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Carlton D.D.,University of Texas at Arlington | Fontenot B.E.,Independent Consultant | Fontenot B.E.,U.S. Environmental Protection Agency | Hildenbrand Z.L.,Inform Environmental LLC | And 3 more authors.
International Journal of Environmental Science and Technology | Year: 2015

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. © 2015, Islamic Azad University (IAU). Source


Hildenbrand Z.L.,University of Texas at Arlington | Hildenbrand Z.L.,Inform Environmental LLC | Osorio A.,Assure Controls Inc. | Carlton D.D.,University of Texas at Arlington | And 9 more authors.
Journal of Chemistry | Year: 2015

Here we present data using a bioluminescent dinoflagellate, Pyrocystis lunula, in a toxicological bioassay to rapidly assess potential instances of groundwater contamination associated with natural gas extraction. P. lunula bioluminescence can be quantified using spectrophotometry as a measurement of organismal viability, with normal bioluminescent output declining with increasing concentration(s) of aqueous toxicants. Glutaraldehyde and hydrochloric acid (HCl), components used in hydraulic fracturing and shale acidization, triggered significant toxicological responses in as little as 4 h. Conversely, P. lunula was not affected by the presence of arsenic, selenium, barium, and strontium, naturally occurring heavy metal ions potentially associated with unconventional drilling activities. If exogenous compounds, such as glutaraldehyde and HCl, are thought to have been introduced into groundwater, quantification of P. lunula bioluminescence after exposure to water samples can serve as a cost-effective detection and risk assessment tool to rapidly assess the impact of putative contamination events attributed to unconventional drilling activity. © 2015 Zacariah L. Hildenbrand et al. Source


Burton T.G.,University of Houston | Rifai H.S.,University of Houston | Hildenbrand Z.L.,Inform Environmental LLC | Hildenbrand Z.L.,University of Texas at Arlington | And 3 more authors.
Science of the Total Environment | Year: 2016

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. © 2015 Elsevier B.V. Source


Avila G.A.,University of Texas at El Paso | Ramirez D.H.,University of Texas at El Paso | Hildenbrand Z.L.,University of Texas at El Paso | Hildenbrand Z.L.,Inform Environmental LLC | And 5 more authors.
Protein Expression and Purification | Year: 2015

Gam1, an early gene product of an avian adenovirus, is essential for viral replication. Gam1 is the first viral protein found to globally inhibit cellular SUMOylation, a critical posttranslational modification that alters the function and cellular localization of proteins. The interaction details at the interface between Gam1 and its cellular targets remain unclear due to the lack of structural information. Although Gam1 has been previously characterized, the purity of the protein was not suitable for structural investigations. In the present study, the gene of Gam1 was cloned and expressed in various bacterial expression systems to obtain pure and soluble recombinant Gam1 protein for in vitro functional and structural studies. While Gam1 was insoluble in most expression systems tested, it became soluble when it was expressed as a fusion protein with trigger factor (TF), a ribosome associated bacterial chaperone, under the control of a cold shock promoter. Careful optimization indicates that both low temperature induction and the chaperone function of TF play critical roles in increasing Gam1 solubility. Soluble Gam1 was purified to homogeneity through sequential chromatography techniques. Monomeric Gam1 was obtained via size exclusion chromatography and analyzed by dynamic light scattering. The SUMOylation inhibitory function of the purified Gam1 was confirmed in an in vitro assay. These results have built the foundation for further structural investigations that will broaden our understanding of Gam1's roles in viral replication. © 2014 Elsevier Inc. All rights reserved. Source


Hildenbrand Z.L.,University of Texas at Arlington | Hildenbrand Z.L.,Inform Environmental LLC | Carlton D.D.,University of Texas at Arlington | Fontenot B.E.,University of Texas at Arlington | And 15 more authors.
Science of the Total Environment | Year: 2016

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. © 2016 Elsevier B.V.. Source

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