Research, Efforts and Projects

Dissemination of unbiased scientific information from detailed experiments is of paramount importance to CLEAR and its affiliates. Research efforts and products are designed to inform the public, private, and government sectors about new findings on environmental analysis and remediation technologies related to studying and ameliorating potential problems associated with industrial processes. Any questions regarding research efforts and products can be directed to Prof. Kevin Schug, CLEAR Director

Current Projects

Cline Shale Time Lapse
Since initial sampling in December 2012, unconventional oil and gas extraction in the region around a series of approximately 40 water wells has increased substantially.

Time Course Groundwater Investigation in the Cline Shale

CLEAR has completed an initial time course investigation on the potential impact of unconventional oil extraction on groundwater quality in the Cline shale of west Texas. Approximately 40 water wells were sampled prior to, during, and after the onset of unconventional drilling and hydraulic stimulation. This represents the first comprehensive time course investigation. This work was supported by The University of Texas at Arlington Press Release:

Characterizing Microbial COntamination in Groundwater
Characterizing bacterial populations in a variety of groundwater samples.

Characterizing Microbial Contamination of Groundwater

CLEAR takes a comprehensive view of water quality analysis. Recently, new tests have shown that populations of bacteria can be altered in conjunction with chemical contamination of water supplies. This is a very new development in an understudied area of research. Our working hypothesis is that the presence of chemical constituents can upset the natural balance of microbial communities, enabling the grow of bacteria, which in some cases, could be more deleterious than the chemicals themselves with respect to human exposure. We are currently drafting our first manuscript on this topic for peer review. Featured will be our use of both mass spectrometric and biochemical methods for characterizing bacterial populations in a variety of groundwater samples.



Peer-Reviewed Publications

  • Ines C. Santos, Zacariah L. Hildenbrand, Kevin A. Schug Application of MALDI-TOF MS in environmental microbiology Analyst 2016 141, 2827-2837

    http://pubs.acs.org/doi/abs/10.1021/acs.est.5b05582?journalCode=esthag

    Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is an emerging technique for microbial identification, characterization, and typing. The single colony method can be used for obtaining a protein fingerprint or profile unique to each microorganism. This technique has been mainly used in the clinical field, but it also has significant potential in the environmental field. The applications of MALDI-TOF MS in environmental microbiology are discussed in this review. An overview on the use of MALDI-TOF MS for environmental proteomics and metabolomics is given as well as its use for bacterial strain typing and bioremediation research. A more detailed review on the use of this technique for the identification, differentiation, and categorization of environmental microorganisms is given. Some of the parameters that can influence the results and reproducibility of MALDI-TOF MS are also discussed.

  • Zacariah L. Hildenbrand, Doug D. Carlton, Brian E. Fontenot, Jesse M. Meik, Jayme L. Walton, Jonathan B. Thacker, Stephanie Korlie, C. Phillip Shelor, Atkinde F. Kadjo, Adelaide Clark, Sascha Usenko, Jason S. Hamilton, Phillip M. Mach, Guido F. Verback IV, Paul Hudak, Kevin A Schug Temporal variation in groundwater quality in the Permian Basin of Texas a region of increasin unconventional oil and gas development Science of the Total Environment 2016 562, 906-913

    http://www.sciencedirect.com/science/article/pii/S0048969716308476

    The recent expansion of natural gas and oil extraction using unconventional oil and gas development (UD) practices such as horizontal drilling and hydraulic fracturing has raised questions about the potential for environmental impacts. Prior research has focused on evaluations of air and water quality in particular regions without explicitly considering temporal variation; thus, little is known about the potential effects of UD activity on the environment over longer periods of time. Here, we present an assessment of private well water quality in an area of increasing UD activity over a period of 13 months. We analyzed samples from 42 private water wells located in three contiguous counties on the Eastern Shelf of the Permian Basin in Texas. This area has experienced a rise in UD activity in the last few years, and we analyzed samples in four separate time points to assess variation in groundwater quality over time as UD activities increased. We monitored general water quality parameters as well as several compounds used in UD activities. We found that some constituents remained stable over time, but others experienced significant variation over the period of study. Notable findings include significant changes in total organic carbon and pH along with ephemeral detections of ethanol, bromide, and dichloromethane after the initial sampling phase. These data provide insight into the potentially transient nature of compounds associated with groundwater contamination in areas experiencing UD activity.

