Vera Samburova

Identification of water-soluble organic carbon in non-urban aerosols using ultrahigh-resolution FT-ICR mass spectrometry: organic anions

Water-soluble organic carbon (WSOC) is a complex mixture of thousands of organic compounds which may have significant influence on the climate-relevant properties of atmospheric aerosols. An improved understanding of the molecularcompositionofWSOCisneededtoevaluatetheeffectofaerosol compositionuponaerosolphysicalproperties. Inthiswork,ultrahigh-resolutionFouriertransform-ioncyclotronresonancemassspectrometry(FT-ICRMS)wasusedto characterise aerosol WSOC collected during the summer of 2010 at the Storm Peak Laboratory (3210m ASL) near Steamboat Springs, CO. Approximately 4000 molecular formulas were assigned in the mass range of 100-800Da after negative-ion electrospray ionisation and more than 50% of them contained nitrogen or sulfur. The double bond equivalents (DBEs) of the molecular formulas were inversely proportional to the O:C ratio, despite a relatively constant H:C ratio of ,1.5. Despite the range of DBE values, the elemental ratios and the high number of oxygen atoms per formula indicate that a majority of the compounds are aliphatic to olefinic in nature. These trends indicate significant non-oxidative accretion reaction pathways for the formation of high molecular weight WSOC components. In addition, a significant number of molecular formulas assigned in this work matched those previously identified as secondary organic aerosol components of monoterpene and sesquiterpene ozonolysis. Additional keywords: atmospheric organic matter, electrospray ionisation, FT-ICR MS, high-resolution MS, humic- like substances, nitrooxy organosulfates, organonitrates, organosulfates, secondary organic aerosol.

Polycyclic aromatic hydrocarbons in biomass-burning emissions and their contribution to light absorption and aerosol toxicity.

In recent years, brown carbon (BrC) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (UV) part of the solar spectrum. Emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (PAHs) were determined for combustion of five globally important fuels: Alaskan, Siberian, and Florida swamp peat, cheatgrass (Bromus tectorum), and ponderosa pine (Pinus ponderosa) needles. The emission factors of total analyzed PAHs were between 1.9±0.43.0±0.6 and 9.6±1.2-42.2±5.4mgPAHkg(-1)fuel for particle- and gas phase, respectively. Spectrophotometric analysis of the identified PAHs showed that perinaphthenone, methylpyrenes, and pyrene contributed the most to the total PAH light absorption with 17.2%, 3.3 to 10.5%, and 7.6% of the total particle-phase PAH absorptivity averaged over analyzed emissions from the fuels. In the gas phase, the top three PAH contributors to BrC were acenaphthylene (32.6%), anthracene (8.2%), and 2,4,5-trimethylnaphthalene (8.0%). Overall, the identified PAHs were responsible for 0.087-0.16% (0.13% on average) and 0.033-0.15% (0.11% on average) of the total light absorption by dichloromethane-acetone extracts of particle and gas emissions, respectively. Toxic equivalency factor (TEF) analysis of 16 PAHs prioritized by the United States Environmental Protection Agency (EPA) showed that benzo(a)pyrene contributed the most to the PAH carcinogenic potency of particle phase emissions (61.8-67.4% to the total carcinogenic potency of Σ16EPA PAHs), while naphthalene played the major role in carcinogenicity of the gas phase PAHs in the biomass-burning emission analyzed here (35.4-46.0% to the total carcinogenic potency of Σ16EPA PAHs). The 16 EPA-prioritized PAHs contributed only 22.1±6.2% to total particle and 23.4±11% to total gas phase PAH mass, thus toxic properties of biomass-burning PAH emissions are most likely underestimated.

