Repository for Oil and Gas Energy Research (ROGER)

Abstract:
Limited air monitoring studies with long-term measurements during all phases of development and production of natural gas and natural gas liquids have been conducted in close proximity to unconventional natural gas well pads.

Abstract:
Over the past decade, the shale gas boom has led to increasing public concerns regarding communities' exposure to air pollutants from shale gas development resulting in concentrations higher than the EPA's National Ambient Air Quality Standards. This study investigates the sufficiency of current policy in Pennsylvania to protect people from exposure to fine particulate matter (PM2.5) emissions from such development. We used a Gaussian plume model to simulate PM2.5 concentrations over the Marcellus shale region of Pennsylvania, and using census block data, we estimated the potential number of people who experienced exceedance of the PM2.5 standard between 2005 and 2017. Results demonstrate that these emissions could increase the number of exceedances by more than 36,000 persons in a single year which is almost 1% of the Marcellus shale regional population in Pennsylvania. This number has largely been proportional to the overall number of developed wells, but development histories show that similar levels of development could occur with reduced population exposure. Setback policy is shown to be an effective method to reduce exposure exceedances, but results suggest that it should be revised based on the number of wells per wellpad as well as the local conditions to further limit air quality impacts.

Abstract:
Recently, oil and natural gas (O&NG) production activities in the Denver-Julesburg Basin have expanded rapidly. Associated nonmethane hydrocarbon (NMHC) emissions contribute to photochemical formation of ground-level ozone and include benzene as well as other hazardous air pollutants. Using positive matrix factorization (PMF) and chemical mass balance (CMB) methods, we estimate how much O&NG activities and other sources contribute to morning NMHC mixing ratios measured from 2013 to mid-2016 at a site in Platteville, CO, in the Denver-Julesburg Basin, and at a contrasting site in downtown Denver. A novel adjoint sensitivity analysis method is then used to estimate corresponding contributions to ozone and ozone-linked mortality in the Denver region. Average 6–9 am NMHC mixing ratios in Platteville were seven times higher than those in Denver in 2013 but four times higher in 2016. CMB estimates that O&NG activities contributed to the Platteville (Denver) site an average of 96% (56%) of NMHC on a carbon basis while PMF indicated 92% (33%). Average vehicle-related contributions of NMHC are estimated as 41% by CMB and 53% by PMF in Denver. Estimates of the fractional contribution to potential ozone and ozone-linked mortality from O&NG activities are smaller while those from vehicles are larger than the NMHC contributions. CMB (PMF) indicate that greater than 78% (40%) of annual average benzene in Denver is attributable to vehicle emissions while greater than 75% (67%) of benzene in Platteville is attributable to O&NG activities.

Abstract:
In this study, a ground-based mobile measurement system was developed to provide rapid and cost-effective emission surveillance of both methane (CH4) and volatile organic compounds (VOCs) from oil and gas (O&G) production sites. After testing in several controlled release experiments, the system was deployed in a field campaign in the Eagle Ford basin, TX. We found fat-tail distributions for both methane and total VOC (C4–C12) emissions (e.g., the top 20% sites ranked according to methane and total VOC (C4–C12) emissions were responsible for ∼60 and ∼80% of total emissions, respectively) and a good correlation between them (Spearman’s R = 0.74). This result suggests that emission controls targeting relatively large emitters may help significantly reduce both methane and VOCs in oil and wet gas basins, such as the Eagle Ford. A strong correlation (Spearman’s R = 0.84) was found between total VOC (C4–C12) emissions estimated using SUMMA canisters and data reported from a local ambient air monitoring station. This finding suggests that this system has the potential for rapid emission surveillance targeting relatively large emitters, which can help achieve emission reductions for both greenhouse gas (GHG) and air toxics from O&G production well pads in a cost-effective way.

Abstract:
This study explores the effect of different phases of unconventional shale gas well-pad development on ambient air quality and the relationship between ambient concentrations of air pollutants and operator activity. The U.S. Department of Energy’s National Energy Technology Laboratory operated a mobile air-monitoring laboratory on two shale well pad sites in Pennsylvania and six shale well pad sites in West Virginia. The purpose of this study is to integrate expert knowledge and collected ambient air monitoring data by developing a Bayesian network (BN) model. The monitoring period included well-pad site development; construction, including vertical and horizontal drilling; hydraulic fracturing; flowback; and production. The observed data includes meteorological data with high time resolution and air quality data (volatile organic compounds (VOCs), ozone, methane and carbon isotopes in methane, carbon dioxide (CO2) and carbon isotopes in CO2, coarse and fine particulate matter (PM10 and PM2.5), and organic and elemental carbon). The results provide useful information for evaluating the influence of on- and off-site pollutant sources and determining future research efforts for building the BN model. The overall results of the developed six scenarios show that the prediction power of the proposed model for the vertical drilling phase is 94%. The high concentration of methane increases the probability of fracturing phase as source; the low concentration of PM10 and O3 occurrence increases the same probability to 82%; the low concentration of ethane and CO2 increases the probability to 98%. This study shows how expert Bayesian models can improve our ability to predict future air pollution risk associated with unconventional shale gas development.

Abstract:
Unconventional oil and natural gas development (UOGD) expanded extensively in the United States from the early 2000s. However, the influence of UOGD on the radioactivity of ambient particulate is not well understood. We collected the ambient particle radioactivity (PR) measurements of RadNet, a nationwide environmental radiation monitoring network. We obtained the information of over 1.5 million wells from the Enverus database. We investigated the association between the upwind UOGD well count and the downwind gross-beta radiation with adjustment for environmental factors governing the natural emission and transport of radioactivity. Our statistical analysis found that an additional 100 upwind UOGD wells within 20 km is associated with an increase of 0.024 mBq/m3 (95% confidence interval [CI], 0.020, 0.028 mBq/m3) in the gross-beta particle radiation downwind. Based on the published health analysis of PR, the widespread UOGD could induce adverse health effects to residents living close to UOGD by elevating PR.

Abstract:
Chemical additives used in hydraulic fracturing fluids (HFFs) are made up of various organic compounds that are potential human carcinogens. To estimate the emissions from these organic constituents in on-site liquid storage tanks, studies were performed using the AP-42 model on data collected from 72,023 wells put into production using hydraulic fracturing between 2008 and 2014 in the United States. Results show that a total of 8.11 × 105 kg volatile organic compounds (VOCs) were potentially emitted from liquid storage tanks during fracturing operations, which was relatively low compared to other sources/activities in well fracturing. The median well emission roughly increased from 0.110 to 0.786 kg per well in 2008 and 2014, respectively, and was primarily due to the increase in the volume of chemical additives for fracturing one well. Of NMVOC emissions, 95.1% was contributed by 60 compounds listed on the priority list of hazardous substances defined by the Agency for Toxic Substances & Disease Registry (ATSDR), while 16.7% was caused by 15 carcinogenic compounds. Specially, methanol, formaldehyde, 2-propanol, and ethanol accounted for 55.5%, 16.6%, 11.7%, and 8.31% of NMVOC emissions. Our study highlights methanol, formaldehyde, 2-propanol, and ethanol as the targeted compounds for reducing organic emissions and occupational inhalation exposures related to storage tank operations.

