., near roadways or in polluted urban air). Due to its stability and representativeness, the use of a thermally cleared particulate matter matrix for validation purposes is probably expandable to additional sample pretreatment and instrumental techniques also being applied to quantify organic molecular markers in source and atmospheric aerosols.

A Modified Multisite Stern−Volmer Equation for the Determination of Conditional Stability Constants and Ligand Concentrations of Soil Fulvic Acid with Metal Ions

In this work, we modify the multisite Stern-Volmer (MSV) equation for fitting fluorescence titration curves. Under the condition of a static quenching mechanism, the MSV postulates an underlying 1:1 fulvic acid (FA)/copper coordination ratio at multisites. Approximates of six fitting parameters characterize the stability constants (K1 and K2) of FA ligands with Cu2+, micromolar ligand site concentrations (CL1 and CL2), the unquenched, steady-state fractional fluorescence contributions (fx), and the residual fluorescence intensity (IRES). Prior to its application to actual FA titration data, the MSV function is simulated, and its predictive ability is confirmed by titrating a mixture of model fluorophores, glycyl-L-tryptophan and L-tryptophan with Cu2+ at pH 6. Molecular fluorescence measurements of FA are acquired at a fixed spectral position (lambda(ex) = 335 nm; lambda(em) = 450 nm), and FA is titrated with copper in triplicate at three pH values-5, 6, and 7. An objective analysis of log K(1) and K(2) values supports several site organization schemes, including (i) subtle, cooperative interaction, (ii) interfering molecular conformations, and (iii) aggregate forms. Site densities (CL1 and CL2) are consistent across varied pH. The f(1) is indicative of a pH-induced spectral shift of a fluorophore and convincingly associates with a transect in the Deltalambda = 25 synchronous fluorescence spectrum and with the preexponential terms describing the time-dependent fluorescence decay. The MSV and its parent one-site version are equivalent for data fitting but are only simple approximations of a FA ligand system with more complex molecular fundamentals.

PCDD/F, PCB, HxCBz, PAH, and PM emission factors for fireplace and woodstove combustion in the San Francisco Bay region

Emissions from residential fireplace and woodstove appliances burning fuels available from the San Francisco Bay area were sampled for polychlorinated dibenzodioxins and dibenzofurans (PCDDs/Fs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HxCBz), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs, and the monosaccharide levoglucosan. Emission factors for these pollutants were determined, the first known characterization of this extent. Common California natural firewoods and manufactured artificial logs were tested under operating conditions intended to reflect domestic use patterns in the Bay area, which are primarily episodic burning for aesthetic reasons. Emission factors were determined by fuel type, fuel weight, mass emission rates, and energy output, highlighting differences between fuel and combustion facility type. Average PCDD/F emissions factors ranged from 0.25 to 1.4 ng toxic equivalency (TEQ)/kg of wood burned for natural wood fuels and 2.4 ng TEQ/kg for artificial logs. The natural wood emission factors are slightly lower than those which had been estimated for the U.S. inventory. Background-corrected PCBs emitted from woodstove/oak combustion (8370 ng/kg) are 3 orders of magnitude higher in mass than total PCDDs/Fs; however, their toxicity (0.014 ng TEQ/kg) is significantly lower. HxCBz emission factors varied from 13 to 990 ng/kg and were likely fuel- and appliance-specific. Relative PAH concentrations of particle-phase compounds and emission factors were consistent with others' findings. A total of 32 PAH compounds, ranging in concentration from 0.06 to 7 mg/kg, amounted to between 0.12 and 0.38% of the PM mass, depending on the wood and facility type. Preliminary analyses suggest relationships between wood combustion markers and PCDD/F levels.

Multi-wavelength fluorescence-quenching model for determination of Cu2+ conditional stability constants and ligand concentrations of fulvic acid