  • Sabrina Habib, Melanie Sberno Hinojosa Research Article: Representation of fracking in mainstream American newspapers Environmental Practice 2016 18, 83-93

    http://www.tandfonline.com/doi/full/10.1017/S1466046616000089?scroll=top&needAccess=true

    This study employed deductive content analysis how hydraulic fracturing, also known as fracking, in online versions of elite American newspapers. The media sources The New York Times, Los Angeles Times, and The Washington Post were chosen as the best outlets to analyze to gain insight into the print and digital media that influence public opinion in the United States. A total of 349 articles published from 1851 to May 2014 were included in this study. The study instrument was based on previous media framing studies, including those on hydraulic fracturing and climate change communication, in addition to observations of patterns noted by the authors during an initial round of coding in the interest of relevance. This study examined the tone in which media coverage portrays hydraulic fracturing, thereby influencing social perceptions of the practice. Significant findings from the study are (a) hydraulic fracturing is presented by elite news outlets through conflict, responsibility (blame), and environmental concerns; and (b) water pollution was the main concern portrayed in the articles, which presents hydraulic fracturing mostly as a water-related issue while leaving out other important aspects of natural gas extraction.

  • Zacariah L. Hildenbrand, Phillip M. Mach, Ethan M. McBride, M. Navid Dorreyatim, Josh T. Taylor, Doug D. Carlton, Jesse M. Meik, Brian E. Fontenot, Kenneth C. Wright, Kevin A. Schug, Guido F. Verbeck Point Ssource attribution of ambient contamination events near unconventional oil and gas development Science of the Total Environment 2016 573, 382-388

    http://www.sciencedirect.com/science/article/pii/S0048969716318150

    We present an analysis of ambient benzene, toluene, and xylene isomers in the Eagle Ford shale region of southern Texas. In situ air quality measurements using membrane inlet mobile mass spectrometry revealed ambient benzene and toluene concentrations as high as 1000 and 5000 parts-per-billion, respectively, originating from specific sub-processes on unconventional oil and gas well pad sites. The detection of highly variant contamination events attributable to natural gas flaring units, condensate tanks, compressor units, and hydrogen sulfide scavengers indicates that mechanical inefficiencies, and not necessarily the inherent nature of the extraction process as a whole, result in the release of these compounds into the environment. This awareness of ongoing contamination events contributes to an enhanced knowledge of ambient volatile organic compounds on a regional scale. While these reconnaissance measurements on their own do not fully characterize the fluctuations of ambient BTEX concentrations that likely exist in the atmosphere of the Eagle Ford Shale region, they do suggest that contamination events from unconventional oil and gas development can be monitored, controlled, and reduced.

  • Bryce F. Payne, Robert Ackley, A. Paige Wicker, Zacariah L. Hildenbrand, Doug D. Carlton, Kevin A Schug Characterization of methane plumes downwind of natural gas compressor stations in Pennsylvania and New York Science of the Total Environment 2016

    http://www.sciencedirect.com/science/article/pii/S004896971632770X

    The extraction of unconventional oil and natural gas from shale energy reservoirs has raised concerns regarding upstream and midstream activities and their potential impacts on air quality. Here we present in situ measurements of ambient methane concentrations near multiple natural gas compressor stations in New York and Pennsylvania using cavity ring-down laser spectrometry coupled with global positioning system technology. These data reveal discernible methane plumes located proximally to compressor stations, which exhibit high variability in their methane emissions depending on the weather conditions and on-site activities. During atmospheric temperature inversions, when near-ground mixing of the atmosphere is limited or does not occur, residents and properties located within 1 mile of a compressor station can be exposed to rogue methane from these point sources. These data provide important insight into the characterization and potential for optimization of natural gas compressor station operations.

  • Taylour G Burton, Hanadi S Rifai, Zacariah L. Hildenbrand, Doug D. Carlton, Brian E Fontenot, Kevin A. Schug Elucidating hydraulic fracturing impacts on groundwater quality using a regional geospatial statistical modeling approach Science of the Total Environment 2016 545, 114-126

    http://pubs.acs.org/doi/abs/10.1021/acs.est.5b05582?journalCode=esthag

    Hydraulic fracturing operations have been viewed as the cause of certain environmental issues including groundwater contamination. The potential for hydraulic fracturing to induce contaminant pathways in groundwater is not well understood since gas wells are completed while isolating the water table and the gas-bearing reservoirs lay thousands of feet below the water table. Recent studies have attributed ground water contamination to poor well construction and leaks in the wellbore annulus due to ruptured wellbore casings. In this paper, a geospatial model of the Barnett Shale region was created using ArcGIS. The model was used for spatial analysis of groundwater quality data in order to determine if regional variations in groundwater quality, as indicated by various groundwater constituent concentrations, may be associated with the presence of hydraulically fractured gas wells in the region. The Barnett Shale reservoir pressure, completions data, and fracture treatment data were evaluated as predictors of groundwater quality change. Results indicated that elevated concentrations of certain groundwater constituents are likely related to natural gas production in the study area and that beryllium, in this formation, could be used as an indicator variable for evaluating fracturing impacts on regional groundwater quality. Results also indicated that gas well density and formation pressures correlate to change in regional water quality whereas proximity to gas wells, by itself, does not. The results also provided indirect evidence supporting the possibility that micro annular fissures serve as a pathway transporting fluids and chemicals from the fractured wellbore to the overlying groundwater aquifers.