Abstract:
This study models emissions quantities and neighboring exposure concentrations of six airborne pollutants, including PM10, PM2.5, crystalline silica, arsenic, uranium, and barium, that result from the disposal of Marcellus shale drill cuttings waste during the 2011-to-2017 period. Using these predicted exposures, this study evaluates current setback distances required in Pennsylvania from waste facilities. For potential residents living at the perimeter of the current setback distance, 274 m (900 ft), a waste disposal rate of 612.4 metric tons per day at landfills (the 99th percentile in record) does not result in exceedances of the exposure limits for any of the six investigated pollutants. However, the current setback distance can result in exceedance with respect to the 24-hr daily concentration standards for PM10 and PM2.5 established in the National Air Ambient Quality Standards (NAAQS), if daily waste disposal rate surpasses 900 metric tons per day. Dry depositions of barium-containing and uranium-containing particulate matter should not be a danger to public health based on these results. To investigate the air quality impacts of waste transportation and the potential for reductions, this paper describes an optimization of landfill locations in Pennsylvania indicating the potential benefits in reduced environmental health hazard level possible by decreasing the distance traveled by waste disposal trucks. This strategy could reduce annual emissions of PM10 and PM2.5 by a mean of 64% and reduce the expected number of annual fatal accidents by nearly half and should be considered a potential risk management goal in the long run. Therefore, policy to limit or encourage reduction of distances traveled by waste removal trucks and manage setback distances as a function of delivered waste quantities is merited. Implications This study shows the necessity of reviewing current setback distance required in Pennsylvania, which might not ensure 24-hr mean PM10 and PM2.5 levels below the values stated in National Ambient Air Quality Standards for the residents living at the perimeter. Furthermore, this study also reveals potential tremendous benefits from optimizing location of landfills accepting drill cuttings within Pennsylvania, with PM10 and PM2.5 emission, total distance traveled shrinking, and number of fatal accidents shrinking by nearly half.

Abstract:
Since 2009, unconventional natural gas development (UNGD) has significantly increased in Appalachia’s Marcellus Shale formation. Elevations of fine particulate matter <2.5 µm (PM2.5), have been documented in areas surrounding drilling operations during well stimulation. Furthermore, many communities are experiencing increased industrial activities and probable UNGD air pollutant exposures. Recent studies have associated UNGD emissions with health effects based on distances from well pads. In this study, PM2.5 filter samples were collected on an active gas well pad in Morgantown, West Virginia, and three locations downwind during hydraulic stimulation. Fine particulate samples were analyzed for major and trace elements. An experimental source identification model was developed to determine which elements appeared to be traceable downwind of the UNGD site and whether these elements corresponded to PM2.5 measurements. Results suggest that 1) magnesium may be useful for detecting the reach of UNGD point source emissions, 2) complex surface topographic and meteorological conditions in the Marcellus Shale region could be modeled and confounding sources discounted, and 3) well pad emissions may be measurable at distances of at least 7 km. If shown to be more widely applicable, future tracer studies could enhance epidemiological studies showing health effects of UNGD-associated emissions at ≥15 km.

Abstract:
Background:Prior studies suggest exposure to oil and gas development (OGD) adversely affects birth outcomes, but no studies have examined flaring—the open combustion of natural gas—from OGD.Objectives:We investigated whether residential proximity to flaring from OGD was associated with shorter gestation and reduced fetal growth in the Eagle Ford Shale of south Texas.Methods:We conducted a retrospective cohort study using administrative birth records from 2012 to 2015 (N=23,487N=23,487$N=\mathrm{23,487}$) and satellite observations of flaring activity during pregnancy within 5km5km$5\mathrm{km}$ of maternal residence. Multivariate logistic and linear regression models were used to estimate associations between four outcomes (preterm birth, small-for-gestational age, continuous gestational age, and term birthweight) and exposure to a low (1–9) or high (≥10≥10$\ge 10$) number of nightly flare events, as compared with no exposure, while controlling for known maternal risk factors. We also examined associations with the number of oil and gas wells within 5km5km$5\mathrm{km}$ using data from DrillingInfo (now Enverus).Results:Exposure to a high number of nightly flare events was associated with a 50% higher odds of preterm birth [odds ratio (OR)=1.50odds ratio (OR)=1.50$\text{odds ratio (OR)}=1.50$ (95% CI: 1.23, 1.83)] and shorter gestation [mean difference=−1.9mean difference=−1.9$\text{mean difference}=-1.9$ (95% CI: −2.8−2.8$-2.8$, −0.9−0.9$-0.9$) d] compared with no exposure. Effect estimates were slightly reduced after adjustment for the number of wells within 5km5km$5\mathrm{km}$. In stratified models these associations were present only among Hispanic women. Flaring and fetal growth outcomes were not significantly associated. Women exposed to a high number of wells (fourth quartile, ≥27≥27$\ge 27$) vs. no wells within 5km5km$5\mathrm{km}$ had a higher odds of preterm birth [OR=1.31OR=1.31$\text{OR}=1.31$ (95% CI: 1.14, 1.49)], shorter gestation [−1.3−1.3$-1.3$ (95% CI: −1.9−1.9$-1.9$, −0.8−0.8$-0.8$) d], and lower average birthweight [−19.4−19.4$-19.4$ (95% CI: −36.7−36.7$-36.7$, −2.0−2.0$-2.0$) g].Discussion:Our study suggests exposure to flaring from OGD is associated with an increased risk of preterm birth. Our findings need to be confirmed in other populations. https://doi.org/10.1289/EHP6394

Abstract:
Northeast British Columbia (BC) Canada, is a region in which natural gas production has undergone rapid development since 2007. We used nitrogen dioxide (NO2) and sulphur dioxide (SO2) data products of the Ozone Monitoring Instrument (OMI) to assess the impact of natural gas development activity on air quality in this region from 2005 to 2018. We noticed that values of both pollutants were elevated in the immediate vicinity of large emission sources within the Montney formation and Horn River Basin – regions, which have experienced an increase in unconventional natural gas activities. Places with elevated NO2 Vertical Column Densities (VCDs) are Fort St. John, Taylor, and Dawson Creek located in the Montney formation, and higher SO2 VCDs are found near the Fort Nelson gas plant situated in the Horn River and Liard Basin areas. Although all the OMI data products consistently reported relatively high NO2 VCDs in the same areas, VCD values vary substantially with data products largely due to differences in Air Mass Factor (AMF) calculations. The rate of increase in NO2 VCDs and mass between 2005 and 2018 in the Dawson Creek area was assessed at 2.34% yr−1 and 4.32% yr−1, respectively, and these rates of change are statistically significant. Although we obtained an overall increasing trend for NO2 in Northeast BC, we also noticed a decreasing trend in the period of 2011–2013, which may be attributed, in part, to compliance and enforcement of regulations concerning flaring activities from oil and gas activities in Northeast BC, or due to less development activities. From our analysis, we suggest that the current air quality monitoring network in Northeast BC should be expanded to capture the spatial distribution of SO2 by deploying one additional station near Fort Nelson equipped with meteorology and SO2 monitoring systems.

