| 1. |
- Andersson, P. S., et al.
(författare)
-
Particle transport of 234U-238U in the Kalix River and in the Baltic Sea
- 1998
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 62:3, s. 385-392
-
Tidskriftsartikel (refereegranskat)abstract
- The role of particles for U isotope transport was investigated in the Kalix River watershed, a particle-poor, Fe/Mn-rich river in northern Sweden, and in the Baltic Sea estuary. Particles >0.45 μm are strongly enriched in U and contain 20-50% of the total riverine uranium budget and <1% of the total U in brackish waters (3-7 PSU). The particles have high δ234U which is close to that of dissolved U in the associated water, indicating that U on particles is dominantly nondetrital and isotopically exchanges rapidly with the ambient dissolved U. Particles at the river mouth are dominated by nondetrital Fe-Mn oxyhydroxides. Uranium and Fe are strongly correlated, clearly demonstrating that secondary Fe-oxyhydroxide is the major carrier of U in river water. There is no evidence for significant association of U with Mn-oxyhydroxide. Apparent U distribution coefficients ... were calculated for U between the authigenic Fe on particles and the solution. These values appear to be relatively constant throughout the year. This suggests an equilibrium between Fe in solution and authigenic Fe-oxyhydroxides on detrital particles. High values of .... calculated for one summer as well as high U concentrations in brackish waters can be explained by U scavenging by biogenic phases with low authigenic Fe content.
|
|
| 2. |
- Andersson, Per S., et al.
(författare)
-
The importance of colloids for the behavior of uranium isotopes in the low-salinity zone of a stable estuary
- 2001
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 65:1, s. 13-25
-
Tidskriftsartikel (refereegranskat)abstract
- Particle-mediated removal processes of U isotopes were investigated during spring flood discharge in the low-salinity zone (LSZ, up to 3 practical salinity units [psu]) of a stable estuary. A shipboard ultrafiltration cross-flow filtration (CFF) technique was used to separate particles (>0.2 μm) and colloids (between 3000 daltons (3 kD) and 0.2 μm) from ultrafiltered water (<3 kD) containing "dissolved" species. Sediment traps were used to collect sinking material. Concentration of Fe and organic C, which are indicators of the major U carrier phases, were used to interpret the behavior of 234U-238U during estuarine mixing. Colloids dominated the river water transport of U, carrying ≈90% of the U. On entering the estuary, colloids accounted for the dominant fraction of U to about a salinity of 1 psu, but only a minor fraction (<5%) at 3 psu. A substantial fraction of the total U is removed at <1 psu by Fe-organic rich colloids that aggregate and sink during initial estuarine mixing in the Kalix River estuary. In contrast, at salinities >1 psu, there is a general correlation between U and salinity in all filtered fractions. The 234U/238U ratios in different filtered fractions and sinking particles were generally indistinguishable at each station and showed enrichment in 234U, compared with secular equilibrium (δ234U = 266-567). This clearly shows that all size fractions are dominated by nondetrital U. Consideration of U isotope systematics across the estuary reveals that substantial U exchange must occur involving larger particles at least to 1 psu and involving colloids at least to ≈1.5 psu. Further exchange at higher salinities may also occur, as the proportion of U on colloids decreases with increasing salinity. This may be due to decreasing colloid concentration and increasing stabilization of uranyl carbonate complexes during mixing in the estuary. The results show that although U is a soluble element that shows generally conservative mixing in estuaries, removal occurs in the very low salinity zone, and this zone represents a significant sink of U. Variation in composition and concentration of colloidal particles between different estuaries might thus be an important factor for determining the varying behavior of U between estuaries.
|
|
| 3. |
- Andersson, Per S., et al.
(författare)
-
The isotopic composition of Nd in a boreal river : a reflection of selective weathering and colloidal transport
- 2001
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 65:4, s. 521-527
-
Tidskriftsartikel (refereegranskat)abstract
- In this study the Nd concentrations (CNd) from 18 months of weekly sampling of filtered water (<0.45 μm) in the Kalix River, northern Sweden, are reported with εNd(0) and 147Sm/144Nd ratios determined in samples representing major flow events as well as maxima and minima in CNd. The CNd varies by a factor of ten, between 200 pmol/L to 2100 pmol/L, and there is a strong relation between high discharge and high CNd. The Nd in the Kalix River is mainly transported on particles (>90%), dominated by a colloidal phase primarily composed of organic C and Fe. The εNd(0) and 147Sm/144Nd only vary within a narrow range, -27.1 to -24.8 and 0.103 to 0.110 respectively, with no obvious relationship to CNd and discharge. The εNd(0) and 147Sm/144Nd in the river water is significantly lower than in the unweathered till and average bedrock in the catchment and show a closer resemblance with the isotopic characteristics found in humic substances and plant material. These data show that the isotopic composition of Nd exported from a large boreal drainage basin does not directly reflect that of the bulk bedrock in the catchment. The isotopic composition is controlled by selective weathering and the Nd transport is dominated by organic colloidal particles.
