ALBERT

Description: Emissions of methane (CH 4 ) and volatile organic compounds (VOCs) from oil and gas production may have large impacts on air quality and climate change. Methane and VOCs were measured over the Haynesville and Marcellus shale gas plays onboard the NCAR C-130 and NOAA WP-3D research aircraft in June-July of 2013. We used an eddy covariance technique to measure in situ fluxes of CH 4 and benzene from both C-130 flights with high-resolution data (10 Hz) and WP-3D flights with low-resolution data (1 Hz). Correlation (R=0.65) between CH 4 and benzene fluxes was observed when flying over shale gas operations and the enhancement ratio of fluxes was consistent with the corresponding concentration observations. Fluxes calculated by the eddy covariance method show agreement with a mass balance approach within their combined uncertainties. In general, CH 4 fluxes in the shale gas regions follow a lognormal distribution, with some deviations for relatively large fluxes (〉10 µg m −2 s −1 ). Statistical analysis of the fluxes shows that a small number of facilities (i.e. ~10%) are responsible for up to ~40% of the total CH 4 emissions in the two regions. We show that the airborne eddy covariance method can also be applied in some circumstances when meteorological conditions do not favor application of the mass balance method. We suggest that the airborne eddy covariance method is a reliable alternative and complementary analysis method to estimate emissions from oil and gas extraction.

Description: Tropospheric O 3 has been decreasing across much of the eastern U.S. but has remained steady or even increased in some western regions. Recent increases in VOC and NO x emissions associated with the production of oil and natural gas (O&NG) may contribute to this trend in some areas. The Northern Front Range of Colorado has regularly exceeded O 3 air quality standards during summertime in recent years. This region has VOC emissions from a rapidly developing O&NG basin and low concentrations of biogenic VOC in close proximity to urban-Denver NO x emissions. Here, VOC OH reactivity (OHR), O 3 production efficiency (OPE), and an observationally constrained box model are used to quantify the influence of O&NG emissions on regional summertime O 3 production. Analyses are based on measurements acquired over two summers at a central location within the Northern Front Range that lies between major regional O&NG and urban emission sectors. Observational analyses suggest that mixing obscures any OPE differences in air primarily influenced by O&NG or urban emissions sectors. The box model confirms relatively modest OPE differences that are within the uncertainties of the field observations. Box model results also indicate that maximum O 3 at the measurement location is sensitive to changes in NO x mixing ratio but also responsive to O&NG VOC reductions. Combined, these analyses show that O&NG alkanes contribute over 80% to the observed carbon mixing ratio, roughly 50% to the regional VOC OHR, and approximately 20% to regional photochemical O 3 production.

Description: We use a 0-D photochemical box model and a 3-D global chemistry-climate model, combined with observations from the NOAA Southeast Nexus (SENEX) aircraft campaign, to understand the sources and sinks of glyoxal over the Southeast United States. Box model simulations suggest a large difference in glyoxal production among three isoprene oxidation mechanisms (AM3ST, AM3B, and MCM v3.3.1). These mechanisms are then implemented into a 3-D global chemistry-climate model. Comparison with field observations shows that the average vertical profile of glyoxal is best reproduced by AM3ST with an effective reactive uptake coefficient γ glyx of 2 × 10 -3 , and AM3B without heterogeneous loss of glyoxal. The two mechanisms lead to 0-0.8 µg m -3 secondary organic aerosol (SOA) from glyoxal in the boundary layer of the Southeast U.S. in summer. We consider this to be the lower limit for the contribution of glyoxal to SOA, as other sources of glyoxal other than isoprene are not included in our model. In addition, we find that AM3B shows better agreement on both formaldehyde and the correlation between glyoxal and formaldehyde ( R GF  = [GLYX]/[HCHO]), resulting from the suppression of δ-isoprene peroxy radicals (δ-ISOPO 2 ). We also find that MCM v3.3.1 may underestimate glyoxal production from isoprene oxidation, in part due to an underestimated yield from the reaction of IEPOX peroxy radicals (IEPOXOO) with HO 2 . Our work highlights that the gas-phase production of glyoxal represents a large uncertainty in quantifying its contribution to SOA.

