Repository for Oil and Gas Energy Research (ROGER)

Abstract:
Unconventional drilling (the combination of hydraulic fracturing and horizontal drilling) to extract oil and natural gas is expanding rapidly around the world. The rate of expansion challenges scientists and regulators to assess the risks of the new technologies on drinking water resources. One concern is the potential for subsurface drinking water resource contamination by naturally occurring radioactive materials co-extracted during unconventional drilling activities. Given the rate of expansion, opportunities to test drinking water resources in the pre- and post-fracturing setting are rare. This pilot study investigated the levels of natural uranium, lead-210, and polonium-210 in private drinking wells within 2000 m of a large-volume hydraulic fracturing operation – before and approximately one-year following the fracturing activities. Observed radionuclide concentrations in well waters tested did not exceed maximum contaminant levels recommended by state and federal agencies. No statistically-significant differences in radionuclide concentrations were observed in well-water samples collected before and after the hydraulic fracturing activities. Expanded monitoring of private drinking wells before and after hydraulic fracturing activities is needed to develop understanding of the potential for drinking water resource contamination from unconventional drilling and gas extraction activities.

Abstract:
In modeling and prediction of natural gas fracking pad landscapes in the Marcellus Shale region, USA, the author asserts that landscape and environmental characteristics are the driving factors behind the siting of natural gas pads in the southwestern area of the Marcellus Shale, Pennsylvania, USA. In the article, the author largely dismisses the importance of geology for site prediction. Although the study is useful for understanding landscape characteristics in a small area of the Marcellus Shale, his premise that “the key variables for natural gas fracking can be landscape and environmental variables rather than geological variables” is flawed and thus could lead to erroneous assumptions when creating land use plans. A more reasonable assumption is that the surface siting of natural gas wells is secondary to geologic considerations, as the current topography bears little influence on the geology.

Abstract:
Fugitive losses from natural gas distribution systems are a significant source of anthropogenic methane. Here, we report on a national sampling program to measure methane emissions from 13 urban distribution systems across the U.S. Emission factors were derived from direct measurements at 230 underground pipeline leaks and 229 metering and regulating facilities using stratified random sampling. When these new emission factors are combined with estimates for customer meters, maintenance, and upsets, and current pipeline miles and numbers of facilities, the total estimate is 393 Gg/yr with a 95% upper confidence limit of 854 Gg/yr (0.10% to 0.22% of the methane delivered nationwide). This fraction includes emissions from city gates to the customer meter, but does not include other urban sources or those downstream of customer meters. The upper confidence limit accounts for the skewed distribution of measurements, where a few large emitters accounted for most of the emissions. This emission estimate is 36% to 70% less than the 2011 EPA inventory, (based largely on 1990s emission data), and reflects significant upgrades at metering and regulating stations, improvements in leak detection and maintenance activities, as well as potential effects from differences in methodologies between the two studies.

Abstract:
Emissions from oil and natural gas development during winter in the Upper Green River basin of Wyoming are known to drive episodic ozone (O3) production. Contrasting O3 distributions were observed in the winters of 2011 and 2012, with numerous episodes (hourly O3 ≥ 85 ppbv) in 2011 compared to none in 2012. The lack of O3 episodes in 2012 coincided with a reduction in measured ambient levels of total non-methane hydrocarbons (NMHC). Measurements of speciated NMHC, and other air quality parameters, were performed to better understand emission sources and to determine which compounds are most active in promoting O3 formation. Positive matrix factorization (PMF) analyses of the data were carried out to help achieve these goals. PMF analyses revealed three contributing factors that were identified with different emission source types: factor 1, combustion/traffic; factor 2, fugitive natural gas; and factor 3, fugitive condensate. Compositional signatures of the three contributing factors were identified through comparison with independently derived emission source profiles. Fugitive emissions of natural gas and of condensate were the two principal emission source types for NMHC. A water treatment and recycling facility was found to be a significant source of NMHC that are abundant in condensate, in particular toluene and m+p-xylene. Emissions from water treatment have an influence upon peak O3 mixing ratios at downwind measurement sites.

Abstract:
Natural gas extraction, often referred to as "fracking," has increased rapidly in the U.S. in recent years. To address potential health impacts, passive air samplers were deployed in a rural community heavily affected by the natural gas boom. Samplers were analyzed for 62 polycyclic aromatic hydrocarbons (PAHs). Results were grouped based on distance from each sampler to the nearest active well. PAH levels were highest when samplers were closest to active wells. Additionally, PAH levels closest to natural gas activity were an order of magnitude higher than levels previously reported in rural areas. Sourcing ratios indicate that PAHs were predominantly petrogenic, suggesting that elevated PAH levels were influenced by direct releases from the earth. Quantitative human health risk assessment estimated the excess lifetime cancer risks associated with exposure to the measured PAHs. Closest to active wells, the risk estimated for maximum residential exposure was 2.9 in 10,000, which is above the U.S. EPA's acceptable risk level. Overall, risk estimates decreased 30% when comparing results from samplers closest to active wells to those farthest. This work suggests that natural gas extraction may be contributing significantly to PAHs in air, at levels that are relevant to human health.

Abstract:
We present a study of methane emissions from oil and gas producing well pad facilities in the Barnett Shale region of Texas, measured using an innovative ground-based mobile flux plane (MFP) measurement system, as part of the Barnett Coordinated Campaign.1 Using only public roads, we measured the emissions from nearly 200 well pads over 2 weeks in October 2013. The population of measured well pads is split into well pads with detectable emissions (N = 115) and those with emissions below the detection limit of the MFP instrument (N = 67). For those well pads with nonzero emissions, the distribution was highly skewed, with a geometric mean of 0.63 kg/h, a geometric standard deviation of 4.2, and an arithmetic mean of 1.72 kg/h. Including the population of nonemitting well pads, we find that the arithmetic mean of the well pads sampled in this study is 1.1 kg/h. This distribution implies that 50% of the emissions is due to the 6.6% highest emitting well pads, and 80% of the emissions is from the 22% highest emitting well pads.

Abstract:
Quantification of leaks from natural gas (NG) infrastructure is a key step in reducing emissions of the greenhouse gas methane (CH4), particularly as NG becomes a larger component of domestic energy supply. The United States Environmental Protection Agency (USEPA) requires measurement and reporting of emissions of CH4 from NG transmission, storage, and processing facilities, and the high flow sampler (or high volume sampler) is one of the tools approved for this by the USEPA. The Bacharach Hi-Flow® Sampler (BHFS) is the only commercially available high flow instrument, and it is also used throughout the NG supply chain for directed inspection and maintenance, emission factor development, and greenhouse gas reduction programs. Here we document failure of the BHFS to transition from a catalytic oxidation sensor used to measure low NG ( 5% or less) concentrations to a thermal conductivity sensor for higher concentrations (from 5% to 100%), resulting in underestimation of NG emission rates. Our analysis includes both our own field testing as well as analysis of data from two other studies (Modrak et al., 2012; City of Ft Worth, 2011). Although this failure is not completely understood, and although we do not know if all BHFS models are similarly affected, sensor transition failure has been observed under one or more of these conditions: 1), calibration is more than 2 weeks old; 2), firmware is out of date; or 3), the composition of the NG source is less than 91% CH4. The extent to which this issue has affected recent emission studies is uncertain, but the analysis presented here suggests that the problem could be widespread. Furthermore, it is critical that this problem be resolved before the onset of regulations on CH4 emissions from the oil and gas industry, as the BHFS is a popular instrument for these measurements. ImplicationsAn instrument commonly used to measure leaks in natural gas infrastructure has a critical sensor transition failure issue that results in underestimation of leaks, with implications for greenhouse gas emissions estimates as well as safety.

