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  • 101.
    Aullón Alcaine, Anna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Miljögeokemi och ekoteknik.
    Bhattacharya, Prosun
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Miljögeokemi och ekoteknik.
    Jacks, Gunnar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Miljögeokemi och ekoteknik.
    Schulz, C.
    Universidad Nacional de la Pampa, Argentina.
    Bundschuh, Jochen
    University of Southern Queensland, Australia.
    Thunvik, Roger
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Biogeofysik.
    Mörth, Carl-Magnus
    Stockholms Universitet, Institutionen för geologiska vetenskaper.
    Geogenic arsenic and fluoride in shallow aquifers of northeastern La Pampa, Argentina: mobility constraints2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    High concentrations of geogenic arsenic (As) and fluoride (F-) in groundwater have been reported at elevated concentrations in different parts of the Chaco-Pampean Plain, in Argentina, where more than 2 million people may be exposed to high levels of these toxic elements through drinking water. Groundwater from the shallow aquifer is far exceeding the permissible WHO Standard limits of 10 μg/L for As and 1.5 mg/L for fluoride, as well as the Argentinean Standard limit of 50 μg/L for As. Geogenic As results due to the weathering of ash originated by volcanic eruptions from the Andean Cordillera and transported by wind and deposited along with the sediments and also as discrete layers and lenses over large geographical area containing around 90% of rhyolitic glass. Groundwater is hosted in a sandy silty interconnected system of aquifers and aquitards within the The Pampean aquifer. A total of 44 groundwater samples were collected from the shallow aquifers in NE of La Pampa province. Two rural areas covering an area of 600km2 in Quemú Quemú (QQ) and 300km2 in Intendente Alvear (IA) were investigated in the present study. Groundwater was circum-neutral to alkaline (pH 7.43-9.18), predominantly oxidizing (Eh ~0.24 V) with widely variable EC range (456-11,400 μS/cm). The major cation dissolved in groundwater was Na+, while the predominant anions were HCO3-, Cl- and SO42-, respectively. Water type in QQ was mostly Na-HCO3- while in IA, the composition differed between Na-HCO3- and Na-Cl-SO42- water types. Groundwater composition showed high degree of mineralization and high salinity evidenced by high EC. In discharge areas, high evaporation rates result in high salinity of shallow groundwater and visible salts incrustations on the surface of the lakes. Elevated concentrations of NO3- and PO43- observed in some wells indicated possible anthropogenic contamination. Total As concentration in groundwater from QQ ranged from 5.58 to 535 μg/L, where 94% of the wells exceeded the WHO standard limit for safe drinking water of 10 μg/L, and 56% of the wells exceeded the old Argentine standard limit of 50 μg/L. F- concentrations revealed heterogeneity and high concentrations in some wells (0.5-14.2 mg/L), 78% of samples in QQ study area exceeded the WHO standard limit of 1.5 mg/L. Under oxidizing conditions and neutral to alkaline pH, arsenate (AsV) species predominated, mainly in HAsO42- forms. As "hotspots" indicated locally contamination and correlated positively with F-, HCO3-, B and V and showed negative correlation with salinity, dissolved Fe, Al and Mn. The mechanisms involved in the mobilization of As in the shallow aquifers are controlled by the rise of pH, variations in Eh conditions and the presence of competitor ions (HCO3-, PO43-, Si, V oxyanions). Geochemical processes like adsorption/desorption, precipitation/dissolution and redox reactions may trigger to As mobilization in the shallow aquifers of La Pampa region.

  • 102.
    Axelsson, Mikael D.
    Luleå tekniska universitet.
    Multi-element analysis of environmental samples using LA-ICP-MS: method developments with emphasis on calibration strategies2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Analytical applications based on the use of laser ablation-inductively coupled plasma-sector field mass spectrometry (LA-ICP-SFMS) have shown great potential for both quantitative and qualitative determination of elements in a variety of materials, although the weak point is finding a suitable calibration approach. The major focus of this work has, therefore, been internal standardisation and calibration. Methods for quantitative and qualitative analysis of geological (coal, ferromanganese concretions, sulphide minerals) and biological (nail and hair) samples have been developed. For coal, two reference materials were analysed after microwave (MW) treatment with different combinations of HNO3, aqua regia, HF and H2O2. Lithium metaborate (LMB) fusion with and without ashing of samples, as well as LA solid sampling on pressed coal pellets were also evaluated. External calibration for LA-ICP-SFMS was conducted using matrix-matched standard dopeds with standard solutions. This approach resulted in good accuracy for 46 out of 47 elements tested in the coal fly ash reference material. The precision was assessed in this work by replicate analyses of coal samples and was found to be, as average values for all elements, 4-5% and 10-15% relative standard deviation (RSD) for procedures involving digestion and LA sampling, respectively. For ferromanganese concretions, improvement of existing sample preparation schemes was necessary in order to expand the element coverage. The optimised and validated (for about 60 elements) method has the potential to replace the multitude of sample preparation and instrumental analytical techniques previously used to determine specific groups of elements in ferromanganese nodules. By using this improved method, it was possible to successfully quantify more than 50 elements by LA-ICP-SFMS using external calibration against matrix-matched standards. The results also show how different LA parameters affect the isotopic response and RSD. For sulphide minerals, LA-ICP-SFMS analysis was performed directly on polished crystalline sections. In sphalerite, a number of major and trace elements were determined by a ‘single-standard’ method using Zn for internal standardisation, together with correction for FeS impurities in the mineral, allowing straightforward quantification without using external methods for the determination of the actual Zn content. Results obtained by this approach were in good agreement with those from using external calibration. In order to evaluate the possibility to use crystalline sections of sphalerite and four other sulphide minerals as in-house standards, an analytical method was developed for multi-elemental analysis of such samples after preparation based on both MW digestion using different acid mixtures and LMB fusion. The performance of the sample preparation and analysis stages was evaluated using powdered pyrite and galena reference materials. It was found possible to use the selected minerals as matrix-matched standards for the determination of about 20 trace and ultra-trace elements by LA-ICP-SFMS. The second group of matrices concerned in this work comprises hair and nail samples. The first part of this study was focused on method validation for the determination of 71 elements by conventional ICP-SFMS analysis after MW-assisted digestion, with special attention paid to the correction of spectral interferences and to accuracy assessment. In the follow up study, the main concern was to evaluate the capabilities of LA-ICP-SFMS for quantitative multi-elemental analysis of hair and nail samples, emphasising the collection of spatially resolved information. Quantification was performed by means of an in-house, multi-element, matrix-matched standard using 32S+ as internal standard. A major conclusion of this thesis is that each sample type is in many respects unique, and therefore demands careful selection of a suitable calibration protocol, in order to ensure that reliable analytical results are delivered. The developed methods will make it possible to quantitatively analyse samples such as geological thin-sections, single sulphide grains, ferromanganese concretions, fingernails and hair. The results also show that LA-ICP-SFMS potentially can be used for obtaining quantitative analyses with good spatial resolution in a variety of materials.

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  • 103.
    Axelsson, Mikael D.
    Luleå tekniska universitet.
    Multielemental analysis of geological and biological samples using laser ablation ICP-SFMS2000Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The analytical performance of laser ablation (LA) for multielemental determination of geological and biological samples has been investigated. In the present study, LA has been used for sample introduction in inductively coupled plasma sector field mass spectrometry (ICP-SFMS). Although LA can provide semi-quantitative results rapidly and easily, the calibration process still remains the "Achilles heel" of the technique. The major goal of this study has been to investigate the capabilities of LA-ICP-SFMS for qualitative and quantitative analysis of various solid materials. LA was used for analyses of coal were calibration was performed by using coal powder doped with analyte elements. This was done by adding solution standards (including analyte and internal standard elements) to the coal, drying and finally homogenising, followed by pressing tablets. LA results were compared with data obtained by conventional solution nebulisation (SN) after preparation of coal samples using microwave (MW) digestion or fusion. In spite of a relatively poor agreement for elements such as As, Se, Sn, Re, Te, and Tl, accuracy obtained with LA in the present study is otherwise generally superior to previously reported data for LA and slurry nebulisation. For about 50 elements, results obtained with LA fall within 20% of those obtained by SN. The study shows the potential of LA quantification, based on solution-doped powders. However, the necessity of sample grinding and homogenising results in loss of spatial distribution information and makes the approach more vulnerable to sample contamination. The possibilities of sulphide minerals analysis by ICP-SFMS have been investigated. Seven elements (Co, Fe, Cd, Ag, Mn, Cu and S) have been quantitatively determined in sphalerite samples from the Zinkgruvan mine, using Zn as internal standard (IS). A straightforward calibration procedure allows on-line correction for possible Fe impurities at percent levels. Consequently, the use of complimentary techniques for determination of actual Zn content in the samples is avoided. The LA-ICP-SFMS results were compared with data from conventional SN introduction of sample solutions following acid digestion. Good agreement was found between the methods. For homogeneously distributed elements the overall precision for LA was found to be better than 10% RSD. A method for total mineral dissolution of five sulphides (sphalerite, pyrite, galena, pyrrhotite and chalcopyrite) has been developed, followed by multielemental analysis by ICP-SFMS. By performing this mineral characterisation the intention was to determine whether the analysed bulk mineral samples could be used as in-house LA calibration standards. The use of LA was focused towards elucidating whether the observed deviations in results obtained by ICP-SFMS for the two reference material powders used were caused by sample inhomogeneity or by inefficient matrix dissolution. It was found that the reference materials showed lack of accuracy in recommended concentrations for many trace and ultra trace elements, as well as possible inhomogeneity when using 50 mg sample amounts. The sulphide minerals studied appears to be suitable as matrix matched calibration standards for the determination of about 20 trace and ultra trace elements by LA. Laser ablation was also used for analysing element to sulphur ratios in washed human nails. The element ratios were then used to display the effectiveness of the applied washing method applied prior to MW digestion and analysis by ICP-SFMS. Based on the LA analysis, it was found that, even after the applied nail washing procedure, many elements are enriched in the surface of the nail.

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  • 104.
    Axelsson, Mikael
    et al.
    Luleå tekniska universitet.
    Rodushkin, Ilia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Baxter, Douglas
    Ingri, Johan
    Öhlander, Björn
    High spatial resolution analysis of ferromanganese concretions by LA-ICP-MS2002Ingår i: Geochemical Transactions, ISSN 1467-4866, E-ISSN 1467-4866, Vol. 3, nr 5, s. 40-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A procedure was developed for the determination of element distributions in cross-sections of ferromanganese concretions using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The effects of carrier flow rates, rf forward power, ablation energy, ablation spot size, repetition rate and number of shots per point on analyte intensity were studied. It is shown that different carrier gas flow rates are required in order to obtain maximum sensitivities for different groups of elements, thus complicating the optimisation of ICP parameters. On the contrary, LA parameters have very similar effects on almost all elements studied, thus providing a common optimum parameter set for the entire mass range. However, for selected LA parameters, the use of compromise conditions was necessary in order to compensate for relatively slow data acquisition by ICP-MS and maintain high spatial resolution without sacrificing the multielemental capabilities of the technique. Possible variations in ablation efficiency were corrected for mathematically using the sum of Fe and Mn intensities. Quantification by external calibration against matrix-matched standards was successfully used for more than 50 elements. These standards, in the form of pressed pellets (no binder), were prepared in-house using

  • 105.
    Axelsson, Mikael
    et al.
    Luleå tekniska universitet.
    Rodushkin, Ilya
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Determination of major and trace elements in sphalerite using laser ablation double focusing sector field ICP-MS2001Ingår i: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 72, nr 2, s. 81-89Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The analytical performance of laser ablation (LA) for the determination of Co, Fe, Cd, Ag, Mn, Cu and S in sphalerite was evaluated using double focusing sector field inductively coupled plasma mass spectrometry (ICP-SFMS). Samples were collected from Zinkgruvan, situated in the south central Sweden. The use of Zn for internal standardisation, together with correction for FeS impurities in sphalerite, allows straightforward quantification without using external methods for the determination of the actual Zn content. LA-ICP-SFMS results were compared with data obtained by conventional pneumatic nebulisation introduction of sample solutions following acid digestion. Good agreement between the two methods was obtained for homogeneously distributed elements. For the majority of the elements under consideration, LA-ICP-SFMS precision was better than 10% RSD.

