Pennsylvania produces roughly one-fifth of the natural gas extracted in the United States, but beneath the state’s long history of energy development lies a less visible question: what happens to drinking water when underground chemistry is disturbed? A new Penn State-led study suggests that unconventional oil and gas operations may be linked to conditions that mobilize radium, a naturally occurring radioactive element, into shallow groundwater. The findings do not show that fracking universally contaminates private wells, nor do they establish a simple cause-and-effect relationship. Instead, they reveal a more complicated chain of events in which increased salinity, geological conditions and localized spills or mismanagement may combine to release radium and other metals from surrounding rock.
The researchers investigated groundwater in Washington and Greene Counties in southwestern Pennsylvania, a region marked by extensive shale-gas development and a dense network of private wells and springs. They collected untreated drinking-water samples from 91 residences located at varying distances from unconventional oil and gas operations. The sampling strategy included homes within approximately half a mile of drilling activity, locations just under two miles away and sites more than three miles from operations. By collecting water before it passed through household filtration or treatment systems, the researchers aimed to measure the chemical conditions in the aquifer itself rather than the quality of water after household interventions.
The study, published in Environmental Science & Technology, focused on radium as well as indicators of salinity, including dissolved salts associated with deep geological brines. Radium is present at very low concentrations throughout the environment, but it can become more mobile when groundwater chemistry changes. In particular, highly saline water can alter the balance of chemical reactions occurring between groundwater and mineral surfaces. Those reactions may displace radium that is naturally bound to rock, allowing it to dissolve into groundwater and move through shallow aquifers. The researchers therefore examined whether wells closer to unconventional drilling operations showed both higher salt concentrations and higher radium levels.
The results pointed to an association rather than a universal signature of fracking. Samples collected nearer to energy-development sites tended to contain greater salinity, and some drilling operations were associated with elevated radium concentrations. However, the relationship was not strong or consistent enough to conclude that unconventional oil and gas activity alone explained the pattern across the entire study area. Radium levels were more likely to be elevated in samples taken within three kilometers of operations, a distance just under two miles, but the trend did not reach a level that would support a broad, generalized correlation. The findings instead suggest that local geology and other sources of salts may be decisive in determining whether radium becomes a drinking-water concern.
That distinction matters because salinity in rural groundwater can come from many sources. Road de-icing salts, septic systems, animal waste and other forms of land use can introduce dissolved ions into aquifers without any connection to oil or gas extraction. The chemical fingerprints of these sources can overlap, making it difficult to identify where a particular contaminant originated from a single water sample. The Penn State team reported that six of the 91 samples could potentially be associated with fracking wastewater. Such a result does not indicate widespread contamination, but it does show how spills, leaks or inadequate wastewater management could create highly localized impacts that might be missed by broad regional surveys.
Radium is particularly important because of the way the human body handles it. Chemically, radium resembles calcium, an element the body actively transports and incorporates into bones. When radium is consumed in drinking water, some of it can follow similar biological pathways and become deposited in bone tissue. As radium decays, it emits ionizing radiation capable of damaging cells and DNA. Long-term exposure to elevated concentrations is associated with increased cancer risk. The researchers emphasized that all radium measurements in the sampled homes remained below the U.S. Environmental Protection Agency’s legal limit. Nevertheless, detecting the geochemical conditions that can move radium into groundwater remains important, especially for residents who rely on private wells that are not routinely monitored like public water systems.
The underlying mechanism is tied to the chemistry of water moving through fractured rock. Conventional oil and gas wells historically targeted concentrated underground reservoirs, while unconventional development reaches shale formations that require horizontal drilling and hydraulic fracturing. In this process, operators inject large volumes of water, sand and chemical additives at high pressure to create and prop open fractures in deep rock. The approach dramatically expands the amount of rock contacted by a well and increases the volume of water involved in drilling and production. Deep formations can contain naturally salty brines rich in sodium, chloride, barium and strontium. If these fluids reach shallow groundwater through a spill, faulty containment or pathways associated with old wells, they may increase salinity and promote the release of radium from mineral surfaces.
The study builds on earlier Penn State research that identified elevated salt “hotspots” near unconventional oil and gas operations across the Northern Appalachian Basin, a geological region extending from Alabama toward upstate New York. According to the researchers, areas with increased salinity may carry as much as a 200% higher risk of radium-related health effects compared with less saline settings, because saltier water can enhance radium mobilization. That estimate describes a change in potential risk under particular chemical conditions, not evidence that every nearby household faces such an increase. The new work adds radium measurements to a body of research that has more often tracked deep-brine indicators without directly examining radioactive elements.
For the participating communities, the project also provided residents with information about the quality of their own drinking water. Researchers said that building long-term relationships with homeowners was essential because private wells can vary substantially over short distances, and residents often have the greatest need for information about contaminants that may not be routinely tested. The team plans to expand sampling with larger datasets and more targeted investigations around active and abandoned oil and gas wells. Historical wells are a particular focus because aging infrastructure can remain as a potential pathway between deep formations and shallow groundwater long after production has stopped.
The researchers describe radium as one piece of a larger groundwater puzzle rather than a standalone measure of industrial impact. The study’s observational design can identify patterns and plausible mechanisms, but it cannot by itself prove that a specific drilling operation caused contamination in a particular well. Future work combining repeated sampling, detailed chemical tracers, well records, geological mapping and measurements of additional elements could help separate the influence of energy development from road salt, septic systems and agricultural activity. For now, the findings offer a more nuanced warning: unconventional oil and gas operations may contribute to the chemical conditions that release naturally occurring radium, while the greatest risks appear to arise from localized interactions between industrial activity, geology and groundwater chemistry.
Article Title: Matrix-Derived Radium Mobilization in Shallow Aquifers Near Unconventional Oil and Gas Operations
Web References: https://doi.org/10.1021/acs.est.6c05003; https://www.psu.edu/news/earth-and-mineral-sciences/story/research-links-shale-gas-legacy-energy-development-groundwater; https://www.eia.gov/states/PA/analysis
References: Environmental Science & Technology, DOI: 10.1021/acs.est.6c05003
Image Credits: Provided by Nathaniel Warner
Keywords
Radium, groundwater, hydraulic fracturing, fracking, unconventional oil and gas, shale gas, Pennsylvania, drinking water, salinity, environmental health, environmental engineering, natural gas extraction
