Date of Award

August 2018

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor(s)

Zunli Lu

Keywords

Groundwater, Iodine, Methane, Tracer

Subject Categories

Physical Sciences and Mathematics

Abstract

Due to the ban on hydraulic fracturing for natural gas in New York State (NYS), it serves as an ideal location to study the natural processes that control the migration of dissolved methane and high salinity fluids found at depth. The hydrogeologic setting of NYS is analogous to that of Northern Pennsylvania where unconventional exploration has not been restricted. Halogens geochemically behave conservatively and can be found in unique proportions. Therefore, they serve as useful tracers for the natural movement of groundwater. The focus of our study is to: 1) establish a more cohesive baseline for groundwater quality data for NYS prior to the onset of unconventional natural gas development than currently available; 2) evaluate the spatial variability and hydrologic controls over dissolved methane, chloride, bromine, and iodine; and 3) further evaluate the extent to which bromine-iodine mass ratios (Br/I) may be useful as a geochemical tracer in groundwater in the Appalachian Basin.

Sampling occurred throughout the late summer and fall of 2016 and 2017. Water was collected from domestic and public supply groundwater wells (n=108) located in five distinct NYS hydrologic regions defined by major drainage basins: western NYS, central NYS, Broome and Tioga Counties of southern NYS, the Mohawk River Basin, and the Upper Hudson River Basin. The majority of samples (54%) had methane concentrations between 1-10 mg/L, 40% of samples fell below the detection limit, and 6% of samples had methane greater than 10 mg/L, the actionable level implemented by the US Department of the Interior Office of Surface Mining. Mann-Whitney statistical tests on this dataset suggest that landscape position did not serve as a strong control for elevated methane as suggested in previous studies. In contrast, the strongest predictors for methane in potable groundwater appear to be: general bedrock type (i.e. sedimentary or crystalline), height of the well bore above the Marcellus Shale, sodium (Na)-rich water type, and degree of confinement. Halogen concentrations, particularly bromine and iodine, can characterize saline formation waters naturally mixing with potable waters. The quality of groundwater wells often consists of both shallow groundwater flow and some measure of Upper and Middle Devonian (Marcellus Formation) waters from the bedrock below. Our results show that iodine in conjunction with bromine can be utilized to identify the degree of formation water influence in potable groundwater.

Access

Open Access

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