328 research outputs found
Lead Isotopes as a New Tracer for Detecting Coal Fly Ash in the Environment
Lead (Pb) isotopes have been widely used to delineate Pb pollutants in the environment. Here, we present, for the first time, a systematic analysis of Pb isotopes in coal fly ash derived from coals from the three major coal-producing basins in the United States. Fly ash samples from Powder River Basin coals have higher 206Pb/207Pb ratios (1.2271 ± 0.0086, n = 7) than Appalachian Basin fly ash (1.2173 ± 0.0060, n = 16), while Illinois Basin fly ash samples are much more variable (1.2270 ± 0.0140, n = 22). The Pb isotopic signature of fly ash is distinguishable from that of major anthropogenic Pb sources in the United States, including leaded gasoline and paint, as well as the Pb isotope ratios of naturally occurring sediments and soils. Lead isotopic analysis of sediments from Sutton Lake in North Carolina, where other indicators have identified the occurrence of fly ash solids from unmonitored coal ash spills, shows a well-defined mixing between the Pb of unimpacted sediments and that of Appalachian Basin fly ash. This result further validates the applicability of Pb isotopes as a new tracer for detecting the occurrence of coal fly ash in the environment
Assessing connectivity between an overlying aquifer and a coal seam gas resource using methane isotopes, dissolved organic carbon and tritium
Coal seam gas (CSG) production can have an impact on groundwater quality and quantity in adjacent or overlying aquifers. To assess this impact we need to determine the background groundwater chemistry and to map geological pathways of hydraulic connectivity between aquifers. In south-east Queensland (Qld), Australia, a globally important CSG exploration and production province, we mapped hydraulic connectivity between the Walloon Coal Measures (WCM, the target formation for gas production) and the overlying Condamine River Alluvial Aquifer (CRAA), using groundwater methane (CH4) concentration and isotopic composition (ÎŽ13C-CH4), groundwater tritium (3H) and dissolved organic carbon (DOC) concentration. A continuous mobile CH4 survey adjacent to CSG developments was used to determine the source signature of CH4 derived from the WCM. Trends in groundwater ÎŽ13C-CH4 versus CH4 concentration, in association with DOC concentration and 3H analysis, identify locations where CH4 in the groundwater of the CRAA most likely originates from the WCM. The methodology is widely applicable in unconventional gas development regions worldwide for providing an early indicator of geological pathways of hydraulic connectivity
Occurrence and sources of radium in groundwater associated with oil fields in the southern San Joaquin Valley, California
Author Posting. © American Chemical Society, 2019. This is an open access article published under an ACS AuthorChoice License. The definitive version was published in Environmental Science and Technology 53(16), (2019): 9398-9406, doi:10.1021/acs.est.9b02395.Geochemical data from 40 water wells were used to examine the occurrence and sources of radium (Ra) in groundwater associated with three oil fields in California (Fruitvale, Lost Hills, South Belridge). 226Ra+228Ra activities (range = 0.010â0.51 Bq/L) exceeded the 0.185 Bq/L drinking-water standard in 18% of the wells (not drinking-water wells). Radium activities were correlated with TDS concentrations (p < 0.001, Ï = 0.90, range = 145â15,900 mg/L), Mn + Fe concentrations (p < 0.001, Ï = 0.82, range = <0.005â18.5 mg/L), and pH (p < 0.001, Ï = â0.67, range = 6.2â9.2), indicating Ra in groundwater was influenced by salinity, redox, and pH. Ra-rich groundwater was mixed with up to 45% oil-field water at some locations, primarily infiltrating through unlined disposal ponds, based on Cl, Li, noble-gas, and other data. Yet 228Ra/226Ra ratios in pond-impacted groundwater (median = 3.1) differed from those in oil-field water (median = 0.51). PHREEQC mixing calculations and spatial geochemical variations suggest that the Ra in the oil-field water was removed by coprecipitation with secondary barite and adsorption on MnâFe precipitates in the near-pond environment. The saline, organic-rich oil-field water subsequently mobilized Ra from downgradient aquifer sediments via Ra-desorption and Mn/Fe-reduction processes. This study demonstrates that infiltration of oil-field water may leach Ra into groundwater by changing salinity and redox conditions in the subsurface rather than by mixing with a high-Ra source.This article was improved by the reviews of John Izbicki and anonymous reviewers for the journal. This work was funded by the California State Water Resources Control Boardâs Regional Groundwater Monitoring in Areas of Oil and Gas Production Program and the USGS Cooperative Water Program. A.V., A.J.K., and Z.W were supported by USDA-NIFA grant (#2017-68007-26308). Any use of trade, firm, or product names is for description purposes only and does not imply endorsement by the U.S. Government
Elevated levels of diesel range organic compounds in groundwater near Marcellus gas operations are derived from surface activities
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of American 112 (2015): 13184-13189, doi: 10.1073/pnas.1511474112
.Hundreds of organic chemicals are utilized during natural gas extraction via high volume
hydraulic fracturing (HVHF). However, it is unclear if these chemicals, injected into deep
shale horizons, reach shallow groundwater aquifers and impact local water quality, either
from deep underground injection sites or from the surface or shallow subsurface. Here,
we report detectable levels of organic compounds in shallow groundwater samples from
private residential wells overlying the Marcellus Shale in northeastern Pennsylvania.