Abstract:
Article: Modeling the impact of a potential shale gas industry in Germany and the United Kingdom on ozone with WRF-Chem

Abstract:
Some states and localities restrict siting of new oil and gas (O&G) wells relative to public areas. Colorado includes a 500-foot exception zone for building units, but it is unclear if that sufficiently protects public health from air emissions from O&G operations. To support reviews of setback requirements, this research examines potential health risks from volatile organic compounds (VOCs) released during O&G operations.We used stochastic dispersion modeling with published emissions for 47 VOCs (collected on-site during tracer experiments) to estimate outdoor air concentrations within 2,000 feet of hypothetical individual O&G facilities in Colorado. We estimated distributions of incremental acute, subchronic, and chronic inhalation non-cancer hazard quotients (HQs) and hazard indices (HIs), and inhalation lifetime cancer risks for benzene, by coupling modeled concentrations with microenvironmental penetration factors, human-activity diaries, and health-criteria levels.Estimated exposures to most VOCs were below health criteria at 500–2,000 feet. HQs were < 1 for 43 VOCs at 500 feet from facilities, with lowest values for chronic exposures during O&G production. Hazard estimates were highest for acute exposures during O&G development, with maximum acute HQs and HIs > 1 at most distances from facilities, particularly for exposures to benzene, 2- and 3-ethyltoluene, and toluene, and for hematological, neurotoxicity, and respiratory effects. Maximum acute HQs and HIs were > 10 for highest-exposed individuals 500 feet from eight of nine modeled facilities during O&G development (and 2,000 feet from one facility during O&G flowback); hematologic toxicity associated with benzene exposure was the critical toxic effect. Estimated cancer risks from benzene exposure were < 1.0 × 10−5 at 500 feet and beyond.Implications: Our stochastic use of emissions data from O&G facilities, along with activity-pattern exposure modeling, provides new information on potential public-health impacts due to emissions from O&G operations. The results will help in evaluating the adequacy of O&G setback distances. For an assessment of human-health risks from exposures to air emissions near individual O&G sites, we have utilized a unique dataset of tracer-derived emissions of VOCs detected at such sites in two regions of intense oil-and-gas development in Colorado. We have coupled these emission stochastically with local meteorological data and population and time-activity data to estimate the potential for acute, subchronic, and chronic exposures above health-criteria levels due to air emissions near individual sites. These results, along with other pertinent health and exposure data, can be used to inform setback distances to protect public health.

Abstract:
Unconventional natural gas (UNG) extraction activities have become important contributors to regional NOx emissions inventories. Currently, there is a knowledge gap in the amount of total N deposition surrounding well pads undergoing UNG extraction despite the fact that some areas with extensive natural gas extraction activity are already in exceedance of nitrogen critical loads. In this study, we measured the magnitude of total dry N deposition from NO2, HNO3, and NH3 attributable to the development of two UNG wells at a Marcellus Shale well pad study site. This study documents concentrations, deposition fluxes, and isotope values of NO2, HNO3, O3, and NH3 up- and down-wind along a 750-m well pad passive sampling transect across a 16-acre well pad containing two unconventional wells during all phases of development and extraction comprising fifteen distinct sampling periods. An access road transect was also utilized to explore reactive N dynamics in a near-road environment on the well pad where NO2 concentration and isotope dynamics were highly correlated with daily traffic count (r2 = 0.78–0.88, p < 0.01). An onsite chemiluminescent NO2 source apportionment model was compared against δ15N–NO2 and δ18O–NO2 source apportionment models (r2 = 0.57 and 0.82 respectively), demonstrating the possible utility of δ18O–NO2 as a source apportionment tool in near-source environments. In addition, the δ15N–NO2 source apportionment method compared well against a background-subtraction method (slope = 0.82, r2 = 0.88, p < 0.001) during non-wintertime conditions and was used to find N loadings directly attributable to well pad activities. In total, the total N deposition across the transect, attributable to well pad activities, utilizing industry's best management practices, ranged from 0.16 to 0.55 kg N ha−1 yr−1. This magnitude of well pad attributable N deposition is high enough to result in exceedances of nitrogen critical loads in areas with high well count densities and high baseline N deposition.

Abstract:
During the 2004–16 shale-gas development in the Appalachian basin, United States, premature mortality from lower air quality and employment followed a boom-and-bust cycle, whereas climate impacts will persist for generations beyond the activity.

Abstract:
Flux estimates of volatile organic compounds (VOCs) from oil and gas (O&G) production facilities are fundamental in understanding hazardous air pollutant concentrations and ozone formation. Previous off-site emission estimates derive fluxes by ratioing VOCs measured in canisters to methane fluxes measured in the field. This study uses the Environmental Protection Agency's Other Test Method 33A (OTM 33A) and a fast-response proton transfer reaction mass spectrometer to make direct measurements of VOC emissions from O&G facilities in the Upper Green River Basin, Wyoming. We report the first off-site direct flux estimates of benzene, toluene, ethylbenzene and xylenes from upstream O&G production facilities and find that these estimates can vary significantly from flux estimates derived using both the canister ratio technique and from the emission inventory. The 32 OTM 33A flux estimates had arithmetic mean (and 95% CI) as follows: benzene 17.83 (0.22, 98.05) g/h, toluene 34.43 (1.01, 126.76) g/h, C8 aromatics 37.38 (1.06, 225.34) g/h, and methane 2.3 (1.7, 3.1) kg h-1. 20% of facilities measured account for ~67% of total BTEX emissions. While this heavy tail is less dramatic than previous observations of methane in other basins, it is more prominent than predicted by the emission inventory.

Abstract:
The Barnett Shale play in North Texas is one of the largest active onshore shale gas regions in the United States. Over the past two decades, unconventional energy production from shale gas in North Texas has grown rapidly. The energy production peaked in 2012 and has declined since. The city of Denton is located at the edge of the Barnett Shale play and is within the Dallas-Fort Worth metropolitan area. In this paper, we describe a long-term trend study of 84 total non-methane organic carbon (TNMOC) species measured at the Denton Airport South monitoring station, an exurban site. The annual mean TNMOC concentrations measured during 2000–2017 increased by +8.03 ± 12.92 ppb-C/year (+12.75%/year). The year-to-year increase in the mean TNMOC concentrations mirrored the energy production volume changes from natural gas wells and liquid condensate facilities within 2-km from the ambient air quality monitoring station. Concentrations of alkanes increased significantly, especially the natural gas species of ethane, propane, n-butane, and isobutane. The annual variations in the ethane concentrations were similar to changes observed in the natural gas and liquid condensate production from nearby wells. High levels of ethane, a dominant natural gas species, were originating from regions with a higher density of gas wells within close proximity of the monitoring site. In contrast, the concentrations of alkene and aromatic species have declined during the study period as a result of decreases from traditional urban emission sources. However, the trend in benzene, a carcinogenic aromatic species found in vehicular and natural gas emissions, and xylene concentrations were similar to the n-alkane trend, suggesting the influence of energy production activities on key ambient aromatic compounds.