  • Jesse M Meik, Brian E Fontenot, Zacariah L. Hildenbrand, Doug D. Carlton Jr, Jayme L Walton, Josh T Taylor, Jonathan B Thacker, Stephanie Korlie, C Phillip Shelor, Drew J Henderson, Akinde F Kadjo, Corey E Roelke, Paul Hudak, Taylour Burton, Hanadi Rifai, Kevin A. Schug Response to Comment on “A Comprehensive Analysis of Groundwater Quality in The Barnett Shale Region Environmental Science and Technology 2015 50, (1), 498-499

    http://pubs.acs.org/doi/abs/10.1021/acs.est.5b05582?journalCode=esthag

    In a recent analysis of groundwater quality in the Barnett Shale region, we detected elevated levels of volatile organic compounds, chlorinated compounds, alcohols, and metal ions throughout the Trinity and Woodbine aquifers across 13 contiguous counties, and suggested that some impacts on water quality might have resulted indirectly or directly from unconventional oil and gas (UOG) activities. McHugh et al. present three main arguments to dispute this assertion:(i) Several elevated compounds did not covary strongly,(ii) some ..

  • Kevin A. Schug, Doug D. Carlton Jr., Zacariah L. Hildenbrand Analytical Efforts Toward Monitoring Groundwater in Regions of Unconventional Oil and Gas Exploration 2015 30, 10,

    http://www.spectroscopyonline.com/analytical-efforts-toward-monitoring-groundwater-regions-unconventional-oil-and-gas-exploration-0

    Gas chromatography (GC), inductively coupled plasma–mass spectrometry (ICP-MS), ICP‐optical emission spectrometry (OES), and other bulk analysis methods are applied to groundwater in proximity to unconventional oil and natural gas extraction activities.

  • Zacariah L. Hildenbrand, Doug D. Carlton Jr., Brian E. Fontenot, Jesse M. Meik, Jayme L. Walton, Josh T. Taylor†, Jonathan B. Thacker, Stephanie Korlie, C. Phillip Shelor, Drew Henderson, Akinde F. Kadjo, Corey E. Roelke, Paul F. Hudak, Taylour Burton, Hanadi S. Rifai, and Kevin A. Schug A Comprehensive Analysis of Groundwater Quality in The Barnett Shale Region Environmental Science and Technology 2015 49, 13, 8254-8262

    http://pubs.acs.org/doi/abs/10.1021/acs.est.5b01526

    The exploration of unconventional shale energy reserves and the extensive use of hydraulic fracturing during well stimulation have raised concerns about the potential effects of unconventional oil and gas extraction (UOG) on the environment. Most accounts of groundwater contamination have focused primarily on the compositional analysis of dissolved gases to address whether UOG activities have had deleterious effects on overlying aquifers. Here, we present an analysis of 550 groundwater samples collected from private and public supply water wells drawing from aquifers overlying the Barnett shale formation of Texas. We detected multiple volatile organic carbon compounds throughout the region, including various alcohols, the BTEX family of compounds, and several chlorinated compounds. These data do not necessarily identify UOG activities as the source of contamination; however, they do provide a strong impetus for further monitoring and analysis of groundwater quality in this region as many of the compounds we detected are known to be associated with UOG techniques.

  • Jonathan B. Thacker, Doug D. Carlton Jr., Zacariah L. Hildenbrand, Akinde F. Kadjo and Kevin A. Schug Chemical Analysis of Wastewater from Unconventional Drilling Operations Water 2015 7, 1568-1579

    http://www.mdpi.com/2073-4441/7/4/1568/htm

    Trillions of liters of wastewater from oil and gas extraction are generated annually in the US. The contribution from unconventional drilling operations (UDO), such as hydraulic fracturing, to this volume will likely continue to increase in the foreseeable future. The chemical content of wastewater from UDO varies with region, operator, and elapsed time after production begins. Detailed chemical analyses may be used to determine its content, select appropriate treatment options, and identify its source in cases of environmental contamination. In this study, one wastewater sample each from direct effluent, a disposal well, and a waste pit, all in West Texas, were analyzed by gas chromatography-mass spectrometry, inductively coupled plasma-optical emission spectroscopy, high performance liquid chromatography-high resolution mass spectrometry, high performance ion chromatography, total organic carbon/total nitrogen analysis, and pH and conductivity analysis. Several compounds known to compose hydraulic fracturing fluid were detected among two of the wastewater samples including 2-butoxyethanol, alkyl amines, and cocamide diethanolamines, toluene, and o-xylene. Due both to its quantity and quality, proper management of wastewater from UDO will be essential.