Impact of emissions from natural gas production facilities on ambient air quality in the Barnett Shale area: A pilot study

Rapid and extensive development of shale gas resources in the Barnett Shale region of Texas in recent years has created concerns about potential environmental impacts on water and air quality. The purpose of this study was to provide a better understanding of the potential contributions of emissions from gas production operations to population exposure to air toxics in the Barnett Shale region. This goal was approached using a combination of chemical characterization of the volatile organic compound (VOC) emissions from active wells, saturation monitoring for gaseous and particulate pollutants in a residential community located near active gas/oil extraction and processing facilities, source apportionment of VOCs measured in the community using the Chemical Mass Balance (CMB) receptor model, and direct measurements of the pollutant gradient downwind of a gas well with high VOC emissions. Overall, the study results indicate that air quality impacts due to individual gas wells and compressor stations are not likely to be discernible beyond a distance of approximately 100 m in the downwind direction. However, source apportionment results indicate a significant contribution to regional VOCs from gas production sources, particularly for lower-molecular-weight alkanes (<C6). Although measured ambient VOC concentrations were well below health-based safe exposure levels, the existence of urban-level mean concentrations of benzene and other mobile source air toxics combined with soot to total carbon ratios that were high for an area with little residential or commercial development may be indicative of the impact of increased heavy-duty vehicle traffic related to gas production Implications Rapid and extensive development of shale gas resources in recent years has created concerns about potential environmental impacts on water and air quality. This study focused on directly measuring the ambient air pollutant levels occurring at residential properties located near natural gas extraction and processing facilities, and estimating the relative contributions from gas production and motor vehicle emissions to ambient VOC concentrations. Although only a small-scale case study, the results may be useful for guidance in planning future ambient air quality studies and human exposure estimates in areas of intensive shale gas production.

Do 16 Polycyclic Aromatic Hydrocarbons Represent PAH Air Toxicity

Estimation of carcinogenic potency based on analysis of 16 polycyclic aromatic hydrocarbons (PAHs) ranked by U.S. Environmental Protection Agency (EPA) is the most popular approach within scientific and environmental air quality management communities. The majority of PAH monitoring projects have been focused on particle-bound PAHs, ignoring the contribution of gas-phase PAHs to the toxicity of PAH mixtures in air samples. In this study, we analyzed the results of 13 projects in which 88 PAHs in both gas and particle phases were collected from different sources (biomass burning, mining operation, and vehicle emissions), as well as in urban air. The aim was to investigate whether 16 particle-bound U.S. EPA priority PAHs adequately represented health risks of inhalation exposure to atmospheric PAH mixtures. PAH concentrations were converted to benzo(a)pyrene-equivalent (BaPeq) toxicity using the toxic equivalency factor (TEF) approach. TEFs of PAH compounds for which such data is not available were estimated using TEFs of close isomers. Total BaPeq toxicities (∑88BaPeq) of gas- and particle-phase PAHs were compared with BaPeq toxicities calculated for the 16 particle-phase EPA PAH (∑16EPABaPeq). The results showed that 16 EPA particle-bound PAHs underrepresented the carcinogenic potency on average by 85.6% relative to the total (gas and particle) BaPeq toxicity of 88 PAHs. Gas-phase PAHs, like methylnaphthalenes, may contribute up to 30% of ∑88BaPeq. Accounting for other individual non-EPA PAHs (i.e., benzo(e)pyrene) and gas-phase PAHs (i.e., naphthalene, 1- and 2-methylnaphthalene) will make the risk assessment of PAH-containing air samples significantly more accurate.

Composition of water-soluble organic carbon in non-urban atmospheric aerosol collected at the Storm Peak Laboratory

