Abstract
Abstract. The United States has experienced a sharp increase in unconventional natural gas (UNG) development due to the technological development of hydraulic fracturing. The objective of this study is to investigate the emissions at an active Marcellus Shale well pad at the Marcellus Shale Energy and Environment Laboratory (MSEEL) in Morgantown, West Virginia, USA. Using an ambient air monitoring laboratory, continuous sampling started in September 2015 during horizontal drilling and ended in February 2016 when wells were in production. High-resolution data were collected for the following air quality contaminants: volatile organic compounds (VOCs), ozone (O3), methane (CH4), nitrogen oxides (NO and NO2), and carbon dioxide (CO2), as well as typical meteorological parameters (wind speed and direction, temperature, relative humidity, and barometric pressure). Positive matrix factorization (PMF), a multivariate factor analysis tool, was used to identify possible sources of these pollutants (factor profiles) and determine the contribution of those sources to the air quality at the site. The results of the PMF analysis for well pad development phases indicate that there are three potential factor profiles impacting air quality at the site: natural gas, regional transport/photochemistry, and engine emissions. There is a significant contribution of pollutants during the horizontal drilling stage to the natural gas factor. The model outcomes show that there is an increasing contribution to the engine emission factor over different well pad drilling periods through production phases. Moreover, model results suggest that the regional transport/photochemistry factor is more pronounced during horizontal drilling and drillout due to limited emissions at the site.
Highlights
There has been a rapid increase in unconventional natural gas exploration by recent technological advances (USEIA, 2020)
Non-methane hydrocarbons (NMHCs) and nitrogen oxides (NOx) are of the most interest as some NMHCs can be toxic (Edwards et al, 2014); several studies focus on increases in methane, NMHC, and ozone in oil- and gas-producing regions (Pacsi et al, 2015; Roest and Schade, 2017)
There was an increase in NOx (25th percentile (q1) = 12.5 ppb) and NO (q1 = 2.7 ppb) during the fracturing phase compared to other phases
Summary
There has been a rapid increase in unconventional natural gas exploration by recent technological advances (USEIA, 2020). There is growing attention by the public on the potential public health impacts of unconventional natural gas (UNG) extraction. In response to emerging public concern regarding the process of hydraulic fracturing for UNG extraction, several studies have investigated the potential public health risks of UNG development (Adgate et al, 2014; Hays et al, 2015, 2017; Werner et al, 2015). The majority of environmental impact studies focus on water quality impacts of unconventional natural gas development (Annevelink et al, 2016; Butkovskyi et al, 2017; Jackson et al, 2015; Torres et al, 2016).
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