Repository for Oil and Gas Energy Research (ROGER)

Abstract:
Wastewaters from oil and gas development pose largely unknown risks to environmental resources. In January 2015, 11.4 M L (million liters) of wastewater (300 g/L TDS) from oil production in the Williston Basin was reported to have leaked from a pipeline, spilling into Blacktail Creek, North Dakota. Geochemical and biological samples were collected in February and June 2015 to identify geochemical signatures of spilled wastewaters as well as biological responses along a 44-km river reach. February water samples had elevated chloride (1030 mg/L) and bromide (7.8 mg/L) downstream from the spill, compared to upstream levels (11 mg/L and < 0.4 mg/L, respectively). Lithium (0.25 mg/L), boron (1.75 mg/L) and strontium (7.1 mg/L) were present downstream at 5–10 times upstream concentrations. Light hydrocarbon measurements indicated a persistent thermogenic source of methane in the stream. Semi-volatile hydrocarbons indicative of oil were not detected in filtered samples but low levels, including tetramethylbenzenes and di-methylnaphthalenes, were detected in unfiltered water samples downstream from the spill. Labile sediment-bound barium and strontium concentrations (June 2015) were higher downstream from the Spill Site. Radium activities in sediment downstream from the Spill Site were up to 15 times the upstream activities and, combined with Sr isotope ratios, suggest contributions from the pipeline fluid and support the conclusion that elevated concentrations in Blacktail Creek water are from the leaking pipeline. Results from June 2015 demonstrate the persistence of wastewater effects in Blacktail Creek several months after remediation efforts started. Aquatic health effects were observed in June 2015; fish bioassays showed only 2.5% survival at 7.1 km downstream from the spill compared to 89% at the upstream reference site. Additional potential biological impacts were indicated by estrogenic inhibition in downstream waters. Our findings demonstrate that environmental signatures from wastewater spills are persistent and create the potential for long-term environmental health effects.

Abstract:
Beginning in the 1860s, fracturing was used to stimulate or rather shoot rock formations for oil production. To increase both initial flow and ultimate extraction, liquid and solidified nitroglycerin was used in these years. The concept of (hydraulic) fracturing with pressure instead of explosives grew in the 1930s. Beginning in 1953, water-based fluids were developed using different types of gelling agents. Nowadays, aqueous fluids such as acid, water, brines, and water-based foams are used in most fracturing treatments. The breakdown of the fluids to decrease viscosity is mostly carried out by use of oxidizing agents. Thereby, the technology is facing concerns regarding microseismicity, air emissions, water consumption, and the endangerment of groundwater due to the risk of perforating protective layers and the ooze of chemicals through the surface. Furthermore, particularly both cross-linking and breaking agents pose serious risks for humans respectively are environmentally hazardous in terms of eco-toxicity—while the degradation effect of common oxidizing agents is relatively low in cases of high-temperature fracturing treatments. According to our comparative viscosity tests, the viscosity of both common hydrogels with and without oxidizing agents can be reduced to the same level when heated to 130 °C or above. Furthermore, in both cases no non-Newtonian behavior could be observed after the temperature treatment (anymore). Therefore, we developed a hydrogel that allows for optimized cross-linking without toxic linkers and that can be dissolved without environmentally hazardous chemicals. Furthermore, it avoids the clogging of pores by hydrogel residues and improves oil and gas exploitation.

Abstract:
We provide a critical review of existing research and information regarding the sources of risk associated with on-site shale gas and tight oil wastewater storage in the United States, the gaps that exist in knowledge regarding these risks, policy and technology options for addressing the risks, and the relative merits of those options. Specifically, we (a) identify the potential risks to human and ecological health associated with on-site storage of shale gas and tight oil wastewater via a literature survey and analysis of data on wastewater spills and regulatory violations, (b) provide a detailed description of government regulations or industry actions that may mitigate these risks to human and ecological health, and (c) provide a critical review of this information to help generate progress toward concrete action to make shale gas and tight oil development more sustainable and more acceptable to a skeptical public, while keeping costs down.

Abstract:
A holistic risk assessment of surface water (SW) contamination due to lead-210 (Pb-210) in oil produced water (PW) from the Bakken Shale in North Dakota (ND) was conducted. Pb-210 is a relatively long-lived radionuclide and very mobile in water. Because of limited data on Pb-210, a simulation model was developed to determine its concentration based on its parent radium-226 and historical total dissolved solids levels in PW. Scenarios where PW spills could reach SW were analyzed by applying the four steps of the risk assessment process. These scenarios are: (1) storage tank overflow, (2) leakage in equipment, and (3) spills related to trucks used to transport PW. Furthermore, a survey was conducted in ND to quantify the risk perception of PW from different stakeholders. Findings from the study include a low probability of a PW spill reaching SW and simulated concentration of Pb-210 in drinking water higher than the recommended value established by the World Health Organization. Also, after including the results from the risk perception survey, the assessment indicates that the risk of contamination of the three scenarios evaluated is between medium-high to high.

Abstract:
Hydraulic fracturing is an industrial process allowing for the extraction of gas or oil. To fracture the rocks, a proprietary mix of chemicals is injected under high pressure, which later returns to the surface as flowback and produced water (FPW). FPW is a complex chemical mixture consisting of trace metals, organic compounds, and often, high levels of salts. FPW toxicity to the model freshwater crustacean, Daphnia magna, was characterized utilizing acute (48 h median lethal concentrations; LC50) and chronic (21 d) exposures. A decrease in reproduction was observed, with a mean value of 18.5 neonates produced per replicate over a 21-d chronic exposure to 0.04% FPW, significantly decreased from the average of 64 neonates produced in controls. The time to first brood was delayed in the highest FPW (0.04%) treatment. Neonates exhibited an LC50 of 0.19% of full-strength FPW, making them more sensitive than adults, which displayed an LC50 value of 0.75%. Quantitative PCR highlighted significant changes in expression of genes encoding xenobiotic metabolism (cyp4) and moulting (cut). This study is the first to characterize chronic FPW toxicity and will help development of environmental monitoring and risk assessment of FPW spills.