Abstract:
Rural observations of air quality and meteorological parameters (NOx, O3, NMHCs, SO2, PM) were made over a 2.5-year period (2016–2018) before, during and after preparations for hydraulic fracturing (fracking) at a shale gas exploration site near Kirby Misperton, North Yorkshire, England. As one of the first sites to apply for permits to carry out hydraulic fracturing, it has been subject to extensive regulatory and public scrutiny, as well as the focus for a major programme of long-term environmental monitoring. A baseline period of air quality monitoring (starting 2016) established the annual climatology of atmospheric composition against which a 20-week period of intensive activity on the site in preparation for hydraulic fracturing could be compared. During this ‘pre-operational phase’ of work in late 2017, the most significant effect was an increase in ambient NO (3-fold) and NOx (2-fold), arising from a combination of increased vehicle activity and operation of equipment on site. Although ambient NOx increased, air quality limit values for NO2 were not exceeded, even close to the well-site. Local ozone concentrations during the pre-operational period were slightly lower than the baseline phase due to titration with primary emitted NO. The activity on site did not lead to significant changes in airborne particulate matter or non-methane hydrocarbons. Hydraulic fracturing of the well did not subsequently take place and the on-site equipment was decommissioned and removed. Air quality parameters then returned to the original (baseline) climatological conditions. This work highlights the need to characterise the full annual climatology of air quality parameters against which short-term local activity changes can be compared. Based on this study, changes to ambient NOx appear to be the most significant air quality ahead of hydraulic fracturing. However, in rural locations, concentrations at individual sites are expected to be below ambient air quality limit thresholds.

Abstract:
Since advances in horizontal drilling and hydraulic fracturing technologies have opened oil and gas development in previously unreachable areas, air pollution emissions have increased from the burning (i.e., flaring) or releasing (i.e., venting) of natural gas at oil and gas extraction sites. While venting and flaring is a growing concern, accounting of how much gas is vented and flared, and where this occurs, remains limited. The purpose of this paper is to describe two methods for estimating venting and flaring volumes - self-reports required by state law and satellite imagery radiant heat measurements - and to compare these methods using the case of Texas Eagle Ford and Permian Basin venting and flaring practices from 2012 to 2015. First, we used data self-reported by companies to the Texas Railroad Commission (TxRRC), and National Oceanic and Atmospheric Administration (NOAA) data captured by satellite-based Visible Infrared Imaging Radiometer Suite sensors, to estimate the annual total volumes of gas vented and flared in the Eagle Ford and Permian Basin from 2012 to 2015. Next, we developed a method using a geographic information system to link and compare TxRRC and NOAA county-based and point-based volume estimates. Finally, we conducted case studies of two oil and gas fields to better understand how TxRRC and NOAA venting and flaring volumes differ. We find both TxRRC and NOAA estimated venting and/or flaring volumes steadily increased from 2012 to 2015. Additionally, TxRRC reports captured about half the volumes estimated by NOAA. This suggests that self-reported volumes significantly underestimate the volume of gas being vented or flared. However, this research is limited by the data currently available. As such, future research and policy should further develop methods to systemically capture the extent to which oil and gas extraction facilities vent and flare natural gas.

Abstract:
Unconventional oil and gas development (UOGD) in the United States is increasingly being conducted on multi-well pads (MWPs) and in residential areas. We measured air pollution, noise, and truck traffic during four distinct phases of UOGD: drilling, hydraulic fracturing, flowback, and production. We monitored particulate matter (PM2.5), black carbon (BC), A-weighted (dBA) and C-weighted (dBC) noise using real-time instruments on 1 and 5-minute timescales, and truck traffic for 4-7 days per phase at a large 22-well pad sited in a residential area of Weld County, Colorado. Hydraulic fracturing, which requires frequent truck trips to move supplies and diesel engines to power the process, had the highest median air pollution levels of PM2.5 and BC and experienced the greatest number of heavy trucks per hour compared to other phases. Median air pollution was lowest during drilling at this MWP, possibly because an electric drill rig was used. The equivalent continuous noise level (Leq) exceeded guidelines of 50 dBA and 65 dBC for A-weighted and C-weighted noise, respectively, during all development phases. Our data show that these multiple stressors are present around the clock at these sites, and this work provides baseline measurements on likely human exposure levels near similarly sized MWPs.

Abstract:
Article: Emission scenarios of a potential shale gas industry in Germany and the United Kingdom

Abstract:
A large-scale study of methane emissions from well pads was conducted in the Marcellus shale (Pennsylvania), the largest producing natural gas shale play in the United States, to better identify the prevalence and characteristics of superemitters. Roughly 2100 measurements were taken from 673 unique unconventional well pads corresponding to ∼18% of the total population of active sites and ∼32% of the total statewide unconventional natural gas production. A log-normal distribution with a geometric mean of 2.0 kg h–1 and arithmetic mean of 5.5 kg h–1 was observed, which agrees with other independent observations in this region. The geometric standard deviation (4.4 kg h–1) compared well to other studies in the region, but the top 10% of emitters observed in this study contributed 77% of the total emissions, indicating an extremely skewed distribution. The integrated proportional loss of this representative sample was equal to 0.53% with a 95% confidence interval of 0.45–0.64% of the total production of the sites, which is greater than the U.S. Environmental Protection Agency inventory estimate (0.29%), but in the lower range of other mobile observations (0.09–3.3%). These results emphasize the need for a sufficiently large sample size when characterizing emissions distributions that contain superemitters.

Abstract:
Over the past decade, increases in high-volume hydraulic fracturing for oil and gas extraction in the United States have raised concerns with residents living near wells. Flaring, or the combustion of petroleum products into the open atmosphere, is a common practice associated with oil and gas exploration and production, and has been under-examined as a potential source of exposure. We leveraged data from the Visible Infrared Imaging Spectroradiometer (VIIRS) Nightfire satellite product to characterize the extent of flaring in the Eagle Ford Shale region of south Texas, one of the most productive in the nation. Spatiotemporal hierarchical clustering identified flaring sources, and a regression-based approach combining VIIRS information with reported estimates of vented and flared gas from the Railroad Commission of Texas enabled estimation of flared gas volume at each flare. We identified 43,887 distinct oil and gas flares in the study region from 2012-2016, with a peak in activity in 2014 and an estimated 4.5 billion cubic meters of total gas volume flared over the study period. A comparison with well permit data indicated the majority of flares were associated with oil-producing (82%) and horizontally-drilled (92%) wells. Of the 49 counties in the region, 5 accounted for 71% of the total flaring. Our results suggest flaring may be a significant environmental exposure in parts of this region.

Abstract:
While New York has banned fracking, new and expanded natural gas pipelines are being constructed across the state. Our previous studies have reported that compressor stations are a major source of air pollution at fracking sites. We have used two federal datasets, the U.S. Environmental Protection Agency’s (EPA) National Emissions Inventory and Greenhouse Gas Inventory, to determine what is known concerning emissions from the compressor stations along natural gas pipelines in the state. From a total of 74 compressor stations only 18 report to EPA on emissions. In the seven year period between 2008 and 2014 they released a total of 36.99 million pounds of air pollutants, not including CO2 and methane. This included emissions of 39 chemicals known to be human carcinogens. There was in addition 6.1 billion pounds of greenhouse gases release from ten stations in a single year. These data clearly underestimate the total releases from the state’s natural gas transportation and distribution system. However, they demonstrate significant releases of air pollutants, some of which are known to cause human disease. In addition, they release large amounts of greenhouse gases that contribute to climate change.