  • 106.
    Axelsson, Mikael
    et al.
    Luleå tekniska universitet.
    Rodushkin, Ilya
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Multielemental analysis of Mn-Fe nodules by ICP-MS: optimisation of analytical method2002Ingår i: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 127, nr 1, s. 76-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two acid digestion procedures (microwave-assisted and room temperature) were developed for the quantitative analysis of ferromanganese nodules by inductively coupled plasma double focusing sector field mass spectrometry (ICP-SFMS). Different compositions of the acid mixture, dilution factors and corrections for spectral interferences were tested. A combination of nitric, hydrochloric and hydrofluoric acids is necessary for complete sample digestion, with lowest acid to sample ratios (v/m) of 15 and 1.5. respectively, for the last two acids. Sample dilution factors higher than 2 X 104 should be used in order to decrease matrix effects and provide robust long-term instrumental operation. In spite of high dilution. method detection limits in the sub-mug g(-1) range were obtained for 54 out of 71 elements tested. due to the high detection capability of ICP-SFMS, as well as the special care taken to ensure the purity of reagents, to clean the instrument sample introduction system and to minimise sample handling. Owing to the presence of unresolved (at the resolution available) spectral interferences, accurate determination of Au, Hg, Os, Pd, Re and Rh is impossible without matrix separation. The accuracy of the entire analytical method was tested by the analysis of two nodule reference materials. The results generated agreed to within +/-2% for about 10, within +/-10% for more than 40 and within +/-20% for about 50 of 53 elements for which certified, recommended or literature values are available. A precision better than 3%, expressed as the between-digestion relative standard deviation (n=4). was obtained for the majority of elements, except in cases limited by low analyte concentrations

  • 107.
    Aydin, Faruk
    et al.
    Karadeniz Technical University, Department of Geological Engineering.
    Saka, Simge Oguz
    Karadeniz Technical University, Department of Geological Engineering.
    Sen, Cüneyt
    Karadeniz Technical University, Department of Geological Engineering.
    Dokuz, Abdurrahman
    Gümüşhane University, Department of Geological Engineering.
    Aiglsperger, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Uysal, Ibrahim
    Karadeniz Technical University, Department of Geological Engineering.
    Kandemir, Raif
    Recep Tayyip Erdoğan University, Department of Geological Engineering.
    Karsli, Orhan
    Recep Tayyip Erdoğan University, Department of Geological Engineering.
    Sari, Bilal
    Dokuz Eylül University, Department of Geological Engineering.
    Baser, Rasim
    Karadeniz Technical University, Department of Geological Engineering.
    Temporal, geochemical and geodynamic evolution of the Late Cretaceous subduction zone volcanism in the eastern Sakarya Zone, NE Turkey: Implications for mantle-crust interaction in an arc setting2020Ingår i: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 192, artikel-id 104217Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Late Cretaceous Artvin volcanic rocks (LCAVs) from the eastern Sakarya zone (ESZ) of NE Turkey are composed of mafic/basaltic (S1-Çatak and S2-Çağlayan) and felsic/acidic (S1-Kızılkaya and S2-Tirebolu) rock types that occurred in two successive stages: (i) first stage (S1: Turonian–Early Santonian) and (ii) second stage (S2: Late Santonian–Campanian). Clinopyroxene thermobarometric results point that the S2-Çağlayan basaltic rocks have crystallised at higher temperatures and under deeper crustal conditions than those of the S1-Çatak basaltic rocks.

    The LCAVs show a wide compositional spectrum, ranging from tholeiite to calc-alkaline/shoshonite and are typically represented by a geochemical composition resembling subduction-related arc rocks although the 87Sr/86Sr(i) (0.7044–0.7071) and ɛNd(i) values (−0.63 to + 3.47) as well as 206Pb/204Pb(i) (18.07–18.56), 207Pb/204Pb(i) (15.57–15.62) and 208Pb/204Pb(i) (37.12–38.55) ratios show very limited variation. The parent magmas of the S1-Çatak and S2-Çağlayan mafic volcanic rocks were derived from underplated basaltic melts that originated by partial melting of metasomatised spinel lherzolite and spinel-garnet lherzolite, respectively. It is proposed that the compositions of the S1-Kızılkaya (mainly dacitic) and S2-Tirebolu (rhyolitic to trachytic) felsic rocks were particularly controlled by metasomatised mantle–crust interaction and MASH zone + shallow crustal fractionation processes. Our data, together with data from previous studies, suggest that the S1- and S2-mafic and felsic rocks of the LCAVs (~95–75 Ma) are the products of two-stage volcanic event that took place during the northward subduction of the northern Neotethys Ocean (NNO).

  • 108.
    Babechuk, Michael
    et al.
    Isotope Geochemistry Group, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen, Germany.
    Weimar, Nadine
    Isotope Geochemistry Group, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen, Germany.
    Kleinhanns, Ilka
    Isotope Geochemistry Group, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen, Germany.
    Eroglu, Suemeyya
    Isotope Geochemistry Group, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen, Germany.
    Swanner, Elizabeth
    Department of Geological & Atmospheric Sciences, Iowa State University, Ames, USA.
    Kenny, Gavin
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Kamber, Balz
    Department of Geology, Trinity College Dublin, Dublin, Ireland.
    Schoenberg, Ronny
    Isotope Geochemistry Group, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen, Germany.
    Pervasively anoxic surface conditions at the onset of the Great Oxidation Event: New multi-proxy constraints from the Cooper Lake paleosol2019Ingår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 323, s. 126-163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oceanic element inventories derived from marine sedimentary rocks place important constraints on oxidativecontinental weathering in deep time, but there remains a scarcity in complementary observations directly fromcontinental sedimentary reservoirs. This study focuses on better defining continental weathering conditions nearthe Archean-Proterozoic boundary through the multi-proxy (major and ultra-trace element, Fe and Cr stableisotopes, μ-XRF elemental mapping, and detrital zircon U-Pb geochronology) investigation of the ca. 2.45 billionyear old (giga annum, Ga) Cooper Lake paleosol (saprolith) developed on a sediment-hosted mafic dike withinthe Huronian Supergroup (Ontario, Canada).Throughout the variably altered Cooper Lake saprolith, ratios of immobile elements (Nb, Ta, Zr, Hf, Th, Al, Ti)are constant, indicating a uniform pre-alteration dike composition, lack of extreme pH weathering conditions,and no major influence from ligand-rich fluids during weathering or burial metasomatism/metamorphism. Theloss of Mg, Fe, Na, Sr, and Li, a signature of albite and ferromagnesian silicate weathering, increases towards thetop of the preserved profile (unconformity) and dike margins. Coupled bulk rock behaviour of Fe-Mg-Mn and colocalizationof Fe-Mn in clay minerals (predominantly chlorite) indicates these elements were solubilized primarilyin their divalent state without Fe/Mn-oxide formation. A lack of a Ce anomaly and immobility of Mo, V, and Cr further support pervasively anoxic weathering conditions. Subtle U enrichment, if primary, is the onlygeochemical evidence that could be consistent with oxidative element mobilization. The leaching of ferromagnesiansilicates was accompanied by variable mobility and depletion of transition metals with a relativedepletion order of Fe≈Mg≈Zn > Ni > Co > Cu (Cu being significantly influenced by secondary sulfideformation). Mild enrichment of heavy Fe isotopes (δ56/54Fe from 0.169 to 0.492‰) correlating with Fe depletionin the saprolith indicates open-system loss of isotopically light aqueous Fe(II). Minor REE+Y fractionation withincreasing alteration intensity, including a decreasing Eu anomaly and Y/Ho ratio, is attributed to albitebreakdown and preferential scavenging of HREE > Y by clay minerals, respectively. Younger metasomatismresulted in the addition of several elements (K, Rb, Cs, Be, Tl, Ba, Sn, In, W), partly or wholly obscuring theirearlier paleo-weathering trends.The behavior of Cr at Cooper Lake can help test previous hypotheses of an enhanced, low pH-driven continentalweathering flux of Cr(III) to marine reservoirs between ca. 2.48–2.32 Ga and the utility of the stable Crisotope proxy of Mn-oxide induced Cr(III) oxidation. Synchrotron μ-XRF maps and invariant Cr/Nb ratios revealcomplete immobility of Cr despite its distribution amongst both clay-rich groundmass and Fe-Ti oxides.Assuming a pH-dependent, continental source of Cr(III) to marine basins, the Cr immobility at Cooper Lakeindicates either that signatures of acidic surface waters were localized to uppermost and typically unpreservedregolith horizons or were geographically restricted to acid-generating point sources. However, given detritalpyrite preservation in overlying fluvial sequences, it is probable that the oxidative sulfide corrosion required todrive surface pH < 4 lagged behind in this region relative to other early Proterozoic sequences. The entiresaprolith exhibits a consistently light stable Cr isotope composition (δ53/52Cr: −0.321 ± 0.038‰, 2sd, n=34)that cannot be linked to Cr(III) oxidation and is instead interpreted to have a magmatic origin.

  • 109.
    Bagherbandi, Mohammad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Tenzer, Robert
    Sjöberg, Lars E.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Moho depth uncertainties in the Vening-Meinesz Moritz inverse problem of isostasy2014Ingår i: Studia Geophysica et Geodaetica, ISSN 0039-3169, E-ISSN 1573-1626, Vol. 58, nr 2, s. 227-248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We formulate an error propagation model based on solving the Vening Meinesz-Moritz (VMM) inverse problem of isostasy. The system of observation equations in the VMM model defines the relation between the isostatic gravity data and the Moho depth by means of a second-order Fredholm integral equation of the first kind. The corresponding error model (derived in a spectral domain) functionally relates the Moho depth errors with the commission errors of used gravity and topographic/bathymetric models. The error model also incorporates the non-isostatic bias which describes the disagreement, mainly of systematic nature, between the isostatic and seismic models. The error analysis is conducted at the study area of the Tibetan Plateau and Himalayas with the world largest crustal thickness. The Moho depth uncertainties due to errors of the currently available global gravity and topographic models are estimated to be typically up to 1-2 km, provided that the GOCE gravity gradient observables improved the medium-wavelength gravity spectra. The errors due to disregarding sedimentary basins can locally exceed similar to 2 km. The largest errors (which cause a systematic bias between isostatic and seismic models) are attributed to unmodeled mantle heterogeneities (including the core-mantle boundary) and other geophysical processes. These errors are mostly less than 2 km under significant orogens (Himalayas, Ural), but can reach up to similar to 10 km under the oceanic crust.