Abstract:
The large volume of wastewater produced during unconventional oil and gas (UOG) extraction is a significant challenge for the energy industry and of environmental concern, as the risks due to leaks, spills, and migration of these fluids into natural waters are unknown. UOG wastewater is often hypersaline, and contains myriad organic and inorganic substances added for production purposes and derived from the source rock or formation water. In this study, we examined the organic composition and toxicology of water and sediments in a stream adjacent to an underground injection disposal facility that handles UOG wastewaters. We sampled water and streambed sediments from an unnamed tributary of Wolf Creek upstream from the disposal facility, near the injection well, and downstream. Two sites downstream from the disposal facility contained organic compounds in both water and sediments that were consistent with a source from UOG wastewater. These compounds included: 2-(2-butoxyethoxy)-ethanol, tris(1-chloro-2-propyl)phosphate, α, α-dimethyl-benzenemethanol, 3-ethyl-4-methyl-1H-pyrrole-2,5-dione, and tetrahydro-thiophene-1,1-dioxide in water, diesel fuel hydrocarbons (e.g. pentacosane, Z-14-nonacosane), and halogenated hydrocarbons (e.g., 1-iodo-octadecane, octatriacontyl trifluoroacetate, dotriacontyl pentafluoropropionate) in sediments. Concentrations of UOG-derived organic compounds at these sites were generally low, typically 4 to <1 μg/L in the water, and <70 μg/g (dry wt.) in the sediment. In addition, water and sediment at a site immediately downstream from the facility contained many chromatographically unresolved and unidentified hydrocarbons. In contrast, sites upstream from the facility or in nearby watersheds not influenced by the disposal well facility contained primarily natural (biologically produced) organic substances from the local environment. Toxicological assays of human cell line exposures to water and sediment showed minimal effects. Results indicate that UOG wastewater has entered the stream and that UOG-derived organic substances are present. The contamination level, however, is low and appears to be restricted to sites immediately downstream from the disposal facility at this time.

Abstract:
Produced water is a type of wastewater generated from hydraulic fracturing, which may pose a risk to the environment and humans due to its high ionic strength and the presence of elevated concentrations of metals/metalloids that exceed maximum contamination levels. The mobilization of As(V) and Se(VI) in produced water and selected soils from Qingshankou Formation in the Songliao Basin in China were investigated using column experiments and synthetic produced water whose quality was representative of waters arising at different times after well creation. Temporal effects of produced water on metal/metalloid transport and sorption/desorption were investigated by using HYDRUS-1D transport modelling. Rapid breakthrough and long tailings of As(V) and Se(VI) transport were observed in Day 1 and Day 14 solutions, but were reduced in Day 90 solution probably due to the elevated ionic strength. The influence of produced water on the hydrogeological conditions (i.e., change between equilibrium and non-equilibrium transport) was evidenced by the change of tracer breakthrough curves before and after the leaching of produced water. This possibly resulted from the sorption of polyacrylamide (PAM (-CH2CHCONH2-)n) onto soil surfaces, through its use as a friction reducer in fracturing solutions. The sorption was found to be reversible in this study. Minimal amounts of sorbed As(V) were desorbed whereas the majority of sorbed Se(VI) was readily leached out, to an extent which varied with the composition of the produced water. These results showed that the mobilization of As(V) and Se(VI) in soil largely depended on the solution pH and ionic strength. Understanding the differences in metal/metalloid transport in produced water is important for proper risk management.

Abstract:
Surface water is at risk from Marcellus Shale operations because of chemical storage on drill pads during hydraulic fracturing operations, and the return of water high in total dissolved solids (up to 345 g/L) from shale gas production. This research evaluated how two commercial, off-the-shelf water quality sensors responded to simulated surface water pollution events associated with Marcellus Shale development. First, peak concentrations of contaminants from typical spill events in monitored watersheds were estimated using regression techniques. Laboratory measurements were then conducted to determine how standard in-stream instrumentation that monitor conductivity, pH, temperature, and dissolved oxygen responded to three potential spill materials: ethylene glycol (corrosion inhibitor), drilling mud, and produced water. Solutions ranging from 0 to 50 ppm of each spill material were assessed. Over this range, the specific conductivity increased on average by 19.9, 27.9, and 70 μS/cm for drilling mud, ethylene glycol, and produced water, respectively. On average, minor changes in pH (0.5–0.8) and dissolved oxygen (0.13–0.23 ppm) were observed. While continuous monitoring may be part of the strategy for detecting spills to surface water, these minor impacts to water quality highlight the difficulty in detecting spill events. When practical, sensors should be placed at the mouths of small watersheds where drilling activities or spill risks are present, as contaminant travel distance strongly affects concentrations in surface water systems.

Abstract:
A review of the literature published in 2015 on topics relating to public and environmental health risks associated with wastewater treatment, reuse, and disposal is presented. This review is divided into the following sections: wastewater management, microbial hazards, chemical hazards, wastewater treatment, wastewater reuse, agricultural reuse in different regions, greywater reuse, wastewater disposal, hospital wastewater, industrial wastewater, and sludge and biosolids.

Abstract:
Despite growing concerns over the potential for hydraulic fracturing to impact drinking water resources, there are limited data available to identify chemicals used in hydraulic fracturing fluids that may pose public health concerns. In an effort to explore these potential hazards, a multi-criteria decision analysis (MCDA) framework was employed to analyze and rank selected subsets of these chemicals by integrating data on toxicity, frequency of use, and physicochemical properties that describe transport in water. Data used in this analysis were obtained from publicly available databases compiled by the United States Environmental Protection Agency (EPA) as part of a larger study on the potential impacts of hydraulic fracturing on drinking water. Starting with nationwide hydraulic fracturing chemical usage data from EPA's analysis of the FracFocus Chemical Disclosure Registry 1.0, MCDAs were performed on chemicals that had either noncancer toxicity values (n=37) or cancer-specific toxicity values (n=10). The noncancer MCDA was then repeated for subsets of chemicals reported in three representative states (Texas, n=31; Pennsylvania, n=18; and North Dakota, n=20). Within each MCDA, chemicals received scores based on relative toxicity, relative frequency of use, and physicochemical properties (mobility in water, volatility, persistence). Results show a relative ranking of these chemicals based on hazard potential, and provide preliminary insight into chemicals that may be more likely than others to impact drinking water resources. Comparison of nationwide versus state-specific analyses indicates regional differences in the chemicals that may be of more concern to drinking water resources, although many chemicals were commonly used and received similar overall hazard rankings. Several chemicals highlighted by these MCDAs have been reported in groundwater near areas of hydraulic fracturing activity. This approach is intended as a preliminary analysis, and represents one possible method for integrating data to explore potential public health impacts.

Abstract:
One of the environmental risks associated with use of hydraulic fracturing stimulation technologies for oil and natural gas recovery is the potential release of used fluids into surface waters, soils, and groundwater that could contaminate drinking water resources. To better characterize biodegradability of organic additives, we developed a synthetic fracturing fluid (SFF) based on industry-disclosed formulas, compared its organic carbon composition to fluids used in Pennsylvania's Marcellus shale, and amended agricultural soil–groundwater microcosms with three different SFF concentrations to determine organic carbon degradation rates, changes in system biogeochemistry, and microbial community dynamics under aerobic and anaerobic conditions. Microorganisms indigenous to soils and groundwater were able to degrade between 70% and 92% of the amended dissolved organic carbon within 39 days, suggesting significant mineralization, transformation, or biomass assimilation of organic additives across anaerobic and aerobic redox conditions. Sequencing analysis of the 16S rRNA gene revealed a greater abundance of Pseudomonas in aerobic treatments and a higher relative portion of Desulfovibrio in anaerobic treatments amended with SFF, indicating that these taxa may be involved in SFF biodegradation processes under specific redox conditions. Results provide insight into biodegradability of hydraulic fracturing fluid organic additives in shallow agricultural soils and groundwater and biogeochemical processes that may attenuate their migration if accidentally released or spilled at the surface during hydraulic fracturing activities.