Description: For the C4 perennial grasses, Miscanthus  ×  giganteus and Panicum virgatum (switchgrass) to be successful for bioenergy production they must maintain high yields over the long term. Previous studies under the less conducive climate for productivity in N.W. Europe found little or no yield decline in M . ×  giganteus in the long term. This study provides the first analysis of whether yield decline occurs in M . ×  giganteus under United States. Midwest conditions in side-by-side trials with P. virgatum over 8–10 years at seven locations across Illinois. The effect of stand age was determined by using a linear regression model that included effects of weather. Miscanthus  ×  giganteus produced yields more than twice that of P. virgatum averaging 23.4 ± 1.2 Mg ha −1  yr −1 and 10.0 ± 0.9 Mg ha −1  yr −1 , respectively, averaged over 8–10 years. Relationships of yield with precipitation and growing degree days were established and used to estimate yields corrected for the stochastic effects of weather. Across all locations and in both species, yield initially increased until it reached a maximum during the fifth growing season and then declined to a stable, but lower level in the eighth. This pattern was more pronounced in M . ×  giganteus . The mean yields observed over this longer term period of 8–10 years were lower than the yields of the first 5 years. However, this decline was proportionately greater in M . ×  giganteus than in P. virgatum, suggesting a stronger effect of stand age on M . ×  giganteus . Based on the average yield over the period of this study, meeting the United States Renewable Fuel Standard mandate of 60 billion liters of cellulosic ethanol by 2022, would require 6.8 Mha of M . ×  giganteus or 15.8 Mha of P. virgatum . These appear manageable numbers for the United States, given the 16.0 Mha in the farmland Conservation Reserve Program in addition to another 13.0 Mha abandoned from agriculture in the last decade.

Description: [1]  A combined field and laboratory study was conducted to improve our understanding of the chemical and hygroscopic properties of organic compounds in aerosols sampled in the background continental atmosphere. PM 2.5 (particles with aerodynamic diameters smaller than 2.5 µm) aerosols were collected from 24 June to 28 July, 2010 at Storm Peak Laboratory in the Park Range of northwestern Colorado. New particle formation was frequent at Storm Peak Laboratory during this campaign, and the samples were not influenced by regional dust storms. Filter samples were analyzed for organic carbon (OC) and elemental carbon (EC), water soluble OC (WSOC), major inorganic ions, and detailed organic speciation. WSOC was isolated from inorganic ions using solid phase absorbents. Hygroscopic growth factors and cloud condensation nucleus (CCN) activity of the WSOC were measured in the laboratory. Organic compounds comprised the majority (average of 64% with a standard deviation of 9%) of the mass of measured species and WSOC accounted for an average of 89% (with a standard deviation of 21%) of OC mass. Daily samples were composited according to back-trajectories. On average, organic acids, sugars, and sugar alcohols accounted for 12.5 ± 6.2% (average ± standard deviation) of WSOC. Based on the composition of these compounds and that of high molecular weight compounds identified using ultra high resolution mass spectrometry, the organic mass to organic carbon ratio of the WSOC is estimated to be 2.04. The average hygroscopic growth factors at RH = 80% (GF 80 ) were 1.10 ± 0.03 for particles derived from isolated WSOC and 1.27 ± 0.03 for particles derived from the total water-soluble material (WSM). CCN activity followed a similar pattern. The critical diameters at a super-saturation of 0.35% were 0.072 ± 0.009 and 0.094 ± 0.006 µm for particles derived from WSM and isolated WSOC, respectively. These growth factor results compare favorably with estimates from thermodynamic models, which explicitly relate the water activity (RH) to concentration for the total soluble material identified in this study.

