Date of Award

Summer 7-1-2022

Degree Type


Degree Name

Master of Science (MS)


Earth Sciences


Wen, Tao

Subject Categories

Earth Sciences | Environmental Sciences | Geology | Physical Sciences and Mathematics


Over the past decade, the rapid growth of unconventional oil and gas development (UOGD) has raised public concerns about its potential impact on groundwater quality. High methane and salt levels in groundwater have been the most widely cited UOGD-related impairments. The attribution of these contaminants to UOGD is usually complex, especially in regions with mixed land uses. Here, we compiled a large hydrogeochemistry dataset containing 13 geochemical analytes for 17,794 groundwater samples from the rural northern Appalachia, i.e., 19 counties located on the boundary between Pennsylvania (PA; UOGD is permitted) and New York (NY; UOGD is banned). With this dataset, we explored if statistical and geospatial analysis tools can help shed light on the sources of inorganic and methane solutes in groundwater in regions with mixed land uses. The Wilcoxon-Mann-Whitney test reveals statistically significant higher chloride and methane concentrations in UOGD counties than in non-UOGD ones. The Principal Component Analysis or PCA results indicate NY and PA groundwater samples mainly consist of Appalachian Basin Brine (ABB), septic effluent, shallow groundwater, and rainwater. In contrast, the Non-negative Matrix Factorization or NMF analysis highlights the dominant contribution of road salts (in addition to ABB) to the salt content in groundwater. The PCA fails to identify road salts as an additional water source, likely due to its geochemical similarity with ABB. Neither PCA nor NMF detects the regional impact of UOGD-related wastewater. The further geospatial analysis – Sliding Window Geospatial Tool corroborates 1) road salting is the major regional salt source in groundwater, and its impact is enhanced in proximity to the highways; 2) UOGD-related groundwater quality deterioration is primarily limited to a few localities in PA, where elevated levels of salinity and dissolved methane are observed in counties with dense unconventional oil and gas wells.


Open Access



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