Abstract:
Underground injection (UI) is an effective and efficient means of disposing of wastewater from shale gas production. However, the influence of UI on groundwater systems should be examined carefully to protect drinking groundwater sources. A regional hydrogeological model based on TOUGH2-MP/EOS7R of part of the Sichuan Basin is established to simulate pressure changes and solute transport in response to wastewater injection into deep aquifers. Wastewater is assumed to be injected through a well at a rate of 5.45 kg s−1 for 5 years and a post-injection period of 45 years. The simulation results indicate that UI will cause significant pressure buildup during the injection period, after which pressure will dissipate during the post-injection period. The mass fraction of solute increased over the entire simulation period. The draft regulation under the Safe Drinking Water Act and the level III groundwater quality standards regulated by the Chinese government is referenced as the criteria for evaluating the influence of UI on groundwater systems. It is found that maximum pressure levels caused by UI may exceed safe levels. Uncertainties with respect to permeability are analyzed from previous studies and injection test results. Lower levels of permeability incur higher degrees of pressure buildup when UI is implemented. Different injection schemes are discussed, and we verify that pressure buildup from time-variant injection schemes is less than that from constant injection schemes for the same total injection volume. Injection schemes should be carefully evaluated before implementing UI in a shale gas reservoir.

Abstract:
Chemistry of flowback and produced waters from unconventional gas wells is controlled by reactions between fluids injected for well stimulation and the target geologic formation. Release of salts and metals from the formations are well documented, however, the fate of organic additives under down-hole conditions is not. One outcrop and six core samples of Marcellus Shale were obtained from locations throughout Pennsylvania and sequentially extracted to determine metal associations within various mineral matrices. Metal concentrations in different matrices varied significantly across the shale samples analyzed. In comparison to core samples, lower metal and salt concentrations were detected in the shale outcrop likely due to carbonate and salt dissolution during oxidative weathering processes. The shale outcrop was reacted with synthetic hydraulic fracturing fluids (SFFs) of high or low organic content to study the fate of organic additives and their influence on metal mobilization. The organic content of the fluid and high pressure and temperature (HPT; 1200 PSI and 80°C) conditions had little effect on metal dissolution. However, the organic composition changed significantly depending on the reaction conditions (pH and temperature effects). Major findings of this work include the following: (1) addition of oxidants to hydraulic fracturing fluids promotes degradation of organic additives in hydraulic fracturing fluids; (2) mineral composition of shale will effect solution pH, and low pH conditions will promote organic degradation and metal mobilization during hydraulic fracturing; and (3) surfactant additives are persistent under HPT conditions and will return in flowback waters.

Abstract:
Unconventional natural gas development (UNGD) generates large volumes of wastewater, the detailed composition of which must be known for adequate risk assessment and treatment. In particular, transformation products of geogenic compounds and disclosed additives have not been described. This study investigated six Fayetteville Shale wastewater samples for organic composition using a suite of one- and two-dimensional gas chromatographic techniques to capture a broad distribution of chemical structures. Following the application of strict compound-identification-confidence criteria, we classified compounds according to their putative origin. Samples displayed distinct chemical distributions composed of typical geogenic substances (hydrocarbons and hopane biomarkers), disclosed UNGD additives (e.g., hydrocarbons, phthalates such as diisobutyl phthalate, and radical initiators such as azobis(isobutyronitrile)), and undisclosed compounds (e.g., halogenated hydrocarbons, such as 2-bromohexane or 4-bromoheptane). Undisclosed chloromethyl alkanoates (chloromethyl propanoate, pentanoate, and octanoate) were identified as potential delayed acids (i.e., those that release acidic moieties only after hydrolytic cleavage, the rate of which could be potentially controlled), suggesting they were deliberately introduced to react in the subsurface. In contrast, the identification of halogenated methanes and acetones suggested that those compounds were formed as unintended byproducts. Our study highlights the possibility that UNGD operations generate transformation products and underscores the value of disclosing additives injected into the subsurface.

Abstract:
Currently, > 95% of end disposal of hydraulic fracturing wastewater from unconventional oil and gas operations in the US occurs via injection wells. Key data gaps exist in understanding the potential impact of underground injection on surface water quality and environmental health. The goal of this study was to assess endocrine disrupting activity in surface water at a West Virginia injection well disposal site. Water samples were collected from a background site in the area and upstream, on, and downstream of the disposal facility. Samples were solid-phase extracted, and extracts assessed for agonist and antagonist hormonal activities for five hormone receptors in mammalian and yeast reporter gene assays. Compared to reference water extracts upstream and distal to the disposal well, samples collected adjacent and downstream exhibited considerably higher antagonist activity for the estrogen, androgen, progesterone, glucocorticoid and thyroid hormone receptors. In contrast, low levels of agonist activity were measured in upstream/distal sites, and were inhibited or absent at downstream sites with significant antagonism. Concurrent analyses by partner laboratories (published separately) describe the analytical and geochemical profiling of the water; elevated conductivity as well as high sodium, chloride, strontium, and barium concentrations indicate impacts due to handling of unconventional oil and gas wastewater. Notably, antagonist activities in downstream samples were at equivalent authentic standard concentrations known to disrupt reproduction and/or development in aquatic animals. Given the widespread use of injection wells for end-disposal of hydraulic fracturing wastewater, these data raise concerns for human and animal health nearby.

Abstract:
Hydraulic fracturing frequently occurs on agricultural land. Yet the extent of sorption, transformation, and interactions among the numerous organic frac fluid and oil and gas wastewater constituents upon environmental release is hardly known. Thus, this study aims to advance our current understanding of processes that control the environmental fate and toxicity of commonly used hydraulic fracturing chemicals. Poly(ethylene glycol) surfactants were completely biodegraded in agricultural topsoil within 42-71 days, but their transformation was impeded in the presence of the biocide glutaraldehyde and was completely inhibited by salt at concentrations typical for oil and gas wastewater. At the same time, aqueous glutaraldehyde concentrations decreased due to sorption to soil and were completely biodegraded within 33-57 days. While no aqueous removal of polyacrylamide friction reducer was observed over a period of 6 months, it cross-linked with glutaraldehyde, further lowering the biocide's aqueous concentration. These findings highlight the necessity to consider co-contaminant effects when we evaluate the risk of frac fluid additives and oil and gas wastewater constituents in agricultural soils in order to fully understand their human health impacts, likelihood for crop uptake, and potential for groundwater contamination.

Abstract:
The rapid rise of unconventional oil production during the past decade in the Bakken region of North Dakota raises concerns related to water contamination associated with the accidental release of oil and gas wastewater to the environment. Here, we characterize the major and trace element chemistry and isotopic ratios (87Sr/86Sr, δ18O, δ2H) of surface waters (n = 29) in areas impacted by oil and gas wastewater spills in the Bakken region of North Dakota. We establish geochemical and isotopic tracers that can identify Bakken brine spills in the environment. In addition to elevated concentrations of dissolved salts (Na, Cl, Br), spill waters also consisted of elevated concentrations of other contaminants (Se, V, Pb, NH4) compared to background waters, and soil and sediment in spill sites had elevated total radium activities (228Ra + 226Ra) relative to background, indicating accumulation of Ra in impacted soil and sediment. We observed that inorganic contamination associated with brine spills in North Dakota is remarkably persistent, with elevated levels of contaminants observed in spills sites up to 4 years following the spill events.