|
|
| 4. |
|
|
| 5. |
- Ingri, Johan, et al.
(författare)
-
Rare earth abundance patterns in ferromanganese concretions from the Gulf of Bothnia and the Barents Sea
- 1987
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 51:1, s. 155-161
-
Tidskriftsartikel (refereegranskat)abstract
- Ferromanganese concretions from the Svalbard shelf in the Barents Sea show slightly convex shale-normalized REE patterns with no Eu anomalies. Concretions from the Gulf of Bothnia, northern part of the Baltic Sea, exhibit an enrichment of light REE and negative Eu anomalies. This difference is interpreted as a consequence of different conveyor mechanisms of the REE to the sediment. It is suggested that dissolving biogenic debris contributes to the convex pattern obtained in the Barents Sea, whereas an inorganic suspended fraction with scavenged REE is the main carrier in the Gulf of Bothnia. During oxic diagenesis in the sediment, the scavenged REE are set free into the porewater and contribute to the distribution pattern in concretions found in the Gulf of Bothnia. Small Mn-rich spheroidal concretions are enriched two to five times in REE compared to average shale, whereas Mn-poor flat concretions are low in REE. Specific surface area of the concretion and the depth of burial in the oxidized surface sediment are two factors that strongly affect the enrichment of the REE. Weak Ce anomalies are present in the analysed concretions and a redox level dependence is seen.
|
|
| 6. |
- Ingri, Johan, et al.
(författare)
-
Uptake of alkali and alkaline-earth elements on suspended iron and manganese in the Kalix River, northern Sweden
- 1994
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 58:24, s. 5433-5442
-
Tidskriftsartikel (refereegranskat)abstract
- Scavenging of alkali and alkaline-earth elements by suspended Fe and Mn in the Kalix River, northern Sweden, has been studied for a period of seventeen months. More than 95% (by weight) of suspended nondetrital concentrations of Ca, Mg, and Sr are scavenged on suspended nondetrital Fe throughout all seasons. Barium is correlated to suspended Fe during winter, but during the summer a significant fraction of nondetrital Ba is associated with Mn-rich particles. Porewater profiles for Ca, Mg, and Sr are similar to the dissolved Fe profile, suggesting desorption from a Fe-rich carrier phase. Compared with the river water concentration, Ba is enriched twenty-five times in porewater and shows, together with Mn, a post-depositional subsurface maximum in the solid sediment. The alkali elements Na and K show a linear correlation to suspended nondetrital Fe during the winter. However, the summer concentrations cannot be explained by scavenging onto Fe alone, and sediment and porewater data show no clear association with Fe or Mn. The distribution coefficients for the alkaline-earth elements are two orders of magnitude larger than coefficients obtained for model Fe-oxyhydroxides. This suggests that surface complexation occurs via other functional groups and/or the alkaline-earths are more firmly bound to the natural Fe-rich phase.
|
|
| 7. |
- Nilsson, Nils, et al.
