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Hydrocarbons in upland groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA

June 27, 2019

Water samples from 50 domestic wells located <1 km (proximal) and >1 km (distal) from shale-gas wells in upland areas of the Marcellus Shale region were analyzed for chemical, isotopic, and groundwater-age tracers. Uplands were targeted because natural mixing with brine and hydrocarbons from deep formations is less common in those areas compared to valleys. CH4-isotope, predrill CH4-concentration, and other data indicate that one proximal sample (5% of proximal samples) contains thermogenic CH4 (2.6 mg/L) from a relatively shallow source (Catskill/Lock Haven Formations) that appears to have been mobilized by shale-gas production activities. Another proximal sample contains five other volatile hydrocarbons (0.03–0.4 μg/L), including benzene, more hydrocarbons than in any other sample. Modeled groundwater-age distributions, calibrated to 3H, SF6, and 14C concentrations, indicate that water in that sample recharged prior to shale-gas development, suggesting that land-surface releases associated with shale-gas production were not the source of those hydrocarbons, although subsurface leakage from a nearby gas well directly into the groundwater cannot be ruled out. Age distributions in the samples span ∼20 to >10000 years and have implications for relating occurrences of hydrocarbons in groundwater to land-surface releases associated with recent shale-gas production and for the time required to flush contaminants from the system.

Publication Year 2019
Title Hydrocarbons in upland groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA
DOI 10.1021/acs.est.9b01440
Authors Peter B. McMahon, Bruce D. Lindsey, Matthew D. Conlon, Andrew G. Hunt, Kenneth Belitz, Bryant Jurgens, Brian A. Varela
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Index ID 70204257
Record Source USGS Publications Warehouse
USGS Organization California Water Science Center; Central Energy Resources Science Center; Colorado Water Science Center; Crustal Geophysics and Geochemistry Science Center; Energy Resources Program; Massachusetts Water Science Center; National Water Quality Assessment Program; New England Water Science Center; Pennsylvania Water Science Center; Southwest Regional Director's Office; National Water Quality Program