  • 110.
    Bagherbandi, Mohammad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik. University of Gävle, Sweden.
    Tenzer, Robert
    Sjöberg, Lars E.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Abrehdary, Majid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    On the residual isostatic topography effect in the gravimetric Moho determination2015Ingår i: Journal of Geodynamics, ISSN 0264-3707, E-ISSN 1879-1670, Vol. 83, s. 28-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In classical isostatic models, a uniform crustal density is typically assumed, while disregarding the crustal density heterogeneities. This assumption, however, yields large errors in the Moho geometry determined from gravity data, because the actual topography is not fully isostatically compensated. Moreover, the sub-crustal density structures and additional geodynamic processes contribute to the overall isostatic balance. In this study we investigate the effects of unmodelled density structures and geodynamic processes on the gravity anomaly and the Moho geometry. For this purpose, we define the residual isostatic topography as the difference between actual topography and isostatic topography, which is computed based on utilizing the Vening Meinesz-Moritz isostatic theory. We show that the isostatic gravity bias due to disagreement between the actual and isostatically compensated topography varies between 382 and 596 mGal. This gravity bias corresponds to the Moho correction term of 16 to 25 km. Numerical results reveal that the application of this Moho correction to the gravimetrically determined Moho depths significantly improves the RMS fit of our result with some published global seismic and gravimetric Moho models. We also demonstrate that the isostatic equilibrium at long-to-medium wavelengths (up to degree of about 40) is mainly controlled by a variable Moho depth, while the topographic mass balance at a higher-frequency spectrum is mainly attained by a variable crustal density.

  • 111.
    Baken, Stijn
    et al.
    KU Leuven, Belgium.
    Gustafsson, Jon Petter
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Miljögeokemi och ekoteknik.
    Smolders, Erik
    KU Leuven, Belgium.
    The association between iron and carbon in freshwater colloids2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Iron and carbon are important constituents of natural colloids, which intimately links the fate of these two elements in riverine systems. Iron may strongly affect the binding of trace metals by organic matter, e.g. through competition for binding sites, which highlights the importance of a correct appreciation of the Fe speciation in surface waters. However, the chemistry of Fe and C in natural colloids is complex and depend on many factors including the pH, the Fe:C ratio, and the redox speciation of Fe [1-3]. Two areas with a contrasting Fe chemistry were studied: a lowland area with widespread seepage of iron-rich groundwater, and an upland peat area. Samples of ten oxic, well-mixed streams were subjected to cascade filtration using conventional filtration (1.2 µm, 0.45 µm, 0.1 µm) and cross-flow ultrafiltration (CFF; 5 kDa). The colloidal fraction, here operationally defined as between 0.45 µm and 5 kDa, was isolated by CFF and subsequently freeze-dried. The speciation of colloidal Fe was determined by EXAFS spectroscopy at the Fe K-edge (MAX-lab, Lund, Sweden). In the rivers draining upland peat, Fe and C were predominantly recovered in the fraction between 5 kDa and 0.1 µm. Conversely, in the rivers draining the lowland with extensive seepage of iron-rich groundwater, Fe was most abundant in the > 0.1 µm fraction, whereas C was predominantly present < 0.1 µm. The EXAFS data reveal that colloidal Fe speciation is different in both study areas. It exists as mononuclear Fe complexed by dissolved organic matter, as colloidal hydrous ferric oxides (likely stabilized by adsorbed organic matter), or as a mixture of these. The colloidal Fe concentrations show considerable seasonal variability. Overall, this study contributes to a better understanding of colloidal Fe speciation and of its interaction with organic C.

  • 112. Baken, Stijn
    et al.
    Sjöstedt, Carin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Gustafsson, Jon Petter
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Seuntjens, Piet
    Desmet, Nele
    De Schutter, Jan
    Smolders, Erik
    Characterisation of hydrous ferric oxides derived from iron-rich groundwaters and their contribution to the suspended sediment of streams2013Ingår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 39, s. 59-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When Fe(II) bearing groundwaters surface in streams, particulate authigenic Fe-rich material is produced by oxidation. Such freshly precipitated Fe minerals may be transported as suspended sediment and have a profound impact on the fate of trace metals and nutrients in rivers. The objective of this study was to monitor changes in mineralogy and composition of authigenic material from its source to streams of increasing order. Groundwaters, surface waters, and suspended sediment in streams of different order were sampled in the Kleine Nete catchment (Belgium), a lowland with Fe-rich groundwaters (3.5-53.8 mg Fe/L; pH 6.3-6.9). Fresh authigenic material (>0.45 mu m) was produced by oxidising filtered (<0.45 mu m) groundwater and surface water. This material contained, on average, 44% Fe, and smaller concentrations of C, P, and Ca. Iron EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy showed that the Fe was present as poorly crystalline hydrous ferric oxides with a structure similar to that of ferrihydrite. The Fe concentration in the suspended sediment samples decreased to 36-40% (stream order 2), and further to 18-26% (stream order 4 and 5). Conversely, the concentrations of organic C, Ca, Si, and trace metals increased with increasing stream order, suggesting mixing of authigenic material with suspended sediment from a different source. The Fe speciation in the suspended sediment was similar to that in fresh authigenic material, but more Fe-Fe interactions were observed, i.e. it was increasingly hydrolysed, suggesting ageing reactions. The suspended sediment in the streams of order 4 and 5 is estimated to contain between 31% and 59% of authigenic material, but more data are needed to refine this estimate. The authigenic material is an important sink for P in these streams which may alleviate the eutrophication risk in this catchment.

  • 113. Balic-Zunic, Tonci
    et al.
    Piazolo, Sandra
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Katerinopoulou, Anna
    Schmith, Johan Haagen
    Full analysis of feldspar texture and crystal structure by combining X-ray and electron techniques2013Ingår i: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 98, nr 1, s. 41-52Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Feldspar crystals typically show a range of exsolution and polysynthetic twinning textures that can present problems for their full characterization, but at the same time give important information about their genesis. We present an integrated procedure for the micro-texture analysis, twin law identification plus crystal structure refinement of all components in a feldspar intergrowth. This procedure was applied to perthitic intergrowths in feldspars from two different pegmatites in the Larvik plutonic complex in the southern part of the Oslo region, Norway. It revealed that the two starting high-temperature (HT) feldspars had similar global chemical compositions but underwent significantly different cooling histories, with cooling times probably differing by over an order of magnitude. Powder X-ray diffraction with Rietveld refinement was used for a preliminary identification of the mineral components and concluding quantitative phase analysis. Electron microprobe analysis was used to bracket the chemical compositions of the constituents. Electron backscatter diffraction was used to reveal the texture of the samples, twin laws and spatial distribution and crystallographic orientation of the crystal domains. Single-grain X-ray diffraction recorded by an area detector was applied for a simultaneous integration of reflection intensities for all crystallographic domains with different orientations and severe diffraction overlaps. The crystal structures were refined using the program JANA2006 that allows a simultaneous calculation for structurally different components. Combined results of various methods helped improve accuracy and resolve ambiguities that arise from the application of a single technique. The approach is widely applicable to the study of mineral intergrowths and bridges an existing gap in the routinely accessible data on the structural characteristics of rock constituents.

  • 114. Baresel, Christian
    et al.
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Uncertainty-Accounting Environmental Policy and Management of Water Systems2007Ingår i: Environmental Science & Technology, Vol. 41, nr 10, s. 3653–3659-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Environmental policies for water quality and ecosystem

    management do not commonly require explicit stochastic

    accounts of uncertainty and risk associated with the

    quantification and prediction of waterborne pollutant loads

    and abatement effects. In this study, we formulate and

    investigate a possible environmental policy that does require

    an explicit stochastic uncertainty account. We compare

    both the environmental and economic resource allocation

    performance of such an uncertainty-accounting environmental

    policy with that of deterministic, risk-prone and riskaverse

    environmental policies under a range of different

    hypothetical, yet still possible, scenarios. The comparison

    indicates that a stochastic uncertainty-accounting

    policy may perform better than deterministic policies over

    a range of different scenarios. Even in the absence of

    reliable site-specific data, reported literature values appear

    to be useful for such a stochastic account of uncertainty.

  • 115.
    Barker, Abigail
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Ctr Nat Hazards & Disaster Sci CNDS, Villavagen 16, SE-75236 Uppsala, Sweden.
    Hansteen, Thor H.
    GEOMAR Helmholtz Ctr Ocean Res Kiel, Wischhofstr 1-3, D-24148 Kiel, Germany.
    Nilsson, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Unravelling the Crustal Architecture of Cape Verde from the Seamount Xenolith Record2019Ingår i: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 9, nr 2, artikel-id 90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Cape Verde oceanic plateau hosts 10 islands and 11 seamounts and provides an extensive suite of alkaline lavas and pyroclastic rocks. The volcanic rocks host a range of crustal and mantle xenoliths. These xenoliths provide a spectrum of lithologies available to interact with magma during transport through the lithospheric mantle and crust. We explore the origin and depth of formation of crustal xenoliths to develop a framework of magma-crust interaction and a model for the crustal architecture beneath the Cape Verde oceanic plateau. The host lavas are phononephelinites to phonolites and the crustal xenoliths are mostly mafic plutonic assemblages with one sedimentary xenolith. REE profiles of clinopyroxene in the host lavas are light rare-earth element (LREE) enriched whereas clinopyoxene from the plutonic xenoliths are LREE depleted. Modelling of REE melt compositions indicates the plutonic xenoliths are derived from mid-ocean ridge basalt (MORB)-type ocean crust. Thermobarometry indicates that clinopyroxene in the host lavas formed at depths of 17 to 46 km, whereas those in the xenoliths formed at 5 to 20 km. This places the depth of origin of the plutonic xenoliths in the oceanic crust. Therefore, the xenoliths trace magma-crust interaction to the MORB oceanic crust and overlying sediments located beneath the Cape Verde oceanic plateau.

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  • 116.
    Barker, Abigail
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Holm, Paul Martin
    Unniversity of Copenhagen.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    The role of eclogite in the mantle heterogeneity at Cape Verde2014Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 168, nr 3, s. 1052-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Cape Verde hotspot, like many other Ocean Island Basalt provinces, demonstrates isotopic heterogeneity on a 100–200 km scale. The heterogeneity is represented by the appearance of an EM1-like component at several of the southern islands and with a HIMU-like component present throughout the archipelago. Where the EM1-like component is absent, a local DMM-like component replaces the EM1-like component. Various source lithologies, including peridotite, pyroxenite and eclogite have been suggested to contribute to generation of these heterogeneities; however, attempts to quantify such contributions have been limited. We apply the minor elements in olivine approach (Sobolev et al. in Nature 434:590–597, 2005; Science, doi:10.1126/science.1138113,2007), to determine and quantify the contributions of peridotite, pyroxenite and eclogite melts to the mantle heterogeneity observed at Cape Verde. Cores of olivine phenocrysts of the Cape Verde volcanics have low Mn/FeO and low Ni*FeO/MgO that deviate from the negative trend of the global array. The global array is defined by mixing between peridotite and pyroxenite, whereas the Cape Verde volcanics indicate contribution of an additional eclogite source. Eclogite melts escape reaction with peridotite either by efficient extraction in an area of poor mantle flow or by reaction of eclogite melts with peridotite, whereby an abundance of eclogite can seal off the melt from further reaction. Temporal trends of decreasing Mn/FeO indicate that the supply of eclogite melts is increasing. Modelling suggests the local DMM-like end-member is formed from a relatively peridotite-rich melt, while the EM1-like end-member has a closer affinity to a mixed peridotite–pyroxenite–eclogite melt. Notably the HIMU-like component ranges from pyroxenite–peridotite-rich melt to one with up to 77 % eclogite melt as a function of time, implying that sealing of melt pathways is becoming more effective.