Environmental context The organic fraction of atmospheric aerosols is a complex mixture of thousands of species, which play an important role in many atmospheric processes, such as absorbing and scattering solar radiation. We analysed the water-soluble organic fraction of ambient aerosol samples, and quantified over 45 carboxylic acids, sugars, sugar anhydrides and sugar alcohols. The presence of fairly high concentrations of sugars and sugar-alcohols suggests a significant biological input (e.g. pollen, fungi and bacteria) to the water-soluble organic fraction of non-urban aerosols. Abstract Water-soluble organic constituents of PM2.5 aerosol (particulate matter with an aerodynamic diameter ≤2.5µm) have not been well characterised so far. The goal of this work was to perform quantitative analysis of individual water-soluble organic species in aerosol samples collected in July of 2010 at the Storm Peak Laboratory (3210m above sea level) located in the Colorado Park Range (Steamboat Springs, CO, USA). Aqueous extracts were combined into six composites and analysed for organic carbon (OC), water-soluble organic carbon (WSOC), water-insoluble OC, inorganic ions, organic acids, lignin derivatives, sugar-alcohols, sugars and sugar-anhydrates. Analysis of higher molecular weight water-soluble organics was done using ultrahigh resolution mass spectrometry. Approximately 2400 positive and 4000 negative ions were detected and assigned to monoisotopic molecular formulae in the mass range of 100–800Da. The higher number of negative ions reflects a predominant presence of highly oxidised organic compounds. Individual identified organic species represented up to 30% of the water-soluble organic mass (WSOM). The WSOM fractions of the low molecular weight organic acids, sugars and sugar alcohols were 3–12%, 1.0–16% and 0.4–1.9%. Significant amounts of arabitol, mannitol and oxalic acid are most likely associated with airborne fungal spores and conidia that were observed on the filters using high resolution electron microscopy. Overall, higher concentrations of sugars (glucose, sucrose, fructose etc.) in comparison with biomass burning tracer levoglucosan indicate that a significant mass fraction of WSOC is related to airborne biological species.

Residential and Non-Residential Biomass Combustion: Impacts on Air Quality

Biomass combustion emissions contribute significant amounts of particulate matter (PM), inorganic species (e.g., CO, CO2, elements, and ions), and thousands of organic compounds to ambient air. Wood smoke emissions from residential fireplaces and woodstoves have been shown to be a major source of PM in a number of communities worldwide, especially in the residential neighborhoods where winters are long and firewood is available. Approximately a couple of billion people use biomass fuels for their energy needs. In addition, emissions from wildfires, prescribed fires, and agricultural burning are responsible for occasional severe episodes of air pollution. This article briefly reviews the main constituents of biomass burning emissions from these sources and outlines the differences between them. The impact of each kind of biomass burning on ambient air quality is discussed. The effect of biomass burning on human health and climate is also briefly discussed.

Evaluation of assumptions for estimating chemical light extinction at U.S. national parks

Studies were conducted at Great Smoky Mountains National Park (NP) (GRSM), Tennessee, Mount Rainier NP (MORA), Washington, and Acadia NP (ACAD), Maine, to evaluate assumptions used to estimate aerosol light extinction from chemical composition. The revised IMPROVE equation calculates light scattering from concentrations of PM2.5 sulfates, nitrates, organic carbon mass (OM), and soil. Organics are assumed to be nonhygroscopic. Organic carbon (OC) is converted to OM with a multiplier of 1.8. Experiments were conducted to evaluate assumptions on aerosol hydration state, the OM/OC ratio, OM hygroscopicity, and mass scattering efficiencies. Sulfates were neutralized by ammonium during winter at GRSM (W, winter) and at MORA during summer but were acidic at ACAD and GRSM (S, summer) during summer. Hygroscopic growth was mostly smooth and continuous, rarely exhibiting hysteresis. Deliquescence was not observed except infrequently during winter at GRSM (W). Water-soluble organic carbon (WSOC) was separated from bulk OC with solid-phase absorbents. The average OM/OC ratios were 2.0, 2.7, 2.1, and 2.2 at GRSM (S), GRSM (W), MORA, and ACAD, respectively. Hygroscopic growth factors (GF) at relative humidity (RH) 90% for aerosols generated from WSOC extracts averaged 1.19, 1.06, 1.13, and 1.16 at GRSM (S), GRSM (W), MORA, and ACAD, respectively. Thus, the assumption that OM is not hygroscopic may lead to underestimation of its contribution to light scattering. Implications: Studies at IMPROVE sites conducted in U.S. national parks showed that aerosol organics comprise more PM2.5 mass and absorb more water as a function of relative humidity than is currently assumed by the IMPROVE equation for calculating chemical light extinction. Future strategies for reducing regional haze may therefore need to focus more heavily on understanding the origins and control of anthropogenic sources of organic aerosols.

