Tracing Water and Carbon Sources in Complex Geochemical Settings of the Appalachians: An Isotopic Perspective

Understanding sources of water and carbon are important for tracking recharge sources as well as assessing any changes in water quality associated with shale gas drilling and/or coal mining in the Appalachians. Natural stable isotopes have become an increasingly important tool for determining sources and cycling of water, carbon, nutrients and other trace elements. This is plausible because variations in water-rock interactions, recharge sources, recharge pathways, and residence time can impart unique isotopic fingerprints to different water sources.;The main objective of this study was to use stable isotopes of water (δ18O_H2O and δ2H _H2O), DIC (δ13C_DIC) and SO₄ (δ34S_SO4 and δ18O _SO4) to delineate sources of water and carbon in three different geochemical settings in Appalachians: natural springs, coal mine discharges and co-produced waters produced during Marcellus shale gas drilling in the Appalachian region. At some study sites other geochemical proxies such as major cations, anions (i.e. Na+, Ca2+, Mg2+, HCO ₃-, SO₄2-) as well as field parameters (temperature and pH) were used in conjunction with stable isotope data to better understand the underlying physical, geochemical and biological processes. Our data shows that stable isotopic signatures in natural springs, coal mine discharge and co-produced waters can be used understand sources of carbon and water at each site as well as understanding biogeochemical transformations that lead to isotopic fractionation.