Wanner C.,University of Bern |
Eichinger F.,Hydroisotop GmbH |
Jahrfeld T.,Renerco Plan Consult GmbH |
Diamond L.W.,University of Bern
Geothermics | Year: 2017
The carbonate-dominated Malm aquifer in the Bavarian Molasse Basin in Southern Germany is being widely exploited and explored for geothermal energy. Despite favorable reservoir conditions, the use of geothermal wells for heat and power production is highly challenging. The main difficulty, especially in boreholes >3000 m deep with temperatures >120 °C, is that substantial amounts of calcite scales are hindering the proper operation of the pumps within the wells and of the heat exchangers at the surface. To elucidate the causes of scaling we present an extensive geochemical dataset from the geothermal plant in Kirchstockach. Based on chemical analyses of wellhead water samples, chemical and mineralogical analyses of scales collected along the uppermost 800 m of the production well, and chemical analyses of gas inclusions trapped in calcite-scale crystals, four processes are evaluated that could promote calcite scaling. These are (i) decompression of the produced fluid between the reservoir and the wellhead, (ii) corrosion of the casing that drives pH increase and subsequent calcite solubility decrease, (iii) gas influx from the geothermal reservoir and subsequent stripping of CO2 from the aqueous fluid, and (iv) boiling within the geothermal well. The effectiveness of the four scenarios was assessed by performing geochemical speciation calculations using the codes TOUGHREACT and CHILLER, which explicitly simulate boiling of aqueous fluids (CHILLER) and take into account the pressure dependence of calcite solubility (TOUGHREACT). The results show that process i causes notable calcite supersaturation but cannot act as the sole driver for scaling, whereas ii and iii are negligible in the present case. In contrast, process iv is consistent with all the available observations. That is, scaling is controlled by the exsolution of CO2 upon boiling at the markedly sub-hydrostatic pressure of 4–6 bar within the production well. This process is confirmed by the visible presence of gas inclusions in the calcite scales above the downhole pump, where the production fluid should nominally have been in the homogeneous liquid state. Whereas minor calcite scaling may have been triggered by fluid decompression within the production well, we conclude that the abundant scaling along the pump casing is due to cavitation induced by operating the pump at high production rates. © 2017 Elsevier Ltd
Voerkelius S.,Hydroisotop GmbH
Analytical Chemistry | Year: 2011
We present a comprehensive chemical and mass spectrometric method to determine boron isotopic compositions of plant tissue. The method including dry ashing, a three-step ion chromatographic boron-matrix separation, and 11B/10B isotope ratio determinations using the Cs 2BO2 + graphite technique has been validated using certified reference and quality control materials. The developed method is capable to determine δ11B values in plant tissue down to boron concentrations of 1 mg/kg with an expanded uncertainty of ≥1.7‰ (k = 2). The determined δ11B values reveal an enormous isotopic range of boron in plant tissues covering three-quarters of the natural terrestrial occurring variation in the boron isotopic composition. As the local environment and anthropogenic activity mainly control the boron intake of plants, the boron isotopic composition of plants can be used for food provenance studies. © 2011 American Chemical Society.
PubMed | Karlsruhe Institute of Technology, Tongji University, bbe moldaenke GmbH, Hydroisotop GmbH and 15 more.
Type: Journal Article | Journal: Environmental sciences Europe | Year: 2016
The Taihu (Tai lake) region is one of the most economically prospering areas of China. Due to its location within this district of high anthropogenic activities, Taihu represents a drastic example of water pollution with nutrients (nitrogen, phosphate), organic contaminants and heavy metals. High nutrient levels combined with very shallow water create large eutrophication problems, threatening the drinking water supply of the surrounding cities. Within the international research project SIGN (SinoGerman Water Supply Network, www.water-sign.de), funded by the German Federal Ministry of Education and Research (BMBF), a powerful consortium of fifteen German partners is working on the overall aim of assuring good water quality from the source to the tap by taking the whole water cycle into account: The diverse research topics range from future proof strategies for urban catchment, innovative monitoring and early warning approaches for lake and drinking water, control and use of biological degradation processes, efficient water treatment technologies, adapted water distribution up to promoting sector policy by good governance. The implementation in China is warranted, since the leading Chinese research institutes as well as the most important local stakeholders, e.g. water suppliers, are involved.