  • 117.
    Barker, Abigail
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Univ Las Palmas, GEOVOL, La Palmas Gran Canaria 35017, Spain.
    Carracedo, Juan Carlos
    Univ Las Palmas, GEOVOL, La Palmas Gran Canaria 35017, Spain.
    Nicholls, Peter A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    The magma plumbing system for the 1971 Teneguía eruption on La Palma, Canary Islands2015Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 170, nr 5-6, artikel-id 54Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The 1971 Teneguía eruption is the most recent volcanic event of the Cumbre Vieja rift zone on La Palma. The eruption produced basanite lavas that host xenoliths, which we investigate to provide insight into the processes of differentiation, assimilation and magma storage beneath La Palma. We compare our results to the older volcanomagmatic systems of the island with the aim to reconstruct the temporal development of the magma plumbing system beneath La Palma.

    The 1971 lavas are clinopyroxene-olivine-phyric basanites that contain augite, sodic-augite and Aluminium augite. Kaersutite cumulate xenoliths host olivine, clinopyroxene including sodic-diopside, and calcic-amphibole, whereas an analysed leucogabbro xenolith hosts plagioclase, sodic-augite-diopside, calcic-amphibole and hauyne. Mineral and mineral-melt thermobarometry indicate that clinopyroxene and plagioclase in the 1971 Teneguía lavas crystallised at 20 to 45 km depth, coinciding with clinopyroxene and calcic-amphibole crystallisation in the kaersutite cumulate xenoliths at 25 to 45 km and clinopyroxene, calcic-amphibole and plagioclase crystallisation in the leucogabbro xenolith at 30 to 50 km.

    Combined mineral chemistry and thermobarometry suggest that the magmas had already crystallised, differentiated and formed multiple crystal populations in the oceanic lithospheric mantle. Notably, the magmas that supplied the 1949 and 1971 events appear to have crystallised deeper than the earlier Cumbre Vieja magmas, which suggests progressive underplating beneath the Cumbre Vieja rift zone. In addition, the lavas and xenoliths of the 1971 event crystallised at a common depth, indicating a reused plumbing system and progressive recycling of Ocean Island plutonic complexes during subsequent magmatic activity. 

  • 118.
    Barnes, Christopher
    et al.
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Jarosław, Majka
    Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Schneider, David
    Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, Canada.
    Walczak, Katarzyna
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Bukała, Michał
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Kośmińska, Karolina
    Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland.
    Tokarski, Tomasz
    Academic Center for Materials and NanotechnologyAGH University of Science and TechnologyKrakówPoland.
    Karlsson, Andreas
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    High-spatial resolution dating of monazite and zircon reveals the timing of subduction–exhumation of the Vaimok Lens in the SeveNappe Complex (Scandinavian Caledonides)2019Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 174, nr 1, artikel-id 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In-situ monazite Th–U–total Pb dating and zircon LA–ICP–MS depth-profiling was applied to metasedimentary rocks from the Vaimok Lens in the Seve Nappe Complex (SNC), Scandinavian Caledonides. Results of monazite Th–U–total Pb dating, coupled with major and trace element mapping of monazite, revealed 603 ± 16 Ma Neoproterozoic cores surrounded byrims that formed at 498 ± 10 Ma. Monazite rim formation was facilitated via dissolution–reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y2O3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. Multiple zircon grains also exhibit rims formedby dissolution–reprecipitation that are defined by enrichment of light rare earth elements, U, Th, P, ± Y, and ± Sr. Rims also have subdued Eu anomalies (Eu/Eu* ≈ 0.6–1.2) with respect to the cores. The age of zircon rim formation was calculated from three metasedimentary rocks: 480 ± 22 Ma; 475 ± 26 Ma; and 479 ± 38 Ma. These results show that both monazite and zircon experienced dissolution–reprecipitation under high-pressure conditions. Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation.

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  • 119.
    Barnes, Christopher
    et al.
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Majka, Jaroslaw
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Schneider, David
    Univ Ottawa, Dept Earth & Environm Sci, Ottawa, ON, Canada.
    Walczak, Katarzyna
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Bukala, Michal
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Kosminska, Karolina
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Tokarski, Tomasz
    AGH Univ Sci & Technol, Acad Ctr Mat & Nanotechnol, Krakow, Poland.
    Karlsson, Andreas
    Swedish Museum Nat Hist, Dept Geosci, Stockholm, Sweden.
    High-spatial resolution dating of monazite and zircon revealsthe timing of subduction-exhumation of the Vaimok Lens in the Seve Nappe Complex (Scandinavian Caledonides)2019Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 174, nr 1, artikel-id 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In-situ monazite Th-U-total Pb dating and zircon LA-ICP-MS depth-profiling was applied to metasedimentary rocks from the Vaimok Lens in the Seve Nappe Complex (SNC), Scandinavian Caledonides. Results of monazite Th-U-total Pb dating, coupled with major and trace element mapping of monazite, revealed 603 +/- 16 Ma Neoproterozoic cores surrounded by rims that formed at 498 +/- 10 Ma. Monazite rim formation was facilitated via dissolution-reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y2O3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. Multiple zircon grains also exhibit rims formed by dissolution-reprecipitation that are defined by enrichment of light rare earth elements, U, Th, P, +/- Y, and +/- Sr. Rims also have subdued Eu anomalies ( Eu/Eu* approximate to 0.6-1.2) with respect to the cores. The age of zircon rim formation was calculated from three metasedimentary rocks: 480 +/- 22 Ma; 475 +/- 26 Ma; and 479 +/- 38 Ma. These results show that both monazite and zircon experienced dissolution-reprecipitation under high-pressure conditions. Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation.

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  • 120.
    Barrientos, Natalia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Arctic Ocean benthic foraminifera preservation and Mg/Ca ratios: Implications for bottom water palaeothermometry2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Reconstructions of Arctic Ocean palaeotemperatures are needed to disentangle natural variability from anthropogenic changes and understand the role of ocean heat transport in forcing or providing feedbacks on Arctic climate change. Despite known complications with calcareous microfossil preservation in Arctic Ocean sediments, calcareous benthic foraminifera can be common in interglacial sequences. However, thus far they have been underutilized in palaeoceanographic studies. This thesis explores the application of the Mg/Ca palaeothermometry proxy for reconstructing bottom water temperatures (BWT) in the Arctic Ocean during the late Quaternary. This method, which is supported by previous empirical studies demonstrating a strong temperature control on trace Mg inclusion into foraminiferal shell calcite, has been applied in many ocean regions and time intervals. Until now its application in the Arctic Ocean has been sparingly explored.

    The results of this doctoral thesis are based on benthic foraminifera retrieved from marine sediment cores covering a wide geographical Arctic Ocean area including both the shallow and vast continental shelves and slopes to the intermediate-to-deep waters of the Lomonosov Ridge and Morris Jesup Rise. These provide the first benthic foraminifera Mg/Ca ratios from the central Arctic Ocean region. In the first study, mechanisms that could affect Mg incorporation in Arctic benthic foraminifera are investigated using oceanographic field data and six 'live' modern Arctic species (Elphidium clavatum, Nonionella labradorica, Cassidulina neoteretis, Oridorsalis tener, Cibicidoides wuellerstorfi and Quinqueloculina arctica). The result is new species-specific Mg/Ca–BWT field calibrations that provide important constraints at the cold end of the BWT spectrum (-2 to 1°C) (Paper I). Using the new Mg/Ca–BWT equation for E. clavatum, a palaeotemperature record was generated for the late Holocene (past ca. 4100 yr) from the western Chukchi Sea. The data showed BWT fluctuations from -2 to 1°C that are interpreted as showing pulses of warmer Pacific water inflow at 500–1000 yr periods, thus revealing multi-centennial variability in heat transport into the Arctic Ocean driven by low latitude forcings (Paper II). Complications with foraminiferal calcite preservation that limit Mg/Ca palaeothermometry in the Arctic were discovered and these are tackled in two additional papers. Anomalously high Mg content in benthic foraminifera from the central Arctic Ocean is linked to diagenetic contamination as a result of the unique oceanographic, sedimentary and geochemical environment (Paper III). Lastly, the dramatic post-recovery dissolution of foraminifera from a Chukchi Shelf sediment core during core storage is investigated and attributed to acidification driven by sulphide oxidation in this organic rich and calcite poor shelf setting (Paper IV).

    The findings of this thesis demonstrate that benthic foraminiferal Mg/Ca-palaeothermometry can be applied in the Arctic Ocean and capture small BWT change (on the order of -2 to 2°C) even at low temperatures. In practice, preservational complexities can be limiting and require special sample handling or analysis due to the high potential for diagenetic contamination in the central Arctic Ocean and rapid post coring calcite dissolution in the seasonally productive shelf seas. This Ph.D. project is a component of the multidisciplinary SWERUS-C3 (Swedish-Russian-US Arctic Ocean Climate-Cryosphere- Carbon Interactions) project that included an expedition with Swedish icebreaker Oden to the East Siberian Arctic Ocean.

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  • 121.
    Barrientos, Natalia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Coxall, Helen
    Lear, Caroline
    O'Regan, Matt
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Mörth, Carl-Magnus
    Jakobsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Mg/Ca ratios in late Quaternary benthic foraminifera from the central Arctic OceanManuskript (preprint) (Övrigt vetenskapligt)
  • 122.
    Barrientos, Natalia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Coxall, Helen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Lear, Caroline
    Pearce, Christof
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Muschitiello, Francesco
    O'Regan, Matt
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Stranne, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    de Boer, Agatha
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Cronin, Thomas
    Semiletov, Igor
    Jakobsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Late Holocene variability in Arctic Ocean Pacific Water inflow through the Bering StraitManuskript (preprint) (Övrigt vetenskapligt)
  • 123.
    Barrientos, Natalia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Jakobsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Pearce, Christof
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Miller, Clint
    O'Regan, Matt
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Brüchert, Volker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Johansson, Carina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Coxall, Helen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Post-recovery dissolution of calcareous microfossils in sediments from a highly productive Arctic marine environmentManuskript (preprint) (Övrigt vetenskapligt)
  • 124.
    Barrientos, Natalia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Lear, Caroline H.
    Jakobsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Stranne, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    O'Regan, Matt
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Cronin, Thomas M.
    Gukov, Aleksandr Y.
    Coxall, Helen K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Arctic Ocean benthic foraminifera Mg/Ca ratios and global Mg/Ca-temperature calibrations: New constraints at low temperatures2018Ingår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 236, s. 240-259Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We explore the use of Mg/Ca ratios in six Arctic Ocean benthic foraminifera species as bottom water palaeothermometers and expand published Mg/Ca-temperature calibrations to the coldest bottom temperatures (<1 °C). Foraminifera were analyzed in surface sediments at 27 sites in the Chukchi Sea, East Siberian Sea, Laptev Sea, Lomonosov Ridge and Petermann Fjord. The sites span water depths of 52–1157 m and bottom water temperatures (BWT) of −1.8 to +0.9 °C. Benthic foraminifera were alive at time of collection, determined from Rose Bengal (RB) staining. Three infaunal and three epifaunal species were abundant enough for Mg/Ca analysis. As predicted by theory and empirical evidence, cold water Arctic Ocean benthic species produce low Mg/Ca ratios, the exception being the porcelaneous species Quinqueloculina arctica. Our new data provide important constraints at the cold end (<1 °C) when added to existing global datasets. The refined calibrations based on the new and published global data appear best supported for the infaunal species Nonionella labradorica (Mg/Ca = 1.325 ± 0.01 × e^(0.065 ± 0.01 × BWT), r2 = 0.9), Cassidulina neoteretis (Mg/Ca = 1.009 ± 0.02 × e^(0.042 ± 0.01 × BWT), r2 = 0.6) and Elphidium clavatum (Mg/Ca = 0.816 ± 0.06 + 0.125 ± 0.05 × BWT, r2 = 0.4). The latter is based on the new Arctic data only. This suggests that Arctic Ocean infaunal taxa are suitable for capturing at least relative and probably semi-quantitative past changes in BWT. Arctic Oridorsalis tener Mg/Ca data are combined with existing O. umbonatus Mg/Ca data from well saturated core-tops from other regions to produce a temperature calibration with minimal influence of bottom water carbonate saturation state (Mg/Ca = 1.317 ± 0.03 × e^(0.102 ± 0.01 BWT), r2 = 0.7). The same approach for Cibicidoides wuellerstorfi yields Mg/Ca = 1.043 ± 0.03 × e^(0.118 ± 0.1 BWT), r2 = 0.4. Mg/Ca ratios of the porcelaneous epifaunal species Q. arctica show a clear positive relationship between Mg/Ca and Δ[CO32−] indicating that this species is not suitable for Mg/Ca-palaeothermometry at low temperatures, but may be useful in reconstructing carbonate system parameters through time.