(författare)
-
Competitive surface complexation of o-phthalate and phosphate on goethite (alpha-FeOOH) particles
- 1996
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 60:22, s. 4385-4395
-
Tidskriftsartikel (refereegranskat)abstract
- Complexation of o-phthalate (1,2-benzenedicarboxylate) and competitive complexation of phosphate and phthalate at the goethite-water interface have been studied in 0.1 M Na (NO 3) media at 298.2 K within the range 3.0 < -log [H +] < 8.5. Equilibrium measurements were performed as potentiometric titrations supplemented with spectrophotometric phosphate and phthalate analyses.The binary and ternary chemical subsystems H +-goethite and H +-goethite-H 2PO 4−have been investigated earlier and described according to the constant capacitance model. The adsorption of phthalate showed a strong ionic strength dependence which indicated that phthalate is adsorbed as outer-sphere complexes. The experimental data in the subsystem H +-goethite-phthalate were evaluated on the basis of an extended constant capacitance model with the aid of the computer program FITEQL, version 2.0. One plane for inner sphere complexation and one plane for outer-sphere complexation, each with an associated constant capacitance, were included in the extended constant capacitance model. Surface complexation of phthalate is described by two outer-sphere complexes, ≡FeOH 2+L 2− and ≡FeOH 2+ HL −.In the experiments with simultaneous complexation of phosphate and phthalate, the complexation of phosphate was not influenced by the presence of phthalate. On the other hand, the complexation of phthalate was decreased even at low phosphate concentrations. The equilibrium models determined for the subsystems were used to predict the adsorption of phosphate and phthalate in the quaternary system. It was found that these predictions were in good agreement with experimental titration and phosphate/ phthalate adsorption data.Diffuse reflectance IR-spectra were recorded to obtain structural information of the phthalate complexes. The spectroscopic data did not contradict the outer-sphere model. However, because of the complexity of the phthalate molecule conclusive structural assignment could not be made.
|
|
| 8. |
- Pontér, Christer, et al.
(författare)
-
Geochemistry of manganese in the Kalix River, northern Sweden
- 1992
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 56:4, s. 1485-1494
-
Tidskriftsartikel (refereegranskat)abstract
- Dissolved and suspended Mn in the Kalix River, northern Sweden, were measured weekly over a period of eighteen months. During the same period four lakes in the Kalix catchment were sampled at their outlets and in vertical profiles within the lakes, together with a stream draining a series of mires with shallow lakes. Snow melting in mid-May increased the dissolved Mn concentration in the river tenfold, compared with a concentration of 5 μg L-1 during the winter discharge (January to April). We suggest that the increase was caused by Mn-rich mire water mixing with melting snow and being transported to the river. Large concentrations of dissolved Mn built up in the hypolimnion of the lakes studied during the icecovered period. Break-up of the ice and spring-overturn in June increased the dissolved Mn concentration tenfold in lake discharge and a concomitant peak in the dissolved Mn concentration was observed in the river. Lake-derived Mn was the dominant source for Mn in the river during this time. Suspended Mn in the river was hosted mainly in detrital particles during flood in May. In mid-June, non-detrital suspended Mn started to accumulate and reached a maximum in late July and early August. The Mn/Al ratio was 25 times higher during this period than during flood in May, suggesting the precipitation of an Mn-oxyhydroxide phase. The precipitation of the non-detrital Mn-rich phase was correlated in time with increased temperature, increased pH and increased concentration of suspended biogenic particles. The precipitation of dissolved Mn was biologically mediated. Sedimentation and mineralisation of the non-detrital Mn phase in river and lake sediments resulted in a steady increase of the dissolved Mn concentration in the river water during autumn.
|
|
| 9. |
- Porcelli, D., et al.
(författare)
-
The importance of colloids and mires for the transport of uranium isotopes through the Kalix River watershed and Baltic Sea
- 1997
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 61:19, s. 4095-4113
-
Tidskriftsartikel (refereegranskat)abstract
- The importance of colloids and organic deposits for the transport of uranium isotopes from continental source regions and through the estuarine environment was investigated in the mire-rich Kalix River drainage basin in northern Sweden and the Baltic Sea. Ultrafiltration techniques were used to separate uranium and other elements associated with colloids > 10 kD and >3 kD from "solute" uranium and provided consistent results and high recovery rates for uranium as well as for other elements from large volume samples. Uranium concentrations in 0.45 μm-filtered Kalix River water samples increased by a factor of 3 from near the headwaters in the Caledonides to the river mouth while major cation concentrations were relatively constant. 234U/238U ratios were high (δ234U = 770-1500) throughout the basin, without showing any simple pattern, and required a supply of 234U-rich water. Throughout the Kalix River, a large fraction (30-90%) of the uranium is carried by >10 kD colloids, which is compatible with uranium complexation with humic acids. No isotopic differences were found between colloid-associated and solute uranium. Within the Baltic Sea, about half of the uranium is removed at low salinities. The proportion that is lost is equivalent to that of river-derived colloid-bound uranium, suggesting that while solute uranium behaves conservatively during estuarine mixing, colloid-bound uranium is lost due to rapid flocculation of colloidal material. The association of uranium with colloids therefore may be an important parameter in determining uranium estuarine behavior. Mire peats in the Kalix River highly concentrate uranium and are potentially a significant source of recoil 234U to the mirewaters and river waters. However, mirewater data clearly demonstrate that only small 234U/238U shifts are generated relative to inflowing groundwater. A simple box model of uranium accumulation in peat and transport through the mire that is compatible with the mire data demonstrates that with efficient removal of uranium from solution, only small shifts in 234U/238U ratios can be generated in mirewater uranium. The measurements and model calculations show that mirewaters are not the primary source of the uranium in the river. Bedrock groundwaters with high 234U/238U ratios and uranium concentrations must be the dominant source of riverine uranium.