Abstract:
The United States Environmental Protection Agency (EPA) identified 1,173 chemicals associated with hydraulic fracturing fluids, flowback, or produced water, of which 1,026 (87%) lack chronic oral toxicity values for human health assessments. To facilitate the ranking and prioritization of chemicals that lack toxicity values, it may be useful to employ toxicity estimates from quantitative structure-activity relationship (QSAR) models. Here we describe an approach for applying the results of a QSAR model from the TOPKAT program suite, which provides estimates of the rat chronic oral lowest-observed-adverse-effect level (LOAEL). Of the 1,173 chemicals, TOPKAT was able to generate LOAEL estimates for 515 (44%). To address the uncertainty associated with these estimates, we assigned qualitative confidence scores (high, medium, or low) to each TOPKAT LOAEL estimate, and found 481 to be high-confidence. For 48 chemicals that had both a high-confidence TOPKAT LOAEL estimate and a chronic oral reference dose from EPA’s Integrated Risk Information System (IRIS) database, Spearman rank correlation identified 68% agreement between the two values (permutation p-value = 1x10-11). These results provide support for the use of TOPKAT LOAEL estimates in identifying and prioritizing potentially hazardous chemicals. High-confidence TOPKAT LOAELs were available for 389 of 1,026 hydraulic fracturing-related chemicals that lack chronic oral RfVs and OSFs from EPA-identified sources, including a subset of chemicals that are frequently used in hydraulic fracturing fluids.

Abstract:
The development of unconventional oil and gas (UOG) resources has rapidly increased in recent years; however, the environmental impacts and risks are poorly understood. A single well can generate millions of liters of wastewater, representing a mixture of formation brine and injected hydraulic fracturing fluids. One of the most common methods for wastewater disposal is underground injection; we are assessing potential risks of this method through an intensive, interdisciplinary study at an injection disposal facility in West Virginia. In June 2014, waters collected downstream from the site had elevated specific conductance (416 µS/cm) and Na, Cl, Ba, Br, Sr and Li concentrations, compared to upstream, background waters (conductivity, 74 µS/cm). Elevated TDS, a marker of UOG wastewater, provided an early indication of impacts in the stream. Wastewater inputs are also evident by changes in 87Sr/86Sr in stream water adjacent to the disposal facility. Sediments downstream from the facility were enriched in Ra and had high bioavailable Fe(III) concentrations relative to upstream sediments. Microbial communities in downstream sediments had lower diversity and shifts in composition. Although the hydrologic pathways were not able to be assessed, these data provide evidence demonstrating that activities at the disposal facility are impacting a nearby stream and altering the biogeochemistry of nearby ecosystems.

Abstract:
Spills from oil and gas operations can contaminate water resources, sediment, and soil, but in many cases, information about spill sources and environmental impacts is not available. Here we present age dating methods to estimate the time since the accumulation of radium in impacted soils and sediments from oil and gas wastewater spills. The retention of unsupported Ra-226 and Ra-228 from spill water to soil and sediment and the ingrowth of Ra progeny result in three independent age dating methods using the Th-228/Ra-228, Pb-210/Ra-226 and Ra-228/Ra-226 activity ratios. We tested the Th-228/Ra-228 method on spill sites in North Dakota and West Virginia, where the dates of the spills are known. The Th-228/Ra-228 method yields ages similar to the documented spill ages and can reveal the initial Ra-228/Ra-226 ratios of the spill waters, validating the notion that Ra isotopes and their decay products in contaminated soils and sediments can reveal the ages and origins of spills.

Abstract:
Concerns have been raised about potential public health effects that may arise if hydraulic fracturing-related chemicals were to impact drinking water resources. This study presents an overview of the chronic oral toxicity values?specifically, chronic oral reference values (RfVs) for noncancer effects, and oral slope factors (OSFs) for cancer?that are available for a list of 1,173 chemicals that the United States (US) Environmental Protection Agency (EPA) identified as being associated with hydraulic fracturing, including 1,076 chemicals used in hydraulic fracturing fluids, and 134 chemicals detected in flowback or produced waters from hydraulically fractured wells. EPA compiled RfVs and OSFs using six governmental and intergovernmental data sources. 90 (8%) of the 1,076 chemicals reported in hydraulic fracturing fluids and 83 (62%) of the 134 chemicals reported in flowback/produced water had a chronic oral RfV or OSF available from one or more of the six sources. Furthermore, of the 36 chemicals reported in hydraulic fracturing fluids in at least 10% of wells nationwide (identified from EPA?s analysis of the FracFocus Chemical Disclosure Registry 1.0), 8 chemicals (22%) have an available chronic oral RfV. The lack of chronic oral RfVs and OSFs for the majority of these chemicals highlights the significant knowledge gap that exists to assess the potential human health hazards associated with hydraulic fracturing.

Abstract:
During oil and natural gas production, so-called “produced water” comprises the largest byproduct stream. In addition, many oil and gas operations are augmented via injection of hydraulic fracturing (HF) fluids into the formation. Both produced water and HF fluids may contain hundreds of individual chemicals, some known to be detrimental to public health and the environment. Oil and gas production wastewater may serve a range of beneficial purposes, particularly in arid regions, if managed correctly. Numerous treatment technologies have been developed that allow for injection, discharge to the land surface, or beneficial reuse. Although many papers have addressed the effects of oil and gas production wastewater (OGPW) on groundwater and surface water quality, significantly less information is available on the effects of these fluids on the soil resource. This review paper compiles fundamental information on numerous chemicals used and produced during oil and gas development and their effects on the soil environment. Additionally, pollution prevention technologies relating to OGPW are presented. An understanding of the effects of OGPW on soil chemical, physical, and biological properties can provide a foundation for effective remediation of OGPW-affected soils; additionally, sustainable reuse of oil and gas water for irrigation and industrial purposes may be enhanced.

