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Proc Natl Acad Sci U S A. 2015 Oct 27;112(43):13184-9. doi: 10.1073/pnas.1511474112. Epub 2015 Oct 12.

Elevated levels of diesel range organic compounds in groundwater near Marcellus gas operations are derived from surface activities.

Author information

1
Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06511;
2
Institute of Groundwater Ecology, Helmholtz Zentrum München, 85764 Oberschleissheim, Germany;
3
Department of Civil and Environmental Engineering, Pennsylvania State University, University Park, PA 16802;
4
School of Earth Sciences, The Ohio State University, Columbus, OH 43210;
5
Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708;
6
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;
7
Departments of Civil and Environmental Engineering and Marine and Environmental Sciences, Northeastern University, Boston, MA 02115;
8
Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708;
9
School of Earth, Energy, and Environmental Sciences, Woods Institute for the Environment and Precourt Institute for Energy, Stanford University, Stanford, CA 94305.
10
Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06511; desiree.plata@yale.edu.

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.

KEYWORDS:

groundwater; high-volume hydraulic fracturing; hydrophobic organic contaminants; natural gas extraction; transport mechanisms

PMID:
26460018
PMCID:
PMC4629325
DOI:
10.1073/pnas.1511474112
[Indexed for MEDLINE]
Free PMC Article

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