Impact of Marcellus Shale Natural Gas Development in Southwest Pennsylvania on Volatile Organic Compound Emissions and Regional Air Quality

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 C1-C10 volatile organic compounds (VOCs). Elevated mixing ratios of methane and C2-C8 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 C2-C8 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.

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

“…On a regional scale, Vinciguerra et al (2015) observed increased ethane (C 2 H 6 ), an alkane that is the second largest component of NG, downwind of the Marcellus basin corresponding to increased Marcellus Shale production rates. Another ambient air study in the Marcellus basin observed elevated methane and light alkanes near clusters of shale gas wells, but determined that the wells were only a minor source of alkenes and hazardous air pollutants (HAPs) (Swarthout et al, 2015). Similar results were observed by Goetz et al (2015), where aromatic VOC and other HAPs were not detected at elevated levels in NG emissions from Marcellus Shale infrastructure.…”

“…Results from flask samples detailed in the supporting information of Swarthout et al (2015) were used for comparisons of methane, ethane, acetone, methanol, acetonitrile, acetaldehyde, benzene, and toluene mole fractions in SW PA. Major comparisons were made between the mobile results and results from PTR-MS and Picarro CRDS measurements taken during the National Oceanic and Atmospheric Administration's (NOAA) 2013 Southeast Nexus (SENEX) field study (Warneke et al, 2016). The SENEX campaign performed multiple flights using the NOAA WP-3D aircraft in Southeast U.S. and also directed several flights that focused on areas with unconventional natural gas activity including the Haynesville, the Fayetteville, and the Marcellus Shale regions Yuan et al, 2015).…”

“…Given the known increase of alkanes in the Marcellus region it is possible that NG emissions from Marcellus shale activity play an increasing role in O 3 production in the region and especially in areas with high NO x concentrations. However, other work has shown that in the summer of 2012 biogenic VOC dominated OH reactivity in part of the Marcellus Shale region in Southwestern Pennsylvania (Swarthout et al, 2015).…”

Sources and characteristics of summertime organic aerosol in the Colorado Front Range: perspective from measurements and WRF-Chem modeling

“…In recent decades, stricter regulations by the U.S. Environmental Protection Agency and state agencies have resulted in lower emissions of black carbon, hydrocarbons (including air toxics), and nitrogen oxides in many urban environments (e.g., Parrish et al, 2002;Peischl et al, 2010;Sather and Cavender, 2012;Warneke et al, 2012;Zhou et al, 2014;Kirchstetter et al, 2017) while in other areas, both populated and remote, expansion or emergence of new oil and natural gas (O&G) exploration and production activities has led to higher emissions of air toxics, methane, and non-methane hydrocarbons, e.g., C 2 − C 8 and larger alkanes, benzene, and larger aromatic species (e.g., Petron et al, 2012;Adgate et al, 2014;Helmig et al, 2014;Pekney et al, 2014;Warneke et al, 2014;Field et al, 2015;Koss et al, 2015;Rutter et al, 2015;Swarthout et al, 2015;Helmig et al, 2016;Prenni et al, 2016;Abeleira et al, 2017;Koss et al, 2017). The impact of higher emissions of such hydrocarbons from oil and gas fields of Utah and Wyoming on wintertime ozone has been assessed through recent measurement and modeling studies (Carter and Seinfeld, 2012;Rappenglück et al, 2014;Ahmadov et al, 2015).…”

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

“…76, page 2 of 15 O&NG activities have been found to have high concentrations of non-methane hydrocarbons (NMHCs) (e.g. Edwards et al, 2013;Oltmans et al, 2013;Thompson et al, 2014;Swarthout et al, 2015;Prenni et al, 2016;Gilman et al, 2013), which are comprised of a host of air pollutants that are regulated in some regions as a result of their damaging affects to the environment and public health. Sulphur dioxide (SO 2 ), which when oxidised can contribute to new particle formation (Sipilä et al, 2010) and precipitation and particle acidity (Hegg and Hobbs, 1981;Weber et al, 2016), is also increasing (e.g.…”