Analyses of purgeable and extractable organic compounds from 64 groundwater samples
revealed trace levels of volatile organic compounds, well below the Environmental
Protection Agencyâs maximum contaminant levels, and low levels of both gasoline range
(GRO; 0-8 ppb) and diesel range organic compounds (DRO; 0-157 ppb). A compound-specific analysis revealed the presence of bis(2-ethylhexyl)phthalate, which is a disclosed
HVHF additive, that was notably absent in a representative geogenic water sample and
field blanks. Pairing these analyses with 1) inorganic chemical fingerprinting of deep
saline groundwater, 2) characteristic noble gas isotopes, and 3) spatial relationships
between active shale gas extraction wells and wells with disclosed environmental health
and safety (EHS) violations, we differentiate between a chemical signature associated
with naturally occurring saline groundwater and a one associated with alternative
anthropogenic routes from the surface (e.g., accidental spills or leaks). The data support a
transport mechanism of DRO to groundwater via accidental release of fracturing fluid
chemicals derived from the surface rather than subsurface flow of these fluids from the
underlying shale formation.The authors thank Duke Universityâs Pratt School of Engineering
and the National Science Foundationâs CBET Grant Number 1336702 and NSF EAGER
(EAR-1249255) for financial support.2016-04-1
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Boron isotopic composition of olivine-hosted melt inclusions from Gorgona komatiites, Colombia : new evidence supporting wet komatiite origin
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 312 (2011): 201â212, doi:10.1016/j.epsl.2011.09.033.A fundamental question in the genesis of komatiites is whether 30 these rocks originate
from partial melting of dry and hot mantle, 400â500°C hotter than typical sources of MORB and
OIB magmas, or if they were produced by hydrous melting of the source at much lower
temperatures, similar or only moderately higher than those known today. Gorgona Island,
Colombia, is a unique place where Phanerozoic komatiites occur and whose origin is directly
connected to the formation of the Caribbean Large Igneous Province. The genesis of Gorgona
komatiites remains controversial, mostly because of the uncertain origin of volatile components
which they appear to contain. These volatiles could equally result from shallow level magma
contamination, melting of a âdampâ mantle or fluid-induced partial melting of the source due to
devolatilization of the ancient subducting plate. We have analyzed boron isotopes of olivine40
hosted melt inclusions from the Gorgona komatiites. These inclusions are characterized by
relatively high contents of volatile components and boron (0.2â1.0 wt.% H2O, 0.05â0.08 wt.%
S, 0.02â0.03 wt.% Cl, 0.6â2.0 ÎŒg/g B), displaying positive anomalies in the overall depleted,
primitive mantle (PM) normalized trace element and REE spectra ([La/Sm]n = 0.16â0.35;
[H2O/Nb]n = 8â44; [Cl/Nb]n = 27â68; [B/Nb]n = 9-30, assuming 300 ÎŒg/g H2O, 8 ÎŒg/g Cl and
0.1 ÎŒg/g B in PM; Kamenetsky et al., 2010. Composition and temperature of komatiite melts
from Gorgona Island constrained from olivine-hosted melt inclusions. Geology 38, 1003â1006).