|
|
| 10. |
- Romer, Rolf L., et al.
(författare)
-
Lead mobilization during tectonic reactivation of the western Baltic Shield
- 1993
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 57:11, s. 2555-2570
-
Tidskriftsartikel (refereegranskat)abstract
- Lead isotope data from sulfide deposits of the western part of the Baltic Shield define mixing lines in the 206Pb 204Pb- 207Pb 204Pb diagram. Lead from two types of sulfide deposits have been investigated: 1. (1) Exhalative and volcanogenic deposits that are syngenetic with their host rocks 2. (2) vein deposits. The syngenetic deposits locally show a very wide range of lead isotopic compositions that reflect a variable addition of highly radiogenic lead, while the vein deposits, although they have radiogenic lead isotopic compositions, exhibit only limited isotopic variations. In different provinces of the shield, both types of deposits fall on the same lead mixing array. The slope of the lead mixing lines varies as a function of the age of basement rocks and the age of the tectonic event which produced the lead mobilization and therefore relates the source rock age with the age of lead mobilization. Calculated mixing ages fall into several short time periods that correspond either to orogenic events or to major phases of continental rifting. The orogenic events are the ca 360-430 Ma Caledonian, ca 900-1100 Ma Sveconorwegian, and the ca 1800-1900 Ma Svecofennian orogenic cycles. The rifting events correspond to the formation of the ca 280 Ma Oslo rift and the Ordovician (ca 450 Ma) graben system in the area of the present Gulf of Bothnia. Each mixing age indicates that lead was mobilized, probably as a consequence of mild thermal disturbances, and that the crust was permeable to lead migration. The data show that the geographic distribution of sulfide deposits with highly radiogenic lead isotopic compositions coincides with old graben systems, orogenic belts, and orogenic forelands on the Baltic Shield. The ages of vein deposits and their geographic distribution demonstrate multiple tectonic reactivation of the interior of the Baltic Shield in response to orogenic events at its margin.
|
|
| 11. |
- Romer, Rolf L., et al.
(författare)
-
U-Pb dating of columbites : a geochronologic tool to date magmatism and ore deposits
- 1992
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 56:5, s. 2137-2142
-
Tidskriftsartikel (refereegranskat)abstract
- We have developed techniques for the U-Pb analysis of the mineral columbite [(Fe,Mn)(Ta,Nb)2O6], and report U-Pb ages obtained for three early Proterozoic columbites from the Baltic Shield of northern Sweden. The U-Pb ages of these columbites agree with other available geochronological data. U-Pb dating of columbite is therefore a potentially powerful tool in establishing reliable ages of pegmatites, alkaline and carbonatitic intrusions, and ore deposits of Sn, W, and REEs, all of which often contain columbite. Furthermore, columbite can be used to date peraluminous granites as it often occurs within Li-P-REE pegmatites associated with such granites.
|
|
| 12. |
- Romer, Rolf L.