Description: [1]  We have measured the bidirectional reflectance of analogs of dry, wet and frozen Martian soils over a wide range of phase angles in the visible spectral range. All samples were produced from two geologic samples: the standard JSC Mars-1 soil simulant and Hawaiian basaltic sand. In a first step, experiments were conducted with the dry samples to investigate the effects of surface texture. Comparisons with results independently obtained by different teams with similar samples showed a satisfying reproducibility of the photometric measurements as well as a noticeable influence of surface textures resulting from different sample preparation procedures. In a second step, water was introduced to produce wet and frozen samples and their photometry investigated. Optical microscope images of the samples provided information about their micro-texture. Liquid water, even in relatively low amount, resulted in the disappearance of the backscattering peak and the appearance of a forward scattering peak whose intensity increases with the amount of water. Specular reflections only appeared when water was present in an amount large enough to allow water to form a film at the surface of the sample. Icy samples showed a wide variability of photometric properties depending on the physical properties of the water ice. We discuss the implications of these measurements in terms of the expected photometric behavior of the Martian surface, from equatorial to circum-polar regions. In particular, we propose some simple photometric criteria to improve the identification of wet and/or icy soils from multiple observations under different geometries.

Description: Chemical Reviews DOI: 10.1021/acs.chemrev.6b00180

Description: Chemical Reviews DOI: 10.1021/acs.chemrev.5b00669

Description: Methane (CH 4 ) is the primary component of natural gas and has a larger global warming potential than CO 2 . Recent top-down studies based on observations showed CH 4 emissions in California's South Coast Air Basin (SoCAB) were greater than those expected from population-apportioned bottom-up state inventories. In this study, we quantify CH 4 emissions with an advanced mesoscale inverse modeling system at a resolution of 8 km × 8 km, using aircraft measurements in the SoCAB during the 2010 CalNex campaign to constrain the inversion. To simulate atmospheric transport, we use the FLEXPART-WRF Lagrangian particle dispersion model driven by three configurations of the Weather Research and Forecasting (WRF) mesoscale model. We determine surface fluxes of CH 4 using a Bayesian least squares method in a 4-dimensional inversion. Simulated CH 4 concentrations with the posterior emission inventory achieve much better correlations with the measurements (R 2 =0.7) than using the prior inventory (US EPA's National Emission Inventory 2005, R 2 =0.5). The emission estimates for CH 4 in the posterior, 46.3 ± 9.2 Mg CH 4 /hr, is consistent with published observation-based estimates. Changes in the spatial distribution of CH 4 emissions in the SoCAB between the prior and posterior inventories are discussed. Missing or underestimated emissions from dairies, the oil/gas system, and landfills in the SoCAB seem to explain the differences between the prior and posterior inventories. We estimate that dairies contributed 5.9 ± 1.7 Mg CH 4 /hr and the two sectors of oil and gas industry (production and downstream) and landfills together contributed 39.6 ± 8.1 Mg CH 4 /hr in the SoCAB.

Description: Bacterial assemblages, especially diazotroph assemblages residing in the rhizomes and the rhizosphere soil of Miscanthus ×giganteus contribute to plant growth and nitrogen use efficiency. However, the composition of these microbial communities has not been adequately explored, nor have the potential ecological drivers for these communities been sufficiently studied. This knowledge is needed for understanding and potentially improving M. ×giganteus - microbe interactions, and further enhancing sustainability of M. ×giganteus production. In this study, cultivated M. ×giganteus from four sites in Illinois, Kentucky, Nebraska, and New Jersey were collected to examine the relative influences of soil conditions and plant compartments on assembly of the M. ×giganteus -associated microbiome. Automated ribosomal intergenic spacer (ARISA) and terminal restriction fragment length polymorphism (T-RFLP) targeting the nifH gene were applied to examine the total bacterial communities and diazotroph assemblages that reside in the rhizomes and the rhizosphere. Distinct microbial assemblages were detected in the endophytic and rhizosphere compartments. Site soil conditions had strong correlation with both total bacterial and diazotroph assemblages, but in different ways. Nitrogen treatments showed no significant effect on the composition of diazotroph assemblages in most sites. Endophytic compartments of different M . × giganteus plants tended to harbor similar microbial communities across all sites, whereas, the rhizosphere soil of different plant tended to harbor diverse microbial assemblages that were distinct among sites. These observations offer insight into better understanding of the associative interactions between M. ×giganteus and diazotrophs, and how this relationship is influenced by agronomic and edaphic factors. This article is protected by copyright. All rights reserved.