  • 125. Barão, Lúcia
    et al.
    Vandevenne, Floor
    Clymans, Wim
    Frings, Patrick J
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Ragueneau, Olivier
    Meire, Patrick
    Conley, Daniel J.
    Struyf, Eric
    Alkaline-extractable silicon from land to ocean: A challenge for biogenic silicon determination2015Ingår i: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, s. n/a-n/aArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    The biogeochemical cycling of silicon (Si) along the land-to-ocean continuum is studied by a variety of research fields and for a variety of scientific reasons. However, there is an increasing need to refine the methodology and the underlying assumptions used to determine biogenic silica (BSi) concentrations. Recent evidence suggests that contributions of nonbiogenic sources of Si dissolving during alkaline extractions, not corrected by standard silicate mineral dissolution correction protocols, can be substantial. The ratio between dissolved Si and aluminum (Al) monitored continuously during the alkaline extraction can be used to infer the origin of the Si fractions present. In this study, we applied both a continuous analysis method (0.5 M NaOH) and a traditional 0.1 M Na2CO3 extraction to a wide array of samples: (1) terrestrial vegetation, (2) soils from forest, cropland and pasture, (3) lake sediments, (4) suspended particulate matter and sediments from rivers, (5) sediments from estuaries and salt marshes and (6) ocean sediments. Our results indicate that the 0.1 M Na2CO3 extraction protocol can overestimate the BSi content, by simultaneously dissolving Si fractions of nonbiogenic origin that may represent up to 100% of the Si traditionally considered as biogenic, hampering interpretation especially in some deeper soil horizons, rivers and coastal oceanic sediments. Moreover, although the term amorphous Si was coined to reflect a growing awareness of nonbiogenic phases we show it is actually inappropriate in samples where silicate minerals may account for a large part of the extracted Si even after linear mineral correction.

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  • 126.
    Basapuram, Laxmi Gayatri Devi
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring.
    Lake Victoria - Carbon, Nitrogen, Phosphorus and Stable Isotope (δ13C) comparison between lake and catchment sediments2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Lake Victoria situated in East Africa faces an acute problem with eutrophication. Many reasons like agricultural production, industrialization, anthropogenic processes, the introduction of species, and economic activities have caused a stress to the overall well-being of the lake. Excess carbon, nitrogen, and phosphorus drive an increase in productivity which affects eutrophication. Previous studies on sediments and nutrient concentrations in the lake have concluded that nutrient concentrations increase due to release from the catchment. This study focuses on catchment sediments collected from four different sites and compares the results with sediments from two additional sites in the lake. The sediment core from Siaya indicates the highest concentrations of TOC (180 g/kg), TN (13 g/kg) and TP (17000μg/L). It is a rural site and poor agricultural practices such as the burn and slash, use of too many fertilizers, clearance of land, atmospheric deposition and precipitation increase elemental concentrations in the sediments compared to the more urban sites. In the lake sediments, the BILL core had higher concentrations of TP (430g/kg) and TN (16 g/kg) compared to the other site (LV-95) which is located far away from the margins of the lake. This core, however, had high TOC levels (180g/kg). The increase of nutrient levels in lake sediments is thought to be due to non-point sources from the catchment. Analyses of stable carbon isotope were used to infer the different organic matter source in the sediments. Based on the range of values for δ13C vs. C/N it is inferred that aquatic algal production and C4 vascular plants are the dominant sources for the organic matter input. The chemical characterization of catchment and lake sediments provides a qualitative link to nutrient influx and eutrophication in the lake.

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  • 127.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Svensson, Teresia
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Karlsson, Susanne
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Sandén, Per
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Öberg, Gunilla
    IRES, UBC, Canada.
    Temperature sensitivity indicates enzyme controlled chlorination of soil organic matter2009Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, nr 10, s. 3569-3573Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Old assumptions that chloride is inert and that most chlorinated organic matter in soils is anthropogenic have been challenged by findings of naturally formed organochlorines. Such natural chlorination has been recognized for several decades, but there are still very few measurements of chlorination rates or estimates of the quantitative importance of terrestrial chlorine transformations. While much is known about the formation of specific compounds, bulk chlorination remains poorly understood in terms of mechanisms and effects of environmental factors. We quantified bulk chlorination rates in coniferous forest soil using 36Cl-chloride in tracer experiments at different temperatures and with and without molecular oxygen (O2). Chlorination was enhanced by the presence of O2 and had a temperature optimum at 20 °C. Minimum rates were found at high temperatures (50 °C) or under anoxic conditions. The results indicate (1) that most of the chlorination between 4 and 40 °C was biotic and driven by O2 dependent enzymes, and (2) that there is also slower background chlorination occurring under anoxic conditions at 20 °C and under oxic conditions at 50 °C. Hence, while oxic and biotic chlorination clearly dominated, chlorination by other processes including possible abiotic reactions was also detected.

  • 128.
    Bastviken, David
    et al.
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Svensson, Teresia
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Sandén, Per
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Kylin, Henrik
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Chlorine cycling and fates of 36Cl in terrestrial environments2013Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Klor-36 (36Cl), en radioisotop med en halveringstid på 301 000 år, förekommer i vissa typer av radioaktivt avfall. För att kunna förutse vad som händer om 36Cl når markytan är det viktigt att veta hur klor kan omvandlas och transporteras i olika ekosystem. Denna rapport syftar till att sammanfatta kunskapsläget om klor i naturmiljöer med fokus på landmiljöer.

    Synen på klor i naturen är under omfattande förändring till följd av de senaste decenniernas forskning. Det står nu helt klart att klorid (Cl) som tidigare betraktats som icke-reaktiv och totalt dominerande, istället är i hög grad reaktiv och inte alltid utgör den dominerande klorformen.

    Utifrån de studier som presenteras i rapporten är det tydligt att:

    • Det sker en omfattande naturlig klorering av organiskt material i många miljöer och inte minst i ytliga marklager.
    • Mängden organiskt bunden klor (Clorg) är i många miljöer betydligt högre än mängden Cl. Därmed dominerar Clorg ofta det totala klorförrådet i exempelvis mark.
    • Detta har stor inverkan på transporten av klor eftersom Clorg till stor del finns i partikulärt organiskt material medan Cl är mycket vattenlösligt. Cl som når ytliga marklager är t ex inte lämpligt som spårämne för markvattenflöden såsom tidigare antagits. Cl kommer till stor del att bindas in till Clorg -förrådet och därmed förlänga uppehållstiden i ekosystemen.
    • Cl dominerar både importen och exporten från terrestra ekosystem medan Clorg kan dominera stationära klorförråd i systemen.
    • Framtida mätningar med syfte att klargöra kloromsättning och klorflöden behöver beakta Cl och Clorg separat.

    Därtill finns ett antal troligen viktiga indikationer som skulle behöva bekräftas av ytterligare studier. Dessa inkluderar att:

    • Det sker ett snabbt och omfattande upptag av Cl av organismer och klor tycks ackumuleras i grön växtbiomassa. En stor andel av den totala klormängden i avrinningsområden (upp till 60% i en studie) har påträffats i den terrester biomassa.
    • Avgång av flyktiga klorerade kolväten kan vara en stor okänd exportväg för klor från ekosystem.
    • En del Clorg verkar vara betydligt mer motståndskraftigt mot nedbrytning än det genomsnittliga organiska materialet. Detta kan leda till att Clorg bevaras selektivt i mark och därmed också mindre tillgängligt för mikroorganismer.
    • Det sker en klorering av organiskt material i levande biomassa och klor kan ansamlas som klorerade fettsyror i organismer.

    Övriga aspekter på klor i naturen är till stora delar okända. Centrala okända aspekter inkluderar:

    • Hur klor-förråden utvecklas över tid. Detta är centralt för att förstå förändringar över tid och reglering i förråden.
    • Reglering av klorerings-, deklorerings- och transportprocesser, samt hur dessa påverkas av olika miljövariabler och miljöförhållanden.
    • Den ekologiska förklaringen till varför så många organismer utför klorering av organiskt material.
    • Omsättning av klor i akvatiska system. Här saknas separata data gällande Cl– och Clorg både i sediment och i vattenfasen.

     

    Rapporten fokuserar framför allt på terrestra aspekter av klorcykeln och innehåller också information om vanliga metoder för mätning av olika klorföreningar.

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    Chlorine cycling and fates of 36Cl in terrestrial environments
  • 129.
    Bastviken, David
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi. Geokemi.
    Thomsen, Frida
    Karlsson, Susanne
    Svensson, Teresia
    Sanden, Per
    Shaw, George
    Matucha, Miroslav
    Öberg, Gunilla
    Chloride retention in forest soil by microbial uptake and by natural chlorination of organic matter2007Ingår i: Geochimica Cosmochimica Acta, ISSN 0016-7037, Vol. 71, nr 13, s. 3182-3192Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inorganic chlorine (i.e. chloride; Cl-in) is generally considered inert in soil and is often used as a tracer of soil and ground water movements. However, recent studies indicate that substantial retention or release of Cl-in can occur in soil, but the rates and processes responsible under different environmental conditions are largely unknown. We performed Cl-36 tracer experiments which indicated that short-term microbial uptake and release of Cl-in, in combination with more long-term natural formation of chlorinated organic matter (Cl-org), caused Cl-in imbalances in coniferous forest soil. Extensive microbial uptake and release of Cl-in occurred over short time scales, and were probably associated with changes in environmental conditions. Up to 24% of the initially available Clin within pore water was retained by microbial uptake within a week in our experiments, but most of this Cl-in, was released to the pore water again within a month, probably associated with decreasing microbial populations. The natural formation of Clorg resulted in a net immobilization of 4% of the initial pore water Clin over four months. If this rate is representative for the area where soil was collected, Clorg formation would correspond to a conversion of 25% of the yearly wet deposition of Cl-in. The study illustrates the potential of two Clin retaining processes in addition to those previously addressed elsewhere (e.g. uptake of chloride by vegetation). Hence, several processes operating at different time scales and with different regulation mechanisms can cause Clin imbalances in soil. Altogether, the results of the present study (1) provide evidence that Cl-in cannot be assumed to be inert in soil, (2) show that microbial exchange can regulate pore water Cl-in, concentrations and (3) confirm the controversial idea of substantial natural chlorination of soil organic matter.

