The osmotic effect of hyper-saline hydraulic fracturing fluid on rainbow trout, Oncorhynchus mykiss.

Flowback and produced water (FPW) is a complex, often brackish, solution formed during the process of hydraulic fracturing. Despite recent findings on the short-term toxicity of FPW on aquatic biota, longer-term impacts of FPW on fish have not yet been investigated and the mechanisms of chronic effects remain unknown. The aim of the present study was to observe the effect of a diluted FPW on ionoregulatory endpoints in the rainbow trout Oncorhynchus mykiss, following a 28-d sub-chronic exposure. A salinity-matched control solution (SW), recreating the salt content of the FPW, was used to differentiate the specific effect of the salts from the effects of the other FPW components (i.e. organics and metals). Overall, fish ionoregulation was not impacted by the chronic exposure. An accumulation of strontium (Sr) and bromide (Br) occurred in the plasma of the FPW-exposed fish only, however no change of plasma ions (Na, K, Cl, Ca, Mg) was observed in SW- or FPW-exposed fish. Similarly, exposures did not alter branchial activity of the osmoregulatory enzymes sodium/potassium ATPase and proton ATPase. Finally, FPW exposure resulted in modifications of gill morphology over time, with fish exposed to the fluid displaying shorter lamellae and increased interlamellar-cell mass. However, these effects were not distinct from morphological changes that also occurred in the gills of control groups.

Accuracy of methods for reporting inorganic element concentrations and radioactivity in oil and gas wastewaters from the Appalachian Basin, U.S. based on an inter-laboratory comparison.

Accurate and precise analyses of oil and gas (O&G) wastewaters and solids (e.g., sediments and sludge) are important for the regulatory monitoring of O&G development and tracing potential O&G contamination in the environment. In this study, 15 laboratories participated in an inter-laboratory comparison on the chemical characterization of three O&G wastewaters from the Appalachian Basin and four solids impacted by O&G development, with the goal of evaluating the quality of data and the accuracy of measurements for various analytes of concern. Using a variety of different methods, analytes in the wastewaters with high concentrations (i.e., >5 mg L-1) were easily detectable with relatively high accuracy, often within ±10% of the most probable value (MPV). In contrast, often less than 7 of the 15 labs were able to report detectable trace metal(loid) concentrations (i.e., Cr, Ni, Cu, Zn, As, and Pb) with accuracies of approximately ±40%. Despite most labs using inductively coupled plasma mass spectrometry (ICP-MS) with low instrument detection capabilities for trace metal analyses, large dilution factors during sample preparation and low trace metal concentrations in the wastewaters limited the number of quantifiable determinations and likely influenced analytical accuracy. In contrast, all the labs measuring Ra in the wastewaters were able to report detectable concentrations using a variety of methods including gamma spectroscopy and wet chemical approaches following Environmental Protection Agency (EPA) standard methods. However, the reported radium activities were often greater than ±30% different to the MPV possibly due to calibration inconsistencies among labs, radon leakage, or failing to correct for self-attenuation. Reported radium activities in solid materials had less variability (±20% from MPV) but accuracy could likely be improved by using certified radium standards and accounting for self-attenuation that results from matrix interferences or a density difference between the calibration standard and the unknown sample. This inter-laboratory comparison illustrates that numerous methods can be used to measure major cation, minor cation, and anion concentrations in O&G wastewaters with relatively high accuracy while trace metal(loid) and radioactivity analyses in liquids may often be over ±20% different from the MPV.

Synergistic effect of cationic surfactants on perchloroethylene degradation by zero-valent iron.

Zero-valent iron (ZVI) as a permeable barrier material for degradation of chlorinated organic compounds has been extensively studied recently. One of the focal areas in ZVI studies is to increase the contaminant reduction rate. In this research, batch tests were performed to evaluate the synergistic effect of sorbed cationic surfactants on degradation of perchloroethylene (PCE). Sorption of cationic surfactants on ZVI was a function of hydrophobic chain length of the surfactanttail group. Minimal counterion sorption indicated that the sorbed surfactant molecules form a patchy monolayer on ZVI. Both PCE and trichloroethylene (TCE) degradation by ZVI with and without sorbed surfactant followed pseudo-first-order reaction kinetics. In general, the PCE degradation rate increases as the chain length of sorbed surfactant increases. Compared to unmodified ZVI, both apparent rate constants of PCE degradation and TCE accumulation increased by an order of magnitude when ZVI was modified by hexadecyltrimethylammonium. The rate of PCE degradation by ZVI modified to lower surfactant loading was relatively higher than that by ZVI modified to higher surfactant loading. It was speculated that longer chain length will result in better admicelle formations, and thus, promote PCE partition and increase PCE surface concentration or surface admicelle catalysis, while low surfactant loading makes significant amounts of surface reduction sites still available. The PCE reduction rate constants were not affected by solution ionic strength, but high initial solution pH, buffered by sodium carbonate and sodium bicarbonate, significantly reduced the PCE degradation rate.