IDENTIFICATION OF THE CAUSES AND EXTENT OF ELEVATED METHANE CONCENTRATIONS IN THE GROUNDWATER OF EASTERN KENTUCKY

Recent development of unconventional oil and gas (UOG) resources has prompted concerns about its potential impact on public health and the quality of water and air resources. Elevated dissolved methane concentrations (\u3e 1 mg/L) have been associated with proximity to UOG development and stray gas, but also with natural microbial activity. Baseline gas data, local hydrogeology and geochemistry context can aid assessment of methane sources and interactions. Methane concentrations in eastern Kentucky groundwater are above the “immediate action” level in some private/domestic water wells, show wide variations over small distances, and have been hypothesized to have different relationships to mining. This study suggests that groundwater in areas with extensive coal mining often has low methane concentrations due to sulfate production by pyrite oxidation. Microbial production of methane is common in groundwater, but sulfate-rich groundwater can limit methane production and sulfate-reducing conditions can be coupled with methane oxidation. Areas with a high density of oil and gas wells appear to be more likely to introduce thermogenic methane in groundwater. These results suggest that anthropogenic activities directly and indirectly influence geochemical conditions and methane distribution in groundwater in eastern Kentucky. Similar effects would be expected throughout the Appalachian Basin and in areas with different levels of mining and oil and gas development