Geochemical Evidence of Potential Groundwater Contamination with Human Health Risks Where Hydraulic Fracturing...

Area of Science:

• Environmental Science
• Hydrogeology
• Geochemistry

Background:

• Unconventional oil and gas development (UOGD) poses risks to water resources, including methane migration and contamination from spills.
• Previous research suggests potential for increased water contamination where UOGD overlaps with legacy fossil fuel extraction sites.

Purpose of the Study:

• To test the hypothesis that groundwater contamination from UOGD is more frequent in areas with dense legacy coal, oil, and gas extraction.
• To identify regional correlations between UOGD activities and specific groundwater contaminants.

Main Methods:

• Utilized data mining techniques on approximately 7000 groundwater analyses from the Marcellus Shale play.
• Compared groundwater chloride and methane concentrations in relation to UOGD proximity and density in areas with varying legacy extraction intensity.

Main Results:

• Found statistically significant regional correlations between groundwater chloride and UOGD in southwestern Pennsylvania (dense legacy extraction), but not in northeastern Pennsylvania (minimal legacy extraction).
• No regional correlation was detected between methane and UOGD in southwestern Pennsylvania, suggesting legacy shallow gas extraction may reduce current gas leakage.
• Identified hotspots where chloride and methane concentrations increase with UOGD density, with potential for thallium to exceed EPA limits.

Conclusions:

• Groundwater contamination from UOGD, particularly with chloride, is more likely in regions with extensive historical fossil fuel extraction.
• Legacy extraction may influence current methane migration patterns.
• Specific UOGD hotspots present potential human health risks due to elevated contaminant levels.