Abstract:
Recent studies in northeastern Pennsylvania report higher concentrations of dissolved methane in domestic water wells associated with proximity to nearby gas-producing wells [Osborn et al. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 8172] and [Jackson et al. Proc. Natl. Acad. Sci. U. S. A., 2013, 110, 11250]. We test this possible association by using Chesapeake Energy?s baseline data set of over 11,300 dissolved methane analyses from domestic water wells, densely arrayed in Bradford and nearby counties (Pennsylvania), and near 661 pre-existing oil and gas wells. The majority of these, 92%, were unconventional wells, drilled with horizontal legs and hydraulically fractured. Our data set is hundreds of times larger than data sets used in prior studies. In contrast to prior findings, we found no statistically significant relationship between dissolved methane concentrations in groundwater from domestic water wells and proximity to pre-existing oil or gas wells. Previous analyses used small sample sets compared to the population of domestic wells available, which may explain the difference in prior findings compared to ours.

Abstract:
Hydraulic fracturing is becoming an important technique worldwide to recover hydrocarbons from unconventional sources such as shale gas. In Quebec (Canada), the Utica Shale has been identified as having unconventional gas production potential. However, there has been a moratorium on shale gas exploration since 2010. The work reported here was aimed at defining baseline concentrations of methane in shallow aquifers of the St. Lawrence Lowlands and its sources using δ13C methane signatures. Since this study was performed prior to large-scale fracturing activities, it provides background data prior to the eventual exploitation of shale gas through hydraulic fracturing. Groundwater was sampled from private (n=81), municipal (n=34) and observation (n=15) wells between August 2012 and May 2013. Methane was detected in 80% of the wells with an average concentration of 3.8 ± 8.8 mg/L, and a range of < 0.0006 to 45.9 mg/L. Methane concentrations were linked to groundwater chemistry and distance to the major faults in the studied area. The methane δ13C signature of 19 samples was > -50‰, indicating a potential thermogenic source. Localized areas of high methane concentrations from predominantly biogenic sources were found throughout the study area. In several samples, mixing, migration and oxidation processes likely affected the chemical and isotopic composition of the gases, making it difficult to pinpoint their origin. Energy companies should respect a safe distance from major natural faults in the bedrock when planning the localization of hydraulic fracturation activities to minimize the risk of contaminating the surrounding groundwater since natural faults are likely to be a preferential migration pathway for methane.

Abstract:
Results of mobile ground-based atmospheric measurements conducted during the Barnett Shale Coordinated Campaign in spring and fall of 2013 are presented. Methane and ethane are continuously measured downwind of facilities such as natural gas processing plants, compressor stations, and production well pads. Gaussian dispersion simulations of these methane plumes, using an iterative forward plume dispersion algorithm, are used to estimate both the source location and the emission magnitude. The distribution of emitters is peaked in the 0-5 kg/h range, with a significant tail. The ethane/methane molar enhancement ratio for this same distribution is investigated, showing a peak at ∼1.5% and a broad distribution between ∼4% and ∼17%. The regional distributions of source emissions and ethane/methane enhancement ratios are examined: the largest methane emissions appear between Fort Worth and Dallas, while the highest ethane/methane enhancement ratios occur for plumes observed in the northwestern potion of the region. Individual facilities, focusing on large emitters, are further analyzed by constraining the source location.

Abstract:
The quality and availability of unconventional oil and gas (O&G) data in the United States have never been compared methodically state-to-state. By conducting such an assessment, this study seeks to better understand private and publicly sourced data variability and to identify data availability gaps. We developed an exploratory data-grading tool - Data Accessibility and Usability Index (DAUI) - to guide the review of O&G data quality. Between July and October 2013, we requested, collected, and assessed 5 categories of unconventional O&G data (wells drilled, violations, production, waste, and Class II disposal wells) from 10 states with active drilling activity. We based our assessment on eight data quality parameters (accessibility, usability, point location, completeness, metadata, agency responsiveness, accuracy, and cost). Using the DAUI, two authors graded the 10 states and then averaged their scores. The average score received across all states, data categories, and parameters was 67.1 out of 100, largely insufficient for proper data transparency. By state, Pennsylvania received the highest average ( = 93.5) and ranked first in all but one data category. The lowest scoring state was Texas ( = 44) largely due to its policy of charging for certain data. This article discusses the various reasons for scores received, as well as methodological limitations of the assessment metrics. We argue that the significant variability of unconventional O&G data—and its availability to the public—is a barrier to regulatory and industry transparency. The lack of transparency also impacts public education and broader participation in industry governance. This study supports the need to develop a set of data best management practices (BMPs) for state regulatory agencies and the O&G industry, and suggests potential BMPs for this purpose.

Abstract:
Elevated concentration of naturally occurring radioactive material (NORM) in wastewater generated from Marcellus Shale gas extraction is of great concern due to potential environmental and public health impacts. Development of a rapid and robust method for analysis of Ra-226, which is the major NORM component in this water, is critical for the selection of appropriate management approaches to properly address regulatory and public concerns. Traditional methods for Ra-226 determination require long sample holding time or long detection time. A novel method combining Inductively Coupled Mass Spectrometry (ICP-MS) with solid-phase extraction (SPE) to separate and purify radium isotopes from the matrix elements in high salinity solutions is developed in this study. This method reduces analysis time while maintaining requisite precision and detection limit. Radium separation is accomplished using a combination of a strong-acid cation exchange resin to separate barium and radium from other ions in the solution and a strontium-specific resin to isolate radium from barium and obtain a sample suitable for analysis by ICP-MS. Method optimization achieved high radium recovery (101±6% for standard mode and 97±7% for collision mode) for synthetic Marcellus Shale wastewater (MSW) samples with total dissolved solids as high as 171,000 mg/L. Ra-226 concentration in actual MSW samples with TDS as high as 415,000 mg/L measured using ICP-MS matched very well with the results from gamma spectrometry. The Ra-226 analysis method developed in this study requires several hours for sample preparation and several minutes for analysis with the detection limit of 100 pCi/L with RSD of 45% (standard mode) and 67% (collision mode). The RSD decreased to below 15% when Ra-226 concentration increased over 500 pCi/L.

Abstract:
Facility-level methane emissions were measured at 114 gathering facilities and 16 processing plants in the United States natural gas system. At gathering facilities, the measured methane emission rates ranged from 0.7 to 700 kg per hour (kg/h) (0.6 to 600 standard cubic feet per minute (scfm)). Normalized emissions (as a % of total methane throughput) were less than 1% for 85 gathering facilities and 19 had normalized emissions less than 0.1%. The range of methane emissions rates for processing plants was 3 to 600 kg/h (3 to 524 scfm), corresponding to normalized methane emissions rates <1% in all cases. The distributions of methane emissions, particularly for gathering facilities, are skewed. For example, 30% of gathering facilities contribute 80% of the total emissions. Normalized emissions rates are negatively correlated with facility throughput. The variation in methane emissions also appears driven by differences between inlet and outlet pressure, as well as venting and leaking equipment. Substantial venting from liquids storage tanks was observed at 20% of gathering facilities. Emissions rates at these facilities were, on average, around four times the rates observed at similar facilities without substantial venting.