De Canniere P.,Belgian Nuclear Research Center |
Schwarzbauer J.,RWTH Aachen |
Hohener P.,French National Center for Scientific Research |
Lorenz G.,Hydroisotop GmbH |
And 4 more authors.
Applied Geochemistry | Year: 2011
Data interpretation of the Porewater Chemistry (PC) experiment at the Mont Terri Rock Laboratory has led to unexpected observations of anaerobic microbial processes which caused important geochemical perturbations of the Opalinus Clay water in the borehole. The increases of acetate to 146mgC/L, of DIC to 109mgC/L and of CH4 to 0.5mgC/L were unexpected and could not be explained without the presence of a C source in the system. The organic C fuelling the observed microbial activity was until then unknown. Leaching tests were performed on several polymers used for the fabrication of the PC equipment to identify the source of organic matter (OM). Polyethylene (PE) appears to be very inert and does not release detectable concentrations of dissolved organic C (DOC) (<1ppb) into the water. Polyurethane (PU) leaches out a dozen different organic compounds accounting for only 13μg DOC/gPU. Under the conditions of the leaching tests, 1g of polyamide (PA, Nylon) also releases ∼512μg of the plasticizer N-Butyl-Benzene-Sulfonamide (NBBS). Soaking tests with polyethylene samples immersed in acetone under conditions similar to those used to remove grease spots on the porous PE filter prior to installation showed that acetone could have been trapped in the PE filter, corresponding to an initial concentration of 1.5gacetone/L of water. However, the accumulated amount of organic C taken into account from all these components was insufficient to satisfactorily explain the observed microbially mediated reducing perturbation. Finally, large amounts of dissolved organic C were found to be released in the system by the jelly polymer filling the reference compartment of the pH and Eh electrodes permanently installed over 5years in flow-through cells on the water circulation loop of the PC experiment. Glycerol was further identified by chromatographic analysis as the main organic compound released by the electrodes. From the analysis results, as well as from the geochemical calculations, the most likely primary organic C source fuelling the microbial perturbation was glycerol released from the polymeric gel filling the reference electrodes (1.6g glycerol/electrode). Other sources, such as acetone, may also have contributed to microbial processes, but only to a minor extent. © 2011 Elsevier Ltd.
Voerkelius S.,Hydroisotop GmbH |
Lorenz G.D.,Hydroisotop GmbH |
Rummel S.,Bayerische Staatssammlung fur Palaontologie und Geologie |
Quetel C.R.,European Commission |
And 9 more authors.
Food Chemistry | Year: 2010
This paper presents the investigation of strontium isotope ratios of about 650 different European natural mineral waters as part of the food traceability project "TRACE" funded by the EU. Analysed 87Sr/86Sr values in the natural mineral waters range from 0.7035 to 0.7777, which indicates an influence by a great diversity of rocks from young mantle derived basaltic rocks to very old silicic continental crust. The results of the large scale investigation are used to elaborate a novel spatial prediction for strontium isotope ratios by combining the measured data with a GIS based geological map of Europe. The resulting map can be used to predict the strontium isotopic composition of groundwater and thus the composition of bio-available strontium, which is available for uptake by plants and subsequently transferred into the food chain. We also show, as an example, that the strontium isotopic composition of honey and wheat from specific sample regions within the TRACE project correlates well with that of the natural mineral water as predicted by our map. The proof of principle shown in our paper is highly relevant for geographical food authentication as it allows an assessment of the origin of food products without the immediate need for geographically authenticated materials which may not always be available. Our approach provides a cost effective first instance screening tool. © 2009 Elsevier Ltd. All rights reserved.
Gilg H.A.,TU Munich |
Kruger Y.,University of Bern |
Taubald H.,University of Tübingen |
van den Kerkhof A.M.,University of Gottingen |
And 2 more authors.
