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Made available in DSpace on 2015-03-18T15:53:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-11-01Bitstream added on 2015-03-18T16:29:16Z : No. of bitstreams: 1 WOS000343628100021.pdf: 2001774 bytes, checksum: 4dc6b3e037ddf418606b7ac85c1a5a50 (MD5) UK Natural Environment Research Council NERC Natural, dissolved U-238-series radionuclides (U, Ra-226, Rn-222) and activity ratios (A.R.s: U-234/U-238; Ra-228/Ra-226) in Continental Intercalaire (Cl) groundwaters and limited samples from the overlying Complexe Terminal (CT) aquifers of Algeria and Tunisia are discussed alongside core measurements for U/Th (and K) in the contexts of radiological water quality, geochemical controls in the aquifer, and water residence times. A redox barrier is characterised downgradient in the Algerian Cl for which a trend of increasing U-234/U-238 A.R.s with decreasing U-contents due to recoil-dominated U-234 solution under reducing conditions allows residence time modelling similar to 500 ka for the highest enhanced A.R. = 3.17. Geochemical modelling therefore identifies waters towards the centre of the Grand Erg Oriental basin as palaeowaters in line with reported C-14 and Cl-36 ages. A similar U-234/U-238 trend is evidenced in a few of the Tunisian CI waters. The paleoage status of these waters is affirmed by both noble gas recharge temperatures and simple modelling of dissolved, radiogenic He-4-contents both for sampled Algerian and Tunisian CI and CT waters. For the regions studied these waters therefore should be regarded as "fossil" waters and treated effectively as a non-renewable resource. (C) 2014 The Authors. Published by Elsevier Ltd. Queens Univ Belfast, Sch Planning Architecture & Civil Engn, Environm Tracers Lab, Belfast BT9 5AG, Antrim, North Ireland IGCE UNESP, Dept Petrol & Metalogenia, BR-13506900 Rio Claro, SP, Brazil Univ Bath, Sch Chem, Bath BA2 7AY, Avon, England IGCE UNESP, Dept Petrol & Metalogenia, BR-13506900 Rio Claro, SP, Brazil UK Natural Environment Research Council NERCGT/84/AAPS/58

Made available in DSpace on 2018-12-11T17:32:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-04-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This investigation was carried out in the Guarani Aquifer System (GAS) following a transect in São Paulo State, Brazil, and involved the analysis of trace elements, REEs and stable isotopes (B, Sr) in both rainwater and groundwater samples (the latter sampled from tube wells drilled in 10 cities). The Brazilian Code for Mineral Waters (BCMW) has been adopted for classifying the groundwaters according to their temperature and was useful for identifying the major trends of the hydrochemical data. Three water categories are identified: (38 °C). The hyperthermal waters exhibited geostatic pressures >250 bar, whereas the cold/hypothermal waters values

Carbon stable isotope ((13)C) fractionation in chlorofluorocarbon (CFC) compounds arising from abiotic (chemical) degradation using zero-valent iron (ZVI) and biotic (landfill gas attenuation) processes is investigated. Batch tests (at 25 °C) for CFC-113 and CFC-11 using ZVI show quantitative degradation of CFC-113 to HCFC-123a and CFC-1113 following pseudo-first-order kinetics corresponding to a half-life (τ(1/2)) of 20.5 h, and a ZVI surface-area normalized rate constant (k(SA)) of -(9.8 ± 0.5) × 10(-5) L m(-2) h(-1). CFC-11 degraded to trace HCFC-21 and HCFC-31 following pseudo-first-order kinetics corresponding to τ(1/2) = 17.3 h and k(SA) = -(1.2 ± 0.5) × 10(-4) L m(-2) h(-1). Significant kinetic isotope effects of ε(‰) = -5.0 ± 0.3 (CFC-113) and -17.8 ± 4.8 (CFC-11) were observed. Compound-specific carbon isotope analyses also have been used here to characterize source signatures of CFC gases (HCFC-22, CFC-12, HFC-134a, HCFC-142b, CFC-114, CFC-11, CFC-113) for urban (UAA), rural/remote (RAA), and landfill (LAA) ambient air samples, as well as in situ surface flux chamber (FLUX; NO FLUX) and landfill gas (LFG) samples at the Dargan Road site, Northern Ireland. The latter values reflect biotic degradation and isotopic fractionation in LFG production, and local atmospheric impact of landfill emissions through the cover. Isotopic fractionations of Δ(13)C ∼ -13‰ (HCFC-22), Δ(13)C ∼ -35‰ (CFC-12) and Δ(13)C ∼ -15‰ (CFC-11) were observed for LFG in comparison to characteristic solvent source signatures, with the magnitude of the isotopic effect for CFC-11 apparently similar to the kinetic isotope effect for (abiotic) ZVI degradation.