Abstract:
The Marcellus Shale is the largest natural gas deposit in the U.S. and rapid development of this resource has raised concerns about regional air pollution. A field campaign was conducted in the southwestern Pennsylvania region of the Marcellus Shale to investigate the impact of unconventional natural gas (UNG) production operations on regional air quality. Whole air samples were collected throughout an 8050 km(2) grid surrounding Pittsburgh and analyzed for methane, carbon dioxide, and C-1-C-10 volatile organic compounds (VOCs). Elevated mixing ratios of methane and C-2-C-8 alkanes were observed in areas with the highest density of UNG wells. Source apportionment was used to identify characteristic emission ratios for UNG sources, and results indicated that UNG emissions were responsible for the majority of mixing ratios of C-2-C-8 alkanes, but accounted for a small proportion of alkene and aromatic compounds. The VOC emissions from UNG operations accounted for 17 +/- 19% of the regional kinetic hydroxyl radical reactivity of nonbiogenic VOCs suggesting that natural gas emissions may affect compliance with federal ozone standards. A first approximation of methane emissions from the study area of 10.0 +/- 5.2 kg s(-1) provides a baseline for determining the efficacy of regulatory emission control efforts.

Abstract:
Public health concerns related to the expansion of unconventional oil and gas drilling have sparked intense debate. In 2012, we published case reports of animals and humans affected by nearby drilling operations. Because of the potential for long-term effects of even low doses of environmental toxicants and the cumulative impact of exposures of multiple chemicals by multiple routes of exposure, a longitudinal study of these cases is necessary. Twenty-one cases from five states were followed longitudinally; the follow-up period averaged 25 months. In addition to humans, cases involved food animals, companion animals and wildlife. More than half of all exposures were related to drilling and hydraulic fracturing operations; these decreased slightly over time. More than a third of all exposures were associated with wastewater, processing and production operations; these exposures increased slightly over time. Health impacts decreased for families and animals moving from intensively drilled areas or remaining in areas where drilling activity decreased. In cases of families remaining in the same area and for which drilling activity either remained the same or increased, no change in health impacts was observed. Over the course of the study, the distribution of symptoms was unchanged for humans and companion animals, but in food animals, reproductive problems decreased and both respiratory and growth problems increased. This longitudinal case study illustrates the importance of obtaining detailed epidemiological data on the long-term health effects of multiple chemical exposures and multiple routes of exposure that are characteristic of the environmental impacts of unconventional drilling operations.

Abstract:
Reports of ground water contamination in a southwestern Pennsylvania community coincided with unconventional shale gas extraction activities that started late 2009. Residents participated in a survey and well water samples were collected and analyzed. Available pre-drill and post-drill water test results and legacy operations (e.g., gas and oil wells, coal mining) were reviewed. Fifty-six of the 143 respondents indicated changes in water quality or quantity while 63 respondents reported no issues. Color change (brown, black, or orange) was the most common (27 households). Well type, when known, was rotary or cable tool, and depths ranged from 19 to 274 m. Chloride, sulfate, nitrate, sodium, calcium, magnesium, iron, manganese and strontium were commonly found, with 25 households exceeding the secondary maximum contaminate level (SMCL) for manganese. Methane was detected in 14 of the 18 houses tested. The 26 wells tested for total coliforms (2 positives) and E. coli (1 positive) indicated that septic contamination was not a factor. Repeated sampling of two wells in close proximity (204 m) but drawing from different depths (32 m and 54 m), revealed temporal variability. Since 2009, 65 horizontal wells were drilled within a 4 km (2.5 mile) radius of the community, each well was stimulated on average with 3.5 million gal of fluids and 3.2 million lbs of proppant. PA DEP cited violations included an improperly plugged well and at least one failed well casing. This study underscores the need for thorough analyses of data, documentation of legacy activity, pre-drill testing, and long term monitoring.

Abstract:
Flowback and produced wastewaters from unconventional hydraulic fracturing during oil and gas explorations typically brings to the surface Naturally Occurring Radioactive Materials (NORM), predominantly radioisotopes from the U238 and Th232 decay chains. Traditionally, radiological sampling are performed by sending collected small samples for laboratory tests either by radiochemical analysis or measurements by a high-resolution High-Purity Germanium (HPGe) gamma spectrometer. One of the main isotopes of concern is Ra226 which requires an extended 21-days quantification period to allow for full secular equilibrium to be established for the alpha counting of its progeny daughter Rn222. Field trials of a sodium iodide (NaI) scintillation detector offers a more economic solution for rapid screenings of radiological samples. To achieve the quantification accuracy, this gamma spectrometer must be efficiency calibrated with known standard sources prior to field deployments to analyze the radioactivity concentrations in hydraulic fracturing waste products.

Abstract:
Mercury (Hg) is a persistent element in the environment that has the ability to bioaccumulate and biomagnify up the food chain with potentially harmful effects on ecosystems and human health. Twenty-four streams remotely located in forested watersheds in northwestern PA containing naturally reproducing Salvelinus fontinalis (brook trout), were targeted to gain a better understanding of how Marcellus shale natural gas exploration may be impacting water quality, aquatic biodiversity, and Hg bioaccumulation in aquatic ecosystems. During the summer of 2012, stream water, stream bed sediments, aquatic mosses, macroinvertebrates, crayfish, brook trout, and microbial samples were collected. All streams either had experienced hydraulic fracturing (fracked, n = 14) or not yet experienced hydraulic fracturing (non-fracked, n = 10) within their watersheds at the time of sampling. Analysis of watershed characteristics (GIS) for fracked vs non-fracked sites showed no significant differences (P > 0.05), justifying comparisons between groups. Results showed significantly higher dissolved total mercury (FTHg) in stream water (P = 0.007), lower pH (P = 0.033), and higher dissolved organic matter (P = 0.001) at fracked sites. Total mercury (THg) concentrations in crayfish (P = 0.01), macroinvertebrates (P = 0.089), and predatory macroinvertebrates (P = 0.039) were observed to be higher for fracked sites. A number of positive correlations between amount of well pads within a watershed and THg in crayfish (r = 0.76, P < 0.001), THg in predatory macroinvertebrates (r = 0.71, P < 0.001), and THg in brook trout (r = 0.52, P < 0.01) were observed. Stream-water microbial communities within the Deltaproteobacteria also shared a positive correlation with FTHg and to the number of well pads, while stream pH (r = −0.71, P < 0.001), fish biodiversity (r = −0.60, P = 0.02), and macroinvertebrate taxa richness (r = −0.60, P = 0.01) were negatively correlated with the number of well pads within a watershed. Further investigation is needed to better elucidate relationships and pathways of observed differences in stream water chemistry, biodiversity, and Hg bioaccumulation, however, initial findings suggest Marcellus shale natural gas exploration is having an effect on aquatic ecosystems.

Abstract:
Natural gas extraction activities, including the use of horizontal drilling and hydraulic fracturing, may pose potential health risks to both human and animal populations in close proximity to sites of extraction activity. Because animals may have increased exposure to contaminated water and air as well as increased susceptibility to contaminant exposures compared to nearby humans, animal disease events in communities living near natural gas extraction may provide “sentinel” information useful for human health risk assessment. Community health evaluations as well as health impact assessments (HIAs) of natural gas exploration should therefore consider the inclusion of animal health metrics in their assessment process. We report on a community environmental health survey conducted in an area of active natural gas drilling, which included the collection of health data on 2452 companion and backyard animals residing in 157 randomly-selected households of Washington County, Pennsylvania (USA). There were a total of 127 reported health conditions, most commonly among dogs. When reports from all animals were considered, there were no significant associations between reported health condition and household proximity to natural gas wells. When dogs were analyzed separately, we found an elevated risk of ‘any’ reported health condition in households less than 1km from the nearest gas well (OR = 3.2, 95% CI 1.07–9.7), with dermal conditions being the most common of canine disorders. While these results should be considered hypothesis generating and preliminary, they suggest value in ongoing assessments of pet dogs as well as other animals to better elucidate the health impacts of natural gas extraction on nearby communities.