(författare)
-
U-Pb systematics of stilbite-bearing low-temperature mineral assemblages from the Malmberget iron ore, northern Sweden
- 1996
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 60:11, s. 1951-1961
-
Tidskriftsartikel (refereegranskat)abstract
- Minerals with a low thermal stability strongly constrain the history of cooling and later tectonic reworking of an area, provided these minerals can be dated. The possible use of stilbite, a Ca---Al-silicate of the zeolite group, for geochronologic studies was investigated. Open fractures in the Palaeoproterozoic Malmberget iron ore, northern Sweden, contain low-temperature mineral assemblages with various combinations of apatite, stilbite, calcite, biotite, and less commonly titanite and monazite. Two generations of fractures, that are characterized by calcite and stilbite with distinctly radiogenic initial 87Sr/86Sr at ca. 0.720 and ca. 0.708, are dated at ca. 1740 Ma (monazite) and 1620-1613 Ma (titanite), respectively. Apatite samples, even those intimately intergrown with ca. 1740 Ma old monazite, yield U-Pb ages at 1620-1600 Ma, which indicates that apatite apparently recrystallized and reset its U---Pb system. Older stilbite yields a secondary lead isochron at 1730 ± 6.4 Ma (2σ), which unequivocally demonstrates that the ambient temperature in the Malmberget area from then on remained below the thermal stability of stilbite (ca. 150°C). Stilbite is a natural ion-exchanger and its U-Pb systematics indicates recent mobility of uranium and lead. However, the 1730 ± 6.4 Ma (2σ) age demonstrates that some of the older stilbite was not disturbed during younger fracturing. Hydrothermally altered and secondary stilbite samples yield scattered lead arrays that correspond to secondary isochrons at ca. 1650-1600 D4a, which agrees with the U-Pb titanite and apatite ages. Thus, in combination with other geochronometers, the generally imprecise stilbite ages provide information on the cooling history of an area.
|
|
| 13. |
- Öhlander, Björn, et al.
(författare)
-
Change of Sm-Nd isotope composition during weathering of till
- 2000
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 64:5, s. 813-820
-
Tidskriftsartikel (refereegranskat)abstract
- Weathering of till in northern Sweden results in the formation of well-developed spodosols. The till is dominated by 1.9–1.8 Ga granitic material. The REE are among the elements most strongly depleted during weathering, and the loss of REE from the E-horizon decreases as the atomic number increases. To study if weathering leads to a change of the Nd isotope composition, we have analysed the Nd isotopic composition of the various horizons including living plants and humus of two profiles of weathered till (typic haplocryods) in northern Sweden. As much as between 65.6 and 75.3% of the Sm and Nd in the <0.2 mm fraction has been lost from the E-horizon, and between 32.5 and 54.7% from the B-horizon. Nd has been lost to a slightly greater extent than Sm. The two C-horizon samples have εNd(0) values of −22.1 and −23.2. Corresponding E-horizon values are −18.1 and −20.2. The B-horizon values are intermediate between the values of the E and C horizons. It is concluded that the weathering leads to a change in the Sm/Nd ratio resulting in a change of the Sm-Nd isotope composition. The plant and humus samples deviate even more from the unweathered till. For one station the results could be interpreted as if the Sm and Nd taken up by the plants had similar isotope characteristics as the amounts of these elements released by weathering in the E-horizon. For the other station it is probable that the Nd isotope composition of the organic samples is dominated by Nd released by till weathering which, however, is mixed with another Nd-source, possibly an airborne component. The explanation to the change of isotope compostion in the till is that a larger proportion of the Nd released by weathering is released from minerals with a lower Sm/Nd ratio than the bulk soil, compared with the amount released from minerals with a higher Sm/Nd ratio. Although the various REE-carrying minerals had the same initial Nd isotopic composition, 1.8–1.9 Ga of decay of 147Sm to 143Nd has resulted in a higher present 143Nd/144Nd ratio in the minerals with a higher Sm/Nd ratio.
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
- Ahmed, Engy, et al.
(författare)
-
The effect of soil horizon and mineral type on the distribution of siderophores in soil
- 2014
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 131, s. 184-195
-
Tidskriftsartikel (refereegranskat)abstract
- Iron is a key component of the chemical architecture of the biosphere. Due to the low bioavailability of iron in the environment, microorganisms have developed specific uptake strategies like production of siderophores. Siderophores are operationally defined as low-molecular-mass biogenic Fe(III)-binding compounds, that can increase the bioavailability of iron by promoting the dissolution of iron-bearing minerals. In the present study, we investigated the composition of dissolved and adsorbed siderophores of the hydroxamate family in the soil horizons of podzol and the effect of specific mineral types on siderophores. Three polished mineral specimens of 3 cm x 4 cm x 3 mm (apatite, biotite and oligioclase) were inserted in the soil horizons (O (organic), E (eluvial) and B (upper illuvial)). After two years, soil samples were collected from both the bulk soil of the whole profile and from the soil attached to the mineral surfaces. The concentration of ten different fungal tri-hydroxamates within ferrichromes, fusigen and coprogens families, and five bacterial hydroxamates within the ferrioxamine family were detected. All hydroxamate types were determined in both soil water (dissolved) and soil methanol (adsorbed) extracts along the whole soil profile by high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS); hence, the study is the most extensive of its kind. We found that coprogens and fusigen were present in much higher concentrations in bulk soil than were ferrioxamines and ferrichromes. On the other hand, the presence of the polished mineral completely altered the distribution of siderophores. In addition, each mineral had a unique interaction with the dissolved and adsorbed hydroxamates in the different soil horizons. Thus siderophore composition in the soil environment is controlled by the chemical, physical and biological characteristics of each soil horizon and also by the available mineral types.
|
|
| 18. |
- Alakangas, Linda J., et al.
