USING LONG-TERM LEACHATE TESTS TO IDENTIFY POTENTIAL CONTAMINANTS OF CONCERN IN DRILL CUTTINGS FROM THE MARCELLUS SHALE, OTSEGO COUNTY, NEW YORK

Proposed natural gas development in New York State using horizontal drilling and hydro-fracturing techniques has been a topic of intense public debate due to concerns over potential environmental impacts. One concern is metals leaching from drill cuttings and migrating into surface water or shallow groundwater. The purpose of this experiment was to determine what metals, if any, would leach from weathered rock cuttings collected from the mid to lower Marcellus formation exposed along Route 20 in Cherry Valley, NY. In the experiment these cuttings were hand-crushed into twelve 10-gram pebble-sized samples. 1000 mL of de-ionized water was leached, collected, and re-percolated through its respective 10-gram sample once a day for 25-, 53-, 80-, and 110-days. The leachate was analyzed for pH, electrical conductivity, dissolved metals (Al, As, Ba, Cd, Ca, Cr, Fe, Pb, Mg, Mn, K, Na, Sr) using an ICP-ES, anions (SO₄ and Cl) using an adsorption spectrophotometer, and carbonate alkalinity by titration. Metal concentrations of whole-rock samples were also completed using X-ray fluorescence. Previous work done by Walsh, Krikorian, and Castendyk (2009) did not investigate Cd, Cr, and Pb. This study found that concentrations of Pb increased in the leachate over time whereas other contaminants of concern (As, Cd, Cr, Mn, and Sr) remained below detection limits. Electrical conductivity also increased as a function of leaching, whereas the dominant anion, SO₄, remained relatively constant over time. By comparing the dissolved metal concentrations in the leachate to whole-rock metal concentrations in unleached rock samples, our study provides an understanding of the mobility of metals from the Marcellus formation, and sheds light on the likely quantities of metals that will leach from drill cuttings exposed to atmospheric weathering.