| 1. |
- Gunnarsson-Robin, Jóhann, et al.
(författare)
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Sulfur isotopes in Icelandic thermal fluids
- 2017
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Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273 .- 1872-6097. ; 346, s. 161-179
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Tidskriftsartikel (refereegranskat)abstract
- Multiple sulfur isotope compositions of thermal fluids from Iceland were measured in order to evaluate the sources and reactions of sulfur and sulfur isotope fractionation in geothermal systems at Icelandic divergent plate boundaries, characterized by MORB-like basalts. The geothermal systems studied had a wide range of reservoir temperatures of 56-296 degrees C and Cl concentrations of 18-21,000 ppm. Dissolved sulfide (Sigma S-II) and SO4 concentrations in liquid water measured <0.01-165 ppm and 1.3-300 ppm, respectively, and H2S(g) concentrations in the vapor 4.9-2000 ppm. The delta S-34 and Delta S-33 values for different phases and oxidation states were highly variable: delta S-34 Sigma s(-II) = -11.6 to 10.5 parts per thousand (n = 99), Delta S-33 Sigma s(-II) = -0.12 to 0.00 parts per thousand (n = 45), delta(34)Sso(4) = -1.0 to 24.9 parts per thousand (n = 125), Delta(33)Sso(4) = -0.04 to 0.02 parts per thousand (n = 50), delta(34)SH(2)s(g) = -2.6 to 5.9 parts per thousand (n = 112) and Delta(33)SH(2)s(g) = -0.03 to 0.00 parts per thousand (n = 56). The multiple sulfur isotope values of the thermal fluids are interpreted to reflect various sources of sulfur in the fluids, as well as isotope fractionation occurring within the geothermal systems associated with fluid-rock interaction, boiling and oxidation and reduction reactions. The results of isotope geochemical modeling demonstrate that the sources of S-II in the thermal fluid are leaching of basalt (MORB) and seawater SO4 reduction for saline systems with insignificant magma gas input, and that the observed ranges of delta S-34 and Delta S-33 for Sigma S-II and H2S(g) reflect isotope fractionation between minerals and aqueous and gaseous species upon fluid -rock interaction and boiling. The sources of SO4 are taken to be multiple, including oxidation of S-II originating from basalt, leaching of S-VI from the basalts and the seawater itself in the case of saline systems. In low-temperature fluids, the delta S-34 and Delta S-33 values reflect the various sources of sulfur. For high-temperature fluids, fluid -rock interaction, Sigma S-II oxidation and SO4 reduction and sulfide and sulfate mineral formation result in a large range of delta S-34 and Delta S-33 values for Sigma S-II and SO4 in the fluids, highlighting the importance and effects of chemical reactions on the isotope systematics of reactive elements like sulfur. Such effects needed to be quantified in order to reveal the various sources of an element.
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| 2. |
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| 3. |
- Jackson, Marie, et al.
(författare)
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Time-lapse characterization of hydrothermal seawater and microbial interactions with basaltic tephra at Surtsey volcano
- 2015
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Ingår i: Scientific Drilling. - Copernicus Publications on behalf of the IODP and the ICDP : Copernicus GmbH. - 1816-8957 .- 1816-3459. ; 20, s. 51-58
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Tidskriftsartikel (refereegranskat)abstract
- A new International Continental Drilling Program (ICDP) project will drill through the 50-yearold edifice of Surtsey Volcano, the youngest of the Vestmannaeyjar Islands along the south coast of Iceland, to perform interdisciplinary time-lapse investigations of hydrothermal and microbial interactions with basaltic tephra. The volcano, created in 1963–1967 by submarine and subaerial basaltic eruptions, was first drilled in 1979. In October 2014, a workshop funded by the ICDP convened 24 scientists from 10 countries for 3 and a half days on Heimaey Island to develop scientific objectives, site the drill holes, and organize logistical support. Representatives of the Surtsey Research Society and Environment Agency of Iceland also participated. Scientific themes focus on further determinations of the structure and eruptive processes of the type locality of Surtseyan volcanism, descriptions of changes in fluid geochemistry and microbial colonization of the subterrestrial deposits since drilling 35 years ago, and monitoring the evolution of hydrothermal and biological processes within the tephra deposits far into the future through the installation of a Surtsey subsurface observatory. The tephra deposits provide a geologic analog for developing specialty concretes with pyroclastic rock and evaluating their long-term performance under diverse hydrothermal conditions.
