Since naturally occurring methane and saline groundwater are nearly ubiquitous in many sedimentary basins, delineating the effects of anthropogenic contamination sources is a major challenge for evaluating the impact of unconventional shale gas development on water quality. This study investigates the geochemical variations of groundwater and surface water before, during, and after hydraulic fracturing and in relation to various geospatial parameters in an area of shale gas development in northwestern West Virginia, United States. To our knowledge, we are the first to report a broadly integrated study of various geochemical techniques designed to apportion natural and anthropogenic sources of natural gas and salt contaminants both before and after drilling. These measurements include inorganic geochemistry (major cations and anions), stable isotopes of select inorganic constituents including strontium (87 Sr/ 86 Sr), boron (δ 11 B), lithium (δ 7 Li), and carbon (δ 13 C-DIC), select hydrocarbon molecular (methane, ethane, propane, butane, and pentane) and isotopic tracers (δ 13 C-CH 4 , δ 13 CC 2 H 6), tritium (3 H), and noble gas elemental and isotopic composition (He, Ne, Ar) in 112 drinking-water wells, with repeat testing in 33 of the wells (total samples=145). In a subset of wells (n=20), we investigated the variations in water quality before and after the installation of nearby (<1 km) shale-gas wells. Methane occurred above 1 ccSTP/L in 37% of the groundwater samples and in 79% of the samples with elevated salinity (chloride >50 mg/L). The integrated geochemical data indicate that the saline groundwater originated via naturally occurring processes, presumably from the migration of deeper methane-rich brines that have interacted extensively with coal lithologies. These observations were consistent with the lack of changes in water quality observed in drinkingwater wells following the installation of nearby shale-gas wells. In contrast to groundwater samples that showed no evidence of anthropogenic contamination, the chemistry and isotope ratios of surface waters near known spills or leaks occurring at disposal sites (n=8) mimicked the composition of the Marcellus flowback fluids, and show direct evidence for impact on surface water by fluids accidentally released from nearby shale-gas well pads and oil and gas wastewater disposal sites. Overall this study presents a comprehensive geochemical framework that can be

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 ((87)Sr/(86)Sr, δ(18)O, δ(2)H) 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 ((228)Ra + (226)Ra) 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.

The expansion of unconventional shale gas and hydraulic fracturing has increased the volume of the oil and gas wastewater (OGW) generated in the U.S. Here we demonstrate that OGW from Marcellus and Fayetteville hydraulic fracturing flowback fluids and Appalachian conventional produced waters is characterized by high chloride, bromide, iodide (up to 56 mg/L), and ammonium (up to 420 mg/L). Br/Cl ratios were consistent for all Appalachian brines, which reflect an origin from a common parent brine, while the I/Cl and NH4/Cl ratios varied among brines from different geological formations, reflecting geogenic processes. There were no differences in halides and ammonium concentrations between OGW originating from hydraulic fracturing and conventional oil and gas operations. Analysis of discharged effluents from three brine treatment sites in Pennsylvania and a spill site in West Virginia show elevated levels of halides (iodide up to 28 mg/L) and ammonium (12 to 106 mg/L) that mimic the composition of OGW and mix conservatively in downstream surface waters. Bromide, iodide, and ammonium in surface waters can impact stream ecosystems and promote the formation of toxic brominated-, iodinated-, and nitrogen disinfection byproducts during chlorination at downstream drinking water treatment plants. Our findings indicate that discharge and accidental spills of OGW to waterways pose risks to both human health and the environment.

The disposal and leaks of hydraulic fracturing wastewater (HFW) to the environment pose human health risks. Since HFW is typically characterized by elevated salinity, concerns have been raised whether the high bromide and iodide in HFW may promote the formation of disinfection byproducts (DBPs) and alter their speciation to more toxic brominated and iodinated analogues. This study evaluated the minimum volume percentage of two Marcellus Shale and one Fayetteville Shale HFWs diluted by fresh water collected from the Ohio and Allegheny Rivers that would generate and/or alter the formation and speciation of DBPs following chlorination, chloramination, and ozonation treatments of the blended solutions. During chlorination, dilutions as low as 0.01% HFW altered the speciation toward formation of brominated and iodinated trihalomethanes (THMs) and brominated haloacetonitriles (HANs), and dilutions as low as 0.03% increased the overall formation of both compound classes. The increase in bromide concentration associated with 0.01-0.03% contribution of Marcellus HFW (a range of 70-200 μg/L for HFW with bromide = 600 mg/L) mimics the increased bromide levels observed in western Pennsylvanian surface waters following the Marcellus Shale gas production boom. Chloramination reduced HAN and regulated THM formation; however, iodinated trihalomethane formation was observed at lower pH. For municipal wastewater-impacted river water, the presence of 0.1% HFW increased the formation of N-nitrosodimethylamine (NDMA) during chloramination, particularly for the high iodide (54 ppm) Fayetteville Shale HFW. Finally, ozonation of 0.01-0.03% HFW-impacted river water resulted in significant increases in bromate formation. The results suggest that total elimination of HFW discharge and/or installation of halide-specific removal techniques in centralized brine treatment facilities may be a better strategy to mitigate impacts on downstream drinking water treatment plants than altering disinfection strategies. The potential formation of multiple DBPs in drinking water utilities in areas of shale gas development requires comprehensive monitoring plans beyond the common regulated DBPs.

