Impact of Oil & Gas Wastewater Disposal on Lake and River Sediments

PI Name: William D. Burgos

Proposal Number: 1703412

In 2015, unconventional Oil & Gas (O&G) wells accounted for more than 1/2 of the oil and 2/3 of the natural gas produced in the US. Unconventional O&G wells typically produce 50 - 60 times more wastewater compared with conventionally drilled O&G wells. The growth in unconventional O&G development has raised concerns about possible risks associated with wastewater management. Some facilities accept O&G wastewater for treatment and then discharge the treated water to streams; however, these facilities may not adequately remove all of the contaminants of concern. This study will provide evidence on potential adverse health and environmental impacts resulting from inadequate O&G wastewater management. The results are expected to help regulators and industry improve O&G wastewater management strategies and prevent chemicals from entering the environment.

The objectives of this project are to determine if chemical signatures in the sediment record can be used to quantify the historical impacts of O&G wastewater disposal, and to evaluate the potential biological toxicity of sediments contaminated by O&G wastewater disposal. A series of tasks will be completed to accomplish these objectives. Watersheds with significant amounts of O&G wastewater disposal and hydrodynamic conditions for sediment retention will be identified. For these reservoirs, sediment deposition models will be developed to reconstruct the sediment stratigraphy and identify sediment sampling locations that retain a coherent temporal record. Field sampling campaigns will be organized to collect intact sediment cores from these locations. Core processing will yield paired samples of sediments and porewaters as a function of depth. Sediment age will be determined based on 210-Pb and 7-Be profiles. The physical, chemical, and toxicological properties of the sediment layers in these cores will be characterized to identify sediment intervals with distinct O&G chemical signatures. Contaminants of concern associated with O&G wastewater include salts, alkaline earth metals, naturally occurring radioactive materials, and specialty organic additives. Porewater samples will be analyzed for indicators of contamination, including anions (Cl, Br, SO4), cations (Na, Ca, Ba, Sr, Mg), and trace metals (e.g., Cd, Cr, As, Pb). Sediments will be dried and analyzed for these same elements. While major element concentrations can indicate potential impacts from O&G wastewater, isotopic ratios (226-Ra/228-Ra and 87-Sr/86-Sr) that can distinguish possible contaminant sources (e.g., conventional versus unconventional O&G formation waters) will also be measured. Organic contaminants in the sediments and porewaters will be characterized by non-targeted analyses. The toxicity of the sediments will be evaluated using a suite of human cell-based bioanalytical assays. Specific receptors will be used to detect toxic responses such as DNA damage, induction of xenobiotic metabolisms, adaptive stress responses, and hormone-mediated activity. Outreach activities are planned to discuss results and implications of the research with policymakers through the American Chemical Society's (ACS) Science & the Congress program, the scientific community through technical sessions at ACS National Meetings, local schools with Creek Connections -- a K-12 teaching training program at Allegheny College, and citizens in local watershed groups.