  • 130. Bauer, Friederike U.
    et al.
    Glasmacher, Ulrich A.
    Ring, Uwe
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Karl, Markus
    Schumann, Andreas
    Nagudi, Betty
    Tracing the exhumation history of the Rwenzori Mountains, Albertine Rift, Uganda, using low-temperature thermochronology2013Ingår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 599, s. 8-28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Rwenzori Mtns form a striking feature within the Albertine Rift of the East African Rift System. They are made up of a dissected Precambrian metamorphic basement block reaching heights of more than 5 km. Applying low-temperature therrnochronology a complex exhumation history becomes evident, where rock and surface uplift can be traced from Palaeozoic to Neogene times. Fission-track and (U-Th-Sm)/He cooling ages and derived cooling histories allow distinguishing different blocks in the Rwenzori Mtns. In the central part a northern and a southern block are separated by a putative NW-SE trending fault; with the northern block showing distinctly younger apatite fission-track ages (similar to 130 Ma) than the southern block (similar to 300 Ma). Cooling ages in both blocks do not vary significantly with elevation, despite considerable differences in elevation. Thermal history modelling reflects protracted cooling histories. Modelled t-T paths show decoupled blocks that were relocated separately along distinct fault planes, which reactivated pre-existing structures, inherited from Palaeozoic folding and thrusting. Initial cooling affected the Rwenzori area in Silurian to Devonian times, followed by Mesozoic and Cainozoic cooling events. Pre-Neogene evolution seems to be triggered by tectonic processes like the opening of the Indian Ocean and the south Atlantic. From thermochronological data the formation of a Mesozoic Albertine high is conceivable. In Cainozoic times the area was affected by rifting, resulting in differentiated surface uplift. Along the western flank of the Rwenzori Mtns, surface uplift was more pronounced. This is also reflected in their recent topography, formed by accelerated rock uplift in the near past (Pliocene to Pleistocene). Erosion could not compensate for this most recent uplift, resulting in apatite He ages of Oligocene to Miocene age or even older.

  • 131.
    Bauer, Susanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Dissolved and suspended transport of tungsten, molybdenum, and vanadium in natural waters2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Some transition metals and metalloids occur primarily as oxyanions in natural waters including antimony, arsenic, chromium, molybdenum, tungsten and vanadium. These oxyanions can pass through cell walls along the same pathways as phosphate or sulfate. Some of these oxyanions are essential for life, but in high concentrations they become all toxic. Recent studies showed that tungsten probably is posing a risk to human health. The growing use of tungsten in industrial and military applications probably leads to an increased release of tungsten to the environment. It has also been shown that the use of studded winter tires in Sweden significantly increases tungsten concentrations in road runoff. Still, little is known about the geochemical cycling of tungsten in the environment as it has been considered to be a more or less inert element. Only a few studies deal with tungsten in natural waters. For example, for the Baltic Sea no concentration data have been published before this work and data on the suspended particulate fraction of tungsten in terrestrial and marine waters are scarce.

    This thesis contributes to the understanding of the distribution and behavior of tungsten, molybdenum and vanadium in natural waters under changing redox conditions, varying pH and different seasons. Particular attention is paid to the suspended particulate fraction of these elements, which is often neglected even though it can be of great importance. Tungsten, molybdenum and vanadium primarily occur as oxyanions in solution and can be adsorbed to particles, which determines their mobility.

    Molybdenum usually is very mobile, while vanadium has a tendency to adsorb to iron oxyhydroxides or to form organic complexes. Tungsten has many similarities with molybdenum, but it seems to be less mobile than molybdenum in natural waters.

    Tungsten and molybdenum have a similar abundance in the upper continental crust, but in the ocean molybdenum is almost 2000 times more abundant. A strong fractionation of these two elements occurs from land to the ocean, indicating a removal of W during mixing of river and seawater.

    This study comprises data from small streams in the boreal landscape of northern Sweden, major rivers (Kalix River and Råne River) and their estuaries discharging into the Baltic Sea. In the marine environment, sediment cores from the Bothnian Bay and water profiles at the stratified Landsort Deep have been studied. Apart from the spatial distribution, the temporal behavior of tungsten, molybdenum, and vanadium in was investigated. In the boreal environment snowmelt is playing a major role for their transport.

    All water samples were filtered through 0.22 pore size filters to define dissolved and suspended particulate fractions. The particulate fraction of all studied elements increases from streams to rivers. Especially during spring flood, particle transport becomes even more important. About 80% tungsten, 70% vanadium and 30% molybdenum occur in the particulate fraction during this event. During estuarine mixing, tungsten and molybdenum are released from the particles again. However, vanadium seems to be removed in both fractions, probably due to a different adsorption behavior. In the dissolved fraction molybdenum increased and vanadium decreased from land to the sea, while tungsten showed small variation in all surface waters.

    All three elements are affected by manganese redox cycling at the transition zone between oxic and sulfidic water at the Landsort Deep in the Baltic Sea. Adsorption of these oxyanions to the freshly formed manganese oxides plays an important role for their transport to the sulfidic zone. In contrast to molybdenum, dissolved tungsten is accumulated in the sulfidic environment. There is no effective removal mechanisms like for molybdenum, which is adsorbed to sulfides. Also in the sediment, redox cycling of manganese and iron affects the distribution of tungsten and molybdenum close to the water-sediment interface.

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  • 132.
    Bauer, Susanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Role of manganese redox cycling for trace metals in the Baltic Sea2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Redox zones are defined by steep gradients of changing concentrations and changing redox potential. They form a transition zone between oxic and anoxic/sulfidic conditions, where nitrate, manganese and iron reduction occurs. These redox zones can be situated in the sediment as well as in the water column. In the Baltic Sea both types are found. In the Bothnian Bay, the northernmost part of the Baltic Sea, the water column is well oxygenated and the redox zone lies within the uppermost sediment (approximately 2 cm in extend). In the Baltic Proper several of the deeper basins are stratified with the redox zone hanging between 75 and 100 m in the water column reaching up to 20 m.The redox-sensitive trace metal manganese can be both electron donor and acceptor in redox zones depending on its oxidation state. Manganese is transformed between the dissolved Mn(II),(III) and the particulate Mn(III/IV). Hence, Mn plays an important role in trace metal cycling across redox zones in natural environments. Manganese particles serve as a carrier for adsorbed trace metals towards the anoxic/sulfidic zone in the water column and as a barrier in the sediment, which restricts dissolved trace elements from diffusing to the oxic zone.In this study water samples (dissolved fraction, <0.22 μm, and particulate fraction, >0.22 μm) from the pelagic redox zone in Landsort Deep, Baltic proper were analyzed. Furthermore, a sedimentary redox zone from the Bothnian Bay has been investigated. A Mn particle peak is detected within the pelagic redox zone at Landsort Deep. A strong correlation between these Mn particles and several oxyanions as Mo, V and W is observed. The oxyanions are adsorbed onto the freshly formed Mn particles in the redox zone, settle with the particles and are released when Mn particles are reduced to Mn2+ and dissolve. This mechanism can act as a pump for trace metals to the sulfidic zone, where the trace metals either can be enriched in the dissolved fraction or form sulfid particles.In the sediment Mn redox cycling leads to enrichment of trace metals in the top layer. The formation of a barrier of Mn-Fe hydroxides restricts trace metal exchange between bottom water and sediment. Freshening of the Bothnian Bay basin has led to an increased sequestering of trace metals in the uppermost sediment. Trace metal proxies show that primary production in the Bothnian Bay has decreased starting approximately 2500 years BP. That led to a shift in the deposition of sulfide forming elements mainly due to the lower input of reactive organic carbon from plankton and to the recent enrichment of elements together with Mn-Fe hydroxides.

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  • 133.
    Bauer, Susanne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Blomqvist, Sven
    Department of Ecology, Environment and Plant Sciences, Stockholm University.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Distribution of dissolved and suspended particulate molybdenum, vanadium, and tungsten in the Baltic Sea2017Ingår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 196, s. 135-147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In natural waters, dissolved oxyanions often dominate over the particle-bound element fraction. Still, the scavenging of oxyanions by suspended particles might contribute significantly to their dynamic cycling and distribution. To investigate how oxyanions are affected by manganese (Mn) redox cycling, detailed depth profiles across the pelagic redox zone at the Landsort Deep, Baltic Sea, were collected for molybdenum (Mo), vanadium (V), and tungsten (W), for both dissolved (<0.22 µm) and suspended particulate (>0.22 µm) fractions.

    All three oxyanions show a non-conservative behavior in the stratified Landsort Deep. Strong linear correlations with Mn in the particulate fraction in the redox zone of the Landsort Deep suggest that Mn redox cycling influences their distribution. In the dissolved fraction, Mo, V, and W exhibited rather different behavior. Molybdenum was depleted below the redox zone, while V was depleted only within the redox zone. Tungsten concentrations increased within the redox zone, being three times higher in the sulfidic zone than in the surface water. Unlike Mo, W shows no tendency for adsorption or co-precipitation under the prevailing weak sulfidic conditions in the deep water of the Landsort Deep and is, therefore, not exported to the underlying sediment.

    The Landsort Deep data were compared with data from the northern Baltic Sea (Bothnian Bay, Kalix River and Råne River estuaries), where particulate iron (Fe) occurs in high abundance. The particulate fractions of Mo, V, and W decreased during mixing in these estuaries. Vanadium showed the most drastic reduction, with a decrease in dissolved and particulate fractions, indicating that different processes influence the distribution of these oxyanions.

  • 134.
    Bauer, Susanne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Conrad, Sarah
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Geochemistry of tungsten and molybdenum during fresh water transport and estuarine mixingManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The geochemistry of tungsten (W) in the environment is still poorly studied. Tungsten is little mobile and usually occurs in low concentrations in natural waters. For this study, we analyzed W together with molybdenum (Mo) in the dissolved and particulate fraction of two boreal estuaries during different seasons. Additionally, we sampled first-order streams, draining different landscape types, and the receiving northern Baltic Sea. Furthermore, surface sediment from the estuaries was analyzed to get a comprehensive overview of the distribution of W and Mo in a boreal environment.

    Both elements showed different distribution patterns during different seasons. While they decreased in dissolved concentrations during spring discharge, their concentrations were elevated in winter and exhibited non-conservative behavior along the salinity gradient in the estuaries. In the particulate fraction, we found an opposing behavior for Mo and W, with higher particulate W and lower particulate Mo during spring discharge.

    Molybdenum and W underwent fractionation from land to sea, indicating different mobility for these oxyanions. The Mo/W ratio in the dissolved fraction was mainly determined by the Mo concentration as the W concentration varied only in a narrow range from first-order streams to the Bothnian Bay. In the particulate fraction, the Mo/W ratio appeared to be affected by scavenging processes and showed only small variations. 

  • 135.
    Bauer, Susanne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Conrad, Sarah
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Geochemistry of tungsten and molybdenum during freshwater transport and estuarine mixing2018Ingår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 93, s. 36-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The geochemistry of tungsten (W) in the environment is poorly studied. Tungsten usually occurs in low concentrations in natural waters and is not very mobile. For this study, we analyzed W together with molybdenum (Mo) in the dissolved and particulate fractions of two boreal estuaries during different seasons. Additionally, we sampled first-order streams that drain different landscape types and the receiving northern Baltic Sea. Furthermore, surface sediment from the estuaries was analyzed to obtain a comprehensive overview of the distribution of W and Mo in a boreal environment.