Abstract:
Increased energy demands and innovations in upstream oil and natural gas (ONG) extraction technologies have enabled the United States to become one of the world's leading producers of petroleum and natural gas hydrocarbons. The US Environmental Protection Agency (EPA) lists 187 hazardous air pollutants (HAPs) that are known or suspected to cause cancer or other serious health effects. Several of these HAPs have been measured at elevated concentrations around ONG sites, but most have not been studied in the context of upstream development. In this review, we analyzed recent global peer-reviewed articles that investigated HAPs near ONG operations to (a) identify HAPs associated with upstream ONG development, (b) identify their specific sources in upstream processes, and (c) examine the potential for adverse health outcomes from HAPs emitted during these phases of hydrocarbon development.

Abstract:
Shale gas has become an important strategic energy source with considerable potential economic benefits and the potential to reduce greenhouse gas emissions in so far as it displaces coal use. However, there still exist environmental health risks caused by emissions from exploration and production activities. In the United States, states and localities have set different minimum setback policies to reduce the health risks corresponding to the emissions from these locations, but it is unclear whether these policies are sufficient. This study uses a Gaussian plume model to evaluate the probability of exposure exceedance from EPA concentration limits for PM2.5 at various locations around a generic wellsite in the Marcellus shale region. A set of meteorological data monitored at ten different stations across Marcellus shale gas region in Pennsylvania during 2015 serves as an input to this model. Results indicate that even though the current setback distance policy in Pennsylvania (500 ft. or 152.4 m) might be effective in some cases, exposure limit exceedance occurs frequently at this distance with higher than average emission rates and/or greater number of wells per wellpad. Setback distances should be 736 m to ensure compliance with the daily average concentration of PM2.5, and a function of the number of wells to comply with the annual average PM2.5 exposure standard.Implications: The Marcellus Shale gas is known as a significant source of criteria pollutants and studies show that the current setback distance in Pennsylvania is not adequate to protect the residents from exceeding the established limits. Even an effective setback distance to meet the annual exposure limit may not be adequate to meet the daily limit. The probability of exceeding the annual limit increases with number of wells per site. We use a probabilistic dispersion model to introduce a technical basis to select appropriate setback distances.

Abstract:
The study objective was to use a preliminary risk based framework to evaluate the sufficiency of existing air data to answer an important public health question in Colorado: Do volatile organic compounds (VOCs) emitted into the air from oil and gas (OG) operations result in exposures to Coloradoans living at or greater than current state setback distances (500 feet) from OG operations at levels that may be harmful to their health? We identified 56 VOCs emitted from OG operations in Colorado and compiled 47 existing air monitoring datasets that measured these VOCs in 34 locations across OG regions. From these data, we estimated acute and chronic exposures and compared these exposures to health guideline levels using maximum and mean air concentrations. Acute and chronic non-cancer hazard quotients were below one for all individual VOCs. Hazard indices combining exposures for all VOCs were slightly above one. Lifetime excess cancer risk estimates for benzene were between 1.0 x 10(-5)-3.6 x 10(-5) and ethylbenzene was 7.3 x 10(-6). This evaluation identified a small sub-set of VOCs, including benzene and n-nonane, which should be prioritized for additional exposure characterization in site-specific studies that collect comprehensive time-series measurements of community scale exposures to better assess community exposures.

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Here, we report the first results of model sensitivity simulations to assess the potential impacts of emissions related to future activities linked to unconventional hydrocarbon extraction (fracking) in the UK on air pollution and human health. These simulations were performed with the Met Office Air Quality in the Unified Model, a new air quality-forecasting model, and included a wide range of extra emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) to reflect emissions from the full life cycle of fracking-related activities and simulate the impacts of these compounds on levels of nitrogen dioxide (NO2) and ozone (O3). These model simulations highlight that increases in NOx and VOC emissions associated with unconventional hydrocarbon extraction could lead to large local increases in the monthly means of daily 1-h maximum NO2 of up to + 30 ppb and decreases in the maximum daily 8-h mean O3 up to − 6 ppb in the summertime. Broadly speaking, our simulations indicate increases in both of these compounds across the UK air shed throughout the year. Changes in the 1-h maximum of NO2 and 8-h mean of O3 are particularly important for their human health impacts. These respective changes in NO2 and O3 would contribute to approximately 110 (range 50–530) extra premature-deaths a year across the UK based on the use of recently reported concentration response functions for changes in annual average NO2 and O3 exposure. As such, we conclude that the release of emissions of VOCs and NOx be highly controlled to prevent deleterious health impacts.

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Abstract: Studies have showed the increasing environmental and public health risks of toxic emissions from natural gas and oil mining, which have become...

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Unconventional oil and gas exploration in the US has become a significant new source of atmospheric hydrocarbons. Field measurements and monitoring have been initiated to determine integral effects from this geographically dispersed source in and downwind of shale areas, driven mostly by concerns related to photochemical ozone production. The Texas Commission on Environmental Quality (TCEQ) deployed its first air quality monitor near the Eagle Ford shale in south Texas in summer 2013, followed by a more centrally located monitor in winter 2014/15. Here, we report on the latter monitor’s 2015 data, showing at times extraordinarily high levels of saturated hydrocarbons, similar to earlier findings in this area. Using hydrocarbon ratios, we establish that the dominant sources at this site appear to be oil and gas exploration. A non-negative matrix factorization (NMF) analysis revealed six consistent source factors, of which two were associated with pre-existing local sources from car traffic and industry, three with regional oil and gas exploration, and one with diesel emissions. The dominant source factors were associated with evaporative and fugitive emissions, and with flaring and (diesel-powered) compressor engine emissions. The former is a major source of saturated hydrocarbons while the latter is a major source of NO x and unsaturated hydrocarbons, confirming earlier findings. Due to the rural nature of the site, road traffic is a minor NO x source in this area, and the NMF results support inventory estimates showing oil and gas exploration to be the dominant regional source of NO x emissions. The NMF based source apportionment results also suggests that benzene levels in this rural area in 2015, while comparable to levels in Houston now, were probably three to five times lower before the shale boom.

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Natural gas from shale plays dominates new production and growth. However, unconventional well development is an energy intensive process. The prime movers, which include over-the-road service trucks, horizontal drilling rigs, and hydraulic fracturing pumps, are predominately powered by diesel engines that impact air quality. Instead of relying on certification data or outdated emission factors, this model uses new in-use emissions and activity data combined with historical literature to develop a national emissions inventory. For the diesel only case, hydraulic fracturing engines produced the most NOx emissions, while drilling engines produced the most CO emissions, and truck engines produced the most THC emissions. By implementing dual-fuel and dedicated natural gas engines, total fuel energy consumed, CO2, CO, THC, and CH4 emissions would increase, while NOx emissions, diesel fuel consumption, and fuel costs would decrease. Dedicated natural gas engines offered significant reductions in NOx emissions. Additional scenarios examined extreme cases of full fleet conversions. While deep market penetrations could reduce fuel costs, both technologies could significantly increase CH4 emissions. While this model is based on a small sample size of engine configurations, data were collected during real in-use activity and is representative of real world activity.

