The Allegheny River is the source of drinking water for the city of Pittsburgh and its surrounding communities. Accurate assessment of contaminant sources in the watershed, and their impact on the river water quality, is complicated by complexity of inputs such as industrial waste water treatment facilities, legacy acid mine drainage (AMD), oil and gas production, and coal combustion waste sites. Our goal is to establish a baseline for water quality and identify contaminant sources that lead to perturbations to background conditions by combining geochemical and Sr isotopic analysis of daily sampling of Allegheny River water at the Pittsburgh Water Treatment Plant intake with seasonal synoptic measurements across 45 sites within the watershed. Sr isotopes are a natural tracer with the potential to indentify inputs to streams from Marcellus produced waters, AMD, and fluids associated with Upper Devonian gas formations in the Allegheny River watershed (Chapman et al 2012, Env. Sci. Tech. 46:3545).
Discipline Categories: Environmental Geoscience, Geochemistry, HydrogeologyPreliminary results from Allegheny River intake samples over a two month period indicate that Sr concentrations ranged from 140 ppb to 260 ppb, and 87Sr/86Sr values ranged from 0.7124 to 0.7127 (εsrsw = +45.5 to +49.8, where εsrsw is the deviation of the 87Sr/86Sr ratio from that of seawater in parts per ten thousand). In comparison, samples taken in April and July 2012 from seven Allegheny headwater tributaries had lower Sr concentrations (mean ~73 ppb; range = 30 to 115 ppb) and εsrsw values varied from +49.1 and +52.6. Ongoing geochemical and isotopic analysis and additional sampling is underway to identify and quantify contaminant fluxes and model the long-term influence of inputs into the watershed.
Preferred Presentation Type: Oral