Table 1.

Mean values ± standard deviation of methane concentrations (as milligrams of CH4 L-1) and carbon isotope composition in methane in shallow groundwater δ13C-CH4 sorted by aquifers and proximity to gas wells (active vs. nonactive)

Water source, n milligrams CH4 L-1δ13C-CH4, ‰
Nonactive Catskill, 51.9 ± 6.3−52.5 ± 7.5
Active Catskill, 1326.8 ± 30.3−33.5 ± 3.5
Nonactive Genesee, 81.5 ± 3.0−57.5 ± 9.5
Active Genesee, 10.3−34.1
Active Lockhaven, 750.4 ± 36.1−40.7 ± 6.7
Total active wells, 2119.2−37 ± 7
Total nonactive wells, 131.1−54 ± 11

The variable n refers to the number of samples.