Abstract:
The Appalachian Basin is home to three major shales, the Upper Devonian, Marcellus, and Utica. Together, they contain significant quantities of tight oil, gas, and mixed hydrocarbons. The Marcellus alone is estimated to contain upwards of 500 trillion cubic feet of natural gas. The extraction of these deposits is facilitated by a combination of horizontal drilling and slick water stimulation (e.g., hydraulic fracturing) or “fracking.” The process of fracking requires large volumes of water, proppant, and chemicals as well as a large well pad (3–7 acres) and an extensive network of gathering and transmission pipelines. Drilling can generate about 1,000 tons of drill cuttings depending on the depth of the formation and the length of the horizontal bore. The flowback and produced waters that return to the surface during production are high in total dissolved solids (TDS, 60,000–350,000 mg L−1) and contain halides (e.g., chloride, bromide, fluoride), strontium, barium, and often naturally occurring radioactive materials (NORMs) as well as organics. The condensate tanks used to store these fluids can off gas a plethora of volatile organic compounds. The waste water, with its high TDS may be recycled, treated, or disposed of through deep well injection. Where allowed, open impoundments used for recycling are a source of air borne contamination as they are often aerated. The gas may be “dry” (mostly methane) or “wet,” the latter containing a mixture of light hydrocarbons and liquids that need to be separated from the methane. Although the wells can produce significant quantities of natural gas, from 2–7 bcf, their initial decline rates are significant (50–75%) and may cease to be economic within a few years. This review presents an overview of unconventional gas extraction highlighting the environmental impacts and challenges.

Abstract:
Equipment- and site-level methane emissions from 45 compressor stations in the transmission and storage (T the highest emitting 10% of sites (including two superemitters) contributed 50% of the aggregate methane emissions, while the lowest emitting 50% of sites contributed less than 10% of the aggregate emissions. Excluding the two superemitters, study-average methane emissions from compressor housings and noncompressor sources are comparable to or lower than the corresponding effective emission factors used in the EPA greenhouse gas inventory. If the two superemitters are included in the analysis, then the average emission factors based on this study could exceed the EPA greenhouse gas inventory emission factors, which highlights the potentially important contribution of superemitters to national emissions. However, quantification of their influence requires knowledge of the magnitude and frequency of superemitters across the entire T&S sector. Only 38% of the methane emissions measured by the comprehensive onsite measurements were reportable under the new EPA GHGRP because of a combination of inaccurate emission factors for leakers and exhaust methane, and various exclusions. The bias is even larger if one accounts for the superemitters, which were not captured by the onsite measurements. The magnitude of the bias varied from site to site by site type and operating state. Therefore, while the GHGRP is a valuable new source of emissions information, care must be taken when incorporating these data into emission inventories. The value of the GHGRP can be increased by requiring more direct measurements of emissions (as opposed to using counts and emission factors), eliminating exclusions such as rod-packing vents on pressurized reciprocating compressors in standby mode under Subpart-W, and using more appropriate emission factors for exhaust methane from reciprocating engines under Subpart-C.

Abstract:
Extraction of oil and gas via unconventional methods is becoming an important aspect of energy production worldwide. Studying the effects of this development in countries where these technologies are being widely used may provide other countries, where development may be proposed, with some insight in terms of concerns associated with development. A fairly recent expansion of unconventional oil and gas development in North America provides such an opportunity. Rapid increases in energy development in North America have caught the attention of managers and scientists as a potential stressor for wildlife and their habitats. Of particular concern in the Northern Great Plains of the U.S. is the potential for chloride-rich produced water associated with unconventional oil and gas development to alter the water chemistry of wetlands. We describe a landscape scale modeling approach designed to examine the relationship between potential chloride contamination in wetlands and patterns of oil and gas development. We used a spatial Bayesian hierarchical modeling approach to assess multiple models explaining chloride concentrations in wetlands. These models included effects related to oil and gas wells (e.g. age of wells, number of wells) and surficial geology (e.g. glacial till, outwash). We found that the model containing the number of wells and the surficial geology surrounding a wetland best explained variation in chloride concentrations. Our spatial predictions showed regions of localized high chloride concentrations. Given the spatiotemporal variability of regional wetland water chemistry, we do not regard our results as predictions of contamination, but rather as a way to identify locations that may require more intensive sampling or further investigation. We suggest that an approach like the one outlined here could easily be extended to more of an adaptive monitoring approach to answer questions about chloride contamination risk that are of interest to managers.

Abstract:
Injection of wastes into the deep subsurface has become a contentious issue, particularly in emerging regions of oil and gas production. Experience in other regions suggests that injection is an effective waste management practice and that widespread environmental damage is unlikely. Over the past several decades, 23 km3 of water has been injected into the Western Canada Sedimentary Basin (WCSB). The oil and gas industry has injected most of this water but large amounts of injection are associated with mining activities. The amount of water injected into this basin during the past century is 2 to 3 orders magnitude greater than natural recharge to deep formations in the WCSB. Despite this large-scale disturbance to the hydrogeological system, there have been few documented cases of environmental problems related to injection wells. Deep injection of waste appears to be a low risk activity based on this experience but monitoring efforts are insufficient to make definitive statements. Serious uncharacterized legacy issues could be present. Initiating more comprehensive monitoring and research programs on the effects of injection in the WCSB could provide insight into the risks associated with injection in less developed sedimentary basins.

Abstract:
This paper reviews major findings and insights from a series of integrated geologic, engineering, economic, and econometric analyses performed on the four largest US. shale gas plays. Developments in the Barnett Shale, Fayetteville Shale, Haynesville Shale, Shale, and Marcellus Shale plays are explained on the basis of a comprehensive data set, including existing wells production histories, drilling path data, geologic attributes and natural gas market parameters. The paper presents the data-driven methodology consistently applied to all four plays. The key insights discussed include the relationship between a play's geology and well production; the impact of technological improvements of well productivity and inventory of future wells; and the dependence of well economics on geology, technology, and regulations.

Abstract:
A necessary element during unconventional gas exploration is the identification of possible environmental hazards. These hazards require quantitative and qualitative assessment to ensure groundwater protection. This is realized using legal-administrative and technical tools. In shale gas exploration areas, the most important method of groundwater protection is groundwater monitoring. Correct design of a monitoring system is based on studies allowing for early recognition of the real impact on groundwater. An optimally operating monitoring network should allow explicit determination of the direction, range and area of water pollution during shale gas exploration. In Poland and other countries, the existing solutions and legal regulations related to water monitoring are generalized and usually not specifically dedicated to assessment of hazard caused by shale gas exploration. There is a need for an individual approach to the concept and design of the monitoring network for each specific investment.

Abstract:
The natural gas supply chain includes production, processing, and transmission of natural gas, which originates from conventional, shale, coal bed, and other reservoirs. Because the hydrocarbon products and the emissions associated with extraction from different reservoir types can differ, when expressing methane emissions from the natural gas supply chain, it is important to allocate emissions to particular hydrocarbon products and reservoir types. In this work, life cycle allocation methods have been used to assign methane emissions from production wells operating in shale formations to oil, condensate, and gas products from the wells. The emission allocations are based on a data set of 489 gas wells in routine operation and 19 well completion events. The methane emissions allocated to natural gas production are approximately 85% of total emissions (mass based allocation), but there is regional variability in the data and therefore this work demonstrates the need to track natural gas sources by both formation type and production region. Methane emissions allocated to salable natural gas production from shale formations, based on this work, are a factor of 2 to 7 lower than those reported in commonly used life cycle data sets.