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| 4. |
- Kaasalainen, Hanna, et al.
(författare)
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Chemical analysis of sulfur species in geothermal waters
- 2011
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 85:4, s. 1897-1903
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Tidskriftsartikel (refereegranskat)abstract
- Analytical methods have been developed to determine sulfur species concentrations in natural geothermal waters using Reagent-Free™ Ion Chromatography (RF™-IC), titrations and spectrophotometry. The sulfur species include SO 4 2-, S 2O 3 2-, and ∑S 2- with additional determination of SO 3 2- and S xO 6 2- that remains somewhat semiquantitative. The observed workable limits of detections were ≤0.5 μM depending on sample matrix and the analytical detection limits were 0.1 μM. Due to changes in sulfur species concentrations upon storage, on-site analyses of natural water samples were preferred. Alternatively, the samples may be stabilized on resin for later elution and analysis in the laboratory. The analytical method further allowed simultaneous determination of other anions including F -, Cl -, dissolved inorganic carbon (DIC) and NO 3 - without sample preservation or stabilization. The power of the newly developed methods relies in routine analysis of sulfur speciation of importance in natural waters using techniques and facilities available in most laboratories doing water sample analysis. The new methods were successfully applied for the determination of sulfur species concentrations in samples of natural and synthetic waters. © 2011 Elsevier B.V. All rights reserved.
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| 5. |
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| 6. |
- Kaasalainen, Hanna, et al.
(författare)
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Geochemistry and speciation of Fe(II) and Fe(III) in natural geothermal water, Iceland
- 2017
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Ingår i: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 87, s. 146-157
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Tidskriftsartikel (refereegranskat)abstract
- The geochemistry of Fe(II) and Fe(III) was studied in natural geothermal waters in Iceland. Samples of surface and spring water and sub-boiling geothermal well water were collected and analyzed for Fe(II), Fe(III) and Fetotal concentrations. The samples had discharge temperatures in the range 27–99 °C, pH between 2.46 and 9.77 and total dissolved solids 155–1090 mg/L. The concentrations of Fe(II) and Fe(III) were determined in the <0.2 μm filtered and acidified fraction using a field-deployed ion chromatography spectrophotometry (IC-Vis) method within minutes to a few hours of sampling in order to prevent post-sampling changes. The concentrations of Fe(II) and Fe(III) were <0.1–130 μmoL/L and <0.2–42 μmoL/L, respectively. In-situ dialysis coupled with Fe(II) and Fe(III) determinations suggest that in some cases a significant fraction of Fe passing the standard <0.2 μm filtration method may be present in colloidal/particulate form. Therefore, such filter size may not truly represent the dissolved fraction of Fe but also nano-sized particles. The Fe(II) and Fe(III) speciation and Fetotal concentrations are largely influenced by the water pH, which in turn reflects the water type formed through various processes. In water having pH of ∼7–9, the total Fe concentrations were <2 μmoL/L with Fe(III) predominating. With decreasing pH, the total Fe concentrations increased with Fe(II) becoming increasingly important and predominating at pH < 3. In particular in waters having pH ∼6 and above, iron redox equilibrium may be approached with Fe(II) and Fe(III) possibly being controlled by equilibrium with respect to Fe minerals. In many acid waters, the Fe(II) and Fe(III) distribution may not have reached equilibrium and be controlled by the source(s), reaction kinetics or microbial reactions
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| 7. |
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| 8. |
- Kaasalainen, Hanna, et al.