Mineralium Deposita | Year: 2014
Fluid inclusion studies in combination with hydrogen, oxygen and sulphur isotope data provide novel insights into the genesis of giant amethyst-bearing geodes in Early Cretaceous Paraná continental flood basalts at Amestita do Sul, Brazil. Monophase liquid inclusions in colourless quartz, amethyst, calcite, barite and gypsum were analysed by microthermometry after stimulating bubble nucleation using single femtosecond laser pulses. The salinity of the fluid inclusions was determined from ice-melting temperatures and a combination of prograde and retrograde homogenisation temperatures via the density maximum of the aqueous solutions. Four mineralisation stages are distinguished. In stage I, celadonite, chalcedony and pyrite formed under reducing conditions in a thermally stable environment. Low δ34SV-CDT values of pyrite (−25 to −32 ‰) suggest biogenic sulphate reduction by organotrophic bacteria. During the subsequent stages II (amethyst, goethite and anhydrite), III (early subhedral calcite) and IV (barite, late subhedral calcite and gypsum), the oxidation state of the fluid changed towards more oxidising conditions and microbial sulphate reduction ceased. Three distinct modes of fluid salinities around 5.3, 3.4 and 0.3 wt% NaCl-equivalent characterise the mineralisation stages II, III and IV, respectively. The salinity of the stage I fluid is unknown due to lack of fluid inclusions. Variation in homogenisation temperatures and in δ18O values of amethyst show evidence of repeated pulses of ascending hydrothermal fluids of up to 80–90 °C infiltrating a basaltic host rock of less than 45 °C. Colourless quartz and amethyst formed at temperatures between 40 and 80 °C, while the different calcite generations and late gypsum precipitated at temperatures below 45 °C. Calculated oxygen isotope composition of the amethyst-precipitating fluid in combination with δD values of amethyst-hosted fluid inclusions (−59 to −51 ‰) show a significant 18O-shift from the meteoric water line. This 18O-shift, high salinities of the fluid inclusions with chloride-sulphate composition, and high δ34S values of anhydrite and barite (7.5 to 9.9 ‰) suggest that sedimentary brines from deeper parts of the Guaraní aquifer system must have been responsible for the amethyst mineralisation. © 2014, Springer-Verlag Berlin Heidelberg.
Alt-Epping P.,University of Bern |
Waber H.N.,University of Bern |
Diamond L.W.,University of Bern |
Eichinger L.,Hydroisotop GmbH
Geothermics | Year: 2013
Mineral scaling, corrosion and chemical reactions between the re-injected fluid and the aquifer rock affect the long-term exploitation of deep geothermal systems. We use numerical models patterned after the geothermal system at Bad Blumau, Austria, to track the passage of the production fluid through the system. As model input we use pressure, temperature, and fluid composition data collected at the ground surface, as well as evidence for CO2 gas exsolution within the production well. From these constraints we infer the chemical conditions in the reservoir, assess the geochemical implications of the extraction of heat and CO2(g) at the surface, examine the consequences of fluid re-injection into the reservoir, and identify geochemical indicators of incipient corrosion. Exsolution and the subsequent extraction of CO2(g) from the fluid decreases the total CO2, increases the pH and, if not suppressed by adding chemical inhibitors, causes precipitation of carbonate minerals. Calculations show that without the inhibition of Ca-bearing carbonates, the production well could be clogged within a few days. The compositional changes caused by CO2 extraction and the lower temperature of the reinjected fluid trigger disequilibrium reactions at the base of the injection well, potentially affecting the injectivity of the system. Owing to the high redox buffering capacity of the fluid, indicators for incipient corrosion include an increase in the fraction of pyrite in the production well and increase in Fe-oxides/hydroxides near the surface under higher pH and lower temperature conditions. © 2012 Elsevier Ltd.
Meier D.B.,University of Bern |
Waber H.N.,University of Bern |
Gimmi T.,University of Bern |
Gimmi T.,Paul Scherrer Institute |
And 2 more authors.