(författare)
-
Diverse fractionation patterns of Rare Earth Elements in deep fracture groundwater in the Baltic Shield - Progress from utilisation of Diffusive Gradients in Thin-films (DGT) at the Aspo Hard Rock Laboratory
- 2020
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533. ; 269, s. 15-38
-
Tidskriftsartikel (refereegranskat)abstract
- Rare earth elements (REEs) were studied in groundwater in fractures at depths between 144 m and 450 m in Proterozoic granitoids on the Baltic Shield at a coastal site in south eastern Sweden (Aspo Hard Rock Laboratory). A specially designed device was used to sample the groundwater under in situ high pressure and low redox conditions. The REEs were measured via both diffusive gradients in thin-films (DGT) samplers after approximately three-week deployment times, and after conventional filtration (0.45 mu m membrane filters). The concentrations of REEDGT were lower than the REE0.45 mu m concentrations in all 14 studied groundwaters. This is explained by development of a diffuse boundary layer (DBL) in the solution at the DGTs caused by the low flow, and in some of the groundwaters additionally by the presence of organically complexed REE that diffuse slowly in the diffusive gel of the DGT. Among the 14 studied groundwaters there was a huge range in REEDGT-fractionation patterns, ranging from enrichment to a nearly three-order-of-magnitude depletion of the heavy REEs (HREEs), despite a relatively homogenous bedrock (granitoids). The HREE enrichment is explained by preservation of the fractionation signature as HREE enriched sea water intruded and flowed through the fractures, supported by the high proportion of modelled REE fulvic-acid complexes in these waters. The strong HREE depletion, which occurred in saline groundwater, was ascribed to an advanced REE equilibrium between the groundwater and primary and/or secondary minerals and the pore water in the bedrock. Yet other groundwaters had flat or moderately HREE depleted patterns, which in some cases may have been caused by mixing of small portions of surficial waters with saline groundwater. (C) 2019 Elsevier Ltd. All rights reserved.
|
|
| 19. |
|
|
| 20. |
- Alessi, Daniel S., et al.
(författare)
-
The product of microbial uranium reduction includes multiple species with U(IV)-phosphate coordination
- 2014
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 131, s. 115-127
-
Tidskriftsartikel (refereegranskat)abstract
- Until recently, the reduction of U(VI) to U(IV) during bioremediation was assumed to produce solely the sparingly soluble mineral uraninite, UO2(s). However, results from several laboratories reveal other species of U(IV) characterized by the absence of an EXAFS U-U pair correlation (referred to here as noncrystalline U(IV)). Because it lacks the crystalline structure of uraninite, this species is likely to be more labile and susceptible to reoxidation. In the case of single species cultures, analyses of U extended X-ray fine structure (EXAFS) spectra have previously suggested U(IV) coordination to carboxyl, phosphoryl or carbonate groups. In spite of this evidence, little is understood about the species that make up noncrystalline U(IV), their structural chemistry and the nature of the U(IV)-ligand interactions. Here, we use infrared spectroscopy (IR), uranium L-III-edge X-ray absorption spectroscopy (XAS), and phosphorus K-edge XAS analyses to constrain the binding environments of phosphate and uranium associated with Shewanella oneidensis MR-1 bacterial cells. Systems tested as a function of pH included: cells under metal-reducing conditions without uranium, cells under reducing conditions that produced primarily uraninite, and cells under reducing conditions that produced primarily biomass-associated noncrystalline U(IV). P X-ray absorption near-edge structure (XANES) results provided clear and direct evidence of U(IV) coordination to phosphate. Infrared (IR) spectroscopy revealed a pronounced perturbation of phosphate functional groups in the presence of uranium. Analysis of these data provides evidence that U(IV) is coordinated to a range of phosphate species, including monomers and polymerized networks. U EXAFS analyses and a chemical extraction measurements support these conclusions. The results of this study provide new insights into the binding mechanisms of biomass-associated U(IV) species which in turn sheds light on the mechanisms of biological U(VI) reduction. (C) 2014 Elsevier Ltd. All rights reserved.
|
|
| 21. |
- Alling, Vanja, et al.
