Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter (<2.5 µm) and 5-22 g/kg volatile organic compounds were observed. Samples were collected using a dilution stack sampler equipped with a 2.5-µm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and semivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C 8 -C 20 ), canister (C 2 -C 12 ), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence, and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and ions were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography.

Emission samples for toxicity testing and detailed chemical characterization were collected from a variety of gasoline- and diesel-fueled in-use vehicles operated on the Unified Driving Cycle on a chassis dynamometer. Gasoline vehicles included normal particle mass (particulate matter [PM]) emitters (tested at 72 and 30 degrees F), "black" and "white" smokers, and a new-technology vehicle (tested at 72 degrees F). Diesel vehicles included current-technology vehicles (tested at 72 and 30 degrees F) and a high PM emitter. Total PM emission rates ranged from below 3 mg/mi up to more than 700 mg/mi for the white smoker gasoline vehicle. Emission rates of organic and elemental carbon (OC/EC), elements (metals and associated analytes), ions, and a variety of particulate and semi-volatile organic compounds (polycyclic aromatic hydrocarbons [PAH], nitro-PAH, oxy-PAH, hopanes, and steranes) are reported for these vehicles. Speciated organic analysis also was conducted on the fuels and lube oils obtained from these vehicles after the emissions testing. The compositions of emissions were highly dependent on the fuel type (gasoline vs. diesel), the state of vehicle maintenance (low, average, or high emitters; white or black smokers), and ambient conditions (i.e., temperature) of the vehicles. Fuel and oil analyses from these vehicles showed that oil served as a repository for combustion byproducts (e.g., PAH), and oil-burning gasoline vehicles emitted PAH in higher concentrations than did other vehicles. These PAH emissions matched the PAH compositions observed in oil.

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The kinetics and nitroarene product yields of the gas-phase reactions of naphthalene-d8, fluoranthene-dl,,, and pyrene with OH radicals in the presence of NO, and in Nz05-NO3-NOz-air mixtures have been investigated at 296 2 2 K and atmospheric pressure of air.Using a relative rate method, naphthalene-d8 was shown to react in Nz05-N03-N0,-air mixtures a factor of 1.22 ? 0.10 times faster than did naphthalene, with the 1-and 2-nitronaphthalene-d, product yields being similar to those of 1-and 2-nitronaphthalene from naphthalene. From the measured PAH concentrations and the nitroarene product yields, formation yields of 2-, 7-, and 8-nitrofluoranthene-d, and 2-and 4-nitropyrene of 0.03, 0.01, 0.003, 0.005, and 0.0006, respectively, were determined from the OH radical-initiated reactions. Effective rate constants for the reactions of fluoranthene-d,, and pyrene with N205 in Nz0,-N03-NOz-air mixtures of ca. 1.8 X lo-', cm3 molecule-'^-^ and ca. 5.6 X 10-l7 cm3 molecule-' s-', respectively, were derived. Formation yields of 2-nitrofluoranthened9 and 4-nitropyrene of ca. 0.24 and ca. 0.0006, respectively, were estimated for these reaction systems. 2-Nitropyrene was also observed to be formed in these Nz05-N03-NOz reactions, but was found to be a function of the NOz concentration and, therefore, would be a negligible product under ambient NOz concentrations. These product and kinetic data are consistent with ambient air measurements of the nitroarene concentrations.

During the past decade, technological advancements in the United States and Canada have led to rapid and intensive development of many unconventional natural gas plays (e.g., shale gas, tight sand gas, coal-bed methane), raising concerns about environmental impacts. Here, we summarize the current understanding of local and regional air quality impacts of natural gas extraction, production, and use. Air emissions from the natural gas life cycle include greenhouse gases, ozone precursors (volatile organic compounds and nitrogen oxides), air toxics, and particulates. National and state regulators primarily use generic emission inventories to assess the climate, air quality, and health impacts of natural gas systems. These inventories rely on limited, incomplete, and sometimes outdated emission factors and activity data, based on few measurements. We discuss case studies for specific air impacts grouped by natural gas life cycle segment, summarize the potential benefits of using natural gas over other fossil fuels, and examine national and state emission regulations pertaining to natural gas systems. Finally, we highlight specific gaps in scientific knowledge and suggest that substantial additional measurements of air emissions from the natural gas life cycle are essential to understanding the impacts and benefits of this resource.

Abstract3-Methylfuran has been identified as a product of the gas-phase reaction of the OH radical with isoprene, and under simulated atmospheric conditions a formation yield of 0.044 -t 0.006 was determined. In an analogous manner, the OH radical reaction with 1,3-butadiene formed furan with a yield of 0.039 ? 0.011. Using a relative rate method, a rate constant for the reaction of the OH radical with 3-methylfuran of 9.35 x lo-" cm3 molecule-' s-l (with an estimated overall uncertainty of 220%) at 296 * 2 K was also determined. These data show that 3-methylfuran is a reactive compound which will be present in the troposphere at concentrations 55% of those of its isoprene precursor.

Environmental contextAerosol water-soluble organic carbon is a complex mixture of thousands of organic compounds which may have a significant influence on the climate-relevant properties of atmospheric aerosols. Using ultrahigh resolution mass spectrometry, more than 4000 individual molecular formulas were identified in non-urban aerosol water-soluble organic carbon. A significant fraction of the assigned molecular formulas were matched to assigned molecular formulas of laboratory generated secondary organic aerosols. AbstractWater-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 molecular composition of WSOC is needed to evaluate the effect of aerosol composition upon aerosol physical properties. In this work, ultrahigh-resolution Fourier transform–ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterise aerosol WSOC collected during the summer of 2010 at the Storm Peak Laboratory (3210 m ASL) near Steamboat Springs, CO. Approximately 4000 molecular formulas were assigned in the mass range of 100–800 Da 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.

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