  • Ling Baia, Jonathan Smutsb, Phillip Walshb, Hui Fana, Zacariah Hildenbrandc, Derek Wongd, David Wetzd, Kevin A. Schuga, Permanent gas analysis using gas chromatography with vacuum ultraviolet detection. Journal of Chromatography A 2015 1388

    http://www.sciencedirect.com/science/article/pii/S0021967315002174

    The analysis of complex mixtures of permanent gases consisting of low molecular weight hydrocarbons, inert gases, and toxic species plays an increasingly important role in today's economy. A new gas chromatography detector based on vacuum ultraviolet (VUV) spectroscopy (GC–VUV), which simultaneously collects full scan (115–240 nm) VUV and UV absorption of eluting analytes, was applied to analyze mixtures of permanent gases. Sample mixtures ranged from off-gassing of decomposing Li-ion and Li-metal batteries to natural gas samples and water samples taken from private wells in close proximity to unconventional natural gas extraction. Gas chromatography separations were performed with a porous layer open tubular column. Components such as C1–C5 linear and branched hydrocarbons, water, oxygen, and nitrogen were separated and detected in natural gas and the headspace of natural gas-contaminated water samples. Of interest for the transport of lithium batteries were the detection of flammable and toxic gases, such as methane, ethylene, chloromethane, dimethyl ether, 1,3-butadiene, CS2, and methylproprionate, among others. Featured is the capability for deconvolution of co-eluting signals from different analytes.

  • Hildenbrand, Z. L.; Carlton, D. D.; Fontenot, B. E.; Meik, J. M.; Walton, J. L.; Taylor, J. T.; Thacker, J. B.; Korlie, S.; Shelor, C. P.; Henderson, D.; Kadjo, A. F.; Roelke, C. E.; Hudak, P. F; Burton, T.; Rifai, H. S.; Schug, K. A. A Comprehensive Analysis of Groundwater Quality in the Barnett Shale Region. Environmental Science and Technology 2015 49 8254-8262

    http://pubs.acs.org/doi/abs/10.1021/acs.est.5b01526

    The exploration of unconventional shale energy reserves and the extensive use of hydraulic fracturing during well stimulation have raised concerns about the potential effects of unconventional oil and gas extraction (UOG) on the environment. Most accounts of groundwater contamination have focused primarily on the compositional analysis of dissolved gases to address whether UOG activities have had deleterious effects on overlying aquifers. Here, we present an analysis of 550 groundwater samples collected from private and public supply water wells drawing from aquifers overlying the Barnett shale formation of Texas. We detected multiple volatile organic carbon compounds throughout the region, including various alcohols, the BTEX family of compounds, and several chlorinated compounds. These data do not necessarily identify UOG activities as the source of contamination; however, they do provide a strong impetus for further monitoring and analysis of groundwater quality in this region as many of the compounds we detected are known to be associated with UOG techniques.

  • D. D. Carlton Jr., B. E. Fontenot, Z. L. Hildenbrand, T. M. Davis, J. L. Walton, K. A. Schug Varying matrix effects for elemental analysis identified from groundwater in the Barnett Shale International Journal of Environmental Science and Technology 2015

    hhttp://link.springer.com/article/10.1007/s13762-015-0803-4

    The quality of analytical measurements can be influenced by the matrix of the sample of interest. The knowledge of the sample matrix allows for appropriate sample preparation, instrumental parameters, and quantification methods in an effort to achieve accurate results. Matrix matching can be difficult when sampling across various water sources with the possible introduction of unknown endogenous contaminants due to various degrees of land use, urbanization, and energy exploration, likely playing a factor. The degree of matrix effects in inductively coupled plasma–optical emission spectroscopy for nineteen metals from twenty groundwater samples across North Texas was assessed using a standard addition method. Matrix effects were characterized in collected groundwater samples (a) with no pretreatment, (b) after reversed-phase solid-phase extraction of possible organic contaminants, and (c) for a matrix of organic material retained on the reversed-phase sorbent. It was found that without any extraction treatment, only 54 % of all measurements experienced no matrix effect. After extracting unknown organic sample constituents, an increase to 74 % of measurements showing no matrix effect was recorded. Reconstituting the extracted organic sample matrix found this fraction to be a significant source of the deviated results with only 13 % experiencing no matrix effect. Results for the metals investigated are also discussed, along with correlations to water quality parameters such as turbidity, total dissolved solids, and salinity.