Journal of Contaminant Hydrology | Year: 2015
Geological site characterisation programmes typically rely on drill cores for direct information on subsurface rocks. However, porosity, transport properties and porewater composition measured on drill cores can deviate from in-situ values due to two main artefacts caused by drilling and sample recovery: (1) mechanical disruption that increases porosity and (2) contamination of the porewater by drilling fluid. We investigated the effect and magnitude of these perturbations on large drill core samples (12-20 cm long, 5 cm diameter) of high-grade, granitic gneisses obtained from 350 to 600 m depth in a borehole on Olkiluoto Island (SW Finland). The drilling fluid was traced with sodium-iodide. By combining out-diffusion experiments, gravimetry, UV-microscopy and iodide mass balance calculations, we successfully quantified the magnitudes of the artefacts: 2-6% increase in porosity relative to the bulk connected porosity and 0.9 to 8.9 vol.% contamination by drilling fluid. The spatial distribution of the drilling-induced perturbations was revealed by numerical simulations of 2D diffusion matched to the experimental data. This showed that the rims of the samples have a mechanically disrupted zone 0.04 to 0.22 cm wide, characterised by faster transport properties compared to the undisturbed centre (1.8 to 7.7 times higher pore diffusion coefficient). Chemical contamination was shown to affect an even wider zone in all samples, ranging from 0.15 to 0.60 cm, in which iodide enrichment was up to 180 mg/kgwater, compared to 0.5 mg/kgwater in the uncontaminated centre. For all samples in the present case study, it turned out that the magnitude of the artefacts caused by drilling and sample recovery is so small that no correction is required for their effects. Therefore, the standard laboratory measurements of porosity, transport properties and porewater composition can be taken as valid in-situ estimates. However, it is clear that the magnitudes strongly depend on site- and drilling-specific factors and therefore our results cannot be transferred simply to other locations. We recommend the approach presented in this study as a route to obtain reliable values in future drilling campaigns aimed at characterising in-situ bedrock properties. © 2015 Elsevier B.V.
Schmidt K.R.,Water Technology Center |
Augenstein T.,Water Technology Center |
Heidinger M.,Hydroisotop GmbH |
Ertl S.,Hydroisotop GmbH |
Tiehm A.,Water Technology Center
Chemosphere | Year: 2010
Cis-1,2-dichloroethene (cDCE) is a compound of concern at many chloroethene-contaminated sites, since it tends to accumulate during reductive dechlorination of the higher chlorinated ethenes. Stable carbon isotope fractionation during aerobic cDCE biodegradation was observed in groundwater microcosms under varying incubation conditions (room temperature/groundwater temperature; with/without inorganic nutrients), and resulted in an average stable carbon isotope enrichment factor of -15.2 ± 0.5‰. A new enrichment culture, obtained from groundwater microcosms, degraded cDCE concentrations up to 100 mg L-1, was active at temperatures between 4 and 23 °C, had a pH optimum of ∼7, and could withstand prolonged periods (250 d) of starvation. Microbial growth during degradation of cDCE as sole carbon and energy source was demonstrated by protein formation in mineral medium not containing any known auxiliary substrate. The obtained growth yield was 12.5 ± 1.9 g of protein Mol-1 of cDCE, with a doubling time of 53 ± 2 h at 23 °C. Aerobic degradation of cDCE as sole carbon and energy source appears to be a promising biological process for site remediation. © 2009 Elsevier Ltd. All rights reserved.
Schmidt K.R.,Water Technology Center |
Gaza S.,Water Technology Center |
Voropaev A.,Hydroisotop GmbH |
Ertl S.,Hydroisotop GmbH |
Tiehm A.,Water Technology Center
Water Research | Year: 2014
Trichloroethene (TCE) represents a priority pollutant and is among the most frequently detected contaminants in groundwater. The current bioremediation measures have certain drawbacks like e.g. the need for auxiliary substrates. Here, the aerobic biodegradation of TCE as the sole growth substrate is demonstrated. This new process of metabolic TCE degradation was first detected in groundwater samples. TCE degradation was stable in an enriched mixed bacterial culture in mineral salts medium for over five years and repeated transfers of the culture resulting in a 1010 times dilution of the original groundwater. Aerobic TCE degradation resulted in stoichiometric chloride formation. Stable carbon isotope fractionation was observed providing a reliable analytical tool to assess this new biodegradation process at field sites. The results suggest that aerobic biodegradation of TCE without auxiliary substrate could be considered as an option for natural attenuation or engineered bioremediation of contaminated sites. © 2014 Elsevier Ltd.