(författare)
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Sulfur speciation in natural hydrothermal waters, Iceland
- 2011
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 75:10, s. 2777-2791
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Tidskriftsartikel (refereegranskat)abstract
- The speciation of aqueous dissolved sulfur was determined in hydrothermal waters in Iceland. The waters sampled included hot springs, acid-sulfate pools and mud pots, sub-boiling well discharges and two-phase wells. The water temperatures ranged from 4 to 210°C, the pHT was between 2.20 and 9.30 at the discharge temperature and the SO4 and Cl concentrations were 0.020-52.7 and <0.01-10.0mmolkg-1, respectively. The analyses were carried out on-site within ~10min of sampling using ion chromatography (IC) for sulfate (SO42-), thiosulfate (S2O32-) and polythionates (SxO62-) and titration and/or colorimetry for total dissolved sulfide (S2-). Sulfite (SO32-) could also be determined in a few cases using IC. Alternatively, for few samples in remote locations the sulfur oxyanions were stabilized on a resin on site following elution and analysis by IC in the laboratory. Dissolved sulfate and with few exceptions also S2- were detected in all samples with concentrations of 0.02-52.7mmolkg-1 and <1-4100μmolkg-1, respectively. Thiosulfate was detected in 49 samples of the 73 analyzed with concentrations in the range of <1-394μmolkg-1 (S-equivalents). Sulfite was detected in few samples with concentrations in the range of <1-3μmolkg-1. Thiosulfate and SO32- were not detected in <100°C well waters and S2O32- was observed only at low concentrations (<1-8μmolkg-1) in ~200°C well waters. In alkaline and neutral pH hot springs, S2O32- was present in significant concentrations sometimes corresponding to up to 23% of total dissolved sulfur (STOT). In steam-heated acid-sulfate waters, S2O32- was not a significant sulfur species. The results demonstrate that S2O32- and SO32- do not occur in the deeper parts of <150°C hydrothermal systems and only in trace concentrations in ~200-300°C systems. Upon ascent to the surface and mixing with oxygenated ground and surface waters and/or dissolution of atmospheric O2, S2- is degassed and oxidized to SO32- and S2O32- and eventually to SO42- at pH >8. In near-neutral hydrothermal waters the oxidation of S2- and the interaction of S2- and S0 resulting in the formation of Sx2- are considered important. At lower pH values the reactions seemed to proceed relatively rapidly to SO42- and the sulfur chemistry of acid-sulfate pools was dominated by SO42-, which corresponded to >99% of STOT. The results suggest that the aqueous speciation of sulfur in natural hydrothermal waters is dynamic and both kinetically and source-controlled and cannot be estimated from thermodynamic speciation calculations. © 2011 Elsevier Ltd.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Marteinsson, Viggo Thor, et al.
(författare)
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Microbial communities in the subglacial waters of the Vatnajokull ice cap, Iceland
- 2013
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Ingår i: The Isme Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 7:2, s. 427-437
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Tidskriftsartikel (refereegranskat)abstract
- Subglacial lakes beneath the Vatnajokull ice cap in Iceland host endemic communities of microorganisms adapted to cold, dark and nutrient-poor waters, but the mechanisms by which these microbes disseminate under the ice and colonize these lakes are unknown. We present new data on this subglacial microbiome generated from samples of two subglacial lakes, a subglacial flood and a lake that was formerly subglacial but now partly exposed to the atmosphere. These data include parallel 16S rRNA gene amplicon libraries constructed using novel primers that span the v3-v5 and v4-v6 hypervariable regions. Archaea were not detected in either subglacial lake, and the communities are dominated by only five bacterial taxa. Our paired libraries are highly concordant for the most abundant taxa, but estimates of diversity (abundance-based coverage estimator) in the v4-v6 libraries are 3-8 times higher than in corresponding v3-v5 libraries. The dominant taxa are closely related to cultivated anaerobes and microaerobes, and may occupy unique metabolic niches in a chemoautolithotrophic ecosystem. The populations of the major taxa in the subglacial lakes are indistinguishable (>99% sequence identity), despite separation by 6 km and an ice divide; one taxon is ubiquitous in our Vatnajokull samples. We propose that the glacial bed is connected through an aquifer in the underlying permeable basalt, and these subglacial lakes are colonized from a deeper, subterranean microbiome. The ISME Journal (2013) 7, 427-437; doi:10.1038/ismej.2012.97; published online 13 September 2012
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| 14. |
- Pfeffer, M. A., et al.