Abstract:
Hydraulic fracturing (HF) is a focal topic in discussions about domestic energy production, yet the American public is largely unfamiliar and undecided about the practice. This study sheds light on how individuals may come to understand hydraulic fracturing as this unconventional production technology becomes more prominent in the United States. For the study, a thorough search of HF photographs was performed, and a systematic evaluation of 40 images using an online experimental design involving participants was conducted. Key indicators of hydraulic fracturing support and beliefs were identified. Participants showed diversity in their support for the practice, with 47 percent expressing low support, 22 percent high support, and 31 percent undecided. Support for HF was positively associated with beliefs that hydraulic fracturing is primarily an economic issue and negatively associated with beliefs that it is an environmental issue. Level of support was also investigated as a perceptual filter that facilitates biased issue perceptions and affective evaluations of economic benefit and environmental cost frames presented in visual content of hydraulic fracturing. Results suggested an interactive relationship between visual framing and level of support, pointing to a substantial barrier to common understanding about the issue that strategic communicators should consider.

Abstract:
We conducted three-dimensional coupled fluid-flow and geomechanical modeling of fault activation and seismicity associated with hydraulic fracturing stimulation of a shale-gas reservoir. We simulated a case in which a horizontal injection well intersects a steeply dipping fault, with hydraulic fracturing channeled within the fault, during a 3-h hydraulic fracturing stage. Consistent with field observations, the simulation results show that shale-gas hydraulic fracturing along faults does not likely induce seismic events that could be felt on the ground surface, but rather results in numerous small microseismic events, as well as aseismic deformations along with the fracture propagation. The calculated seismic moment magnitudes ranged from about −2.0 to 0.5, except for one case assuming a very brittle fault with low residual shear strength, for which the magnitude was 2.3, an event that would likely go unnoticed or might be barely felt by humans at its epicenter. The calculated moment magnitudes showed a dependency on injection depth and fault dip. We attribute such dependency to variation in shear stress on the fault plane and associated variation in stress drop upon reactivation. Our simulations showed that at the end of the 3-h injection, the rupture zone associated with tensile and shear failure extended to a maximum radius of about 200 m from the injection well. The results of this modeling study for steeply dipping faults at 1000 to 2500 m depth is in agreement with earlier studies and field observations showing that it is very unlikely that activation of a fault by shale-gas hydraulic fracturing at great depth (thousands of meters) could cause felt seismicity or create a new flow path (through fault rupture) that could reach shallow groundwater resources.

Abstract:
Huge quantities of unconventional U.S. shale gas augur nothing less than a shift in the global order. An appraisal of global energy trends suggests that the U.S., at the cusp of attaining energy self-sufficiency, should lean more toward a strategy of maintaining energy stability than wielding its new clout in the service of broader geopolitical or economic objectives.

Abstract:
The combined emissions and air quality impacts of electricity generation in the Texas grid and natural gas production in the Eagle Ford shale were estimated at various natural gas price points for the power sector. The increased use of natural gas in the power sector, in place of coal-fired power generation, drove reductions in average daily maximum 8-hr ozone concentration of 0.6 ppb to 1.3 ppb in northeastern Texas for a high ozone episode used in air quality planning. The associated increase in Eagle Ford upstream oil and gas production nitrogen oxide (NOx) emissions caused an estimated local increase, in South Texas, of 0.3 ppb to 0.7 ppb in the same ozone metric. In addition, the potential ozone impacts of Eagle Ford emissions on nearby urban areas were estimated. Based on evidence from this work and a previous study on the Barnett shale, the combined ozone impact of increased natural gas development and use in the power sector is likely to vary regionally and must be analyzed on a case by case basis.

Abstract:
Across vast swaths of mostly rural Pennsylvania, dramatic social, economic, and environmental transformations have occurred in the last five years as these regions have experienced a new natural resource boom in the form of unconventional natural gas extraction from the Marcellus Shale formation. While Pennsylvania's former Governor, Tom Corbett, and shale industry advocates hailed these developments as an economic godsend for Pennsylvania, others have raised serious concerns about the potential social, environmental, and economic consequences. In this paper, we examine youth perspectives in shale gas communities and how young people weigh their education and future prospects in light of local economic, environmental, and community change. We find that youth career decisions are often characterized by a deep ambivalence about the gas industry, its longevity, its capacity to provide desirable and local employment, and its ultimate effects on the livability and social sustainability of Pennsylvania's shale gas communities, complicating pro-industry and neoliberal narratives of opportunity and economic development. This ambivalence raises critical questions about the effects of new labor market opportunities on the educational, career, and residential aspirations of youth within areas of high drilling and gas extraction activity.

Abstract:
Large areas of the United States long considered geologically stable with little or no detected seismicity have recently become seismically active. The increase in earthquake activity began in the mid-continent starting in 2001 (1) and has continued to rise. In 2014, the rate of occurrence of earthquakes with magnitudes (M) of 3 and greater in Oklahoma exceeded that in California (see the figure). This elevated activity includes larger earthquakes, several with M > 5, that have caused significant damage (2, 3). To a large extent, the increasing rate of earthquakes in the mid-continent is due to fluid-injection activities used in modern energy production (1, 4, 5). We explore potential avenues for mitigating effects of induced seismicity. Although the United States is our focus here, Canada, China, the UK, and others confront similar problems associated with oil and gas production, whereas quakes induced by geothermal activities affect Switzerland, Germany, and others. Hazard may be reduced by managing injection activities Hazard may be reduced by managing injection activities

Abstract:
China is seeking to unlock its shale gas in order to curb its notorious urban air pollution, but robust assessment of the impact on PM2.5 pollution of replacing coal with natural gas for winter heating is lacking. Here, using a whole-city heating energy shift opportunity offered by substantial reductions in coal combustion during the heating periods in Urumqi, northwest China, we conducted a four-year study to reveal the impact of replacing coal with natural gas on the mass concentrations and chemical components of PM2.5 We found a significant decline in PM2.5, major soluble ions and metal elements in PM2.5 in January of 2013 and 2014 compared with the same periods in 2012 and 2011, reflecting the positive effects on air quality of using natural gas as a heating fuel throughout the city. This occurred following complete replacement with natural gas for heating energy in October 2012. The weather conditions during winter did not show any significant variation over the four years of the study. Our results indicate that China and other developing nations will benefit greatly from a change in energy source, that is, increasing the contribution of either natural gas or shale gas to total energy consumption with a concomitant reduction in coal consumption.

Abstract:
Baseline groundwater geochemical mapping of inorganic and isotopic parameters across 44,000 km2 of southwestern Ontario (Canada) has delineated a discreet zone of natural gas in the bedrock aquifer coincident with an 8,000-km2 exposure of Middle Devonian shale. This study describes the ambient geochemical conditions in these shales in the context of other strata, including Ordovician shales, and discusses shale-related natural and anthropogenic processes contributing to hydrogeochemical conditions in the aquifer. The three Devonian shales—the Kettle Point Formation (Antrim equivalent), Hamilton Group and Marcellus Formation—have higher DOC, DIC, HCO3, CO2(aq), pH and iodide, and much higher CH4(aq). The two Ordovician shales—the Queenston and Georgian-Bay/Blue Mountain Formations—are higher in Ca, Mg, SO4 and H2S. In the Devonian shale region, isotopic zones of Pleistocene-aged groundwater have halved in size since first identified in the 1980s; potentiometric data implicate regional groundwater extraction in the shrinkage. Isotopically younger waters invading the aquifer show rapid increases in CH4(aq), pH and iodide with depth and rapid decrease in oxidized carbon species including CO2, HCO3 and DIC, suggesting contemporary methanogenesis. Pumping in the Devonian shale contact aquifer may stimulate methanogenesis by lowering TDS, removing products and replacing reactants, including bicarbonate, derived from overlying glacial sedimentary aquifers.

Abstract:
Using data from Pennsylvania and an array of empirical techniques to control for confounding factors, we recover hedonic estimates of property value impacts from nearby shale gas development that vary with water source, well productivity, and visibility. Results indicate large negative impacts on nearby groundwater-dependent homes, while piped-water-dependent homes exhibit smaller positive impacts, suggesting benefits from lease payments. Results have implications for the debate over regulation of shale gas development.