Abstract:
In 2010, a dramatic increase in the levels of total trihalomethane (THM) and the relative proportion of brominated species was observed in finished water at several Pennsylvania water utilities (PDW) using the Allegheny River as their raw water supply. An increase in bromide (Br−) concentrations in the Allegheny River was implicated to be the cause of the elevated water disinfection byproducts. This study focused on quantifying the contribution of Br− from a commercial wastewater treatment facility (CWTF) that solely treats wastes from oil and gas producers and discharges into the upper reaches of the Allegheny River, and impacts on two downstream PDWs. In 2012, automated daily integrated samples were collected on the Allegheny River at six sites during three seasonal two-week sampling campaigns to characterize Br− concentrations and river dispersion characteristics during periods of high and low river discharges. The CWTF discharges resulted in significant increases in Br− compared to upstream baseline values in PDW raw drinking water intakes during periods of low river discharge. During high river discharge, the assimilative dilution capacity of the river resulted in lower absolute halide concentrations, but significant elevations Br− concentrations were still observed at the nearest downstream PDW intake over baseline river levels. On days with active CWTF effluent discharge the magnitude of bromide impact increased by 39 ppb (53%) and 7 ppb (22%) for low and high river discharge campaigns, respectively. Despite a declining trend in Allegheny River Br− (2009–2014), significant impacts from CWTF and coal-fired power plant discharges to Br− concentrations during the low river discharge regime at downstream PDW intakes was observed, resulting in small modeled increases in total THM (3%), and estimated positive shifts (41–47%) to more toxic brominated THM analogs. The lack of available coincident measurements of THM, precursors, and physical parameters limited the interpretation of historical trends.

Abstract:
The objective of this paper is to review different risk assessment techniques applicable to onshore unconventional oil and gas production to determine the risks to water quantity and quality associated with hydraulic fracturing and produced water management. Water resources could be at risk without proper management of water, chemicals, and produced water. Previous risk assessments in the oil and gas industry were performed from an engineering perspective leaving aside important social factors. Different risk assessment methods and techniques are reviewed and summarized to select the most appropriate one to perform a holistic and integrated analysis of risks at every stage of the water life cycle. Constraints to performing risk assessment are identified including gaps in databases, which require more advanced techniques such as modeling. Discussions on each risk associated with water and produced water management, mitigation strategies, and future research direction are presented. Further research on risks in onshore unconventional oil and gas will benefit not only the U.S. but also other countries with shale oil and gas resources.

Abstract:
Elevated levels of bromide have been shown to contribute to increased formation of disinfection byproducts (DBPs). Both produced water from unconventional oil and gas wells, which are hydraulically fractured using high volumes of fluids, and produced water from conventional oil and gas wells, which are also typically hydraulically fractured but with lower volumes of fluids, can contain high levels of bromide. If these produced waters are treated in conventional commercial wastewater treatment plants, bromide may not be removed from the effluent and is discharged to receiving water bodies. Elevated bromide levels at drinking water plant intakes is a concern for public health reasons if elevated bromide levels cause elevated levels of DBPs. This study used data from commercial wastewater treatment plants and river flow data in western Pennsylvania to construct generic discharge scenarios that illustrate the potential impacts from disposal of five classes of water that were developed from flowback and produced water bromide concentrations. Months with the historical high and low flows in the Allegheny River (Pennsylvania) and Blacklick Creek (Pennsylvania) were chosen for simulation, and treatment plant discharge rates were set at 100, 50, 33, and 25% of the permitted value for the purpose of varying the mass loading. Steady-state simulation results showed the highest probably of impact, defined as concentrations above target levels of 0.02 and 0.10 mg/L, for produced water in the creek at both high and low flows (100%), and produced water in the river at low flows (>75%). High probability of impact (>50%) occurred in the river at low flows and all flows in the creek with treated mixed/flowback water discharge. Modeled reduction in the effluent discharge rate reduced downstream impacts proportionally. Transient simulation showed that transient peak concentrations may exceed time-averaged concentration by up to a factor of four when mixing conditions are met.

Abstract:
Hydraulic fracturing has advanced the development of shale gas extraction, while inadvertent spills of flowback water may pose a risk to the surrounding environment due to its high salt content, metals/metalloids (As, Se, Fe and Sr), and organic additives. This study investigated the potential impact of flowback water on four representative soils from shale gas regions in Northeast China using synthetic flowback solutions. The compositions of the solutions were representative of flowback water arising at different stages after fracturing well establishment. The effects of solution composition of flowback water on soil ecosystem were assessed in terms of metal mobility and bioaccessibility, as well as biological endpoints using Microtox bioassay (Vibrio fischeri) and enzyme activity tests. After one-month artificial aging of the soils with various flowback solutions, the mobility and bioaccessibility of As(V) and Se(VI) decreased as the ionic strength of the flowback solutions increased. The results inferred a stronger binding affinity of As(V) and Se(VI) with the soils. Nevertheless, the soil toxicity to Vibrio fischeri only presented a moderate increase after aging, while dehydrogenase and phosphomonoesterase activities were significantly suppressed with increasing ionic strength of flowback solutions. On the contrary, polyacrylamide in the flowback solutions led to higher dehydrogenase activity. These results indicated that soil enzyme activities were sensitive to the composition of flowback solutions. A preliminary human health risk assessment related to As(V) suggested a low level of cancer risk through exposure via ingestion, while holistic assessment of environmental implications is required.

Abstract:
Shale gas exploitation by hydraulic fracturing involves a number of environmental hazards, among which the neutralization and management of fracturing flowback waters is of particular importance. Chemical compounds present in the flowback water mainly constitute a threat to surface waters. The aim of our research was to determine the effects of these compounds on the state of activated sludge in a wastewater treatment plant employing biological treatment processes. Based on the obtained results, it was concluded that prior to the transfer of flowback water to a biological wastewater treatment system, it should be diluted with fresh water to lower the chloride ion concentration to the level of 1,000 mg Cl-/dm3. Although such a procedure would ensure the proper performance of a biological wastewater treatment system, it would not limit the migration of phthalates and thihalomethanes to surface waters.

Abstract:
Unconventional oil and gas (UOG) production produces large quantities of wastewater with complex geochemistry and largely uncharacterized impacts on surface waters. In this study, we assessed shifts in microbial community structure and function in sediments and waters upstream and downstream from a UOG wastewater disposal facility. To do this, quantitative PCR for 16S rRNA and antibiotic resistance genes along with metagenomic sequencing were performed. Elevated conductivity and markers of UOG wastewater characterized sites sampled downstream from the disposal facility compared to background sites. Shifts in overall high level functions and microbial community structure were observed between background sites and downstream sediments. Increases in Deltaproteobacteria and Methanomicrobia and decreases in Thaumarchaeota were observed at downstream sites. Genes related to dormancy and sporulation and methanogenic respiration were 18–86 times higher at downstream, impacted sites. The potential for these sediments to serve as reservoirs of antimicrobial resistance was investigated given frequent reports of the use of biocides to control the growth of nuisance bacteria in UOG operations. A shift in resistance profiles downstream of the UOG facility was observed including increases in acrB and mexB genes encoding for multidrug efflux pumps, but not overall abundance of resistance genes. The observed shifts in microbial community structure and potential function indicate changes in respiration, nutrient cycling, and markers of stress in a stream impacted by UOG waste disposal operations.