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We measured fluxes of methane, a suite of non-methane hydrocarbons (C2–C11), light alcohols, and carbon dioxide from oil and gas produced water storage and disposal ponds in Utah (Uinta Basin) and Wyoming (Upper Green River Basin) United States during 2013–2016. In this paper, we discuss the characteristics of produced water composition and air-water fluxes, with a focus on flux chamber measurements. In companion papers, we will (1) report on inverse modeling methods used to estimate emissions from produced water ponds, including comparisons with flux chamber measurements, and (2) discuss the development of mass transfer coefficients to estimate emissions and place emissions from produced water ponds in the context of all regional oil and gas-related emissions. Alcohols (made up mostly of methanol) were the most abundant organic compound group in produced water (91% of total volatile organic concentration, with upper and lower 95% confidence levels of 89 and 93%) but accounted for only 34% (28 to 41%) of total organic compound fluxes from produced water ponds. Non-methane hydrocarbons, which are much less water-soluble than methanol and less abundant in produced water, accounted for the majority of emitted organics. C6–C9 alkanes and aromatics dominated hydrocarbon fluxes, perhaps because lighter hydrocarbons had already volatilized from produced water prior to its arrival in storage or disposal ponds, while heavier hydrocarbons are less water soluble and less volatile. Fluxes of formaldehyde and other carbonyls were low (1% (1 to 2%) of total organic compound flux). The speciation and magnitude of fluxes varied strongly across the facilities measured and with the amount of time water had been exposed to the atmosphere. The presence or absence of ice also impacted fluxes.

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The use of hydraulic fracturing for production of petroleum and natural gas has increased dramatically in the last decade, but the environmental impacts of this technology remain unclear. Experiments were conducted to quantify airborne emissions from twelve samples of hydraulic fracturing flowback wastewater collected in the Permian Basin, as well as the photochemical processing of these emissions leading to the formation of particulate matter. The concentration of total volatile carbon (TVC, hydrocarbons evaporating at room temperature) averaged 29 mg of carbon (C) L-1. After photochemical oxidation under high NOx conditions the amount of organic particulate matter (PM) formed per milliliter of wastewater evaporated averaged 24 µg; the amount of ammonium nitrate formed averaged 262 µg. Based on the mean PM formation observed in these experiments, the estimated formation of PM from evaporated flowback wastewater in the state of Texas is in the range of estimated PM emissions from diesel engines used in oil rigs. Evaporation of flowback wastewater, a hitherto unrecognized source of secondary pollutants, could significantly contribute to ambient PM concentrations.

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Background & aim Unconventional natural gas (UNG) extraction activities have considerable potential to affect air quality. However, there are few published quantitative observations of the magnitude of such impacts. To provide context, we compared measured exposures to diesel engine exhaust close to industrial fracking equipment at an UNG training simulation site in Łowicz, Poland to pedestrian exposures to traffic-related air pollution in the city centre of Glasgow, UK. Methods We made mobile and static measurements at varying distances from sources in both of the above locations with a portable aethalometer (Aethlabs AE51) for black carbon (BC) and portable monitors (Aeroqual Series-500) for nitrogen dioxide (NO2) and ozone (O3). Duplicate BC measurements were compared with NO2 observations, after correction of the NO2 sensor response for O3 interference effects. Results Duplicate BC instruments provided similar real-time measurements (r = 0.92), which in turn were relatively highly correlated with NO2 observations at 5-min temporal resolution at the UNG experimental site (r = 0.75) and on the walking route in Glasgow city centre (r = 0.64) suggesting common diesel sources for NO2 and BC in both locations. Average BC and NO2 concentrations measured approximately 10 m downwind of diesel fracking pumps were 11 and 113 μg/m3 respectively. These concentrations were approximately 37 times and 4 times higher than upwind background BC and NO2 concentrations at the site; and approximately 3 times higher than average BC and NO2 concentrations measured in traffic influenced areas in Glasgow. Conclusions Marked elevations of BC and NO2 concentrations were observed in downwind proximity to industrial fracking equipment and traffic sources. This suggests that exposure to diesel engine exhaust emissions from fracking equipment may present a significant risk to people working on UNG sites over extended time periods. The short time resolution of the portable instruments used enabled identification of likely sources of occupational and environmental exposure to combustion-related air pollutants.

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Article: A decade of changes in nitrogen oxides over regions of oil and natural gas activity in the United States

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The Eagle Ford Shale in southern Texas is home to a booming unconventional oil and gas industry, the climate and air quality impacts of which remain poorly quantified due to uncertain emission estimates. We used the atmospheric enhancement of alkanes from Texas Commission on Environmental Quality volatile organic compound monitors across the shale, in combination with back trajectory and dispersion modeling, to quantify C-2-C-4 alkane emissions for a region in southern Texas, including the core of the Eagle Ford, for a set of 68 days from July 2013 to December 2015. Emissions were partitioned into raw natural gas and liquid storage tank sources using gas and headspace composition data, respectively, and observed enhancement ratios. We also estimate methane emissions based on typical ethane-to-methane ratios in gaseous emissions. The median emission rate from raw natural gas sources in the shale, calculated as a percentage of the total produced natural gas in the upwind region, was 0.7% with an interquartile range (IQR) of 0.5-1.3 %, below the US Environmental Protection Agency's (EPA) current estimates. However, storage tanks contributed 17% of methane emissions, 55% of ethane, 82% percent of propane, 90% of n-butane, and 83% of isobutane emissions. The inclusion of liquid storage tank emissions results in a median emission rate of 1.0% (IQR of 0.7-1.6 %) relative to produced natural gas, overlapping the current EPA estimate of roughly 1.6 %. We conclude that emissions from liquid storage tanks are likely a major source for the observed non-methane hydrocarbon enhancements in the Northern Hemisphere.

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The benefits and impacts of unconventional natural gas development are realized at different spatial scales, calling into question the appropriate jurisdictional level at which to set and enforce environmental policy. This paper evaluates impact fee allocation under Pennsylvania Act 13, which authorizes Commonwealth payments to Pennsylvania counties to offset damages from unconventional natural gas extraction in exchange for consolidated state-level regulatory authority. We evaluate the adequacy of damage compensation allocation for impacts that are spatially and temporally removed from the well site, using the air emissions associated with natural gas wastewater transport as a case study. Wastewater transport from wells eligible for 2011 impact fee disbursement calculations generated an estimated $11.6 million in air emission damages from 2004-2013, with 35% of damages occurring out-of-state and an average of 94% of damages occurring out-of-county.  We find that compensatory payments from PA Act 13, which are based upon the number of wells drilled in a county in a single year, inadequately account for spatially and temporally distributed impacts from wastewater transport. This case study of PA Act 13 highlights potential issues associated with central regulators using compensatory payments as a means of resolving jurisdictional conflict. In cases where the central regulator benefits from the polluting activity, we argue that there is incentive to focus compensation on local damages and undervalue regional and spatially distributed damages in both compensation algorithms and regulatory standards.

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Emissions of nitrogen oxides (NOx) in the United States (U.S.) from large stationary sources, such as electric generating units, have decreased since 1995, driving decreases in nitrogen deposition. However, increasing NOx emissions from emerging industries, such as unconventional natural gas (UNG) extraction, could offset stationary source emission reductions in shale gas producing regions of the U.S. The Marcellus Shale in the northeastern U.S. has seen dramatic increases in the number of wells and associated natural gas production during the past ten years. In this study, we examine the potential impacts of shale gas development on regional NOx emission inventories and dry deposition fluxes to Clean Air Status and Trends (CASTNET) sites in Pennsylvania and New York. Our results demonstrate that the current distribution of CASTNET sites is ineffective for monitoring the influence of Marcellus well NOx emissions on regional nitrogen deposition. Despite the fact that existing CASTNET sites are not influenced by UNG extraction activity, NOx emissions densities from shale gas extraction are substantial and are estimated to reach up to 21 kg NOx ha-1 year-1 in some regions. If these emissions deposit locally, UNG extraction activity could contribute to critical nitrogen load exceedances in areas of high well density.