    Both elements showed different distribution patterns during different seasons. While they decreased in the dissolved fraction during spring discharge, in winter, their concentrations were elevated. Molybdenum exhibited non-conservative behavior along the salinity gradient in winter, which was probably caused by its release from underlying sediments. In the particulate fraction, we found opposite behaviors for Mo and W, with higher particulate W and lower particulate Mo during spring discharge.

    Molybdenum and W underwent fractionation from land to sea, indicating the different mobilities of these oxyanions. The Mo/W ratio in the dissolved fraction was mainly determined by the Mo concentration, as the W concentration varied only in a narrow range from first-order streams to the Bothnian Bay. In the particulate fraction, the Mo/W ratio appeared to be affected by scavenging processes and showed only small variations.

  • 136.
    Bauer, Susanne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Conrad, Sarah
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Seasonal behavior of molybdenum, vanadium, and tungsten in boreal riversManuskript (preprint) (Övrigt vetenskapligt)
  • 137.
    Bauer, Susanne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Conrad, Sarah
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The geochemistry of tungsten in the Baltic Sea2015Konferensbidrag (Övrigt vetenskapligt)
  • 138.
    Bauer, Susanne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Role of Mn for cycling of oxyanions (Mo, V and W) across the pelagic redox zone, Landsort Deep2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The Landsort Deep in the Baltic Sea is a stratified basin with a pelagic redox zone separating the oxic water from the sulphidic water below. In this zone redox cycling of Mn plays an important role for the distribution of trace elements. Freshly formed Mn oxide acts as carrier for trace elements across the redox zone. In the underlying sulphidic zone the adsorbed trace elements are released when Mn is reduced and the Mn particles dissolve. Mn oxide has a negative surface charge at seawater pH conditions. Oxyanions would most likely adsorb on Fe oxides instead of Mn oxide due to the surface charge. The particulate Fe concentration in the redox zone of the Landsort Deep is 10-40 times lower than the concentration of particulate Mn. Therefore the Landsort Deep is an excellent place to study the role of Mn for cycling of oxyanions. This study shows uptake of Mo, V and W on Mn particles in the redox zone. Insights from this study may also be applicable for other oxyanion forming elements as P. The Landsort Deep in the Baltic Sea was sampled over a two-year period. Detailed profiles for the dissolved (<0.22 m) and particulate (>0.22 m) fraction were taken across the pelagic redox zone. While the pattern of dissolved Mn is constant during the sampling period maxima for particulate Mn vary in concentration and depth. Throughout the sampling period Mo, V and W are following Mn in the particulate fraction within the redox zone.

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  • 139.
    Bauer, Susanne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Älvtransporterade spårmetaller till Bottenviken: Genomgång av monitoringdata2012Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Data visar att det är svårt att karakterisera och ta fram en ”typ-älv” för spårmetalltransportentill Bottenviken. Det är stora skillnader i transporten av spårmetaller mellan kustnära vattendrag,som dränerar sediment som tidigare avsatts i Bottenviken, skogsälvar och fjällälvar. Dessutom ärskillnaderna stora mellan älvar av samma typ. Trots att Kalixälv och Torneälv dränerar samma typav berggrund och lösa avlagringar är kemin olika för flera spårmetaller. Skillnaderna är i grundenberoende på vittringsförhållanden i dräneringsområdet och vattenföringen, men späds på av analyssvårigheteroch avsaknaden av filtrerade prov.I stort sett visar järn, krom, aluminium och totalt organiskt kol liknade mönster, även om de iblandinte är korrelerade i varje älv. Zink, kadmium, kobolt och nickel är korrelerade till mangan, meni flera älvar är inte sambandet uppenbart. Arsenik är linjärt korrelerat till järn söder om Piteälven.Halterna av järn är låga i utbyggda älvar, vilket indikerar att järntransporten minskar när en älvbyggs ut. Zinkvärdena i monitoringdata verkar vara påverkade av kontamination. De flesta kadmiumvärdenligger nära detektionsgränsen och överlag är kadmiumhalterna inte tillförlitliga.Övervakningsprogrammet bygger på ofiltrerade syrasatta vattenprov. Problemet med sådana provär att analysvärdena ”hoppar”. Syrasättningen löser inte upp bergartsfragment men löser järnmanganoxidhydroxidpartiklar.Partiklar påverkar med andra ord analysen på ett oregelbundet sätteftersom mängden, och typen a partiklar, varierar kraftigt speciellt vid höga flöden.Proven bör filtreras i fält, enklast genom sprutfiltrering. Filtren kan sparas för analys eller baralagras. Oberoende om filtren analyseras eller inte blir den lösta fraktionen bättre definierad än utanfiltrering. Filtrering förändrar inte nämnvärt provtagningskostnaden och analyskostnaden blir densamma (utan filteranalys). Filtrering bör införas omgående. För att kunna jämföra med tidigare årbör både ofiltrerad och filtrerad fas analyseras under ett eller två år.I vissa system bör även den partikulära fasen bestämmas. Detta är speciellt viktigt för att förståförändringar i järn och mangantransporten, eftersom dessa grundämnen styr flera spårmetaller ochfosfor. Brunifieringen av svenska vattendrag är tydlig i flera större och mindre vattendrag. Brunifieringenberor på förhöjda halter av bla. järn och mangan. För att förstå orsakerna till brunifieringmåste både filtrerade prov och partiklar analyseras.Markanvändning och dess betydelse för transporten av järn och mangan är en viktig forskningsfråga.Dels för att det finns gränsvärden uppsatta för säker mänsklig konsumtion, dels för attdessa grundämnen styr biotillgängligheten av fosfor i Östersjön, via en serie av komplicerade biogeokemiskaprocesser. Detaljerade kunskaper, på molekylnivå, om järn-mangan oxidhydroxideroch deras biogeokemi är viktig.Eftersom det är järn-mangan oxidhydroxider som till stor del reglerar utbytet mellan vatten ochsediment blir tillgången av dessa grundämnen central. Källorna för både järn och mangan är påland. Hanteringen av markfrågor kan med andra ord direkt påverka tillflödet av järn och mangan.Kopplingen mellan marktyp-markanvändning och utflödet av järn och mangan är idag litestuderat. Fosfortransporten i sötvatteninflödet är också starkt korrelerad till järnoxidhydroxider.Biotillgängligheten av den tillförda fosforn är lite studerat. Nya data antyder att fosforn inte ärdirekt biotillgänglig. Detta kan bero på ett komplext samspel mellan fosfor-järn-fotoreduktion, enkoppling som inte studerats i Östersjön.2Höga halter fosfor sitter bundet i ytsediment i Bottniska viken. En sänkning av redoxnivån skullefrigöra fosforn och systemet skulle snabbt bli eutroft. Tröskelvärdet för hur mycket näringsämnensom kan tillföras utan att förändra syreförhållandena är okänt. Bottenhavet och Bottenvikenär idag viktiga sänkor för fosfor. Hur stabila dessa sänkor är för miljöförändringar blir därför enviktig fråga. Eftersom Bottenhavet i stort sett saknar Mn-barriären så är denna bassäng troligenkänsligare för förändringar jämfört med Bottenviken.Kadmium visar en stigande trend i sedimentdata från Bottenviken. Inga andra metaller, förutombly, visar en sådan klar förändring. Orsaken till förändringen kan bero på landhöjningen (exponeringav sulfidleror på land) och oligotrofieringen av Bottenviken, men mekanismen är inte klarlagdoch bör studeras i detalj.

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  • 140.
    Bax, Gerhard
    et al.
    Stockholms Universitet.
    Lundén, B.
    Stockholms Universitet.
    Wester, K.
    Stockholms Universitet.
    Romer, Rolf L.
    Luleå tekniska universitet.
    Remote sensing techniques as mineral exploration tools in the Scandinavian Caledonides and their Fennoscandian foreland1991Ingår i: IGARSS 91: remote sensing: global monitoring for earth managementt : Espoo, Finland, June 3-6, 1991, New York: IEEE Communications Society, 1991, s. 2061-2064Konferensbidrag (Refereegranskat)
  • 141. Baxter, Douglas
    et al.
    Faarinen, Mikko
    ALS Scandinavia AB.
    Österlund, Helene
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Rodushkin, Ilya
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Christensen, Morten
    ALS Scandinavia AB, Täby.
    Serum/plasma methylmercury determination by isotope dilution gas chromatography: inductively coupled plasma mass spectrometry2011Ingår i: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 701, nr 2, s. 134-138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for the determination of methylmercury in plasma and serum samples was developed. The method uses isotope dilution with 198Hg-labelled methylmercury, extraction into dichloromethane, back-extraction into water, aqueous-phase ethylation, purge and trap collection, thermal desorption, separation by gas chromatography, and mercury isotope specific detection by inductively coupled plasma mass spectrometry. By spiking 2 mL sample with 1.2 ng tracer, measurements in a concentration interval of (0.007–2.9) μg L−1 could be performed with uncertainty amplification factors <2. A limit of quantification of 0.03 μg L−1 was estimated at 10 times the standard deviation of concentrations measured in preparation blanks. Within- and between-run relative standard deviations were <10% at added concentration levels of 0.14 μg L−1, 0.35 μg L−1 and 2.8 μg L−1, with recoveries in the range 82% to 110%. Application of the method to 50 plasma/serum samples yielded a median (mean; range) concentration of methylmercury of 0.081 (0.091; <0.03–0.19) μg L−1. This is the first time methylmercury has been directly measured in this kind of specimen, and is therefore the first estimate of a reference range.

  • 142. Baxter, Douglas
    et al.
    Rodushkin, Ilia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Engström, Emma
    Malinovskiy, Dmitry
    Revised exponential model for mass bias correction using an internal standard for isotope abundance ratio measurements by multi-collector inductively coupled plasma mass spectrometry2006Ingår i: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 21, nr 4, s. 427-430Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An internal standard (IS) can be used to account for moderate, matrix-related shifts in mass bias using multi-collector inductively coupled plasma mass spectrometry through the empirical, linear relationship between measured isotope abundance ratios for different elements in ln-ln space. Unfortunately, erroneous mass bias corrected isotope abundance ratios may be returned by the model, requiring artificial adjustment of the true isotope abundance ratio of the IS. Although inadequate correction for peak tailing has been convincingly used to explain this problem, our analysis of the literature describing the development of the mass bias correction model using an IS reveals the presence of a source of systematic error. The origin of this error is purely mathematical and is eliminated in the revised model presented, in which mass bias corrected isotope abundance ratios are independent of the isotopic composition of the IS. An expression for computing the total combined uncertainty in the corrected ratio, incorporating contributions from the linear model, the isotopic reference material, and measurements of analyte element and IS in the sample, is also derived.