Abstract:
The number of Marcellus Shale gas wells drilled in the Appalachian basin has increased rapidly over the past decade, leading to increased interest in the highly saline water produced with the natural gas which must be recycled, treated, or injected into deep disposal wells. New geochemical and isotopic analyses of produced water for 3 time-series and 13 grab samples from Marcellus Shale gas wells in southwest and north central Pennsylvania (PA) are used to address the origin of the water and solutes produced over the long term (>12 months). The question of whether the produced water originated within the Marcellus Shale, or whether it may have been drawn from adjacent reservoirs via fractures is addressed using measurements of and activity. These parameters indicate that the water originated in the Marcellus Shale, and can be more broadly used to trace water of Marcellus Shale origin. During the first 1–2 weeks of production, rapid increases in salinity and positive shifts in values were observed in the produced water, followed by more gradual changes until a compositional plateau was reached within approximately 1 yr. The values and relationships between Na, Cl, and Br provide evidence that the water produced after compositional stabilization is natural formation water, the salinity for which originated primarily from evaporatively concentrated paleoseawater. The rapid transition from injected water to chemically and isotopically distinct water while of the injected water volume had been recovered, supports the hypothesis that significant volumes of injected water were removed from circulation by imbibition.

Abstract:
We present measurements of methane (CH4) taken aboard a NOAA WP-3D research aircraft in 2013 over the Haynesville shale region in eastern Texas/northwestern Louisiana, the Fayetteville shale region in Arkansas, and the northeastern Pennsylvania portion of the Marcellus shale region, which accounted for the majority of Marcellus shale gas production that year. We calculate emission rates from the horizontal CH4 flux in the planetary boundary layer downwind of each region after subtracting the CH4 flux entering the region upwind. We find one-day CH4 emissions of (8.0 ± 2.7) × 107 g/hr from the Haynesville region, (3.9 ± 1.8) × 107 g/hr from the Fayetteville region, and (1.5 ± 0.6) × 107 g/hr from the Marcellus region in northeastern Pennsylvania. Finally, we compare the CH4 emissions to the total volume of natural gas extracted from each region to derive a loss rate from production operations of 1.0–2.1% from the Haynesville region, 1.0–2.8% from the Fayetteville region, and 0.18–0.41% from the Marcellus region in northeastern Pennsylvania. The climate impact of CH4 loss from shale gas production depends upon the total leakage from all production regions. The regions investigated in this work represented over half of the U.S. shale gas production in 2013, and we find generally lower loss rates than those reported in earlier studies of regions that made smaller contributions to total production. Hence, the national average CH4 loss rate from shale gas production may be lower than values extrapolated from the earlier studies.

Abstract:
Rapid global expansion of unconventional natural gas development (UNGD) raises environmental health concerns. Many studies present information on these concerns, yet the strength of epidemiological evidence remains tenuous. This paper is a review of the strength of evidence in scientific reporting of environmental hazards from UNGD activities associated with adverse human health outcomes. Studies were drawn from peer-reviewed and grey literature following a systematic search. Five databases were searched for studies published from January 1995 through March 2014 using key search terms relevant to environmental health. Studies were screened, ranked and then reviewed according to the strength of the evidence presented on adverse environmental health outcomes associated with UNGD. The initial searches yielded > 1000 studies, but this was reduced to 109 relevant studies after the ranking process. Only seven studies were considered highly relevant based on strength of evidence. Articles spanned several relevant topics, but most focussed on impacts on typical environmental media, such as water and air, with much of the health impacts inferred rather than evidenced. Additionally, the majority of studies focussed on short-term, rather than long-term, health impacts, which is expected considering the timeframe of UNGD; therefore, very few studies examined health outcomes with longer latencies such as cancer or developmental outcomes. Current scientific evidence for UNGD that demonstrates associations between adverse health outcomes directly with environmental health hazards resulting from UNGD activities generally lacks methodological rigour. Importantly, however, there is also no evidence to rule out such health impacts. While the current evidence in the scientific research reporting leaves questions unanswered about the actual environmental health impacts, public health concerns remain intense. This is a clear gap in the scientific knowledge that requires urgent attention.

Abstract:
The data provided by the PA DEP are incomplete because confidential data are not released. It is impossible to make firm conclusions about water quality impacts when data availability is limited. Nonetheless, the PA experience appears to be characterized by a low rate of problems per gas well or unit of gas produced. Only about 160 of the complaints from homeowners about groundwater to the PA DEP between 2008 and 2012 were problems attributed to oil and gas activity—and only half of these were caused by companies known to drill unconventional shale wells. These problematic wells in turn represent only 0.1 to 1% of the unconventional shale gas wells drilled in that time period (Brantley et al. 2014). Management practices appear to be improving as well; the rate of problems has decreased since 2010 (Figure 1). Apparently, however, the public responds not only to the number of problems per gas well or per unit of gas produced but rather to the number of problems per unit time and per unit area. Thus, even though the r ate of problems with shale gas wells has remained small on a per well basis, pushback has grown in areas of increasing density of drilling and fracking. This may be especially true when consequences are fearsome such as flaming tapwater, toxic contamination, or earthquakes. It is natural that the social license for shale gas development is influenced by short-term, local thinking. But, such thinking may not be helpful given that Marcellus Shale gas wells generate one third the waste per unit volume of gas as compared to conventional shallow gas wells (Vidic et al. 2013). In addition, the release of pollutants such as carbon dioxide, particulates, mercury, nitrogen, and sulfur generated per unit of heat energy is lower f or unconventional shale gas than for fuels such as coal (Heath et al. 2014). Public pushback could nonetheless be a blessing. After all, pushback represents intensified interest in environmental issues. This interest may be seen in the PA DEP data for the rate of well integrity issues in conventional oil and gas wells—the increase in problem rate from 2008 to 2012 (Figure 1) is more likely due to heightened public attention and inspector scrutiny rather than a sudden deterioration in the management practices of the drilling companies (Brantley et al. 2014) During the next decades, the rate of hydraulic fracturing in PA will eventually slow. At some point, the use of produced brines to hydrofracture new wells will cease. Once recycling of brine to frack new wells stops, hundreds of gallons of brine will accumulate as waste at each well per day (Rahm et al. 2013). Disposal of this slightly radioactive brine will then become increasingly problematic. Interest on the part of the public for such issues is warranted. Public engagement today is needed to develop sustainable waste management and sustainable energy practices for the future.

Abstract:
This study analyzes how incremental U.S. liquefied natural gas (LNG) exports affect global greenhouse gas (GHG) emissions. Emissions of LNG exported from U.S. ports to Asian and European markets account for only 3.5-5.5% of pre-combustion life cycle emissions, hence shipping distance is not a major driver of GHGs. This study finds exported U.S. LNG has mean pre-combustion emissions of 37g CO2-equiv/MJ when regasified in Europe and Asia. A scenario-based analysis addressing how potential end uses (electricity and industrial heating) and displacement of existing fuels (coal and Russian natural gas) affect GHG emissions shows the mean emissions for electricity generation using U.S. exported LNG were 655 g CO2-equiv/kWh (with a 90% confidence interval of 562-770), an 11% increase over U.S. natural gas electricity generation. Mean emissions from industrial heating were 104 g CO2-equiv/MJ (90% CI: 87-123). By displacing coal, LNG saves 550 g CO2-equiv per kWh of electricity and 20 g per MJ of heat. LNG saves GHGs under upstream fugitive emissions rates up to 9% and 5% for electricity and heating, respectively. GHG reductions were found if Russian pipeline natural gas was displaced for electricity and heating use regardless of GWP, as long as U.S. fugitive emission rates remain below the estimated 5-7% rate of Russian gas. However, from a country specific carbon accounting perspective, there is an imbalance in accrued social costs and benefits. Assuming a mean social cost of carbon of $49/metric ton, mean global savings from U.S. LNG displacement of coal for electricity generation are $1.50 per thousand cubic feet (Mcf) of gaseous natural gas exported as LNG ($.027/kWh). Conversely, the U.S. carbon cost of exporting the LNG is $1.80/Mcf ($.013/kWh), or $0.50-$5.50/Mcf across the range of potential discount rates. This spatial shift in embodied carbon emissions is important to consider in national interest estimates for LNG exports.

