title: Elevated levels of diesel range organic compounds in groundwater near Marcellus gas operations are derived from surface activities.
abstract: Hundreds of organic chemicals are used during natural gas extraction via high-volume hydraulic fracturing (HVHF). However, it is unclear whether these chemicals, injected into deep shale horizons, reach shallow groundwater aquifers and affect local water quality, either from those deep HVHF injection sites or from the surface or shallow subsurface. Here, we report detectable levels of organic compounds in shallow groundwater samples from private residential wells overlying the Marcellus Shale in northeastern Pennsylvania. Analyses of purgeable and extractable organic compounds from 64 groundwater samples revealed trace levels of volatile organic compounds, well below the Environmental Protection Agency's maximum contaminant levels, and low levels of both gasoline range (0-8 ppb) and diesel range organic compounds (DRO; 0-157 ppb). A compound-specific analysis revealed the presence of bis(2-ethylhexyl) phthalate, which is a disclosed HVHF additive, that was notably absent in a representative geogenic water sample and field blanks. Pairing these analyses with (i) inorganic chemical fingerprinting of deep saline groundwater, (ii) characteristic noble gas isotopes, and (iii) spatial relationships between active shale gas extraction wells and wells with disclosed environmental health and safety violations, we differentiate between a chemical signature associated with naturally occurring saline groundwater and one associated with alternative anthropogenic routes from the surface (e.g., accidental spills or leaks). The data support a transport mechanism of DRO to groundwater via accidental release of fracturing fluid chemicals derived from the surface rather than subsurface flow of these fluids from the underlying shale formation.
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06511;
authors.forename: Brian D
authors.initials: BD
authors.lastname: Drollette
authors.affiliation: Institute of Groundwater Ecology, Helmholtz Zentrum München, 85764 Oberschleissheim, Germany;
authors.forename: Kathrin
authors.initials: K
authors.lastname: Hoelzer
authors.affiliation: Department of Civil and Environmental Engineering, Pennsylvania State University, University Park, PA 16802;
authors.forename: Nathaniel R
authors.initials: NR
authors.lastname: Warner
authors.affiliation: School of Earth Sciences, The Ohio State University, Columbus, OH 43210;
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Darrah
authors.affiliation: Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708;
authors.forename: Osman
authors.initials: O
authors.lastname: Karatum
authors.affiliation: Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708;
authors.forename: Megan P
authors.initials: MP
authors.lastname: O'Connor
authors.affiliation: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;
authors.forename: Robert K
authors.initials: RK
authors.lastname: Nelson
authors.affiliation: Departments of Civil and Environmental Engineering and Marine and Environmental Sciences, Northeastern University, Boston, MA 02115;
authors.forename: Loretta A
authors.initials: LA
authors.lastname: Fernandez
authors.affiliation: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Reddy
authors.affiliation: Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708;
authors.forename: Avner
authors.initials: A
authors.lastname: Vengosh
authors.affiliation: School of Earth, Energy, and Environmental Sciences, Woods Institute for the Environment and Precourt Institute for Energy, Stanford University, Stanford, CA 94305.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Jackson
authors.affiliation: Institute of Groundwater Ecology, Helmholtz Zentrum München, 85764 Oberschleissheim, Germany;
authors.forename: Martin
authors.initials: M
authors.lastname: Elsner
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06511; desiree.plata@yale.edu.
authors.forename: Desiree L
authors.initials: DL
authors.lastname: Plata
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D005742:Gasoline / Q000032:analysis*; D060587:Groundwater / Q000737:chemistry*; D000066388:Oil and Gas Industry; D009930:Organic Chemicals / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D005742:Gasoline; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical
keywords: groundwater; high-volume hydraulic fracturing; hydrophobic organic contaminants; natural gas extraction; transport mechanisms