The fungal genus Stemphylium (Ascomycota) contains selfing species that evolved from outcrossing ancestors. To find out how selfing originated, we analyzed the Stemphylium MAT loci that regulate sexual reproduction in ascomycetes and compared MAT structures and phylogeny with a multigene Stemphylium species phylogeny. We found that some Stemphylium species' MAT loci contained a single gene, either MAT1-1 or MAT1-2, whereas others contained a unique fusion of the MAT1-1 and MAT1-2 regions. In all fused MAT regions, MAT1-1 was inverted and joined to a forward-oriented MAT1-2 region. As in the closely related Cochliobolus, Stemphylium species with fused MAT regions were able to self. Structural and phylogenetic analyses of the MAT loci showed that the selfingconferring fused MAT regions were monophyletic with strong support. However, in an organismal phylogeny of Stemphylium species based on 106 isolates and four loci unrelated to mating, selfing arose in two clades, each time with strong support. Isolates with identical fused MAT regions were present in both clades. We showed that a one-time origin of the fused MAT loci, followed by a horizontal transfer across lineages, was compatible with the data. Another group of selfers in Stemphylium only had forward-oriented MAT1-1 at their MAT loci, constituting an additional and third origin of selfing in Stemphylium.filamentous ascomycetes ͉ nonvertical inheritance ͉ evolution ͉ Pleospora ͉ horizontal transfer A mong bacteria, lateral gene flow has redistributed characters of evolutionary importance (1). In eukaryotes including fungi, evolution through lateral gene transfer is often proposed, but alternative explanations for character distributions have been difficult to rule out (2). The mating type locus in the ascomycetous fungal genus Stemphylium has provided an opportunity to detect an ancient lateral transfer that changed a fungal breeding system. We used phylogenetic analyses based on five loci in conjunction with gene rearrangement data to show that the distribution of mating strategies in Stemphylium is best explained by a lateral transfer of the genes controlling mating.In haploid filamentous ascomycetes, self-sterility and self-fertility depend on the configuration of genes at MAT, the mating type locus (3). Each self-sterile individual has only one of the two alternative single-copy genes, MAT1-1 or MAT1-2, at its MAT locus. Like large portions of the human X and Y chromosomes, the DNA and amino acid sequences of MAT1-1 and MAT1-2 are no more similar than expected by chance. Outside of the Ϸ1,100-to 4,200-bp MAT region, sequence similarity between homologous chromosomes reappears and haploid individuals of opposite mating types have syntenous flanking genes (4, 5).In contrast to self-sterile species, haploid self-fertile species in Stemphylium (this study), as in the closely related Cochliobolus (6), contain both MAT1-1 and MAT1-2 genes in the same genome. Demonstrating that the presence of a MAT1-1͞MAT1-2 fusion was enough to confer self-fertility, transform...

Coal combustion residuals (CCRs), the largest industrial waste in the United States, are mainly stored in surface impoundments and landfills. Here, we examine the geochemistry of seeps and surface water from seven sites and shallow groundwater from 15 sites in five states (Tennessee, Kentucky, Georgia, Virginia, and North Carolina) to evaluate possible leaking from coal ash ponds. The assessment for groundwater impacts at the 14 sites in North Carolina was based on state-archived monitoring well data. Boron and strontium exceeded background values of 100 and 150 μg/L, respectively, at all sites, and the high concentrations were associated with low δ(11)B (-9‰ to +8‰) and radiogenic (87)Sr/(86)Sr (0.7070 to 0.7120) isotopic fingerprints that are characteristic of coal ash at all but one site. Concentrations of CCR contaminants, including SO4, Ca, Mn, Fe, Se, As, Mo, and V above background levels, were also identified at all sites, but contamination levels above drinking water and ecological standards were observed in 10 out of 24 samples of impacted surface water. Out of 165 monitoring wells, 65 were impacted with high B levels and 49 had high CCR-contaminant levels. Distinct isotope fingerprints, combined with elevated levels of CCR tracers, provide strong evidence for the leaking of coal ash ponds to adjacent surface water and shallow groundwater. Given the large number of coal ash impoundments throughout the United States, the systematic evidence for leaking of coal ash ponds shown in this study highlights potential environmental risks from unlined coal ash ponds.

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Hexavalent chromium [Cr­(VI)] is a known pulmonary carcinogen. Recent detection of Cr­(VI) in drinking water wells in North Carolina has raised public concern about contamination of drinking water wells by nearby coal ash ponds. Here we report, for the first time, the prevalence of Cr and Cr­(VI) in drinking water wells from the Piedmont region of central North Carolina, combined with a geochemical analysis to determine the source of the elevated Cr­(VI) levels. We show that Cr­(VI) is the predominant species of dissolved Cr in groundwater and elevated levels of Cr and Cr­(VI) are found in wells located both near and far (>30 km) from coal ash ponds. The geochemical characteristics, including the overall chemistry, boron to chromium ratios, and strontium isotope (87Sr/86Sr) variations in groundwater with elevated Cr­(IV) levels, are different from those of coal ash leachates. Alternatively, the groundwater chemistry and Sr isotope variations are consistent with water–rock interactions as the major source for Cr­(VI) in groundwater. Our results indicate that Cr­(VI) is most likely naturally occurring and ubiquitous in groundwater from the Piedmont region in the eastern United States, which could pose health risks to residents in the region who consume well water as a major drinking water source.