The Monkstown zero-valent iron permeable reactive barrier (ZVI PRB), Europe's oldest commercially-installed ZVI PRB, had been treating trichloroethene (TCE) contaminated groundwater for about 10 years on the Nortel Network site in Northern Ireland when cores from the reactive zone were collected in December, 2006. Groundwater data from 2001-2006 indicated that TCE is still being remediated to below detection limits as the contaminated groundwater flows through the PRB. Ca and Fe carbonates, crystalline and amorphous Fe sulfides, and Fe (hydr)oxides have precipitated in the granular ZVI material in the PRB. The greatest variety of minerals is associated with a approximately 1-2 cm thick, slightly cemented crust on top (up-gradient influent entrance) of the ZVI section of the PRB and also with the discontinuous cemented ZVI material ( approximately 23 cm thick) directly below it. The greatest presence of microbial communities also occurred in the up-gradient influent portion of the PRB compared to its down-gradient effluent section, with the latter possibly due to less favorable conditions (i.e., high pH, low oxygen) for microbial growth. The ZVI filings in the down-gradient effluent section of the PRB have a projected life span of >10 years compared with ZVI filings from the continuous to discontinuous cemented up-gradient ZVI section (upper approximately 25 cm) of the PRB, which may have a life span of only approximately 2-5 more years. Supporting Information from applied, multi-tracer testing indicated that restricted groundwater flow is occurring in the upper approximately 25 cm of the ZVI section and preferential pathways have also formed in this PRB over its 10 years of operation.

A pre-concentration system has been validated for use with a gas chromatography/mass spectrometry/isotope ratio mass spectrometer (GC/MS/IRMS) to determine ambient air C-13/C-12 ratios for methyl halides (MeCl and MeBr) and chlorofluorocarbons (CFCs). The isotopic composition of specific compounds can provide useful information on their atmospheric budgets and biogeochemistry that cannot be ascertained from abundance measurements alone. Although pre-concentration systems have been previously used with a GC/MS/IRMS for atmospheric trace gas analysis, this is the first study also to report system validation tests. Validation results indicate that the preconcentration system and subsequent separation technologies do not significantly alter the stable isotopic ratios of the target methyl halides, CFC-12 (CCl2F2) and CFC-113 (C2Cl3F3). Significant, but consistent, isotopic shifts of -27.5parts per thousand to -25.6parts per thousand do occur within the system for CFC-11 (CCl3F), although the shift is correctible. The method presented has the capacity to separate these target halocarbons from more than 50 other compounds in ambient air samples. Separation allows for the determination of stable carbon isotope ratios of five of these six target trace atmospheric constituents within ambient air for large volume samples (! 10 L). Representative urban air analyses from Belfast City are also presented which give carbon isotope results similar to published values for C-13/C-12 analysis of MeCl (-39.1parts per thousand) and CFC-113 (-28.1parts per thousand). However, this is the first paper reporting stable carbon isotope signatures for CFC-11 (-29.4parts per thousand) and CFC-12 (-37.0parts per thousand). Copyright (C) 2005 John Wiley Sons, Ltd.

The tritium concentrations in 13 groundwater samples from boreholes throughout the Upper Devonian sandstone aquifer of Fife have been measured. Due to atmospheric variations in tritium concentrations over the last century, this radioactive tracer can be used as a groundwater age indicator. In this study, the groundwater tritium concentrations have allowed for the area to be divided into three zones, and the variable chemistry of the groundwater samples, including the problem of recent elevated nitrate levels in the Fife Aquifer, has been interpreted in terms of their relative ages.