  • Fontenot, B.E.; Hunt, L.R.; Hildenbrand, Z.L.; Carlton Jr., D.D.; Oka, H.; Walton, J.L.; Hopkins, D.; Osorio, A.; Bjorndal, B.; Hu, Q.; Schug, K.A. RAn evaluation of water quality in private drinking water wells near natural gas extraction sites in the Barnett Shale Formation. Environ. Sci. Tech. 2013 47, 10032-10040

    http://pubs.acs.org/doi/abs/10.1021/es4011724

    This is an initial study, which incorporated a multi-disciplinary approach to measure groundwater quality in the Barnett Shale using both analytical chemistry and geospatial analysis. Our analytical work focused on the determination of harmful compounds thought to be associated with unconventional drilling such as methanol, ethanol, heavy metals (arsenic, strontium, selenium, barium, etc.), and BTEX compounds (benzene, toluene, ethylbenzene, and xylenes). Using inductively coupled plasma mass spectrometry (ICP-MS), we found arsenic in 99 of the 100 wells sampled. Notably, 29 of the 91 samples within active extraction areas had arsenic concentrations above the U.S. Environmental Protection Agency’s Maximum Contaminant Limit (MCL) of 10 μg/L. The maximum concentration of arsenic we detected within active extraction areas was 161 μg/L, a value nearly 18 times greater than both the maximum concentration among the non-active/reference area samples and historical levels. This is particularly relevant given that arsenic in drinking water has been found to increase the risk for developing liver, kidney and bladder cancers, and developmental problems in children. We also found selenium and strontium at elevated concentrations, with selenium detected exclusively within 2 kilometers of natural gas wells. Using gas chromatography - mass spectrometry (GC-MS) and headspace gas chromatography with flame ionization detection (HS-GC-FID), common tools for the measurement of volatile chemical compounds, it was determined that several water wells contained quantifiable levels of methanol and/or ethanol, chemicals known to be included in hydraulic fracturing fluids. These alcohols can be formed naturally, but have a very short lifespan in the environment before they disappear; so, the levels we found were unusual. Unlike arsenic, the levels of alcohols were not correlated with distance to nearest gas well, suggesting alternate routes for their introduction into the water samples. No BTEX compounds were detected.

    While our initial study does not conclusively identify the causes of elevated constituents, it does provide an impetus for continued research in the various shale formations of Texas to further characterize and quantify the anthropogenic effects that unconventional natural gas extraction has on groundwater quality. Importantly, significant care has been taken in our previous studies to demonstrate clear impartiality in our scientific findings. This research has been funded by internal funds only, with no external bias.

  • Fontenot, B.E.; Hildenbrand, Z.L.; Carlton Jr., D.D.; Walton, J.L.; Schug, K.A. Response to Comment on “An Evaluation of Water Quality in Private Drinking Water Wells near Natural Gas Extraction Sites in the Barnett Shale Formation” Environ. Sci. Tech. 2014 48, 3597-3599.

    http://pubs.acs.org/doi/abs/10.1021/es500425j

    This is a response to a comment by McHugh et al. regarding our initial study of groundwater quality in 100 private water wells in proximity to natural gas extraction in the Barnett Shale (Fontenot et al., 2013; see above). In our response to the comment, all points raised were carefully addressed and effectively rebutted.

  • Carlton Jr., D.D.; Hildenbrand, Z.L.; Fontenot, B.E.; Schug, K.A. Addressing Concerns About Impacts from Unconventional Drilling using Advanced Analytical Chemistry. In Uddameri, V.; Morse, A.; Tindle, K. (Eds)., Hydraulic Fracturing Impacts and Technologies: A Multi-Disciplinary Perspective. Taylor & Francis/CRC Press 2015

    This book chapter summarizes our analytical chemistry instrumentation and methodology used to investigate groundwater quality. Instrumental methods are based on established standard methods, but adapted to enable both targeted analysis, to determine compounds known to be used in unconventional drilling and hydraulic fracturing, and untargeted analysis, to look for other unanticipated potential contaminants in water samples. Methods have also been optimized to achieve appropriate throughput for broad-scale studies of regional water quality.



  • Contributed Projects (Non-Peer-Reviewed)