In this work, a multi-wavelength model (MWM) is developed. It uses fluorescence bands in the fulvic acid (FA) spectrum that quench upon binding of inorganic Cu2+ to FA. Quenching data at pH values of 5, 6, and 7 are placed in sets, containing fluorescence measures at select wavelengths versus added copper (CM). Intensity data of wavelength set 1 are obtained from 25 nm constant offset synchronous fluorescence spectra (SyF), in which are observed distinct peaks (lambda(ex) = 415 nm, lambda(em) = 440 nm; and lambda(ex) = 471 nm, lambda(em) = 496 nm). Wavelength set 2 intensity data are obtained from the FA fluorescence excitation and emission maxima (lambda(ex) = 335 nm, lambda(em) = 450 nm; and X(ex) = 471 nm, lambda(em) = 496 nm). Application of MWM shows that the multi-wavelength data sets characterize ligands of different binding strength (log K(x)) and concentration (C(Lx)). Corresponding to pH values of 5, 6, and 7, mean and standard deviation values for wavelength set 1 are log K(415/440) = 4.66 (0.12), 5.03 (0.12), and 5.05 (0.08), log K(471/496) = 4.93 (0.06), 5.27 (0.11), and 5.39 (0.09), C(415/440) = 3.1 (1.5), 10.9 (4.5), and 7.9 (3.9) microM, C(471/496) = 14.3 (3.0), 1.7 (0.6), and 1.4 (0.5) microM. And for wavelength set 2, log K(335/450) = 4.50 (0.03), 4.96 (0.27), and 5.22 (0.08), log K(471/496) = 5.02 (0.04), 5.42 (0.32), and 5.71 (0.09), C(335/450) = 8.8 (0.5), 21.9 (7.9), and 18.7 (0.3) microM, C(471/496) = 21.0 (2.5), 7.17 (1.2), and 7.09 (0.3) micrpM. The ability of the 415/440 nm SyF transect to characterize the main excitation and emission maximum of FA at 335/440 nm is evaluated. Relatively low concentration values returned by the model for this transect (415/440 nm) suggest that it is not entirely illustrative of the maximum. The model predictive capability is verified at pH 6 with two fluorescing Cu2+ chelating organic compounds, L-tyrosine and salicylic acid. This test confirms that the model is capable of providing good estimates of equilibrium binding parameters from multi-wavelength measurements of a mixed ligand system.

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

Fine particle matter with aerodynamic diameter <2.5 microm (PM2.5) and gas-phase emissions from open burning of six fine (foliar) fuels common to fire-prone U.S. ecosystems are investigated. PM2.5 distribution is unimodal within the 10-450 nm range, indicative of an accumulation mode. Smoldering relative to flaming combustion shows smaller particle number density per unit time and median size. Over 100 individual organic compounds in the primarily carbonaceous (>70% by mass) PM2.5 are chemically speciated by gas chromatography/mass spectrometry. Expressed as a percent of PM2.5 mass, emission ranges by organic compound class are as follows: n-alkane (0.1-2%), polycyclic aromatic hydrocarbon (PAH) (0.02-0.2%), n-alkanoic acid (1-3%), n-alkanedioic acid (0.06-0.3%), n-alkenoic acid (0.3-3%), resin acid (0.5-6%), triterpenoid (0.2-0.5%), methoxyphenol (0.5-3%), and phytosterol (0.2-0.6%). A molecular tracer of biomass combustion, the sugar levoglucosan is abundant and constitutes a remarkably narrow PM2.5 mass range (2.8-3.6%). Organic chemical signatures in PM2.5 from open combustion of fine fuels differ with those of residential wood combustion and other related sources, making them functional for source-receptor modeling of PM. Inorganic matter [PM2.5 - (organic compounds + elemental carbon)] on average is estimated to make up 8% of the PM2.5. Wavelength dispersive X-ray fluorescence spectroscopy and ion chromatography identify 3% of PM2.5 as elements and water-soluble ions, respectively. Compared with residential wood burning, the PM2.5 of fine fuel combustion is nitrate enriched but shows lower potassium levels. Gas-phase C2-C13 hydrocarbon and C2-C9 carbonyl emissions are speciated by respective EPA Methods T0-15 and T0-11A. They comprise mainly low molecular weight C2-C3 compounds and hazardous air pollutants (48 wt % of total quantified volatile organic carbon).

Anterograde coil closure of patent ductus arteriosus using a modified bioptome delivery technique

Three consecutive patients are presented who underwent successful anterograde catheter coil occlusion of a patent ductus arteriosus using a modified bioptome-assisted technique. Two of the three patients were infants and the procedures were performed without the need for arterial access.

New forceps delivery technique for coil occlusion of patent ductus arteriosus

We remain very enthusiastic about transcatheter coil occlusion of the PDA. However, surgical ligation has been performed successfully and with relatively low risk of complications. Therefore, an alternative nonsurgical technique must demonstrate comparable success and safety. We believe that this new forceps delivery technique has significant advantages over previously reported PDA coil occlusion techniques and should warrant further clinical investigation.