Toxicological Characterization of Hydraulic Fracturing Flowback and Produced Water Exposures to Aquatic Organisms

  • Author / Creator
    Folkerts, Erik John
  • Hydraulic fracturing is an unconventional oil and gas extraction method used to liberate oil and gas reserves from low permeability geological formations by injecting large quantities of fracturing fluid into the well-bore under high pressures. A by-product of this process is flowback and produced water (FPW), a chemically complex and heterogeneous wastewater mixture. Spills and releases of FPW to surface bodies of water is an environmental topic gaining increasing public attention. Freshwater animals are extremely sensitive to FPW, with saline components of the solution responsible for a considerable proportion of the induced lethality. However, other chemical constituents besides saline components (e.g., metal species and numerous toxic dissolved organic compounds, including polycyclic aromatic hydrocarbons [PAHs], organophosphorus compounds, and alkyl ethoxylate carboxylate surfactants) appreciably contribute to the overall toxicological potential of FPW. I demonstrated that in rainbow trout (Oncorhynchus mykiss; RT) acutely exposed to FPW, significant induction of key phase I and II xenobiotic metabolic processes occurs (ethoxyresorufin-o-deethylase activity and cytochrome P450 1A, UDP-glucoronosyl transferase and glutathione-s-transferase transcript expression), implying that biotransformative responses are induced to detoxify organic compounds (specifically PAHs). Furthermore, increased reactive oxygen species is another major physiological stress encountered in FPW exposed organisms while elevated expression of vitellogenin and estrogen receptor α2 genes also demonstrate possible endocrine disruptive effects in exposed organisms. I additionally examined hepatic nutrient handling and energy dynamic processes in FPW exposed RT and showed that an immediate deviation in nutrient handling occurs following/during FPW exposure in trout.
    Embryonic exposure studies revealed that the development and function of cardio-respiratory systems in fish are severely impacted by acute FPW exposure. FPW significantly increased rates of numerous developmental deformities at hatch (including rates of pericardial edema) and decreased heart rates in zebrafish (Danio rerio; ZF) embryos. FPW-mediated impacts to embryo metabolic O2 consumption (MO2) were additionally displayed to persist through development and past initial acute exposures in both ZF and RT. Embryos from both species of fish also displayed elevated expression of critical cardiogenic development and differentiation transcription factors and altered expression of atp2a2a (a key cardiac Ca2+ ATPase required for proper cellular Ca2+ cycling and transport during an excitation-contraction coupling event) following acute FPW exposures. RT embryos additionally displayed altered expression of other cardiac electrochemically related genes responsible for the transport of ions required for action potential propagation and completion, including scn5lab, kcnh6, and kir2.1. These transcriptional changes agree with cellular studies on isolated ventricular mahi mahi (Coryphaena hippurus) cardiomyocytes exposed to low-strength FPW dilutions displayed reduced sarcomere contraction sizes and altered relaxation indices. Finally, I identified that embryonic exposures to FPW significantly decrease juvenile fish swimming performance (Ucrit), with corresponding decreases in maximum metabolic rates and aerobic scope. Additionally, embryonic FPW exposure reduced ventricular compact myocardium thickness that may contribute to the latent effects of embryonic FPW exposure on juvenile fish swimming performance and respirometry. Overall, these results highlight the considerable toxicity of FPW to organisms of aquatic environments and reveal cardio-respiratory development and function in fish as targeted processes affected by FPW exposure.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.