Browsing by Subject "Hydraulic fracturing"

Human activities represent a significant burden on the global water cycle, with large and increasing demands placed on limited water resources by manufacturing, energy production and domestic water use. In addition to changing the quantity of available water resources, human activities lead to changes in water quality by introducing a large and often poorly-characterized array of chemical pollutants, which may negatively impact biodiversity in aquatic ecosystems, leading to impairment of valuable ecosystem functions and services. Domestic and industrial wastewaters represent a significant source of pollution to the aquatic environment due to inadequate or incomplete removal of chemicals introduced into waters by human activities. Currently, incomplete chemical characterization of treated wastewaters limits comprehensive risk assessment of this ubiquitous impact to water. In particular, a significant fraction of the organic chemical composition of treated industrial and domestic wastewaters remains uncharacterized at the molecular level. Efforts aimed at reducing the impacts of water pollution on aquatic ecosystems critically require knowledge of the composition of wastewaters to develop interventions capable of protecting our precious natural water resources.

The goal of this dissertation was to develop a robust, extensible and high-throughput framework for the comprehensive characterization of organic micropollutants in wastewaters by high-resolution accurate-mass mass spectrometry. High-resolution mass spectrometry provides the most powerful analytical technique available for assessing the occurrence and fate of organic pollutants in the water cycle. However, significant limitations in data processing, analysis and interpretation have limited this technique in achieving comprehensive characterization of organic pollutants occurring in natural and built environments. My work aimed to address these challenges by development of automated workflows for the structural characterization of organic pollutants in wastewater and wastewater impacted environments by high-resolution mass spectrometry, and to apply these methods in combination with novel data handling routines to conduct detailed fate studies of wastewater-derived organic micropollutants in the aquatic environment.

In Chapter 2, chemoinformatic tools were implemented along with novel non-targeted mass spectrometric analytical methods to characterize, map, and explore an environmentally-relevant “chemical space” in municipal wastewater. This was accomplished by characterizing the molecular composition of known wastewater-derived organic pollutants and substances that are prioritized as potential wastewater contaminants, using these databases to evaluate the pollutant-likeness of structures postulated for unknown organic compounds that I detected in wastewater extracts using high-resolution mass spectrometry approaches. Results showed that application of multiple computational mass spectrometric tools to structural elucidation of unknown organic pollutants arising in wastewaters improved the efficiency and veracity of screening approaches based on high-resolution mass spectrometry. Furthermore, structural similarity searching was essential for prioritizing substances sharing structural features with known organic pollutants or industrial and consumer chemicals that could enter the environment through use or disposal.

I then applied this comprehensive methodological and computational non-targeted analysis workflow to micropollutant fate analysis in domestic wastewaters (Chapter 3), surface waters impacted by water reuse activities (Chapter 4) and effluents of wastewater treatment facilities receiving wastewater from oil and gas extraction activities (Chapter 5). In Chapter 3, I showed that application of chemometric tools aided in the prioritization of non-targeted compounds arising at various stages of conventional wastewater treatment by partitioning high dimensional data into rational chemical categories based on knowledge of organic chemical fate processes, resulting in the classification of organic micropollutants based on their occurrence and/or removal during treatment. Similarly, in Chapter 4, high-resolution sampling and broad-spectrum targeted and non-targeted chemical analysis were applied to assess the occurrence and fate of organic micropollutants in a water reuse application, wherein reclaimed wastewater was applied for irrigation of turf grass. Results showed that organic micropollutant composition of surface waters receiving runoff from wastewater irrigated areas appeared to be minimally impacted by wastewater-derived organic micropollutants. Finally, Chapter 5 presents results of the comprehensive organic chemical composition of oil and gas wastewaters treated for surface water discharge. Concurrent analysis of effluent samples by complementary, broad-spectrum analytical techniques, revealed that low-levels of hydrophobic organic contaminants, but elevated concentrations of polymeric surfactants, which may effect the fate and analysis of contaminants of concern in oil and gas wastewaters.

Taken together, my work represents significant progress in the characterization of polar organic chemical pollutants associated with wastewater-impacted environments by high-resolution mass spectrometry. Application of these comprehensive methods to examine micropollutant fate processes in wastewater treatment systems, water reuse environments, and water applications in oil/gas exploration yielded new insights into the factors that influence transport, transformation, and persistence of organic micropollutants in these systems across an unprecedented breadth of chemical space.

The innovation and diffusion of new technologies is one of the central concerns of economics. New inventions or technological combinations do not spring fully formed into the world; as firms encounter and learn about new technologies they experiment, refine, and learn about them, improving productivity (and sometimes earning economic rents). Understanding the processes by which firms learn, and how these processes interact with regulations, is fundamental to understanding the emergence of new technologies, their contribution to growth, and the interaction of innovation and regulation.

