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- Ingri, Johan, et al.
(författare)
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Manganese redox cycling in Lake Imandra : Impact on nitrogen and the trace metal sediment record
- 2011
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Ingår i: Biogeosciences Discussions. - : Copernicus GmbH. - 1810-6277 .- 1810-6285. ; 8:1, s. 273-321
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Tidskriftsartikel (refereegranskat)abstract
- Sediment and water samples from the mine-polluted Yokostrovskaya basin in Lake Imandra have been analysed. Three major processes have influenced the accumulation and distribution of metals in the sediment: (1) Development of the apatite-nepheline and the sulfide ore mining industries. (2) Secondary formation of sulphides in the upper sediment column. (3) Redox cycling of Mn in the surface sediment and in the bottom water. This study demonstrate the dominant role of the Mn redox cycling in controlling distribution of several major and trace elements, especially during the winter stratification period. Mn oxides act as a major scavenger and carrier for the non-detrital fraction of Al, Ca, K, Mg, P, Ba, Co, Cu, Ni, Mo and Zn in the bottom water. Aluminium, Ca, K, Mg, P, Cu, Ni and Zn are mainly sorbed at the surface of the particulate Mn phase, while Ba and Mo form a phase (or inner sphere complex) with Mn. Co is associated with the Mn-rich phase, probably by oxidation of Co(II) to a trivalent state by the particulate Mn surface. Formation and dissolution of Mn particles most likely also control anoxic ammonium oxidation to nitrate and reduction of nitrate to N2. It is shown that secondary sulphides in Lake Imandra sediments are fed with trace metals primarily scavenged from the dissolved phase in the water column. This enrichment process, driven by the Mn-redox cycle, therefore changes the sediment record by the transfer of a dissolved pollution signal to the particulate sediment record, thus making it more complicated to trace direct influence of particles from different pollution sources.
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| 2. |
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| 3. |
- Peinerud, Elsa
(författare)
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Geochemistry of suspended material and sediments in boreal lakes
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The geochemistry of suspended material and sediment has been studied in four boreal lakes: Lakes Kutsasjärvi, Sakajärvi, and Ala Lombolo in northern Sweden and Lake Imandra on the Kola Peninsula, Russia. Suspended material and filtered water have been sampled in time series and depth profiles. The suspended material is collected on filters, which are dissolved and analyzed. Sediment cores from all lakes are taken. Major and trace element analyses are mainly performed by ICP–QMS and ICP–AES. The main theme in this thesis is the relation between the suspended material and the sediment, and the geochemical cycling of elements within the lakes. In this context, processes like biological production and decomposition, and precipitation and dissolution of inorganic phases are important. Special attention is paid to redox processes of Fe and Mn, and to the implications of these processes. A thorough discussion of diatom Si in sediments and suspended material is also included. The high concentrations of organic material and diatom Si in the water column of Lake Kutsasjärvi during summer dilutes most other components, rendering these concentrations lower in the suspended material than in the sediment. The non-detrital fractions (i.e., the fraction that is not related to primary mineral particles) of all major elements are, however, higher in the suspended material, partly as a consequence of higher dissolution rates of diatom Si and non-detrital Fe and Mn in the sediment, but also because no sampling of suspended material was performed during spring-flood, when the inflow of detrital particles (i.e., minerogenic particles deriving from the mechanical weathering of rocks) is probably highest. Like the major elements, most trace elements show higher concentrations in the sediment than in the suspended matter. The enrichment of trace elements in the suspended material, compared with detrital particles, is, however, higher. During winter, when Lake Kutsasjärvi is ice-covered, the redox cycle of Fe is a dominant process in the bottom water. There, particulate Ca, Mg, and P co-vary with particulate Fe. Similarly, several trace elements appear to be associated with non-detrital Fe, e.g., As, Mo, U, and V. Barium and Co, that have often been observed to co-vary with Mn, are correlated with both Fe and Mn in Lake Kutsasjärvi, probably as a consequence of the strong dominance of Fe over Mn in the bottom water suspended matter. For, e.g, Ba, Cr, Cu, and Ni, detrital particles are the most important source to the sediment. Besides non-detrital Fe and Mn and detrital particles, organic matter may be an important source of trace metals to the sediment. Further, anthropogenic aerosols are suggested to be important for the flux of Cd, Pb, and Zn to the sediment. The normalization method for estimating diatom Si is evaluated by comparing the calculated non-detrital Si concentrations in sediments and suspended material with the concentration of diatom frustules, as counted under a microscope. The results show a fairly good agreement between the methods, where deviations can be attributed to, e.g., greatly varying diatom cell sizes. Concentration variations of non-detrital Si in three sediment profiles are examined. It is suggested that controlling factors behind the variations may include varying degrees of dilution by detrital material; increasing dissolution rate with depth of the diatom remains, possibly linked to a decreasing redox potential which affects protective coatings; and fluctuations of the primary diatom production. The highly polluted (with regard to, e.g., Ni, S, and P) Lake Imandra presents an interesting object for studying how natural geochemical processes work in disturbed systems. In the nearly anoxic bottom water of the ice- covered Lake Imandra, the redox cycle of Mn plays an important role. It controls the distribution of Ni and some other trace elements between the dissolved and particulate phases. A substantial sulphide formation in the sediment, probably a consequence of the increased SO42- loading into the lake, enables an efficient fixation of metals.
