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Furans are a major class of volatile organic compounds emitted from biomass burning. Their high reactivity with atmospheric oxidants leads to the formation of secondary organic aerosol (SOA), including secondary brown carbon (BrC) that can affect global climate via interactions with solar radiation. Here, we investigate the optical properties and chemical composition of SOA generated via photooxidation of furfural, 2‐methylfuran, and 3‐methylfuran under dry (RH < 5%) and humid (RH ∼ 50%) conditions in the presence of nitrogen oxides (NO_x) and ammonium sulfate seed aerosol. Dry furfural oxidation has the greatest BrC formation, including reduced nitrogen‐containing organic compounds (NOCs) in SOA, which are dominated by amines and amides formed from reactions between carbonyls and ammonia/ammonium. Based on the products detected, we propose novel formation pathways of NOCs in furfural photooxidation, which can contribute to BrC via accretion reactions during the photochemical aging of biomass burning plumes.

 

Anthropogenic organic carbon emissions reporting has been largely limited to subsets of chemically speciated volatile organic compounds. However, new aircraft-based measurements revealed total gas-phase organic carbon emissions that exceed oil sands industry–reported values by 1900% to over 6300%, the bulk of which was due to unaccounted-for intermediate-volatility and semivolatile organic compounds. Measured facility-wide emissions represented approximately 1% of extracted petroleum, resulting in total organic carbon emissions equivalent to that from all other sources across Canada combined. These real-world observations demonstrate total organic carbon measurements as a means of detecting unknown or underreported carbon emissions regardless of chemical features. Because reporting gaps may include hazardous, reactive, or secondary air pollutants, fully constraining the impact of anthropogenic emissions necessitates routine, comprehensive total organic carbon monitoring as an inherent check on mass closure.

 

Volatile chemical products (VCPs) and other non-combustion-related sourceshave become important for urban air quality, and bottom-up calculationsreport emissions of a variety of functionalized compounds that remainunderstudied and uncertain in emissions estimates. Using a new instrumentalconfiguration, we present online measurements of oxygenated organiccompounds in a US megacity over a 10 d wintertime sampling period, whenbiogenic sources and photochemistry were less active. Measurements wereconducted at a rooftop observatory in upper Manhattan, New York City, USAusing a Vocus chemical ionization time-of-flight mass spectrometer, withammonium (NH4+) as the reagent ion operating at 1 Hz. The range ofobservations spanned volatile, intermediate-volatility, and semi-volatileorganic compounds, with targeted analyses of ∼150 ions, whoselikely assignments included a range of functionalized compound classes suchas glycols, glycol ethers, acetates, acids, alcohols, acrylates, esters,ethanolamines, and ketones that are found in various consumer, commercial,and industrial products. Their concentrations varied as a function of winddirection, with enhancements over the highly populated areas of the Bronx,Manhattan, and parts of New Jersey, and included abundant concentrations ofacetates, acrylates, ethylene glycol, and other commonly used oxygenatedcompounds. The results provide top-down constraints on wintertime emissionsof these oxygenated and functionalized compounds, with ratios to commonanthropogenic marker compounds and comparisons of their relative abundancesto two regionally resolved emissions inventories used in urban air qualitymodels.

 

Wildfire impacts on air quality and climate are expected to be exacerbatedby climate change with the most pronounced impacts in the boreal biome.Despite the large geographic coverage, there is limited information onboreal forest wildfire emissions, particularly for organic compounds, whichare critical inputs for air quality model predictions of downwind impacts.In this study, airborne measurements of 193 compounds from 15 instruments,including 173 non-methane organics compounds (NMOG), were used to providethe most detailed characterization, to date, of boreal forest wildfireemissions. Highly speciated measurements showed a large diversity ofchemical classes highlighting the complexity of emissions. Usingmeasurements of the total NMOG carbon (NMOGT), the ΣNMOG wasfound to be 50 % ± 3 % to 53 % ± 3 % of NMOGT, of which, theintermediate- and semi-volatile organic compounds (I/SVOCs) were estimatedto account for 7 % to 10 %. These estimates of I/SVOC emission factorsexpand the volatility range of NMOG typically reported. Despite extensivespeciation, a substantial portion of NMOGT remained unidentified(47 % ± 15 % to 50 % ± 15 %), with expected contributions from morehighly-functionalized VOCs and I/SVOCs. The emission factors derived in thisstudy improve wildfire chemical speciation profiles and are especiallyrelevant for air quality modelling of boreal forest wildfires. Theseaircraft-derived emission estimates were further linked with those derivedfrom satellite observations demonstrating their combined value in assessingvariability in modelled emissions. These results contribute to theverification and improvement of models that are essential for reliablepredictions of near-source and downwind pollution resulting from borealforest wildfires.

