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During the winter of 2012-2013 atmospheric surface ozone mole fractions exceeded the US 8h standard of 75ppb on 39 days in the Uinta Basin of Utah. As part of the Uinta Basin Winter Ozone Study (UBWOS) aircraft flights were conducted throughout the basin with continuous measurements of ozone (O3), methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), nitrogen dioxide (NO2), and discrete whole air flask samples for determination of ~ 50 trace gases including a number of non-methane hydrocarbons (NMHCs). During the course of seven flights conducted between 31 January and 7 February 2013, coinciding with strong, multi-day temperature inversions, O3 levels gradually built up in the shallow boundary layer from ~ 45 ppb to ~ 140 ppb. Near-surface CH4 mole fractions increased during the episode from near background levels of ~2ppm to over 10ppm. Based on elevated levels of CH4 across the basin and high correlations of CH4 with NMHCs from the discrete air samples, O3 precursor NMHCs were also inferred to be elevated throughout the basin. Discrete plumes of high NO2 were observed in the gas production region of the basin suggesting that gas processing plants and compressor facilities were important point sources of reactive nitrogen oxides (NOx). Vertical profiles obtained during the flights showed that the high O3 mole fractions (as well as other elevated constituents) were confined to a shallow layer from near the ground to 300-400 m above ground level (ma.g.l.) capped by a strong temperature inversion. The highest mole fractions of the measured constituents during the study period were in an isothermal cold layer that varied from ~ 300 m depth on 4 February to ~ 150 m on 5 February. A gradient layer with declining mole fractions with altitude extended above the isothermal layer to ~ 1900ma.s.l. (300-400 ma.g.l.) indicative of some mixing of air out of the boundary layer. O3 mole fractions continued to increase within the basin as the high O3 episode developed over the course of a week. CH4 mole fractions, on the other hand, leveled off after several days. On several flights, the aircraft sampled the plume of a coal-fired power plant (located east of the main gas field) flowing above the inversion layer. These measurements ruled out the effluents of the power plant as a significant source of NOx for O3 production beneath the temperature inversion in the basin. The presence of elevated O3 precursors within the basin and the rapid daytime production of O3 in the atmosphere beneath the temperature inversion both indicated that O3 was being produced from precursors emitted within the basin beneath the temperature inversion. Although observations show that horizontal winds in the surface layer were relatively light during the high ozone event, they were sufficient to disperse precursors up to 80 km from primary sources in the main gas field in the southeast quadrant to the balance of the Uinta Basin. [ABSTRACT FROM AUTHOR]

We apply a full year of continuous atmospheric acetone measurements from the University of Minnesota tall tower Trace Gas Observatory (KCMP tall tower; 244ma.g.l.), with a 0.5° x 0.667° GEOS-Chem nested grid simulation to develop quantitative new constraints on seasonal acetone sources over North America, and assess the corresponding impacts on atmospheric chemistry. Biogenic acetone emissions in the model are computed based on the MEGANv2.1 inventory. An inverse analysis of the tall tower observations implies a 37% underestimate of emissions from broadleaf trees, shrubs, and herbaceous plants, and an offsetting 40 % overestimate of emissions from needle-leaf trees plus secondary production from biogenic precursors. The overall result is a small (16 %) model underestimate of the total primary + secondary biogenic acetone source in North America. Our analysis shows that North American primary + secondary anthropogenic acetone sources in the model (based on the EPA NEI 2005 inventory) are accurate to within approximately 20%. An optimized GEOS-Chem simulation incorporating the above findings captures 70% of the variance (R = 0.83) in the hourly measurements at the KCMP tall tower, with minimal bias. The resulting North American acetone source is 10.9Tga-1, including both primary emissions (5.5Tga-1) and secondary production (5.5Tga-1), and with roughly equal contributions from anthropogenic and biogenic sources. The North American acetone source alone is nearly as large as the total continental volatile organic compound (VOC) source from fossil fuel combustion. Using our optimized source estimates as a baseline, we evaluate the atmospheric impact of some potential future shifts in acetone sources over North America. Increased biogenic acetone emissions due to surface warming are likely to provide a significant offset to any future decrease in anthropogenic acetone emissions, particularly during summer. [ABSTRACT FROM AUTHOR]

Gaseous Elemental Mercury (GEM) was monitored at the Niwot Ridge (NWT) longterm ecological research (LTER) site (Colorado, USA, 40°N) from interstitial air extracted from the snowpack at depths ranging from the snow surface to 10 cm above the soil. A highly dynamic cycling of mercury (Hg) in this mid-latitude snowpack was observed. Patterns were driven by both GEM production in surface snow and GEM destruction in the deeper snowpack layers. Thorough mixing and vertical transport processes were observed through the snowpack. GEM was photochemically produced near the snow-air interface leading to enhanced GEM levels in interstitial air of surface snow of up to 8 ngm-3. During low wind periods, GEM in surface snow layers remained significantly above ambient air levels at night as well, which may indicate a potential weak GEM production over night. Analysis of vertical GEM gradients in the snowpack show that surface GEM enhancements efficiently propagated down the snowpack, with a temporal lag in peak GEM levels observed with increasing depth. Downward diffusion was responsible for much of these patterns, although vertical advection also contributed to vertical redistribution. Destruction of GEM in the lower snowpack layers was attributed to dark oxidation of GEM. Analysis of vertical GEM/CO2 flux ratios indicated that this GEM destruction occurred in the snow and not in the underlying soil. The strong, diurnal patterns of photochemical GEM production at the surface ultimately lead to re-emission losses of deposited Hg back to the atmosphere. The NWT data show that highest of GEM production and emission occur shortly after fresh snowfall, indicating that fresh snow possibly resupplies photoreducible Hg to the snowpack. [ABSTRACT FROM AUTHOR]