(författare)
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Ground-Based measurements of the 2014-2015 holuhraun volcanic cloud (Iceland)
- 2018
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Ingår i: Geosciences (Switzerland). - : MDPI AG. - 2076-3263. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The 2014-2015 Bárðarbunga fissure eruption at Holuhraun in central Iceland was distinguished by the high emission of gases, in total 9.6 Mt SO 2 , with almost no tephra. This work collates all ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense cloud with high SO 2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, developing ramparts, and high-latitude winter conditions. Semi-continuous measurements of SO 2 flux with three scanning DOAS instruments were augmented by car traverses along the ring-road and along the lava. The ratios of other gases/SO 2 were measured by OP-FTIR, MultiGAS, and filter packs. Ratios of SO 2 /HCl = 30-110 and SO 2 /HF = 30-130 show a halogen-poor eruption cloud. Scientists on-site reported extremely minor tephra production during the eruption. OPC and filter packs showed low particle concentrations similar to non-eruption cloud conditions. Three weather radars detected a droplet-rich eruption cloud. Top of eruption cloud heights of 0.3-5.5 km agl were measured with ground-and aircraft-based visual observations, web camera and NicAIR II infrared images, triangulation of scanning DOAS instruments, and the location of SO 2 peaks measured by DOAS traverses. Cloud height and emission rate measurements were critical for initializing gas dispersal simulations for hazard forecasting.
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| 15. |
- Pfeffer, M. A., et al.
(författare)
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SO 2 emission rates and incorporation into the air pollution dispersion forecast during the 2021 eruption of Fagradalsfjall, Iceland
- 2024
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Ingår i: Journal of Volcanology and Geothermal Research. - 0377-0273. ; 449
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Tidskriftsartikel (refereegranskat)abstract
- During the low-effusion rate Fagradalsfjall eruption (19 March – 18 September 2021), the emission of sulfur dioxide (SO2) was frequently measured using ground-based UV spectrometers. The total SO2 emitted during the entire eruption was 970 ± 540 kt, which is only about 6% of the SO2 emitted during the similar length Holuhraun eruption (2014–2015). The eruption was divided into five phases based on visual observations, including the number of active vents and the occurrence of lava fountaining. The SO2 emission rate ranged from 44 ± 19 kg/s in Phase 2 to 85 ± 29 kg/s in Phase 5, with an average of 64 ± 34 kg/s for the entire eruption. There was notable variability in SO2 on short timescales, with measurements on 11 August 2021 ranging from 17 to 78 kg/s. SO2 flux measurements were made using scanning DOAS instruments located at different distances from and orientations relative to the eruption site augmented by traverses. Four hundred and forty-four scan and traverse measurements met quality criteria and were used, along with plume height and meteorological data, to calculate SO2 fluxes while accounting for wind-related uncertainties. A tendency for stronger SO2 flux concurrent with higher amplitude seismic tremor and the occurrence of lava fountaining was observed during Phases 4 and 5 which were characterized by intermittent crater activity including observable effusion of lava and gas release interspersed with long repose times. This tendency was used to refine the calculation of the amount of SO2 emitted during variably vigorous activity. The continuous seismic tremor time series was used to quantify how long during these eruption phases strong/weak activity was exhibited to improve the calculated SO2 flux during these Phases. The total SO2 emissions derived from field measurements align closely with results obtained by combining melt inclusion and groundmass glass analyses with lava effusion rate measurements (910 ± 230 kt SO2). Specifically, utilizing the maximum S content found in evolved melt inclusions and the least remaining S content in accompanying quenched groundmasses provides an identical result between field measurements and the petrological calculations. This suggests that the maximum SO2 release calculated from petrological estimates should be preferentially used to initialize gas dispersion models for basaltic eruptions when other measurements are lacking. During the eruption, the CALPUFF dispersion model was used to forecast ground-level exposure to SO2. The SO2 emission rates measured by DOAS were used as input for the dispersion model, with updates made when a significant change was measured. A detailed analysis of one mid-distance station over the entire eruption shows that the model performed very well at predicting the presence of volcanic SO2 when it was measured. However, it frequently predicted the presence of SO2 that was not measured and the concentrations forecasted had no correlation with the concentrations measured. Various approaches to improve the model forecast were tested, including updating plume height and SO2 flux source terms based on measurements. These approaches did not unambiguously improve the model performance but suggest that improvements might be achieved in more-polluted conditions.