(författare)
-
Degradation of terrestrial organic carbon, primary production and out-gassing of CO2 in the Laptev and East Siberian Seas as inferred from delta C-13 values of DIC
- 2012
-
Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 95, s. 143-159
-
Tidskriftsartikel (refereegranskat)abstract
- The cycling of carbon on the Arctic shelves, including outgassing of CO2 to the atmosphere, is not clearly understood. Degradation of terrestrial organic carbon (OCter) has recently been shown to be pronounced over the East Siberian Arctic Shelf (ESAS), i.e. the Laptev and East Siberian Seas, producing dissolved inorganic carbon (DIC). To further explore the processes affecting DIC, an extensive suite of shelf water samples were collected during the summer of 2008, and assessed for the stable carbon isotopic composition of DIC (delta C-13(DIC)). The delta C-13(DIC) values varied between -7.2 parts per thousand to +1.6 parts per thousand and strongly deviated from the compositions expected from only mixing between river water and seawater. Model calculations suggest that the major processes causing these deviations from conservative mixing were addition of (DIC) by degradation of OCter, removal of DIC during primary production, and outgassing of CO2. All waters below the halocline in the ESAS had delta C-13(DIC) values that appear to reflect mixing of river water and seawater combined with additions of on average 70 +/- 20 mu M of DIC, originating from degradation of OCter in the coastal water column. This is of the same magnitude as the recently reported deficits of DOCter and POCter for the same waters. The surface waters in the East Siberian Sea had higher delta C-13(DIC) values and lower DIC concentrations than expected from conservative mixing, consistent with additions of DIC from degradation of OCter and outgassing of CO2. The outgassing of CO2 was equal to loss of 123 +/- 50 mu M DIC. Depleted delta C-13(POC) values of -29 parts per thousand to -32 parts per thousand in the mid to outer shelf regions are consistent with POC from phytoplankton production. The low delta C-13(POC) values are likely due to low delta C-13(DIC) of precursor DIC, which is due to degradation of OCter, rather than reflecting terrestrial input compositions. Overall, the delta C-13(DIC) values confirm recent suggestions of substantial degradation of OCter over the ESAS, and further show that a large part of the CO2 produced from degradation has been outgassed to the atmosphere. (C) 2012 Elsevier Ltd. All rights reserved.
|
|
| 22. |
- Andersson, K, et al.
(författare)
-
Colloidal rare earth elements in a boreal river: Changing sources and distributions during the spring flood
- 2006
-
Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 70:13, s. 3261-3274
-
Tidskriftsartikel (refereegranskat)abstract
- Variations in the physico-chemical speciation of the rare earth elements (REE) have been investigated in a subarctic boreal river during an intense spring flood event using prefiltered (< 100 mu m) samples, cross-flow (ultra)filtration (CFF), flow field-flow fractionation (FIFFF), and diffusive gradients in thin films (DGT). This combination of techniques has provided new information regarding the release and transport of the REE in river water. The colloidal material can be described in terms of two fractions dominated by carbon and iron, respectively. These two fractions, termed colloidal carrier phases, showed significant temporal changes in concentration and size distribution. Before the spring flood, colloidal carbon concentrations were low, the colloids being dominated by relatively large iron colloids. Colloidal concentrations increased sharply during the spring flood, with smaller carbon colloids dominating. Following the spring flood, colloidal concentrations decreased again, smaller carbon colloids still dominating. The REE are transported mainly in the particulate and colloidal phases. Before the spring flood, the REE composition of all measured fractions was similar to local till. During the spring flood, the REE concentrations in the colloidal and particulate fractions increased. The increase was most marked for the lighter REE, which therefore showed a strong enrichment when normalized to local till. Following the spring flood, the REE concentrations decreased again and reverted to a distribution similar to local till. These changes in the concentration and distributions of carbon iron and REE are interpreted in terms of changing hydrological flow paths in soil and bedrock which occur during the spring flood. (c) 2006 Elsevier Inc. All rights reserved.
|
|
| 23. |
- Andersson, P.S., et al.