This dissertation addresses how firms learn and respond to regulations in the context of emerging technologies. Within this framework, I address several questions. When production inputs are socially controversial, do firms respond to disclosure laws by voluntarily constraining their inputs? Do these public disclosure laws facilitate knowledge transmission across firms, and if so, what are the implications for public welfare - for instance, do the gains from trade outweigh any effects of reduced incentives for innovation? I study these questions in the context of hydraulic fracturing, though the results offer insight for more general settings. Panning out to a much broader view, I also explore how energy-related technologies - in both generation and consumption - diffuse across national boundaries over time, and whether innovation and diffusion of energy-efficient technologies has led to more or less energy-efficient economic growth.

In my first paper, I contribute to improved understanding of the conditions in which information-based regulations, which are increasingly common in multiple policy domains, decrease externalities such as environmental pollution. Specifically, I test whether information disclosure regulations applied to hydraulic fracturing chemicals caused firms to decrease their use of toxic inputs. Prior to these mandatory disclosure laws, some operators voluntarily disclosed fluid components for some or all of their wells. I compare the chemical mixtures used prior to the mandatory disclosure laws to those used after the laws took effect, using a difference-in-differences method motivated by the difference in timing of state-level disclosure laws. I use voluntary disclosures to measure the toxicity of fluids prior to mandated disclosure, and thus observe a composite effect of both full reporting and disclosure pressure. These effects likely have opposite signs; I employ several methods to tease them apart so that I can separately identify the effect of disclosure pressure. My analysis, which covers over 70,000 wells in seven states, suggests that state disclosure regulations resulted in a large and persistent decrease in the use of toxic and regulated chemicals in fracturing fluids. This is not the first paper to find that disclosure regulations can change firms' behavior, but it demonstrates such an effect in a setting in which consumer or market pressure is minimal or nonexistent: firms that produce undifferentiated products for an intermediate market, and disclosure policies that do not generate readily accessible or interpretable information.

The second paper tests whether disclosure laws facilitated the transmission of useful knowledge across companies. It is well established that economic agents learn about new technologies in part from other adopters, though even sophisticated firms may not take full advantage of social learning. With my co-authors, I examine whether firms took advantage of environmentally-focused disclosure laws to learn from competitors and improve productivity. We find evidence that they did: following mandatory disclosure we observe convergence in productivity per well, in production inputs, and strong evidence of a link between the two. To our knowledge this is the first study to examine this pathway for social learning in an emerging technology. This could also be interpreted as a form of technology diffusion facilitated by environmental regulation.

In my third paper, I address a broader scale of technology change, looking for evidence that improved technologies for energy generation and consumption have allowed less energy-intensive or pollution-intensive growth in developing countries. I analyze panel data on Gross Domestic Product (GDP) and national energy consumption to look for evidence of technology "leapfrogging" (i.e., decreased intensity of energy consumption for a given level of economic growth). I combine 1960-2014 data on energy consumption from the International Energy Agency with historical data that extends back to 1861 for several countries on energy consumption and fuel source, as well as GDP. I compare countries at the same income level and test whether energy consumption and energy intensity are different for today's less-developed countries compared to today's industrialized countries when they had similar income levels. Compared to prior analysis, my much longer time series allows me to test for leapfrogging over a scale appropriate to the pace of widespread technological change.

Methane is an important greenhouse gas, and an ideal target for greenhouse gas emissions reductions. Unlike carbon dioxide, methane has a relatively short atmospheric lifetime, so reductions in methane emissions could have large and immediate impacts on anthropogenic radiative forcing. A more detailed understanding of the global methane budget could help guide effective emissions reductions efforts.

Humans have greatly altered the methane budget. Anthropogenic methane sources are approximately equal in flux to natural sources, and the current atmospheric methane concentration is ~2.5 times pre-industrial levels. The advent of hydraulic fracturing and resulting increase in unconventional natural gas extraction have introduced new uncertainties in the methane budget. At the same time, the next few decades could be a crucial period for controlling greenhouse gas emissions to avoid irreversible and catastrophic changes in global climate. Natural gas could provide lower-carbon fossil energy, but the climate benefits of this fuel source are highly dependent on the associated methane emissions. In this context of increasing uncertainty and growing necessity, quantifying the impact of natural gas extraction and use on the methane budget is an essential step in making informed decisions about energy.

In the work presented here, I track methane in the environment to address several areas of uncertainty in our present understanding of the methane budget. I apply the tools of methane analysis in a variety of environments, from rural groundwater supplies to an urban atmosphere, and at a range of scales, from individual point sources to regional flux. I first show that carbon isotopes of methane and co-occurrence of ethane are useful techniques for differentiating a range of methane sources. In so doing, I also show that leaks from natural gas infrastructure are a major source of methane in my study area, Boston, MA. I then build on this work by applying the same methane carbon isotope and ethane signatures to partition methane flux for the Boston metro region. I find that 88% of the methane enhancement in the atmosphere above Boston is due to pipeline natural gas.