Abstract:
Precise relative hypocentres of seismic events induced by long-term fluid injection at the Paradox Valley Unit (PVU) brine disposal well provide constraints on the subsurface geological structure and compliment information available from deep seismic reflection and well data. We use the 3-D spatial distribution of the hypocentres to refine the locations, strikes, and throws of subsurface faults interpreted previously from geophysical surveys and to infer the existence of previously unidentified subsurface faults. From distinct epicentre lineations and focal mechanism trends, we identify a set of conjugate fracture orientations consistent with shear-slip reactivation of late-Palaeozoic fractures over a widespread area, as well as an additional fracture orientation present only near the injection well. We propose simple Mohr-Coulomb fracture models to explain these observations. The observation that induced seismicity preferentially occurs along one of the identified conjugate fracture orientations can be explained by a rotation in the direction of the regional maximum compressive stress from the time when the fractures were formed to the present. Shear slip along the third fracture orientation observed near the injection well is inconsistent with the current regional stress field and suggests a local rotation of the horizontal stresses. The detailed subsurface model produced by this analysis provides important insights for anticipating spatial patterns of future induced seismicity and for evaluation of possible additional injection well sites that are likely to be seismically and hydrologically isolated from the current well. In addition, the interpreted fault patterns provide constraints for estimating the maximum magnitude earthquake that may be induced, and for building geomechanical models to simulate pore pressure diffusion, stress changes and earthquake triggering.

Abstract:
We systematically re-analyzed historical seismograms to verify the existence of background seismicity in the Horn River Basin of northeast British Columbia before the start of regional shale gas development. We also carefully relocated local earthquakes that occurred between December 2006 and December 2011 to delineate their spatiotemporal relationship with hydraulic fracturing (HF) operations in the region. Scattered seismic events were detected in the Horn River Basin throughout the study periods. The located seismicity within 100 km of the Fort Nelson seismic station had a clearly increasing trend, specifically in the Etsho area where most local HF operations were performed. The number of events was increased from 24 in 2002-2003 (prior to HF operations) to 131 in 2011 (peak period of HF operations). In addition, maximum magnitude of the events was shifted from M-L 2.9 to M-L 3.6 as the scale of HF operation expanded from 2006-2007 to 2011. Based on our relocated earthquake catalog, the overall b value is estimated at 1.21, which is higher than the average of tectonic/natural earthquakes of similar to 1.0. Our observations highly support the likelihood of a physical relationship between HF operation and induced seismicity in the Horn River Basin. Unfortunately, due to the sparse station density in the region, depth resolution is poor for the vast majority of events in our study area. As new seismograph stations are established in northeast British Columbia, both epicentral mislocation and depth uncertainty for future events are expected to improve significantly.

Abstract:
Hydraulic fracturing fluids contain a mix of organic and inorganic additives in an aqueous media. The compositions of these mixtures vary according to the region or company use, thus making the process of identifying individual compounds difficult. The analytical characterization of such mixtures is important in order to understand the transport, environmental fate and ultimate potential health impact in various water compartments associated with hydraulic fracturing. Organic compound classes include solvents, gels, biocides, scale inhibitors, friction reducers, surfactants and other related compounds. These contaminants are usually present in trace amounts, so sophisticated analytical methodologies are needed in order to fully characterize the chemical composition of fracking fluids. The current state of knowledge of chemical components and approaches for their analysis is reviewed here. In recent years, modern analytical methodologies, such as gas chromatography–mass spectrometry (GC–MS) have been specifically used to identify organic chemical components of fracking fluids and/or flowback and produced waters associated with the process of hydraulic fracturing. Other techniques such as liquid chromatography–mass spectrometry (LC–MS) have not been explored in detail yet. In this review a detailed description of chemical constituents present in hydraulic fracturing waters will be given, as well as an evaluation of the analytical techniques used for their unequivocal determination.

Abstract:
Objective Short-term exposure to ground-level ozone has been linked to adverse respiratory and other health effects; previous studies typically have focused on summer ground-level ozone in urban areas. During 2008–2011, Sublette County, Wyoming (population: ~10,000 persons), experienced periods of elevated ground-level ozone concentrations during the winter. This study sought to evaluate the association of daily ground-level ozone concentrations and health clinic visits for respiratory disease in this rural county. Methods Clinic visits for respiratory disease were ascertained from electronic billing records of the two clinics in Sublette County for January 1, 2008–December 31, 2011. A time-stratified case-crossover design, adjusted for temperature and humidity, was used to investigate associations between ground-level ozone concentrations measured at one station and clinic visits for a respiratory health concern by using an unconstrained distributed lag of 0–3 days and single-day lags of 0 day, 1 day, 2 days, and 3 days. Results The data set included 12,742 case-days and 43,285 selected control-days. The mean ground-level ozone observed was 47±8 ppb. The unconstrained distributed lag of 0–3 days was consistent with a null association (adjusted odds ratio [aOR]: 1.001; 95% confidence interval [CI]: 0.990–1.012); results for lags 0, 2, and 3 days were consistent with the null. However, the results for lag 1 were indicative of a positive association; for every 10-ppb increase in the 8-h maximum average ground-level ozone, a 3.0% increase in respiratory clinic visits the following day was observed (aOR: 1.031; 95% CI: 0.994–1.069). Season modified the adverse respiratory effects: ground-level ozone was significantly associated with respiratory clinic visits during the winter months. The patterns of results from all sensitivity analyzes were consistent with the a priori model. Conclusions The results demonstrate an association of increasing ground-level ozone with an increase in clinic visits for adverse respiratory-related effects in the following day (lag day 1) in Sublette County; the magnitude was strongest during the winter months; this association during the winter months in a rural location warrants further investigation.

Abstract:
Here we compare volatile organic compound (VOC) measurements using a standard proton-transfer-reaction quadrupole mass spectrometer (PTR-QMS) with a new proton-transfer-reaction time of flight mass spectrometer (PTR-TOF) during the Uintah Basin Winter Ozone Study 2013 (UBWOS2013) field experiment in an oil and gas field in the Uintah Basin, Utah. The PTR-QMS uses a quadrupole, which is a mass filter that lets one mass to charge ratio pass at a time, whereas the PTR-TOF uses a time of flight mass spectrometer, which takes full mass spectra with typical 0.1 s–1 min integrated acquisition times. The sensitivity of the PTR-QMS in units of counts per ppbv (parts per billion by volume) is about a factor of 10–35 times larger than the PTR-TOF, when only one VOC is measured. The sensitivity of the PTR-TOF is mass dependent because of the mass discrimination caused by the sampling duty cycle in the orthogonal-acceleration region of the TOF. For example, the PTR-QMS on mass 33 (methanol) is 35 times more sensitive than the PTR-TOF and for masses above 120 amu less than 10 times more. If more than 10–35 compounds are measured with PTR-QMS, the sampling time per ion decreases and the PTR-TOF has higher signals per unit measuring time for most masses. For UBWOS2013 the PTR-QMS measured 34 masses in 37 s and on that timescale the PTR-TOF is more sensitive for all masses. The high mass resolution of the TOF allows for the measurements of compounds that cannot be separately detected with the PTR-QMS, such as oxidation products from alkanes and cycloalkanes emitted by oil and gas extraction. PTR-TOF masses do not have to be preselected, allowing for identification of unanticipated compounds. The measured mixing ratios of the two instruments agreed very well (R2 ≥ 0.92 and within 20%) for all compounds and masses monitored with the PTR-QMS.