Abstract:
Hydraulic fracturing is the process of injecting solutions at high pressure to break apart rock formations and increase efficiency of natural gas extraction. The solutions are recovered and have been land-applied as a disposal technique. The objective of this greenhouse study was to evaluate the effects of inorganic fertilizer, broiler litter, or Milorganite®, and soil depth interval on the growth of Bermuda grass [Cynodon dactylon (L.) Pers] in soil from a site that had been contaminated with fracturing fluid and was devoid of vegetation. In soil from 0–15 cm depth, initial electrical conductivity (ECe), Na, and Cl levels were 14.5 dS/m, 2994 mg/kg, and 5603 mg/kg, respectively. For the 0–30 cm depth, initial ECe, Na, and Cl levels were 14.1 dS/m, 2550 mg/kg, and 5020 mg/kg, respectively. Bermuda grass was sprigged and harvested after nine weeks. Addition of inorganic fertilizer, broiler litter, or Milorganite® resulted in 290, 241, and 172%, respectively, greater shoot biomass compared to unamended soil. Plants grown in the 0–30 cm depth soil had greater root biomass (95%), length (67%), volume (61%), and surface area (65%) compared to those grown in soil from the 0–15 cm depth. Fertilization and cultivation may be useful in revegetating sites contaminated with fracturing fluid.

Abstract:
Oil and gas extraction and coal-fired electrical power generating stations produce wastewaters that are treated and discharged to rivers in Western Pennsylvania with public drinking water system (PDWS) intakes. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to quantify inorganic species in wastewater and river samples using a method based on EPA Method 200.7 rev4.4. A total of 53 emission lines from 30 elements (Al, As, B, Ba, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn) were investigated. Samples were prepared by microwave-assisted acid digestion using a mixture of 2% HNO3 and 0.5% HCl. Lower interferences and better detection characteristics resulted in selection of alternative wavelengths for Al, As, Sb, Mg, Mo, and Na. Radial view measurements offered accurate determinations of Al, Ba, K, Li, Na, and Sr in high-brine samples. Spike recovery studies and analyses of reference materials showed 80–105% recoveries for most analytes. This method was used to quantify species in samples with high to low brine concentrations with method detection limits a factor of 2 below the maximum contaminant limit concentrations of national drinking water standards. Elements B, Ca, K, Li, Mg, Na, and Sr were identified as potential tracers for the sources impacting PDWS intakes. Usability of the ICP-OES derived data for factor analytic model applications was also demonstrated.

Abstract:
The rapid development of high-volume horizontal hydraulic fracturing for mining natural gas from shale has posed potential impacts on human health and biodiversity. The produced flow back waters after hydraulic stimulation are known to carry high levels of saline and total dissolved solids. To understand the toxicity and potential carcinogenic effects of these wastewaters, flow back waters from five Marcellus hydraulic fracturing oil and gas wells were analyzed. The physicochemical nature of these samples was analyzed by inductively coupled plasma mass spectrometry and scanning electron microscopy/energy dispersive X-ray spectroscopy. A cytotoxicity study using colony formation as the endpoint was carried out to define the LC50 values of test samples using human bronchial epithelial cells (BEAS-2B). The BEAS-2B cell transformation assay was employed to assess the carcinogenic potential of the samples. Barium and strontium were among the most abundant metals in these samples and the same metals were found to be elevated in BEAS-2B cells after long-term treatment. BEAS-2B cells treated for 6 weeks with flow back waters produced colony formation in soft agar that was concentration dependent. In addition, flow back water-transformed BEAS-2B cells show better migration capability when compared to control cells. This study provides information needed to assess the potential health impact of post-hydraulic fracturing flow back waters from Marcellus Shale natural gas mining.

Abstract:
The ecologically sensitive Susquehanna River Basin (SRB) is an important recharge area and drinking water source for a large population in the northeastern United States. Seasonal road salt application, the presence of regional brines at shallow depths, and produced waters associated with active and legacy conventional Upper Devonian oil and gas wells could increase total dissolved solids (TDS) in groundwater and streams. This study focused on SRB watersheds along the New York/Pennsylvania border, in order to assess current water quality and to establish baseline geochemistry for ground and surface water in a region with potential for increased development of the Marcellus Shale and other unconventional shale gas units. Geochemical composition was determined for 300 stream samples collected from ten sites in four watersheds over variable seasonal flow conditions, and for groundwater from over 500 drinking water wells in this region. Results indicate that many streams and groundwater wells in the study area have elevated TDS levels that indicate pre-existing contributions from saline sources. Dilution of these inputs with fresh water, and the lack of low-level trace element concentrations and isotopic composition in many water quality analyses, highlight the need for alternate robust and sensitive chemical signatures. Comparison with Cl/Br anion ratios and 87Sr/86Sr isotope ratios indicate that the (Ba + Sr)/Mg ratio can be used to discriminate between road salt and regional brine in these cases, and mixing models show that even small additions (0.1–0.01%) of these contaminants can be detected with this cation ratio. The (Ba + Sr)/Mg ratio may be even more sensitive (by an order of magnitude) to incursions of Marcellus Shale produced water, depending on the composition of Marcellus produced waters in this region. This study highlights the need for baseline sampling of freshwater reservoirs and the characterization of potential high TDS sources at a local and regional scale.

Abstract:
Due to the rapid expansion in hydraulic fracturing (fracking), there is a need for robust, portable and specific water analysis techniques. Early detection of contamination is crucial for the prevention of lasting environmental damage. Bromide can potentially function as an early indicator of water contamination by fracking waste, because there is a high concentration of bromide ions in fracking wastewaters. To facilitate this, a microfluidic paper-based analytical device (μPAD) has been developed and optimized for the quantitative colorimetric detection of bromide in water using a smartphone. A paper microfluidic platform offers the advantages of inexpensive fabrication, elimination of unstable wet reagents, portability and high adaptability for widespread distribution. These features make this assay an attractive option for a new field test for on-site determination of bromide.

Abstract:
Natural gas extraction from Marcellus Shale generates large quantities of flowback water that contain high levels of salinity, heavy metals, and Naturally Occurring Radioactive Material (NORM). This water is typically stored in centralized storage impoundments or tanks prior to reuse, treatment or disposal. The fate of Ra-226, which is the dominant NORM component in flowback water, in three centralized storage impoundments in southwestern Pennsylvania was investigated during a 2.5-year period. Field sampling revealed that Ra-226 concentration in these storage facilities depends on the management strategy but is generally increasing during the reuse of flowback water for hydraulic fracturing. In addition, Ra-226 is enriched in the bottom solids (e.g., impoundment sludge) where it increased from less than 10 pCi/g for fresh sludge to several hundred pCi/g for aged sludge. A combination of sequential extraction procedure (SEP) and chemical composition analysis of impoundment sludge revealed that barite is the main carrier of Ra-226 in the sludge. Toxicity characteristic leaching procedure (TCLP) (EPA Method 1311) was used to assess the leaching behavior of Ra-226 in the impoundment sludge and its implications for waste management strategies for this low-level radioactive solid waste. Radiation exposure for on-site workers calculated using the RESRAD model showed that the radiation dose equivalent for the baseline conditions was well below the NRC limit for the general public.

