Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of American 112 (2015): 13184-13189, doi: 10.1073/pnas.1511474112
.
Description:
Hundreds of organic chemicals are utilized during natural gas extraction via high volume
hydraulic fracturing (HVHF). However, it is unclear if these chemicals, injected into deep
shale horizons, reach shallow groundwater aquifers and impact local water quality, either
from deep underground 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
(GRO; 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 1) inorganic chemical fingerprinting of deep
saline groundwater, 2) characteristic noble gas isotopes, and 3) spatial relationships
between active shale gas extraction wells and wells with disclosed environmental health
and safety (EHS) violations, we differentiate between a chemical signature associated
with naturally occurring saline groundwater and a 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.
Description:
The authors thank Duke University’s Pratt School of Engineering
and the National Science Foundation’s CBET Grant Number 1336702 and NSF EAGER
(EAR-1249255) for financial support.
Description:
2016-04-12
Keywords:
Hydrophobic organic compounds
;
Groundwater
;
High volume hydraulic fracturing
;
Natural gas extraction
;
Transport mechanisms
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
Format:
application/msword