Abstract:
Methane emissions from natural gas delivery and end use must be quantified to evaluate the environmental impacts of natural gas and to develop and assess the efficacy of emission reduction strategies. We report natural gas emission rates for 1 y in the urban region of Boston, using a comprehensive atmospheric measurement and modeling framework. Continuous methane observations from four stations are combined with a high-resolution transport model to quantify the regional average emission flux, 18.5 ± 3.7 (95% confidence interval) g CH4⋅m−2⋅y−1. Simultaneous observations of atmospheric ethane, compared with the ethane-to-methane ratio in the pipeline gas delivered to the region, demonstrate that natural gas accounted for ∼60–100% of methane emissions, depending on season. Using government statistics and geospatial data on natural gas use, we find the average fractional loss rate to the atmosphere from all downstream components of the natural gas system, including transmission, distribution, and end use, was 2.7 ± 0.6% in the Boston urban region, with little seasonal variability. This fraction is notably higher than the 1.1% implied by the most closely comparable emission inventory.

Abstract:
Oil and natural gas development has increased dramatically in native grasslands over the past 25 years. Some grassland songbirds are less abundant in areas with oil and gas development, but the effects vary among species and geographically within a species' range. The reproductive consequences of nesting in areas with oil and gas development are unknown. We assessed how the density and reproductive success of five species of grassland songbird in Alberta, Canada, varied with distance to oil and gas wells, gravel roads, and trails, and cover of crested wheatgrass (Agropyron cristatum), an aggressive alien plant that often becomes established following anthropogenic disturbance. Crested wheatgrass cover had the greatest impact on the grassland songbird community. Sprague's Pipit (Anthus spragueii) nest survival decreased as the amount of crested wheatgrass increased. As crested wheatgrass cover increased from 0% to 60%, density of Savannah Sparrows (Passerculus sandwichensis) declined by 50%, but they fledged 25% more young from successful nests. Density of Savannah Sparrows was twice as high near wells, and fledging success was 40% higher compared with 700 m away. Distance to gravel roads did not influence the density or reproductive success of any species. Sprague's Pipits and Baird's Sparrows (Ammodramus bairdii) avoided nesting within 100 m of trails, and both species fledged fewer young from successful nests near trails. In contrast, Vesper Sparrows (Pooecetes gramineus) nested close to trails and fledged more young from successful nests near trails. Western Meadowlarks (Sturnella neglecta) were not strongly affected by any variable. Brown-headed Cowbird (Molothrus ater) abundance was three times higher in study plots with wells, although we detected no associated increase in brood parasitism. Our results indicate that the introduction and spread of crested wheatgrass and the creation of access trails to well pads have negative reproductive consequences for primary endemic species such as Sprague's Pipit and Baird's Sparrow, although these results do not extend to other grassland birds. The spread of crested wheatgrass and the disturbance of access trails could be reduced by directional drilling of multiple wells from a single well pad.

Abstract:
The expansion of unconventional shale gas and hydraulic fracturing has increased the volume of the oil and gas wastewater (OGW) generated in the U.S. Here we demonstrate that OGW from Marcellus and Fayetteville hydraulic fracturing flowback fluids and Appalachian conventional produced waters is characterized by high chloride, bromide, iodide (up to 56 mg/L), and ammonium (up to 420 mg/L). Br/Cl ratios were consistent for all Appalachian brines, which reflect an origin from a common parent brine, while the I/Cl and NH4/Cl ratios varied among brines from different geological formations, reflecting geogenic processes. There were no differences in halides and ammonium concentrations between OGW originating from hydraulic fracturing and conventional oil and gas operations. Analysis of discharged effluents from three brine treatment sites in Pennsylvania and a spill site in West Virginia show elevated levels of halides (iodide up to 28 mg/L) and ammonium (12 to 106 mg/L) that mimic the composition of OGW and mix conservatively in downstream surface waters. Bromide, iodide, and ammonium in surface waters can impact stream ecosystems and promote the formation of toxic brominated-, iodinated-, and nitrogen disinfection byproducts during chlorination at downstream drinking water treatment plants. Our findings indicate that discharge and accidental spills of OGW to waterways pose risks to both human health and the environment.

Abstract:
Recent increases in oil and natural gas (NG) production throughout the western US have come with scientific and public interest in emission rates, air quality and climate impacts related to this industry. This study uses a regional-scale air quality model (WRF-Chem) to simulate high ozone (O3) episodes during the winter of 2013 over the Uinta Basin (UB) in northeastern Utah, which is densely populated by thousands of oil and NG wells. The high-resolution meteorological simulations are able qualitatively to reproduce the wintertime cold pool conditions that occurred in 2013, allowing the model to reproduce the observed multi-day buildup of atmospheric pollutants and the accompanying rapid photochemical ozone formation in the UB. Two different emission scenarios for the oil and NG sector were employed in this study. The first emission scenario (bottom-up) was based on the US Environmental Protection Agency (EPA) National Emission Inventory (NEI) (2011, version 1) for the oil and NG sector for the UB. The second emission scenario (top-down) was based on estimates of methane (CH4) emissions derived from in situ aircraft measurements and a regression analysis for multiple species relative to CH4 concentration measurements in the UB. Evaluation of the model results shows greater underestimates of CH4 and other volatile organic compounds (VOCs) in the simulation with the NEI-2011 inventory than in the case when the top-down emission scenario was used. Unlike VOCs, the NEI-2011 inventory significantly overestimates the emissions of nitrogen oxides (NOx), while the top-down emission scenario results in a moderate negative bias. The model simulation using the top-down emission case captures the buildup and afternoon peaks observed during high O3 episodes. In contrast, the simulation using the bottom-up inventory is not able to reproduce any of the observed high O3 concentrations in the UB. Simple emission reduction scenarios show that O3 production is VOC sensitive and NOx insensitive within the UB. The model results show a disproportionate contribution of aromatic VOCs to O3 formation relative to all other VOC emissions. The model analysis reveals that the major factors driving high wintertime O3 in the UB are shallow boundary layers with light winds, high emissions of VOCs from oil and NG operations compared to NOx emissions, enhancement of photolysis fluxes and reduction of O3 loss from deposition due to snow cover.

Abstract:
Hydraulic fracturing and horizontal drilling have become major methods to extract new oil and gas deposits, many of which exist in shale formations in the temperate deciduous biome of the eastern United States. While these technologies have increased natural gas production to new highs, they can have substantial environmental effects. We measured the changes in land use within the maturing Fayetteville Shale gas development region in Arkansas between 2001/2002 and 2012. Our goal was to estimate the land use impact of these new technologies in natural gas drilling and predict future consequences for habitat loss and fragmentation. Loss of natural forest in the gas field was significantly higher compared to areas outside the gas field. The creation of edge habitat, roads, and developed areas was also greater in the gas field. The Fayetteville Shale gas field fully developed about 2 % of the natural habitat within the region and increased edge habitat by 1,067 linear km. Our data indicate that without shale gas activities, forest cover would have increased slightly and edge habitat would have decreased slightly, similar to patterns seen recently in many areas of the southern U.S. On average, individual gas wells fully developed about 2.5 ha of land and modified an additional 0.5 ha of natural forest. Considering the large number of wells drilled in other parts of the eastern U.S. and projections for new wells in the future, shale gas development will likely have substantial negative effects on forested habitats and the organisms that depend upon them.