Abstract:
Waters co-produced with hydrocarbons in the Appalachian Basin are of notably poor quality (concentrations of total dissolved solids (TDS) and total radium up to and exceeding 300,000 mg/L and 10,000 pCi/L, respectively). Since 2008, a rapid increase in Marcellus Shale gas production has led to a commensurate rise in associated wastewater while generation of produced water from conventional oil and gas activities has continued. In this study, we assess whether disposal practices from treatment of produced waters from both shale gas and conventional operations in Pennsylvania could result in the accumulation of associated alkali earth elements. The results from our 5 study sites indicate that there was no increase in concentrations of total Ra (Ra-226) and extractable Ba, Ca, Na, or Sr in fluvial sediments downstream of the discharge outfalls (p > 0.05) of publicly owned treatment works (POTWs) and centralized waste treatment facilities (CWTs). However, the use of road spreading of brines from conventional oil and gas wells for deicing resulted in accumulation of Ra-226 (1.2 ×), and extractable Sr (3.0 ×), Ca (5.3 ×), and Na (6.2 ×) in soil and sediment proximal to roads (p < 0.05). Although this study is an important initial assessment of the impacts of these disposal practices, more work is needed to consider the environmental consequences of produced waters management.

Abstract:
Fossil fuel extraction activities generate wastewaters that are often high in total dissolved solids (TDS) and specific constituents that can affect drinking water, if these wastewaters enter surface waters. Control of TDS in source waters is difficult without identification of the potential sources of high TDS wastewater associated with fossil fuel activities. Characteristics of natural waters, oil and gas-produced waters, and coal-related wastewaters were analyzed to extract information about constituent concentrations and anion ratios. Statistical analysis of the anion ratios indicates that the SO4/Cl ratio is higher in coal-related wastewaters than in oil and gas-produced waters, suggesting that wastewaters can be distinguished based on this ratio. An approach that compared the SO4/Cl ratio with bromide concentration for the wastewaters can serve to separate oil and gas-produced waters from brine treatment plant discharges, and from the various coal-related wastewaters. This method was applied to surface water quality data collected from two tributaries in Southwestern Pennsylvania from September 2009 to September 2012. Results show that this constituent and ratio method, combined with mixing curve calculations, can be used to identify water quality changes in these two tributaries. Similar mixing models, when applied to regionally relevant high TDS wastewater data, may be used in other areas experiencing water quality changes resulting from fossil fuel extraction activities. (C) 2014 American Society of Civil Engineers.

Abstract:
Recent increases in the use of hydraulic fracturing (HF) to aid extraction of oil and gas from black shales have raised concerns regarding potential environmental effects associated with predictions of upward migration of HF fluid and brine. Some recent studies have suggested that such upward migration can be large and that timescales for migration can be as short as a few years. In this article, we discuss the physical constraints on upward fluid migration from black shales (e.g., the Marcellus, Bakken, and Eagle Ford) to shallow aquifers, taking into account the potential changes to the subsurface brought about by HF. Our review of the literature indicates that HF affects a very limited portion of the entire thickness of the overlying bedrock and therefore, is unable to create direct hydraulic communication between black shales and shallow aquifers via induced fractures. As a result, upward migration of HF fluid and brine is controlled by preexisting hydraulic gradients and bedrock permeability. We show that in cases where there is an upward gradient, permeability is low, upward flow rates are low, and mean travel times are long (often >106 years). Consequently, the recently proposed rapid upward migration of brine and HF fluid, predicted to occur as a result of increased HF activity, does not appear to be physically plausible. Unrealistically high estimates of upward flow are the result of invalid assumptions about HF and the hydrogeology of sedimentary basins.

Abstract:
Fluids co-produced with oil and gas production (produced waters) are often brines that contain elevated concentrations of bromide. Bromide is an important precursor of several toxic disinfection by-products (DBPs) and the treatment of produced water may lead to more brominated DBPs. To determine if wastewater treatment plants that accept produced waters discharge greater amounts of brominated DBPs, water samples were collected in Pennsylvania from four sites along a large river including an upstream site, a site below a publicly owned wastewater treatment plant (POTW) outfall (does not accept produced water), a site below an oil and gas commercial wastewater treatment plant (CWT) outfall, and downstream of the POTW and CWT. Of 29 DBPs analyzed, the site at the POTW outfall had the highest number detected (six) ranging in concentration from 0.01 to 0.09 μg L− 1 with a similar mixture of DBPs that have been detected at POTW outfalls elsewhere in the United States. The DBP profile at the CWT outfall was much different, although only two DBPs, dibromochloronitromethane (DBCNM) and chloroform, were detected, DBCNM was found at relatively high concentrations (up to 8.5 μg L− 1). The water at the CWT outfall also had a mixture of inorganic and organic precursors including elevated concentrations of bromide (75 mg L− 1) and other organic DBP precursors (phenol at 15 μg L− 1). To corroborate these DBP results, samples were collected in Pennsylvania from additional POTW and CWT outfalls that accept produced waters. The additional CWT also had high concentrations of DBCNM (3.1 μg L− 1) while the POTWs that accept produced waters had elevated numbers (up to 15) and concentrations of DBPs, especially brominated and iodinated THMs (up to 12 μg L− 1 total THM concentration). Therefore, produced water brines that have been disinfected are potential sources of DBPs along with DBP precursors to streams wherever these wastewaters are discharged.

Abstract:
Hydraulic fracturing, combined with horizontal well development, has resulted in rapid expansion of gas production in the Appalachian Marcellus shale formation. In the past three years, over 2000 horizontal/hydraulic fracture (HHF) wells have been developed in Pennsylvania, presenting significant potential for environmental degradation and human health risk if wastes are not isolated and handled properly. This study examined the waste streams from HHF development in the Marcellus formation and proposes protective measures that would minimize exposure. The results showed that flowback, drilling muds, and HHF fluids all exceeded SDWA limits to varying degrees. Due to the contaminants found in these substances, proper handling and containment is essential to prevent harm to the environment. Field evaluations on a subset of pits and impoundments indicated several construction and maintenance deficiencies related to the containment systems and transport pipelines. The geomembrane liners were evaluated for tears and anchoring deficiencies, while liquid transfer pipes were assessed for bracing support against rupture. An out-of-sample probability analysis using the binomial distribution identifies trends to focus field construction and maintenance efforts in order to minimize exposure pathways of frac fluids to the environment.

Abstract:

Abstract:
The safe disposal of liquid wastes associated with oil and gas production in the United States is a major challenge given their large volumes and typically high levels of contaminants. In Pennsylvania, oil and gas wastewater is sometimes treated at brine treatment facilities and discharged to local streams. This study examined the water quality and isotopic compositions of discharged effluents, surface waters, and stream sediments associated with a treatment facility site in western Pennsylvania. The elevated levels of chloride and bromide, combined with the strontium, radium, oxygen, and hydrogen isotopic compositions of the effluents reflect the composition of Marcellus Shale produced waters. The discharge of the effluent from the treatment facility increased downstream concentrations of chloride and bromide above background levels. Barium and radium were substantially (>90%) reduced in the treated effluents compared to concentrations in Marcellus Shale produced waters. Nonetheless, 226Ra levels in stream sediments (544?8759 Bq/kg) at the point of discharge were ?200 times greater than upstream and background sediments (22?44 Bq/kg) and above radioactive waste disposal threshold regulations, posing potential environmental risks of radium bioaccumulation in localized areas of shale gas wastewater disposal.