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Article: Analysis of local-scale background concentrations of methane and other gas-phase species in the Marcellus Shale

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Hydraulic fracturing has been applied as an effective method to increase gas production from shale formations; however, this method has also raised concerns about its adverse impacts on environment. For example, in the Marcellus shale formation, some measured radon-gas concentrations exceeded the safe standard. Therefore, it is important to quantitatively evaluate radon concentration from fractured wells. However, existing researches have not successfully conducted a systematic and predictive study on the relationship between shale gas production and radon concentration at the wellhead of a hydraulically fractured well. To address this issue and quantitatively determine the radon concentration, we present the mechanisms of radon-gas generation and releasing, and conducted numerical simulations on its transport process in the subsurface formation system. The concentration of radon in produced gas is related with the original sources where the natural gas is extracted. Radon, generated from the radium alpha decay process, is trapped in pore spaces before the reservoir development. With the fluid flowing through the subsurface network, released radon will move to surface with the produced streams such as natural gas and flowback water. Our study shows that the radon concentration at wellhead could be significant. Influential factors such as natural-fracture-network properties, formation petrophysical parameters, and fracture dimension are investigated with sensitivity studies through numerical simulations. Analysis results suggest that radon wellhead concentration is strongly related with production rate. Thus, careful production design and protection are necessary to reduce radon hazard regarding the public and environmental impact.

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The Marcellus and Utica shale formations have recently been the focus of intense natural gas development and production, increasing regional air pollutant emissions. Here we examine the effects of these emissions on regional ozone and fine particulate matter (PM2.5) levels using the chemical transport model, CAMx, and estimate the public health costs with BenMAP. Simulations were performed for three emissions scenarios for the year 2020 that span a range potential development storylines. In areas with the most gas development, the ‘Medium Emissions’ scenario, which corresponds to an intermediate level of development and widespread adoption of new equipment with lower emissions, is predicted to increase 8-hourly ozone design values by up to 2.5 ppbv and average annual PM2.5 concentrations by as much as 0.27 μg/m3. These impacts could range from as much as a factor of two higher to a factor of three lower depending on the level of development and the adoption of emission controls. Smaller impacts (e.g. 0.1–0.5 ppbv of ozone, depending on the emissions scenario) are predicted for non-attainment areas located downwind of the Marcellus region such as New York City, Philadelphia and Washington, DC. Premature deaths for the ‘Medium Emissions’ scenario are predicted to increase by 200–460 annually. The health impacts as well as the changes in ozone and PM2.5 were all driven primarily by NOx emissions.

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PURPOSE OF REVIEW: The objective of this review is to demonstrate that the focus on air emissions causing respiratory effects and associated with gas development may be misplaced by attributing those exposures mainly to well pad activities. RECENT FINDINGS: The most recent publications on the health effects of hydraulic fracturing operations seem to parallel findings from studies of diesel particulate exposure near roadways and the health effects associated with those exposures. It seems at least possible that some, if not all, of the respiratory effects associated with unconventional resource development may be traffic-related. Road traffic generated by hydraulic fracturing operations is one possible source of environmental impact whose significance has, until now, been largely neglected in the available literature with 4000 to 6000 vehicles visiting the well pad. SUMMARY: Exposures from well pads diminish rapidly with distances of only a few kilometers but there is evidence showing disease risk multiple kilometers from well pads. This leaves open the possibility that the several thousand vehicle trips per well pad create traffic emissions over wide areas away from the pad. This alternative source of exposure has not previously been well studied but is being more seriously considered.

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Shale gas is an alternative for conventional energy sources. When extracted in compliance with environmental and sustained development rules, it favors the concept of diversification of energy sources, giving spur to the development of economy and technology, and before all, to the energy safety of the country. Poland is among countries, where expectations regarding shale gas are very high. Most of the exploration works for shale gas there are performed with the use of rigs, whose subassemblies are driven by electrical motors powered by mobile generators driven by diesel engines. The number of aggregates and their total power are selected each time on the basis of power balance of particular technological subassemblies and the emergency generation system. Diesel combustion motors used for powering generators are the only source of dust and gaseous emissions to the air. A mobile technological boiler room fed with oil is another source of emissions in the winter period. For the purpose of evaluating impact of rigs on the air environment in the course of prospecting for shale gas an emission model was worked out with five emission points. Four sources were connected with the operation of combustion motors (each 1257 kW) powering generators, and the fifth one (375 kW) feeding technological boiler room. The results of the tests on the environmental impact on motors and boiler room used during shale gas prospecting on the quality of air have been presented in the paper. The tests were performed with the use of mathematical modeling employing real technological data from existing installations.

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In the past decade increased use of hydraulic fracturing and horizontal drilling has dramatically expanded oil and gas production in the Bakken formation region. Long term monitoring sites have indicated an increase in wintertime aerosol nitrate and sulfate in this region from particulate matter (PM2.5) measurements collected between 2000 and 2010. No previous intensive air quality field campaign has been conducted in this region to assess impacts from oil and gas development on regional fine particle concentrations. The research presented here investigates wintertime PM2.5 concentrations and composition as part of the Bakken Air Quality Study (BAQS). Measurements from BAQS took place over two wintertime sampling periods at multiple sites in the United States portion of the Bakken formation and show regionally elevated episodes of PM2.5 during both study periods. Ammonium nitrate was a major contributor to haze episodes. Periods of air stagnation or recirculation were associated with rapid increases in PM2.5 concentrations. Volatile organic compound (VOC) signatures suggest that air masses during these episodes were dominated by emissions from the Bakken region itself. Formation rates of alkyl nitrates from alkanes revealed an air mass aging timescale of typically less than a day for periods with elevated PM2.5. A thermodynamic inorganic aerosol model (ISORROPIA) was used to investigate gas-particle partitioning and to examine the sensitivity of PM2.5 concentrations to aerosol precursor concentrations. Formation of ammonium nitrate, the dominant component, was most sensitive to ammonia concentrations during winter and to nitric acid concentrations during early spring when ammonia availability increases. The availability of excess ammonia suggests capacity for further ammonium nitrate formation if nitrogen oxide emissions increase in the future and lead to additional secondary formation of nitric acid.

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The extraction of unconventional oil and natural gas from shale energy reservoirs has raised concerns regarding upstream and midstream activities and their potential impacts on air quality. Here we present in situ measurements of ambient methane concentrations near multiple natural gas compressor stations in New York and Pennsylvania using cavity ring-down laser spectrometry coupled with global positioning system technology. These data reveal discernible methane plumes located proximally to compressor stations, which exhibit high variability in their methane emissions depending on the weather conditions and on-site activities. During atmospheric temperature inversions, when near-ground mixing of the atmosphere is limited or does not occur, residents and properties located within 1 mile of a compressor station can be exposed to rogue methane from these point sources. These data provide important insight into the characterization and potential for optimization of natural gas compressor station operations.