In the final portion of this thesis and the two appendices, I move from the distribution side of the natural gas production chain to extraction, specifically addressing the potential impacts from hydraulic fracturing in my home state of North Carolina. I combine the methane source identification techniques of the previous sections with additional geochemical analyses to document the pre-drilling water quality in the Deep River Triassic Basin, an area which could be drilled for natural gas in the future. This data set is unique in that North Carolina has no pre-existing commercial oil and gas extraction, unlike other states where unconventional gas extraction is currently taking place. This research is, to my knowledge, the first to examine the hydrogeology of the Deep River Basin, in addition to providing an important background data set that could be used to track changes in water quality accompanying hydraulic fracturing in the region in the future.

Extraction of energy resources and energy production can redistribute and concentrate naturally occurring radioactive materials (NORM), particularly from the uranium (238U t1/2=4.5 x 109 yr) and thorium (232Th t1/2=1.4 x 1010 yr) decay series, posing potential human and environmental health risks if not managed properly. In particular, elevated activities of NORM have been measured in coal combustion residuals (CCRs) generated from coal combustion and oil and gas wastewater (OGW) drawn from both conventional and unconventional oil and gas producing wells. This dissertation characterizes the radioactivity associated with CCRs and OGW and further investigates the use of this radioactivity as a tracer and timer of contamination, particularly from OGW following its accidental or intentional release to the environment.

232Th and its decay product 228Ra and 238U and its decay products 226Ra and 210Pb were measured in coals and CCRs from the majors coal producing basins in the United States as well as in coals and CCRs from high-U coal producing basins in China. 228Ra and 226Ra were measured in OGW from the Appalachian Basin in the United States. Finally, 228Ra, 228Th, 226Ra, and 210Pb were measured in soils and sediments impacted by spills of OGW and the permitted release of treated OGW to surface water.

Characteristic 228Ra and 226Ra activities 228Ra/226Ra activity ratios were found in CCRs and OGW derived from distinct formations, suggesting that the radioactivity can serve as a potential fingerprint of for contamination when CCRs and OGW are accidentally or intentionally released to the environment. Additionally, the decay of 226Ra and 228Ra into their respective decay products 210Pb and 228Th offers the ability to source and age date contamination from OGW. The 228Th/228Ra activity ratio in particular is useful for age dating contamination in impacted sediments up to about 10 years old, which is ideal for age dating recent contamination. The 228Ra/226Ra and 228Th/228Ra activity ratios were successfully used to constrain the age and source of contamination from two scenarios including OGW spills and treated OGW disposal to surface water.

The water energy nexus represents the intersection of water use, energy production, electricity generation, and waste generation and disposal. The rapid rise of unconventional natural gas and oil production through the combined processes of horizontal drilling and hydraulic fracturing have shifted the energy dynamic in the United States. Concurrently, the rising utilization of unconventional gas and oil production has intensified the water use for hydraulic fracturing and generation of flowback and produced water associated with shale gas and tight oil production. Among the major environmental risks associated with the rise of unconventional oil and gas exploration water availability, water contamination from leaking or disposal of wastewater, and adequate disposal of the wastewater are the key issues associated with the water-energy nexus. This dissertation aims to quantify the water use for hydraulic fracturing across the U.S., evaluate the water use for electricity production from natural gas in comparison to coal combustion, estimate the flowback and produced water production, and assess possible recycling of oilfield water through irrigation in California.

This dissertation describes the water footprint of hydraulic fracturing by examining total water use, water use per well, water use per length of horizontal well, and the changes in water use through time. The data show that hydraulic fracturing water use per well has been increasing between early stages (2008-2012) to later stages (2012-2016) of operation. In addition to water use, this dissertation estimated waste water generated from unconventional oil and gas wells and find a concurrent increase in flowback and produced water (FP water) per well through time. Using salinity as a marker to distinguish FP water from water injected for hydraulic fracturing, this dissertation observes the sequestration of the injected freshwater, while the return flow composed primarily of more saline formation brines entrapped within the shale formations.

In addition, this this dissertation explored two downstream impacts of the increasing water use and FP water generation. First, as abundant natural gas resources from the expansion of hydraulic fracturing have shifted the electricity sector from primarily coal- to primarily natural gas-fired, this study examined the impact increasing water use associated with hydraulic fracturing has had on power plant lifecycle water consumption and withdrawal. The study found that despite increasing water use for hydraulic fracturing, natural gas-fired generation on average used less water for cooling relative to coal-fired generation. Finally, this this dissertation examined the risks from recycling of oilfield produced water (OPW) as an agricultural makeup water source. The data from field studies in California show that by using low salinity OPW, farmers are able to successfully recycle OPW without risking metals accumulation in soil and consequently in crop and human health.