Abstract:
Unconventional natural gas development in Pennsylvania has created a new wastewater stream. In an effort to stop the discharge of Marcellus Shale unconventional natural gas development wastewaters into surface waters, on May 19, 2011 the Pennsylvania Department of Environmental Protection (PADEP) requested drilling companies stop disposing their wastewater through wastewater treatment plants (WWTPs). This research includes a chemical analysis of effluents discharged from three WWTPs before and after the aforementioned request. The WWTPs sampled included two municipal, publicly owned treatment works and a commercially operated industrial wastewater treatment plant. Analyte concentrations were quanitified and then compared to water quality criteria, including U.S. Environmental Protection Agency MCLs and "human health criteria." Certain analytes including barium, strontium, bromides, chlorides, total dissolved solids, and benzene were measured in the effluent at concentrations above criteria. Analyte concentrations measured in effluent samples before and after the PADEP's request were compared for each facility. Analyte concentrations in the effluents decreased in the majority of samples after the PADEP's request (p < .05). This research provides preliminary evidence that these and similar WWTPs may not be able to provide sufficient treatment for this wastewater stream, and more thorough monitoring is recommended.

Abstract:
Salts are frequently a major constituent of waste waters produced during oil and gas production. These produced waters or brines must be treated and/or disposed and provide a daily challenge for operators and resource managers. Some elements of salts are regulated with water quality criteria established for the protection of aquatic wildlife, e.g. chloride (Cl−), which has an acute standard of 860 mg/L and a chronic standard of 230 mg/L. However, data for establishing such standards has only recently been studied for other components of produced water, such as bicarbonate (HCO3−), which has acute median lethal concentrations (LC50s) ranging from 699 to > 8000 mg/L and effects on chronic toxicity from 430 to 657 mg/L. While Cl− is an ion of considerable importance in multiple geographical regions, knowledge about the effects of hardness (calcium and magnesium) on its toxicity and about mechanisms of toxicity is not well understood. A multiple-approach design that combines studies of both individuals and populations, conducted both in the laboratory and the field, was used to study toxic effects of bicarbonate (as NaHCO3). This approach allowed interpretations about mechanisms related to growth effects at the individual level that could affect populations in the wild. However, additional mechanistic data for HCO3−, related to the interactions of calcium (Ca2 +) precipitation at the microenvironment of the gill would dramatically increase the scientific knowledge base about how NaHCO3 might affect aquatic life. Studies of the effects of mixtures of multiple salts present in produced waters and more chronic effect studies would give a better picture of the overall potential toxicity of these ions. Organic constituents in hydraulic fracturing fluids, flowback waters, etc. are a concern because of their carcinogenic properties and this paper is not meant to minimize the importance of maintaining vigilance with respect to potential organic contamination.

Abstract:
Produced water from oil and gas development requires management to avoid negative public health effects, particularly those associated with dissolved solids and bromide in drinking water. Rapidly expanding drilling in the Marcellus Shale in Pennsylvania has significantly increased the volume of produced water that must be managed. Produced water management may include treatment followed by surface water discharge, such as at publically owned wastewater treatment plants (POTWs) or centralized brine treatment plants (CWTs). The use of POTWs and CWTs that discharge partially treated produced water has the potential to increase salt loads to surface waters significantly. These loads may cause unacceptably high concentrations of dissolved solids or bromide in source waters, particularly when rivers are at low-flow conditions. The present study evaluates produced water management in Pennsylvania from 2006 through 2011 to determine whether surface water discharges were sufficient to cause salt or bromide loads that would negatively affect drinking water sources. The increase in produced water that occurred in 2008 in Pennsylvania was accompanied by an increase in use of CWTs and POTWs that were exempt from discharge limits on dissolved solids. Estimates of salt loads associated with produced water and with discharges from CWTs and POTWs in 2008 and 2009 indicate that more than 50% of the total dissolved solids in the produced water generated in those years were released to surface water systems. Especially during the low-flow conditions of 2008 and 2009, these loads would be expected to affect drinking water.

Abstract:
Dramatic increases in the development of oil and natural gas from shale formations will result in large quantities of drill cuttings, flowback water, and produced water. These organic-rich shale gas formations often contain elevated concentrations of naturally occurring radioactive materials (NORM), such as uranium, thorium, and radium. Production of oil and gas from these formations will also lead to the development of technologically enhanced NORM (TENORM) in production equipment. Disposal of these potentially radium-bearing materials in municipal solid waste (MSW) landfills could release radon to the atmosphere. Risk analyses of disposal of radium-bearing TENORM in MSW landfills sponsored by the Department of Energy did not consider the effect of landfill gas (LFG) generation or LFG control systems on radon emissions. Simulation of radon emissions from landfills with LFG generation indicates that LFG generation can significantly increase radon emissions relative to emissions without LFG generation, where the radon emissions are largely controlled by vapor-phase diffusion. Although the operation of LFG control systems at landfills with radon source materials can result in point-source atmospheric radon plumes, the LFG control systems tend to reduce overall radon emissions by reducing advective gas flow through the landfill surface, and increasing the radon residence time in the subsurface, thus allowing more time for radon to decay. In some of the disposal scenarios considered, the radon flux from the landfill and off-site atmospheric activities exceed levels that would be allowed for radon emissions from uranium mill tailings. Implications: Increased development of hydrocarbons from organic-rich shale formations has raised public concern that wastes from these activities containing naturally occurring radioactive materials, particularly radium, may be disposed in municipal solid waste landfills and endanger public health by releasing radon to the atmosphere. This paper analyses the processes by which radon may be emitted from a landfill to the atmosphere. The analyses indicate that landfill gas generation can significantly increase radon emissions, but that the actual level of radon emissions depend on the place of the waste, construction of the landfill cover, and nature of the landfill gas control system.

Abstract:
In June 2008, 303,000 L of hydrofracturing fluid from a natural gas well were applied to a 0.20-ha area of mixed hardwood forest on the Fernow Experimental Forest, West Virginia. During application, severe damage and mortality of ground vegetation was observed, followed about 10 d later by premature leaf drop by the overstory trees. Two years after fluid application, 56% of the trees within the fluid application area were dead. Ehrh. was the tree species with the highest mortality, and L. was the least affected, although all tree species present on the site showed damage symptoms and mortality. Surface soils (0-10 cm) were sampled in July and October 2008, June and October 2009, and May 2010 on the fluid application area and an adjacent reference area to evaluate the effects of the hydrofracturing fluid on soil chemistry and to attempt to identify the main chemical constituents of the hydrofracturing fluid. Surface soil concentrations of sodium and chloride increased 50-fold as a result of the land application of hydrofracturing fluids and declined over time. Soil acidity in the fluid application area declined with time, perhaps from altered organic matter cycling. This case study identifies the need for further research to help understand the nature and the environmental impacts of hydrofracturing fluids to devise optimal, safe disposal strategies.