 

Thirdhand smoke (THS) persists in locations where smoking previously occurred and can be transported into non-smoking environments, leading to non-smoker exposure. Laboratory experiments using high-resolution mass spectrometry demonstrate that deposited particulate matter (PM) and smoke-exposed surrogate lung lining fluid (LLF) are substantial, chemically-complex reservoirs of gas-phase THS emissions, including hazardous air pollutants, polycyclic aromatic compounds, and nitrogen/oxygen-containing species. Both PM and LLF are persistent real-world THS reservoirs that chemically evolve over time, and can act as vehicles for the transport and emission of reactive pollutants and their reaction byproducts (e.g., acrolein). Deposited PM on clothes, furnishings, bodies, and/or airways will emit volatile to semi-volatile gases over long lifetimes, which can re-partition to other indoor materials and increase their overall persistence. On the other hand, LLF off-gassing consists predominantly of volatile organic compounds in amounts influenced by their aqueous solubilities, and their persistence in breath will be prolonged by re-distribution across internal aqueous reservoirs, as corroborated by multicompartment modeling in this study. 

Abstract. Nitrogen-containing organic compounds, which may be directly emitted into the atmosphere or which may form via reactions with prevalent reactive nitrogen species (e.g., NH3, NOx, NO3), have important but uncertaineffects on climate and human health. Using gas and liquid chromatographywith soft ionization and high-resolution mass spectrometry, we performed amolecular-level speciation of functionalized organic compounds at a coastal site on the Long Island Sound in summer (during the 2018 Long Island Sound Tropospheric Ozone Study – LISTOS – campaign) and winter. This region often experiences poor air quality due to theemissions of reactive anthropogenic, biogenic, and marine-derived compoundsand their chemical transformation products. We observed a range offunctionalized compounds containing oxygen, nitrogen, and/or sulfur atomsresulting from these direct emissions and chemical transformations,including photochemical and aqueous-phase processing that was more pronounced in summer and winter, respectively. In both summer and winter, nitrogen-containing organic aerosols dominated the observed distribution offunctionalized particle-phase species ionized by our analytical techniques,with 85 % and 68 % of total measured ion abundance containing a nitrogenatom, respectively. Nitrogen-containing particles included reduced nitrogen functional groups (e.g., amines, imines, azoles) and common NOz contributors (e.g., organonitrates). Reduced nitrogen functional groups observed in the particle phase were frequently paired with oxygen-containing groups elsewhere on the molecule, and their prevalence often rivaled that of oxidized nitrogen groups detected by our methods. Supplemental gas-phasemeasurements, collected on adsorptive samplers and analyzed with a novelliquid chromatography-based method, suggest that gas-phase reduced nitrogen compounds are possible contributing precursors to the observed nitrogen-containing particles. Altogether, this work highlights theprevalence of reduced nitrogen-containing compounds in the less-studied northeastern US and potentially in other regions with similar anthropogenic, biogenic, and marine source signatures. 

Abstract. Forest fires are major contributors of reactive gas- and particle-phaseorganic compounds to the atmosphere. We used offline high-resolution tandemmass spectrometry to perform a molecular-level speciation of gas- andparticle-phase compounds sampled via aircraft from an evolving boreal forestfire smoke plume in Saskatchewan, Canada. We observed diversemultifunctional compounds containing oxygen, nitrogen, and sulfur (CHONS),whose structures, formation, and impacts are understudied. Thedilution-corrected absolute ion abundance of particle-phase CHONS compoundsincreased with plume age by a factor of 6.4 over the first 4 h ofdownwind transport, and their relative contribution to the observedfunctionalized organic aerosol (OA) mixture increased from 19 % to 40 %.The dilution-corrected absolute ion abundance of particle-phase compoundswith sulfide functional groups increased by a factor of 13 with plume age,and their relative contribution to observed OA increased from 4 % to40 %. Sulfides were present in up to 75 % of CHONS compounds and theincreases in sulfides were accompanied by increases in ring-bound nitrogen;both increased together with CHONS prevalence. A complex mixture ofintermediate- and semi-volatile gas-phase organic sulfur species wasobserved in emissions from the fire and depleted downwind, representingpotential precursors to particle-phase CHONS compounds. These resultsdemonstrate CHONS formation from nitrogen- and oxygen-containing biomass burningemissions in the presence of reduced sulfur species. In addition, theyhighlight chemical pathways that may also be relevant in situations withelevated emissions of nitrogen- and sulfur-containing organic compounds fromresidential biomass burning and fossil fuel use (e.g., coal), respectively. 

Asphalt-based materials are abundant and a major nontraditional source of reactive organic compounds in urban areas, but their emissions are essentially absent from inventories. At typical temperature and solar conditions simulating different life cycle stages (i.e., storage, paving, and use), common road and roofing asphalts produced complex mixtures of organic compounds, including hazardous pollutants. Chemically speciated emission factors using high-resolution mass spectrometry reveal considerable oxygen and reduced sulfur content and the predominance of aromatic (~30%) and intermediate/semivolatile organic compounds (~85%), which together produce high overall secondary organic aerosol (SOA) yields. Emissions rose markedly with moderate solar exposure (e.g., 300% for road asphalt) with greater SOA yields and sustained SOA production. On urban scales, annual estimates of asphalt-related SOA precursor emissions exceed those from motor vehicles and substantially increase existing estimates from noncombustion sources. Yet, their emissions and impacts will be concentrated during the hottest, sunniest periods with greater photochemical activity and SOA production.