The primary sources and atmospheric chemistry of C2-C5 alkanes were incorporated into the atmospheric chemistry general circulation model EMAC. Model output is compared with new observations from the NOAA/ESRL GMD Cooperative Air Sampling Network. Based on the global coverage of the data, two different anthropogenic emission datasets for C4-C5 alkanes, widely used in the modelling community, are evaluated. We show that the model reproduces the main atmospheric features of the C2-C5 alkanes (e.g., seasonality). While the simulated values for ethane and propane are within a 20% range of the measurements, larger deviations are found for the other tracers. According to the analysis, an oceanic source of butanes and pentanes larger than the current estimates would be necessary to match the observations at some coastal stations. Finally the effect of C2-C5 alkanes on the concentration of acetone and acetaldehyde are assessed. Their chemical sources are largely controlled by the reaction with OH, while the reactions with NO3 and Cl contribute only to a little extent. The total amount of acetone produced by propane, i-butane and i-pentane oxidation is 11.2 Tg/yr, 4.3 Tg/yr, and 5.8 Tg/yr, respectively. Moreover, 18.1, 3.1, 3.4, 1.4 and 4.8 Tg/yr of acetaldehyde are formed by the oxidation of ethane, propane, n-butane, n-pentane and i-pentane, respectively. [ABSTRACT FROM AUTHOR]

Several charts are presented depicting chemical equations set and complete figure set for various chemicals, including ethane, propane, and butane.

The atmospheric chemistry of C3-C5 alkanes has been incorporated in the atmospheric-chemistry general circulation model EMAC. Model output is compared with observations from the NOAA/ESRL GMD cooperative air sampling network. A new series of measurements is used to evaluate the model in representing C3-C5 alkanes (i.e. propane, isobutane, butane, isopentane and pentane). While the representation of propane is within the measurement standard deviation, some deviations are found for the other tracers. The model is able to reproduce the main features of the C3-C5 alkanes (e.g., seasonality). However, in the Northern Hemisphere during winter the mixing ratios of these alkanes are generally overestimated. Conversely, the model shows an underestimation in the Southern Hemisphere. Moreover, only for iso-pentane there is a net overestimation of the mixing ratios, while for the other alkanes, the results are at the higher end of the measurement range. The effects of the C3-C5 alkanes to atmospheric acetone and acetaldehyde are quantified. The total amount of acetone produced by propane, isobutane and isopentane oxidation is 11.6 Tg/yr, 4.2 Tg/yr and 5.8 Tg/yr, respectively. These chemical sources are largely controlled by the reaction with OH, while the reactions with NO3 and Cl contribute only to a little extent. Moreover, 3.1, 4.5, 1.9 and 6.7 Tg/yr of acetaldehyde are formed from the oxidation of propane, butane, pentane and isopentane, respectively. Also for acetaldehyde, the formation is controlled by the reaction of alkanes with OH. However, since isopentane is generally overestimated, its contribution to the production of these oxygenated compounds represents an upper limit. [ABSTRACT FROM AUTHOR]

Airborne radioactivity from fossil fuel production systems is poorly characterized, but a recent study showed elevated ambient levels with proximity to oil and gas production wells. Here, we report year-long, high temporal resolution monitoring results of airborne alpha radioactivity from both radon gas and radon progeny attached to particulates immediately northeast of an oil refinery in Commerce City, Colorado, USA, in an environmental justice community of concern. Gas and particle-associated radioactivity contributed nearly evenly to the total alpha radioactivity. Total radioactivity levels of 30-40 Bq m -3 were 2-3 times higher than background levels (~10-15 Bq m -3 ) when winds were light and southwesterly, suggesting the refinery as the geographic origin. Furthermore, elevated airborne radioactivity tracked most closely with the light hydrocarbon and natural gas tracer ethane. Thus, the data imply natural gas as the radon emission carrier. Our findings are unique and suggest a need for further investigations of radon emissions from oil and gas infrastructure such as natural gas processing plants, compressor stations, petrochemical plants, and oil refineries that process oil and natural gas from unconventional production. Implications : Regulatory agencies currently do not mandate or conduct monitoring of radioactivity releases and public exposure from petroleum industry air emissions. This study reports elevated radioactivity from radon gas and nonvolatile radon decay products attached to particulate matter, at about 2-3 times above background levels in proximity to Colorado's largest oil refinery. Observations were within an environmental justice community of concern that experiences well above-average exposure to many other harmful atmospheric pollutants, suggesting potential adverse health effects from this cumulative exposure. Our findings offer actionable insights for policymakers, industry stakeholders, and affected communities alike.