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| 4. |
- Peinerud, Elsa K.
(författare)
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Interpretation of Si concentrations in lake sediments : three case studies
- 2000
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Ingår i: Environmental Geology. - : Springer. - 0943-0105 .- 1432-0495. ; 40:1-2, s. 64-72
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Tidskriftsartikel (refereegranskat)abstract
- The biogenic Si concentration in a sediment can be determined as the non-detrital Si concentration by normalization of the total Si concentration with Al. This procedure is based upon the assumptions that (1) that Al exists predominantly in detrital, i.e. minerogenic, particles and (2) that biogenic Si (mainly diatom frustules) is the dominating non-detrital Si phase. This paper focuses on the reasons for the variations of the non-detrital Si concentration in these lake sediments. Data from three lakes are presented, representing three principally different cases regarding the Si concentration. The processes controlling the concentrations of detrital and non-detrital Si are discussed.
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| 5. |
- Peinerud, Elsa K., et al.
(författare)
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Non-detrital Si concentrations as an estimate of diatom concentrations in lake sediments and suspended material
- 2001
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Ingår i: Chemical Geology. - 0009-2541 .- 1872-6836. ; 177:3-4, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates a method, based on normalization with Al, to estimate the concentration of diatoms in suspended and deposited sediments. Provided that Al exists primarily in the detrital phase, one can calculate the fraction of non-detrital Si (i.e. biogenic Si). Suspended matter and sediment in two lakes in northern Sweden have been analyzed. Results from the normalization method are compared with microscope count data. The results from the two methods differ somewhat. Partly dissolved diatom frustules may explain part of this discrepancy. These remnants can hardly be recognized as diatoms. Therefore, they are not counted during the microscopic analysis, although they contribute to the concentration of biogenic Si. Another factor is the differences in Si content among different types of diatoms. We show that the calculated concentrations of non-detrital Si are good estimates of the diatom concentrations. By using normalization as a tool, reasonable estimates of the stocks of biogenic Si can be obtained rapidly. Using these estimates as a guide, sites where considerable changes in diatom productivity and/or dissolution rates have occurred can be identified.
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| 9. |
- Pontér, Simon, et al.
(författare)
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Early diagenesis of uranium in lakes receiving deep groundwater from the Kiruna mine, northern Sweden
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 793
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Tidskriftsartikel (refereegranskat)abstract
- The uranium (U) concentrations and isotopic composition of waters and sediment cores were used to investigate the transport and accumulation of U in a water system (tailings pond, two lakes, and the Kalix River) receiving mine waters from the Kiruna mine. Concentrations of dissolved U decrease two orders of magnitude between the inflow of mine waters and in the Kalix River, while the concentration of the element bound to particulate matter increases, most likely due to sorption on iron‑manganese hydroxides and organic matter. The vertical distribution of U in the water column differs between two polluted lakes with a potential indication of dissolved U supply from sediment's pore waters at anoxic conditions. Since the beginning of exposure in the 1950s, U concentrations in lake sediments have increased >20-fold, reaching concentrations above 50 μg g-1. The distribution of anthropogenic U between the lakes does not follow the distribution of other mine water contaminants, with a higher relative proportion of U accumulating in the sediments of the second lake.Concentrations of redox-sensitive elements in the sediment core as well as Fe isotopic composition were used to re-construct past redox-conditions potentially controlling early diagenesis of U in surface sediments. Two analytical techniques (ICP-SFMS and MC-ICP-MS) were used for the determination of U isotopic composition, providing an extra dimension in the understanding of processes in the system. The (234 U)/(238 U) activity ratio (AR) is rather uniform in the tailings pond but varies considerably in water and lake sediments providing a potential tracer for U transport from the Kiruna mine through the water system, and U immobilization in sediments. The U mass balance in the Rakkurijoki system as well as the amount of anthropogenic U accumulated in lake sediments were evaluated, indicating the immobilization in the two lakes of 170 kg and 285 kg U, respectively.
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