title: Indications of Transformation Products from Hydraulic Fracturing Additives in Shale-Gas Wastewater.
abstract: Unconventional natural gas development (UNGD) generates large volumes of wastewater, the detailed composition of which must be known for adequate risk assessment and treatment. In particular, transformation products of geogenic compounds and disclosed additives have not been described. This study investigated six Fayetteville Shale wastewater samples for organic composition using a suite of one- and two-dimensional gas chromatographic techniques to capture a broad distribution of chemical structures. Following the application of strict compound-identification-confidence criteria, we classified compounds according to their putative origin. Samples displayed distinct chemical distributions composed of typical geogenic substances (hydrocarbons and hopane biomarkers), disclosed UNGD additives (e.g., hydrocarbons, phthalates such as diisobutyl phthalate, and radical initiators such as azobis(isobutyronitrile)), and undisclosed compounds (e.g., halogenated hydrocarbons, such as 2-bromohexane or 4-bromoheptane). Undisclosed chloromethyl alkanoates (chloromethyl propanoate, pentanoate, and octanoate) were identified as potential delayed acids (i.e., those that release acidic moieties only after hydrolytic cleavage, the rate of which could be potentially controlled), suggesting they were deliberately introduced to react in the subsurface. In contrast, the identification of halogenated methanes and acetones suggested that those compounds were formed as unintended byproducts. Our study highlights the possibility that UNGD operations generate transformation products and underscores the value of disclosing additives injected into the subsurface.
authors.affiliation: Helmholtz Zentrum München, Institute of Groundwater Ecology , Ingolstaedter Landstrasse 1 85764, Neuherberg, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Hoelzer
authors.affiliation: School of Engineering and Applied Science, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Sumner
authors.affiliation: Department of Civil & Environmental Engineering, Duke University , Hudson Hall, Box 90287, Durham, North Carolina 27705, United States.
authors.forename: Osman
authors.initials: O
authors.lastname: Karatum
authors.affiliation: Fye Laboratory, Woods Hole Oceanographic Institution , Mail Stop No. 4, Woods Hole, Massachusetts 02543, United States.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Nelson
authors.affiliation: School of Engineering and Applied Science, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Drollette
authors.affiliation: Department of Civil & Environmental Engineering, Duke University , Hudson Hall, Box 90287, Durham, North Carolina 27705, United States.
authors.forename: Megan P
authors.initials: MP
authors.lastname: O'Connor
authors.affiliation: Department of Chemistry, University of Washington , Bagley Hall, Seattle, Washington 98195 United States.
authors.forename: Emma L
authors.initials: EL
authors.lastname: D'Ambro
authors.affiliation: Nicholas School of the Environment, Duke University , Gross Chemistry, Durham, North Carolina 27705, United States.
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Getzinger
authors.affiliation: Department of Civil & Environmental Engineering, Duke University , Hudson Hall, Box 90287, Durham, North Carolina 27705, United States.|Nicholas School of the Environment, Duke University , Gross Chemistry, Durham, North Carolina 27705, United States.
authors.forename: P Lee
authors.initials: PL
authors.lastname: Ferguson
authors.affiliation: Fye Laboratory, Woods Hole Oceanographic Institution , Mail Stop No. 4, Woods Hole, Massachusetts 02543, United States.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Reddy
authors.affiliation: Helmholtz Zentrum München, Institute of Groundwater Ecology , Ingolstaedter Landstrasse 1 85764, Neuherberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Elsner
authors.affiliation: School of Engineering and Applied Science, Yale University , 9 Hillhouse Avenue, New Haven, Connecticut 06511, United States.
authors.forename: Desiree L
authors.initials: DL
authors.lastname: Plata
mesh_terms: D000067071:Hydraulic Fracking; D059206:Natural Gas; D062065:Wastewater / Q000737:chemistry*
chemical_list: D059206:Natural Gas; D062065:Wastewater