Response to Comment on “Flavoring Compounds Dominate Toxic Aldehyde Production during E Cigarette Vaping”

The growing popularity of electronic cigarettes (e-cigarettes) raises concerns about the possibility of adverse health effects to primary users and people exposed to e-cigarette vapors. E-Cigarettes offer a very wide variety of flavors, which is one of the main factors that attract new, especially young, users. How flavoring compounds in e-cigarette liquids affect the chemical composition and toxicity of e-cigarette vapors is practically unknown. Although e-cigarettes are marketed as safer alternatives to traditional cigarettes, several studies have demonstrated formation of toxic aldehydes in e-cigarette vapors during vaping. So far, aldehyde formation has been attributed to thermal decomposition of the main components of e-cigarette e-liquids (propylene glycol and glycerol), while the role of flavoring compounds has been ignored. In this study, we have measured several toxic aldehydes produced by three popular brands of e-cigarettes with flavored and unflavored e-liquids. We show that, within the tested e-cigarette brands, thermal decomposition of flavoring compounds dominates formation of aldehydes during vaping, producing levels that exceed occupational safety standards. Production of aldehydes was found to be exponentially dependent on concentration of flavoring compounds. These findings stress the need for a further, thorough investigation of the effect of flavoring compounds on the toxicity of e-cigarettes.

Physical and chemical characterization of aerosol in fresh and aged emissions from open combustion of biomass fuels

Abstract Biomass burning (BB) emissions and their atmospheric oxidation products can contribute significantly to direct aerosol radiative forcing of climate. Limited knowledge of BB organic aerosol chemical and optical properties leads to large uncertainties in climate models. In this article, we describe the experimental setup and the main findings of a laboratory BB study aimed at comprehensive optical, physical, and chemical characterization of fresh and aged BB emissions. An oxidation flow reactor (OFR) was used to mimic atmospheric oxidation processes. The OFR was characterized in terms of OH⋅ production rate, particle transmission efficiency, and characteristic lifetimes of condensible compounds. Emission factors (EFs) of main air pollutants (particulate matter, organic carbon [OC], elemental carbon [EC], carbon monoxide [CO], and nitrogen oxides [NOx]) were determined for five globally and regionally important biomass fuels: Siberian (Russia), Florida (USA), and Malaysian peats; mixed conifer and aspen fuel from Fishlake National Forest, Utah, USA; and mixed grass and brush fuel representative of the Great Basin, Nevada, USA. Measured fuel-based EFs for OC ranged from 0.85 ± 0.24 to 6.56 ± 1.40 mg g−1. Measured EFs for EC ranged from 0.02 ± 0.01 to 0.16 ± 0.01 mg g−1. The ratio of organic mass to total carbon mass for fresh emissions from these fuels ranged from 1.04 ± 0.04 to 1.34 ± 0.24. The effect of OFR aging on aerosol optical properties, size distribution, and concentration is also discussed. Copyright

Emissions and Partitioning of Intermediate-Volatility and Semi-Volatile Polar Organic Compounds (I/SV-POCs) During Laboratory Combustion of Boreal and Sub-Tropical Peat

Burning of peatlands is estimated to be a large source of gas-phase non-methane organic compounds and organic aerosol to the atmosphere. However, little is known about the chemical characteristics of intermediate-volatility and semi-volatile organic compounds (I/SVOC) emitted from peat combustion. Quantifying I/SVOC emissions and their subsequent transformation to secondary organic aerosol (SOA) is critical for elucidating biomass-burning (BB) SOA contributions to ambient aerosol concentrations and reducing uncertainties in aerosol radiative forcing from local to global scales. In this study, we provide one of the first estimates of the emissions of eighty-seven different polar I/SVOCs (I/SV-POCs) in both gas- and particle-phases from the laboratory combustion of peat from Alaska and Florida, USA and Pskov region of Russia. The measured I/SV-POCs include alkanoic, alkenoic, alkanedioic, substituted benzoic, resin, methoxy, and aromatic dicarboxylic acids, methoxy phenols, and anhydrous sugars. To understand the phase-partitioning behavior of the I/SV-POCs, the data is presented in two-dimensional volatility-oxidation state, volatility-solubility, and chemical partitioning space diagrams. For all fuels, methoxy phenols and C