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| 16. |
- Planer-Friedrich, Britta, et al.
(författare)
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Relative Abundance of Thiolated Species of As, Mo, W, and Sb in Hot Springs of Yellowstone National Park and Iceland
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:7, s. 4295-4304
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Tidskriftsartikel (refereegranskat)abstract
- Geothermal waters often are enriched in trace metal(loid)s, such as arsenic, antimony, molybdenum, and tungsten. The presence of sulfide can lead to the formation of thiolated anions; however, their contributions to total element concentrations typically remain unknown because nonsuitable sample stabilization and chromatographic separation methods convert them to oxyanions. Here, the concurrent widespread occurrence of thioarsenates, thiomolybdates, thiotungstates, and thioantimonates, in sulfide-rich hot springs from Yellowstone National Park and Iceland is shown. More thiolation was generally observed at higher molar sulfide to metal(loid) excess (Iceland > Yellowstone). Thioarsenates were the most prominent and ubiquitous thiolated species, with trithioarsenate typically dominating arsenic speciation. In some Icelandic hot springs, arsenic was nearly quantitatively thiolated. Also, for molybdenum, thioanions dominated over oxyanions in many Icelandic hot springs. For tungsten and antimony, oxyanions typically dominated and thioanions were observed less frequently, but still contributed up to a few tens of percent in some springs. This order of relative abundance (thioarsenates > thiomolybdates > thiotungstates ≈ thioantimonates) was also observed when looking at processes triggering transformation of thioanions such as mixing with non-geothermal waters or H2S degassing and oxidation with increasing distance from a discharge. Even though to different extents, thiolation contributed substantially to speciation of all four elements studied, indicating that their analysis is required when studying geothermal systems.
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| 17. |
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| 18. |
- Stefánsson, Andri, et al.
(författare)
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Isotope systematics of Icelandic thermal fluids
- 2017
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Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273 .- 1872-6097. ; 337, s. 146-164
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Forskningsöversikt (refereegranskat)abstract
- Thermal fluids in Iceland range in temperature from <10 degrees C to >440 degrees C and are dominated by water (>97 mol%) with a chloride concentration from <10 ppm to >20,000 ppm. The isotope systematics of the fluids reveal many important features of the source(s) and transport properties of volatiles at this divergent plate boundary. Studies spanning over four decades have revealed a large range of values for delta D (-131 to +3.3%o), tritium (-0.4 to +13.8 TU), delta(18) O(-20.8 to + 2.3%o), He-3/He-4 (3.1 to 30.4 R-A), delta B-11 (-6.7 to+25.0%o), delta C-13 Sigma co(2) (-27.4 to+ 4.6%o), C-1 Sigma co(2), (+0.6 to + 118 pMC), delta C-l3(CH4) (-523 to-17.8%o), delta N-15 (-10.5 to+3.0%o), 8(34)C Sigma s(-ll) (-10.9 to (+)3.4%o), delta S-34(SO4) (-2.0to + 21.2%) and delta Cl-37 (-1.0 to + 2.1%o) in both liquid and vapor phases. Based on this isotopic dataset, the thermal waters originate from meteoric inputs and/or seawater. For other volatiles, degassing of mantle-derived melts contributes to He, CO2 and possibly also to Cl in the fluids. Water-basalt interaction also contributes to CO2 and is the major source of H2S, SO4, Cl and B in the fluids. Redox reactions additionally influence the composition of the fluids, for example, oxidation of H2S to SO4 and reduction of CO2 to CH4. Air water interaction mainly controls N-2, Ar and Ne concentrations. The large range of many non-reactive volatile isotope ratios, such as delta C-13 Sigma co(2)and(34)S Sigma S-u indicate heterogeneity of the mantle and mantle-derived melts beneath Iceland. In contrast, the large range of many reactive isotopes, such as delta C-13 Sigma co(2), and delta S-34 Sigma S-u, are heavily affected by processes occurring within the geothermal systems, including fluid-rock interaction, depressurization boiling, and isotopic fractionation between secondary minerals and the aqueous and vapor species. Variations due to these geothermal processes may exceed differences observed among various crust and mantle sources, highlighting the importance and effects of chemical reactions on the isotope systematics of reactive elements.