The inclusions range in ÎŽ11B values from â11.5 to +15.6 ± 2.2â° (1 SE), forming two distinct
trends in a ÎŽ11B vs. B-concentration diagram. Direct assimilation of seawater, seawater-derived
components, altered oceanic crust or marine sediments by ascending komatiite magma cannot
readily account for the volatile contents and B isotope variations. Alternatively, injection of <3%
of a 11B enriched fluid to the mantle source could be a plausible explanation for the ÎŽ11B range
that also may explain the H2O, Cl and B excess.Financial support
to AAG during data acquisition and manuscript preparation was provided by Northeast National
Ion Microprobe Facility (Woods Hole Oceanographic Institution, USA) and the Centre de
Recherches PĂ©trographiqueset GĂ©ochimiques (France). This research was also supported by the
Australian Research Council (Research Fellowship and Discovery grants to VSK). We
acknowledge partial support of the Alexander von Humboldt Foundation, Germany (F.W. Bessel
Award to VSK and Wolfgang Paul Award to A.V. Sobolev who provided access to the electron
microprobe at the Max Planck Institute, Mainz, Germany
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Superhydrophilic Functionalization of Microfiltration Ceramic Membranes Enables Separation of Hydrocarbons from Frac and Produced Water
The environmental impact of shale oil and gas production by hydraulic fracturing (fracking) is of increasing concern. The biggest potential source of environmental contamination is flowback and produced water, which is highly contaminated with hydrocarbons, bacteria and particulates, meaning that traditional membranes are readily fouled. We show the chemical functionalisation of alumina ceramic microfiltration membranes (0.22 ÎŒm pore size) with cysteic acid creates a superhydrophilic surface, allowing for separation of hydrocarbons from frac and produced waters without fouling. The single pass rejection coefficients wasâ>90% for all samples. The separation of hydrocarbons from water when the former have hydrodynamic diameters smaller than the pore size of the membrane is due to the zwitter ionically charged superhydrophilic pore surface. Membrane fouling is essentially eliminated, while a specific flux is obtained at a lower pressure (<2âbar) than that required achieving the same flux for the untreated membrane (4â8âbar)
Boron isotopes in foraminifera : systematics, biomineralisation, and CO2 reconstruction
Funding: Fellowship from University of St Andrews, $100 (pending) from Richard Zeebe, UK NERC grants NE/N003861/1 and NE/N011716/1.The boron isotope composition of foraminifera provides a powerful tracer for CO2 change over geological time. This proxy is based on the equilibrium of boron and its isotopes in seawater, which is a function of pH. However while the chemical principles underlying this proxy are well understood, its reliability has previously been questioned, due to the difficulty of boron isotope (ÎŽ11B) analysis on foraminferal samples and questions regarding calibrations between ÎŽ11B and pH. This chapter reviews the current state of the ÎŽ11B-pH proxy in foraminfera, including the pioneering studies that established this proxyâs potential, and the recent work that has improved understanding of boron isotope systematics in foraminifera and applied this tracer to the geological record. The theoretical background of the ÎŽ11B-pH proxy is introduced, including an accurate formulation of the boron isotope mass balance equations. Sample preparation and analysis procedures are then reviewed, with discussion of sample cleaning, the potential influence of diagenesis, and the strengths and weaknesses of boron purification by column chromatography versus microsublimation, and analysis by NTIMS versus MC-ICPMS. The systematics of boron isotopes in foraminifera are discussed in detail, including results from benthic and planktic taxa, and models of boron incorporation, fractionation, and biomineralisation. Benthic taxa from the deep ocean have ÎŽ11B within error of borate ion at seawater pH. This is most easily explained by simple incorporation of borate ion at the pH of seawater. Planktic foraminifera have ÎŽ11B close to borate ion, but with minor offsets. These may be driven by physiological influences on the foraminiferal microenvironment; a novel explanation is also suggested for the reduced ÎŽ11B-pH sensitivities observed in culture, based on variable calcification rates. Biomineralisation influences on boron isotopes are then explored, addressing the apparently contradictory observations that foraminifera manipulate pH during chamber formation yet their ÎŽ11B appears to record the pH of ambient seawater. Potential solutions include the influences of magnesium-removal and carbon concentration, and the possibility that pH elevation is most pronounced during initial chamber formation under favourable environmental conditions. The steps required to reconstruct pH and pCO2 from ÎŽ11B are then reviewed, including the influence of seawater chemistry on boron equilibrium, the evolution of seawater ÎŽ11B, and the influence of second carbonate system parameters on ÎŽ11B-based reconstructions of pCO2. Applications of foraminiferal ÎŽ11B to the geological record are highlighted, including studies that trace CO2 storage and release during recent ice ages, and reconstructions of pCO2 over the Cenozoic. Relevant computer codes and data associated with this article are made available online.Publisher PDFPeer reviewe
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