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The Peace River district of Northeastern British Columbia, Canada is a region of natural gas production that has undergone rapid expansion since 2005. In order to assess air quality implications, Willems badge passive diffusive samplers were deployed for six two-week exposure periods between August and November 2013, at 24 sites across the region to assess the ambient concentration of nitrogen dioxide (NO2) and sulfur dioxide (SO2). The highest concentrations of both species (NO2: 9.1 ppb, SO2: 1.91 ppb) during the whole study period (except the 1st exposure period), were observed in Taylor (Site 14), which is consistent with its location near major industrial sources. Emissions from industrial activities, and their interaction with meteorology and topography, result in variations in atmospheric dispersion that can increase air pollution concentrations in Taylor. However, relatively high concentrations of NO2 were also observed near the center of Chetwynd (site F20), indicating the importance of urban emissions sources in the region as well. Observations of both species from the other study sites document the spatial variability and show relatively high concentrations near Fort St. John and Dawson Creek, where unconventional oil and gas development activities are quite high. Although a few sites in Northeastern British Columbia recorded elevated concentrations of NO2 and SO2 during this investigation, the concentrations over the three-month period were well below provincial annual ambient air quality objectives. Nonetheless, given the limited observations in the region, and the accelerated importance of unconventional oil and gas extraction in meeting energy demands, it is imperative that monitoring networks are established to further assess the potential for elevated ambient concentrations associated with industrial emissions sources in the Peace River region.

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This study investigates long-term (i.e., 2007–2014) fluctuations in ambient ozone formation regimes for cities adjacent to shale plays in the Northeast United States (U.S.). Ozone air quality in many cities of the Northeast U.S. does not meet the U.S. National Ambient Air Quality Standards (NAAQS), and understanding ambient ozone formation regimes is essential to develop effective air pollution mitigation strategies for cities violating the air quality standards. Since 2013, the U.S. has become the world’s largest producer of tight oil and natural gas from shale rock, and previous studies show that emissions of air pollutant precursors from shale oil and gas-related activities would have the potential to affect ambient ozone air quality in adjacent cities of shale plays. This work leveraged (1) satellite-retrieved column densities of formaldehyde (HCHO) and nitrogen dioxide (NO2) from multiple instruments (i.e., Ozone Monitoring Instrument (OMI) and Global Ozone Monitoring Experiment-2 (GOME-2)); (2) photochemical air quality modeling and sensitivity analysis; and (3) ratios of satellite-retrieved air pollutant column densities to investigate ambient ozone formation regimes in neighboring cities of shale plays (i.e., Marcellus Shale) in the Northeast U.S. from 2007 to 2014. Our results show that ambient ozone formation in Boston, Pittsburgh, Philadelphia and Washington, D.C. (which are close to Marcellus Shale) was in the NOx -limited or transition regime during the period of study. Ambient ozone formation in New York City was in the transition regime during 2010–2013 and VOC -limited regime during 2007–2009 and in 2014. Based on the result of this study, we conclude that controls NOx emissions would mitigate ozone air pollution from 2007 to 2014 in most of the cities examined in this study. Controls of local VOC emissions would ease ozone air pollution in New York City during the study period. With projected increases in oil and gas production from shale plays in the Northeast U.S., air pollutant emissions from oil and gas-related activities are expected to increase in the future. The results of this study imply that controls of ozone precursor emissions from shale oil and gas-related activities could be a potential strategy for reducing ambient ozone formation in cities adjacent to the shale plays in Northeast U.S. in the future.

Abstract:
The Northern Colorado Front Range (NCFR) has been in exceedance of the ozone National Ambient Air Quality Standard (NAAQS) since 2004, which has led to much debate over the sources of ozone precursors to the region, as this area is home to both the Denver metropolitan area and the Denver-Julesburg Basin, which has experienced rapid growth of oil and natural gas (O&NG) operations and associated emissions. Several recent studies have reported elevated levels of atmospheric volatile organic compounds (VOC) as a result of O&NG emissions and the potential for significant ozone production from these emissions, despite implementation of stricter O&NG VOC emissions regulations in 2008. Approximately 88% of 1-hr elevated ozone events (>75 ppbv) occur from June - August, indicating that elevated ozone levels are driven by regional photochemistry. Analyses of surface ozone and wind observations from two sites, i.e. South Boulder, and the Boulder Atmospheric Observatory, both near Boulder, Colorado, show a preponderance of elevated ozone events associated with east to west air flow from regions with O&NG operations in the N-ESE, and a relatively minor contribution of transport from the Denver Metropolitan area to the SE-S. Transport from upwind areas associated with abundant O&NG operations accounts for on the order of 65% (mean for both sites) of 1-hr averaged elevated ozone levels, while the Denver urban corridor accounts for 9%. These correlations contribute to mounting evidence that air transport from areas with O&NG operation has a significant impact on ozone and air quality in the NCFR.Implication StatementThis article builds on several previous pieces of research that implied significant contributions from oil and natural gas emissions on ozone production in the Northern Colorado Front Range. By correlating increased ozone events with transport analyses we show that there is a high abundance of transport events with elevated ozone originating from the Denver Julesburg oil and gas basin. These findings will help air quality regulators to better assess contributing sources to ozone production and in directing policies to curb ozone pollution in this region.

Abstract:
Oil and natural gas operations have continued to expand and move closer to densely populated areas, contributing to growing public concerns regarding exposure to hazardous air pollutants. During the Barnett Shale Coordinated Campaign in October, 2013, ground-based whole air samples collected downwind of oil and gas sites revealed enhancements in several potentially toxic volatile organic compounds (VOCs) when compared to background values. Molar emissions ratios relative to methane were determined for hexane, benzene, toluene, ethylbenzene, and xylenes (BTEX compounds). Using methane leak rates measured from the Picarro mobile flux plane (MFP) system and a Barnett Shale regional methane emissions inventory, the rates of emission of these toxic gases were calculated. Benzene emissions ranged between 51 ± 4 and 60 ± 4 kg hr-1. Hexane, the most abundantly emitted pollutant, ranged from 642 ± 45 to 1070 ± 340 kg hr-1. While observed hydrocarbon enhancements fall below federal workplace standards, results may indicate a link between emissions from oil and natural gas operations and concerns about exposure to hazardous air pollutants. The larger public health risks associated with the production and distribution of natural gas are of particular importance, and warrant further investigation, particularly as the use of natural gas increases in the United States and internationally.

Abstract:
We present an analysis of ambient benzene, toluene, and xylene isomers in the Eagle Ford shale region of southern Texas. In situ air quality measurements using membrane inlet mobile mass spectrometry revealed ambient benzene and toluene concentrations as high as 1000 and 5000 parts-per-billion, respectively, originating from specific sub-processes on unconventional oil and gas well pad sites. The detection of highly variant contamination events attributable to natural gas flaring units, condensate tanks, compressor units, and hydrogen sulfide scavengers indicates that mechanical inefficiencies, and not necessarily the inherent nature of the extraction process as a whole, result in the release of these compounds into the environment. This awareness of ongoing contamination events contributes to an enhanced knowledge of ambient volatile organic compounds on a regional scale. While these reconnaissance measurements on their own do not fully characterize the fluctuations of ambient BTEX concentrations that likely exist in the atmosphere of the Eagle Ford Shale region, they do suggest that contamination events from unconventional oil and gas development can be monitored, controlled, and reduced.