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| 19. |
- Stefánsson, Andri, et al.
(författare)
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Quantifying mixing, boiling, degassing, oxidation and reactivity of thermal waters at Vonarskard, Iceland
- 2016
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Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273 .- 1872-6097. ; 309, s. 53-62
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Tidskriftsartikel (refereegranskat)abstract
- The chemical composition of geothermal fluids may be altered upon ascent from the reservoir to surface by processes including boiling, degassing, mixing, oxidation and water-rock interaction. In an attempt to quantify these processes, a three step model was developed that includes: (1) defining the composition of the end-member fluid types present in the system, (2) quantifying mixing between the end-members using non-reactive elemental concentrations and enthalpy and (3) quantifying the changes of reactive elements including degassing, oxidation and water-rock interaction. The model was applied to geothermal water at Vonarskard, Iceland, for demonstration having temperatures of 3-98°C, pH of 2.15-9.95 and TDS of 323-2250ppm, and was thought to be produced from boiled reservoir water, condensed steam and non-thermal water. Most geothermal water represented mixture of non-thermal water and condensed steam whereas the boiled reservoir water was insignificantly mixed. CO2 and H2S degassing was found to be quantitative in steam-heated water, with oxidation of H2S to SO4 also occurred. In contrast, major rock forming elements are enriched in steam-heated water relative to their mixing ratios, suggesting water-rock interaction in the surface zone. Boiled reservoir water observed in alkaline hot springs have, however, undergone less geochemical changes upon ascent to surface and within the surface zone.
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| 20. |
- Stefánsson, Andri, et al.
(författare)
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The geochemistry and sequestration of H2S into the geothermal system at Hellisheidi, Iceland
- 2011
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Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273 .- 1872-6097. ; 202:3-4, s. 179-188
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Tidskriftsartikel (refereegranskat)abstract
- The geochemistry and mineralization of H2S in the geothermal system hosted by basaltic rock formation at Hellisheidi, SW Iceland, was studied. Injection of mixtures of H2S with geothermal waste water and condensed steam into the >230°C geothermal aquifer is planned, where H2S will hopefully be removed in the form of sulphides. The natural H2S concentrations in the aquifer average 130ppm. They are considered to be controlled by close approach to equilibrium with pyrite, pyrrhotite, prehnite and epidote. Injection of H2S will increase significantly the reservoir H2S equilibrium concentrations, resulting in mineralization of pyrite and possibly other sulphides as well as affecting the formation of prehnite and epidote. Based on reaction path modelling, the main factors affecting the H2S mineralization capacity are related to the mobility and oxidation state of iron. At temperatures above 250°C the pyrite mineralization is greatly reduced upon epidote formation leading to the much greater basalt dissolution needed to sequestrate the H2S. Based on these findings, the optimum conditions for H2S injection are aquifers with temperatures below ~250°C where epidote formation is insignificant. Moreover, the results suggest that sequestration of H2S into the geothermal system is feasible. The total flux of H2S from the Hellisheidi power plant is 12,950tonnesyr-1. Injection into 250°C aquifers would result in dissolution of ~1000tonnesyr-1 of basalt for mineralization of H2S as pyrite, corresponding to ~320m3yr-1. © 2011 Elsevier B.V.
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