(författare)
-
The importance of river water inflow and shelf sediment-sea water exchange in the East Siberian Sea for the Nd isotopic composition of Arctic Ocean water
- 2009
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 73:13, Suppl. 1, s. A41-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- With data generated from cruises to the Canada Basin in 2000, to the Eurasian and Central Arctic Ocean basins in 2001, to the Fram Strait in 2002 and to the Chuckchi Sea in 2005 we now have a good general view of the distribution and isotopic composition of Nd (εNd) in the Arctic Ocean [1, 2]. The restricted Arctic Ocean basin is surrounded by large continental shelves, covering more than 50% of its total area.Distinct from other oceans, with surface water Nd depletion, there is throughout the Arctic a pattern of high Nd concentrations, up to 58pM, at the surface that gradually diminish with depth to 15-18pM in the deep waters. A range of isotopic variations across the Arctic and within individual depth profiles reflects the different sources of waters. The dominant source of water and Nd is the Atlantic (εNd= -10.7). Radiogenic isotope Nd signatures can be traced in Pacific water flowing into the Canada Basin and further into the Eurasian Basin (up to εNd= -6.5). The variation of εNd and concentration in the Arctic Ocean suggest that Nd input from rivers and shelf sediments is also of great importance.Improving our understanding of the vast Siberian Shelves influence on Nd and trace element behaviour in the Arctic Ocean was one of the main objectives of the International Siberian Shelf Study 2008 (ISSS-08). The ISSS-08 cruise recovered filtered water (<0.2µm), particles and sediments from the Laptev and East Siberian Seas as well as estuarine and river water from Lena, Indigirka and Kolyma. Crucial processes, including loss of river water Nd in the estuarine region and shelf sediment-sea water exchange will be discussed in terms of controlling the Nd concentration and isotopic composition of sea water.[1] Andersson et al. (2008) GCA 72, 2854-2867. [2] Porcelli et al. (2009, in press) GCA. (2009, in press)
|
|
| 24. |
|
|
| 25. |
- Andersson, Stefan S., et al.
(författare)
-
Apatite as a tracer of the source, chemistry and evolution of ore-forming fluids : The case of the Olserum-Djupedal REE-phosphate mineralisation, SE Sweden
- 2019
-
Ingår i: Geochimica et Cosmochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0016-7037 .- 1872-9533. ; 255, s. 163-187
-
Tidskriftsartikel (refereegranskat)abstract
- This study explores the suitability of apatite as a tracer of the source(s), chemistry, and evolution of ore-forming hydrothermal fluids. This is tested by analysing the halogen (F, Cl, Br, and I), stable Cl isotopic, and trace element compositions of fluorapatite from the regional-scale Olserum-Djupedal rare earth element (REE) phosphate mineralisation in SE Sweden, which is dominated by monazite-(Ce), xenotime-(Y), and fluorapatite. The primary hydrothermal fluid flow system is recorded in a sequence from proximal granite-hosted to distal metasediment-hosted fluorapatite. Along this sequence, primary fluorapatite shows a gradual increase of Cl and Br concentrations and in (Gd/Yb)N, a decrease of F and I concentrations, a decrease in δ37Cl values, in (La/Sm)N, and partly in (La/Yb)N and (Y/Ho)N. Local compositional differences of halogen and trace element concentrations have developed along rims and in domains adjacent to fractures of fluorapatite due to late-stage partial reaction with fracture fluids. These differences are insignificant compared to the larger deposit-scale zoning. This suggests that apatite can retain the primary record of the original ore-forming fluid despite later overprinting fluid events. The agreement between Br/Cl and I/Cl ratios of apatite and those of co-existing fluid inclusions at lower temperatures indicates that only a minor fractionation of Br from I occurs during apatite precipitation. The halogen ratios of apatite can thus be used as a first-order estimate for the composition of the ore-forming fluid. Taking the small fractionation factors for Cl isotopes between apatite and co-existing fluid at high temperatures into account, we propose that the Cl isotopic composition of apatite and the halogen ratios derived from the apatite composition can be used jointly to trace the source(s) of ore-forming fluids. By contrast, most trace elements incorporated in apatite are affected by the host rock environment and by fluid-mineral partitioning due to growth competition between co-crystallising minerals. Collectively, apatite is sensitive to changing fluid compositions, yet it is also able to record the character of primary ore-forming fluids. Thus, apatite is suitable for tracing the origin, chemistry, and evolution of fluids in hydrothermal ore-forming settings.
|
|