  • 143. Baxter, Douglas
    et al.
    Rodushkin, Ilya
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Engström, Emma
    Klockare, Dennis
    ALS Analytica AB, Luleå.
    Waara, Hans
    ALS Analytica AB, Luleå.
    Methylmercury measurement in whole blood by isotope-dilution GC-ICPMS with 2 sample preparation methods2007Ingår i: Clinical Chemistry, ISSN 0009-9147, E-ISSN 1530-8561, Vol. 53, nr 1, s. 111-116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Despite its known toxicity, methylmercury is rarely measured directly in clinical studies; instead, conclusions are based on total mercury measurements. We have developed isotope-dilution-based methods for methylmercury-specific analysis of whole blood by coupled gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS). Methods: We analyzed animal and human blood samples after alkaline digestion or extraction of methylmercury into dichloromethane and back extraction into water. Methylmercury was converted to the volatile ethyl derivative, purged, and trapped on a solid-phase collection medium, and then introduced into the GC-ICPMS system. Results: Limits of quantification were 0.4 and 0.03 mu g/L at a signal-to-noise ratio of 10 with the alkaline digestion and extraction methods, respectively. Extraction met our selected acceptable total error criterion, with an SD of 0.58 mu g/L at the critical maternal blood concentration of 5.8 mu g/L.Results obtained with alkaline digestion indicated the need for improved random analytical uncertainty, which was achieved by increasing the enrichment of the isotope dilution. For 37 blood samples, the mean (SD) proportion of total mercury present as methylmercury was 60 (27)%, range 6%-100%.Conclusions: The combination of extraction and isotope-dilution GC-ICPMS meets the requirements for use as a reference method for measuring methylmercury in whole blood.

  • 144.
    Bellucci, Jeremy
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Pb Isotopic Composition of Panamanian Colonial Majolica by LA-ICP-MS2016Ingår i: Recent Advances in Laser Ablation ICP-MS for Archaeology / [ed] L. Dussubieux, Springer Berlin/Heidelberg, 2016Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Panama ́ Viejo, founded in 1519 by the Spanish explorer Pedrarias Da ́vila, was the first permanent European settlement on the Pacific Ocean, and became a city, by royal decree, in 1521. Shortly after its creation, the city became an important base for trade with Spain. In 1671, the English pirate Henry Morgan waged an attack on Panama ́ Viejo, which resulted in a fire that destroyed the entire city. A new settlement built a few miles west, called Casco Antiguo or San Felipe, is now the historic district of modern Panama City. The Pb isotopic compositions of the glazes on the surface of sixteenth to seventeenth century majolica pottery sherds from Panama Viejo and Casco Antiguo (both in Panama), and Lima (Peru) were determined via non-destructive laser ablation multi-collector ICP-MS (LA-MC-ICP-MS). The contrast in Pb isotopic compositions in the glazes on ceramics recovered in different locations demonstrate that early majolica pottery production during this period used Pb obtained from the Andes. However, the Pb used in later majolica production in Panama is of Spanish origin. After Panama ́ Viejo was burned to the ground, Panamanian majolica production ended.

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  • 145.
    Bellucci, Jeremy
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Nemchin, Alexander
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Whitehouse, Martin
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Ross, Kielman
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Snape, Joshua
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Pidgeon, Robert
    Geochronology of Hadean zircon grains from the Jack Hills, Western Australia constrained by quantitative scanning ion imaging2018Ingår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 476, s. 469-480Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Five Hadean (> 4 Ga) aged zircon grains from the Jack Hills metasedimentary belt have been investigated by a secondary ion mass spectrometry scanning ion image technique. This technique has the ability to obtain accurate and precise full U-Pb systematics on a scale < 5 μm, as well as document the spatial distribution of U, Th and Pb. All five of the grains investigated here have complex cathodoluminescence patterns that correlate to different U, Th, and Pb concentration domains. The age determinations for these different chemical zones indicate multiple reworking events that are preserved in each grain and have affected the primary crystalized zircon on the scale of < 10 μm, smaller than conventional ion microprobe spot analyses. In comparison to the spot analyses performed on these grains, these new scanning ion images and age determinations indicate that almost half of the spot analyses have intersected several age and chemical domains in both fractured and unfractured parts of the individual crystals. Some of these unfractured, mixed domain spot analyses have concordant ages that are inaccurate. Thus, if the frequency of spot analyses intersecting mixed domains here is even close to representative of all other studies of the Jack Hills zircon population, it makes the interpretation of any trace element, Hf, or O isotopic data present in the literature tenuous. Lastly, all of the grains analysed here preserve at least two distinguishable 207Pb/206Pb ages. These ages are preserved in core-rim and/or complex internal textural relationships in unfractured domains. These secondary events took place at ca. 4.3, 4.2, 4.1, 4.0, 3.7, and 2.9 Ga, which are coincident with previously determined statistically robust age peaks present in this zircon population.

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  • 146.
    Bellucci, Jeremy
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Nemchin, Alexander
    Whitehouse, Martin
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Snape, Joshua
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Bland, Phil
    Benedix, Gretchen
    Roszjar, Julia
    Pb evolution in the Martian mantle2018Ingår i: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 485, s. 79-87Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The initial Pb compositions of one enriched shergottite, one intermediate shergottite, two depleted shergottites, and Nakhla have been measured by Secondary Ion Mass Spectrometry (SIMS). These values, in addition to data from previous studies using an identical analytical method performed on three enriched shergottites, ALH 84001, and Chassigny, are used to construct a unified and internally consistent model for the differentiation history of the Martian mantle and crystallization ages for Martian meteorites. The differentiation history of the shergottites and Nakhla/Chassigny are fundamentally different, which is in agreement with short-lived radiogenic isotope systematics. The initial Pb compositions of Nakhla/Chassigny are best explained by the late addition of a Pb-enriched component with a primitive, non-radiogenic composition. In contrast, the Pb isotopic compositions of the shergottite group indicate a relatively simple evolutionary history of the Martian mantle that can be modeled based on recent results from the Sm–Nd system. The shergottites have been linked to a single mantle differentiation event at 4504 Ma. Thus, the shergottite Pb isotopic model here reflects a two-stage history 1) pre-silicate differentiation (4504 Ma) and 2) post-silicate differentiation to the age of eruption (as determined by concordant radiogenic isochron ages). The μ-values (238U/204Pb) obtained for these two different stages of Pb growth are μ1 of 1.8 and a range of μ2 from 1.4–4.7, respectively. The μ1-value of 1.8 is in broad agreement with enstatite and ordinary chondrites and that proposed for proto Earth, suggesting this is the initial μ-value for inner Solar System bodies. When plotted against other source radiogenic isotopic variables (Sri, γ187Os, ε143Nd, and ε176Hf), the second stage mantle evolution range in observed mantle μ-values display excellent linear correlations (r2 > 0.85) and represent a spectrum of Martian mantle mixing-end members (depleted, intermediate, enriched).

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  • 147.
    Bellucci, Jeremy
    et al.
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Whitehouse, Martin
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Snape, Joshua
    Naturhistoriska riksmuseet, Enheten för geovetenskap.
    Halogen and Cl isotopic systematics in Martian phosphates: Implications for the Cl cycle and surface halogen reservoirs on Mars2017Ingår i: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 458, s. 192-202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Cl isotopic compositions and halogen (Cl, F, Br, and I) abundances in phosphates from eight Martian meteorites, spanning most rock types and ages currently available, have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Likewise, the distribution of halogens has been documented by x-ray mapping. Halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in Martian samples or on the Martian surface, and the inter-element ratios are highly variable. Similarly, Cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks. Phosphates in ancient (>4 Ga) meteorites (orthopyroxenite ALH 84001 and breccia NWA 7533) have positive d37Cl anomalies (+1.1 to +2.5 ‰).  These samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity. In contrast, the phosphates in the younger basaltic Shergottite meteorites (<600 Ma) have negative d37Cl anomalies (-0.2 to -5.6 ‰).  Phosphates with the largest negative d37Cl anomalies display zonation where the rims of the grains are enriched in all halogens and have significantly more negative d37Cl anomalies indicating interaction with the surface of Mars during the latest stages of basalt crystallization. The phosphates with no textural, major element, or halogen enrichment evidence for mixing with this surface reservoir have an average d37Cl of -0.6 ‰, which suggests a similar Cl isotope composition between Mars, the Earth, and the Moon. The only process known to fractionate Cl isotopes, both positively and negatively, is formation of perchlorate, which has been detected in weight percent concentrations on the Martian surface. The age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines, which have also been observed on the Martian surface, has been active throughout Martian history. 

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  • 148.
    Belonoshko, Anatoly B.
    et al.
    Royal Institute Technology KTH, Sweden.
    Lukinov, Timofei
    Royal Institute Technology KTH, Sweden.
    Fu, Jie
    Royal Institute Technology KTH, Sweden; Dalian University of Technology, Peoples R China.
    Zhao, Jijun
    Dalian University of Technology, Peoples R China.
    Davis, Sergio
    Chilean Comm Nucl Energy CCHEN, Chile.
    Simak, Sergey
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Stabilization of body-centred cubic iron under inner-core conditions2017Ingår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 10, nr 4, s. 312-+Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Earths solid core is mostly composed of iron. However, despite being central to our understanding of core properties, the stable phase of iron under inner-core conditions remains uncertain. The two leading candidates are hexagonal close-packed and body-centred cubic (bcc) crystal structures, but the dynamic and thermodynamic stability of bcc iron under inner-core conditions has been challenged. Here we demonstrate the stability of the bcc phase of iron under conditions consistent with the centre of the core using ab initio molecular dynamics simulations. We find that the bcc phase is stabilized at high temperatures by a diffusion mechanism that arises due to the dynamical instability of the phase at lower temperatures. On the basis of our simulations, we reinterpret experimental data as support for the stability of bcc iron under inner-core conditions. We suggest that the diffusion of iron atoms in solid state may explain both the anisotropy and the low shear modulus of the inner core.

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  • 149.
    Benaiges-Fernandez, Robert
    et al.
    Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Catalonia, Spain. Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Palau, Jordi
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain. Department of Mineralogy, Petrology and Applied Geology, Universitat de Barcelona, Barcelona, Catalonia, Spain.
    Offeddu, Francesco G.
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Cama, Jordi
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Urmeneta, Jordi
    Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Catalonia, Spain. Biodiversity Research Institute (IRBio), Universitat de Barcelona, Barcelona, Catalonia, Spain.
    Soler, Josep M.
    Institute of Environmental Assessment and Water Research (IDAEA, CSIC), Barcelona, Catalonia, Spain.
    Dold, Bernhard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Sustainable Mining Research & Consultancy EIRL, San Pedro de La Paz, Chile.
    Dissimilatory bioreduction of iron(III) oxides by Shewanella loihica under marine sediment conditions2019Ingår i: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 151, artikel-id 104782Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shewanella is a genus of marine bacteria capable of dissimilatory iron reduction (DIR). In the context of deep-sea mining activities or submarine mine tailings disposal, dissimilatory iron reducing bacteria may play an important role in biogeochemical reactions concerning iron oxides placed on the sea bed. In this study, batch experiments were performed to evaluate the capacity of Shewanella loihica PV-4 to bioreduce different iron oxides (ferrihydrite, magnetite, goethite and hematite) under conditions similar to those in anaerobic sea sediments. Results showed that bioreduction of structural Fe(III) via oxidation of labile organic matter occurred in all these iron oxides. Based on the aqueous Fe (II) released, derived Fe(II)/acetate ratios and bioreduction coefficients seem to be only up to about 4% of the theoretical ones, considering the ideal stoichiometry of the reaction. A loss of aqueous Fe (II) was caused by adsorption and mineral transformation processes. Scanning electron microscope images showed that Shewanella lohica was attached to the Fe(III)-oxide surfaces during bioreduction. Our findings suggest that DIR of Fe(III) oxides from mine waste placed in marine environments could result in adverse ecological impacts such as liberation of trace metals in the environment.

  • 150.
    Bengtsson, Lars
    et al.
    Luleå tekniska universitet.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Starius, Göran
    Luleå tekniska universitet.
    Beskrivning av vattenrörelser i den omättade markzonen: litteraturgenomgång, numerisk modell, simuleringar1982Rapport (Övrigt vetenskapligt)
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