The abundance and isotopic composition of He, Ne and Ar have been determined in 19 gas samples taken from the Dosso degli Angeli hydrocarbon gas field, between 3000- and 3750-m depth in the Po Basin. Carbon isotope ratios in these samples vary between δ13C(CH4) = −67.5 and −73.4%, indicating a predominantly biogenic source for the methane. C2+ [=Σ(C2H6 + C3H8 + …)] concentrations increase systematically from 0.04% to 0.17% by volume with depth, suggesting that there is a small additional thermogenic or diagenetic hydrocarbon contribution to these gases. CH4/36Ar ratios in the Dosso degli Angeli gases are in the range predicted for a groundwater which has derived its rare gas by equilibration with the atmosphere, and is CH4-saturated under reservoir conditions. There is also up to 10% excess of CH4 which is not associated with the groundwater. These results are consistent with > 90% of the CH4 in the Dosso degli Angeli reservoir originating from CH4-saturated groundwater. Measured 20Ne/36Ar ratios depart from the predicted ratio in air-equilibrated groundwater. This fractionation is consistent with water/gas phase equilibration under reservoir conditions, and is similar to that observed in gas reservoirs in the Vienna and Pannonian Basins, Austria and Hungary, respectively. The He in the Dosso degli Angeli gases is almost entirely radiogenic and derived from the crust. The concentration of 4He in the reservoir gases requires that He is mostly sourced from outside the reservoir volume. Radiogenic 4He/40Ar ratios input into the reservoir gas must be much higher than averaged crustal production ratios, as no shift from the atmospheric 40Ar/36Ar ratio is observed. Preferential release of 4He over 40Ar from the sites of their production is the preferred explanation. This observation contrasts with previous studies from active extensional basins, in which radiogenic 4He and 40Ar appear to have been stored, released and transported at near production ratio on a regional scale. The most obvious difference between these studies is the comparatively low thermal gradient of the Po Basin.

Self-potential and spectral induced polarization responses associated with microbial processes involved in sulphate reduction have been monitored in a Perspex Winogradsky column filled with glass beads and growth medium. Salt-bridge is utilized as an electrolytic contact between experiment and control column. Equally spaced SP electrodes are used in combination of Ag-AgCl electrodes to compare electrodic and SP signals associated with the microbial processes involved in sulphate reduction. This study reveals that magnitude of SP varies from 5 to -2 mV and Electrodic potential 0 to 20 mV at the time of domination (day 39) of sulphate reducing bacteria which are very small in comparison to those measured by fixing both measuring and reference Ag-AgCl electrodes in experiment column. We observed that real and imaginary parts of complex conductivities increase with increase in production of H2S and CO in the experiment column. Both real and imaginary parts of surface complex conductivity vary at low frequencies similar to typical growth curve of bacterial population. Sodium lactate as a carbon source, dissolved in Lagan River water was flushed into the column for biostimulation on 144 th day. The dissolved oxygen in flushed fluid might have killed the anaerobes in the column and decrease in complex conductivities similar to death phase of bacteria is observed for one week. The results obtained from this experiment should contribute to further understanding the biogeophysical responses involved in complex environments.

We report the performance of a field-scale permeable reactive barrier (PRB) for the biological treatment of nitrate-contaminated groundwater. The reactive material of the PRB consisted of a mixture of gravel and mulch as a carbon source for denitrifying bacteria. The PRB was equipped with a delivery system that allowed injecting NO3− at controlled rates from the surface directly into the up-gradient layer of the PRB. This way, NO3−concentration entering the PRB was varied (from1 to 530mg/L) with the purpose of evaluating the ultimateefficiency of the PRB under different NO3− loadings. The PRB was successful at removing NO3− from groundwater at inlet concentrations up to 280 mg/L (with NO3− removal percentages ≥97%).Monitoring of groundwater at differentdepths within the PRB provided evidence that NO3− underwent denitrification preferably at the deepest part of the PRB, where more favourable reducing conditions were achieved. Among the shortcomings of the PRB were the fluctuations of groundwater fluxes caused by intense rainfalls during the study period, although they generally did not pose concern for the denitrification capacity of the PRB. Emission fluxes of gases (CO2, CH4 and N2O) from the PRB to the atmosphere were also measured. The results are finally compared with thefew others reported existing PRBs for nitrate-contaminated groundwater worldwide.