Monitoring levels of dissolved methane and metals in Maryland streams overlying the Marcellus Shale prior to hydraulic fracturing

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In western Maryland above the Marcellus Shale, 25 streams were monitored for baseline concentrations of dissolved CH4, Sr2+, and Ba2+, constituents that may be affected by fracking activity. Migrated shale CH4 may intrude streams, and Sr2+ and Ba2+ may be introduced by fracking fluid leakages or spills. Stream constituents were also measured in Maryland’s coastal plain for reference. In western Maryland, CH4 concentrations are significantly variable yet in agreement with concentrations reported for other North American pristine rivers. Measurements of δ13C-CH4 suggest CH4 is primarily biogenic. Dissolved Sr2+ and Ba2+ are spatially and temporally variable, although Sr/Ba ratios are relatively stable at most sites, indicating these may be useful fracking fluid tracers. Major ions Na+, K+, Mg2+, Ca2+, Cl−, SO42-, and HCO3– were measured. These were elevated relative to Sr2+ and Ba2+ and are not suitable fracking fluid tracers. Major ions were highly variable, indicative of variable bedrock geology in western MD.