| 1. |
- Alling, Vanja, et al.
(author)
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Tracing terrestrial organic matter by delta S-34 and delta C-13 signatures in a subarctic estuary
- 2008
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In: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 53:6, s. 2594-2602
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Journal article (peer-reviewed)abstract
- A key issue to understanding the transformations of terrestrial organic carbon in the ocean is to disentangle the latter from marine-produced organic matter. We applied a multiple stable isotope approach using delta S-34 and delta C-13 isotope signatures from estuarine dissolved organic matter (DOM), enabling us to constrain the contribution of terrestrial-derived DOM in an estuarine gradient of the northern Baltic Sea. The stable isotope signatures for dissolved organic sulfur (delta S-34(DOS)) have twice the range between terrestrial and marine end members compared to the stable isotope signatures for dissolved organic carbon (delta C-13(DOC)); hence, the share of terrestrial DOM in the total estuarine DOM can be calculated more precisely. DOM samples from the water column were collected using ultrafiltration on board the German RV Maria S Merian during a winter cruise, in the Bothnian Bay, Bothnian Sea, and Baltic proper. We calculated the terrestrial fraction of the estuarine DOC (DOCter) from both delta C-13(DOC) and delta S-34(DOS) signatures and applying fixed C: S ratios for riverine and marine end members to convert S isotope signatures into DOC concentrations. The delta S-34(DOS) signature of the riverine end member was +7.02 parts per thousand, and the mean signatures from Bothnian Bay, Bothnian Sea, and Baltic proper were +10.27, +12.51, and +13.67 parts per thousand, respectively, showing an increasing marine signal southwards (d34SDOS marine end member = 18.1 parts per thousand). These signatures indicate that 87%, 75%, and 67%, respectively, of the water column DOC is of terrestrial origin (DOCter) in these basins. Comparing the fractions of DOCter in each basin-that are still based on few winter values only-with the annual river input of DOC, it appears that the turnover time for DOCter in the Gulf of Bothnia is much shorter than the hydraulic turnover time, suggesting that high-latitude estuaries might be efficient sinks for DOCter.
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| 2. |
- Andersson, Rina Argelia, et al.
(author)
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Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic
- 2012
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In: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 27:6, s. 545-552
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Journal article (peer-reviewed)abstract
- A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (similar to 2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss-dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water-saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. delta 15N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in delta 13C values appear to reflect mainly changes in plant assemblages. Positive shifts in both delta 15N and delta 13C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15N-enrichment.
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| 3. |
- Bhattacharya, Aparajita, et al.
(author)
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Environmental assessment of abandoned mine tailings in Adak, Vasterbotten district (northern Sweden)
- 2006
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In: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 21:10, s. 1760-1780
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Journal article (peer-reviewed)abstract
- Sulfide-rich mine tailings in Adak that are exposed to weathering cause acid mine drainage characterized by low PH (2-4) and high SO4 (UP to 800 mg L-1). Surface water, sediment and soil samples collected in this study contain higher concentrations of As, Cu, Fe and Zn, compared to the target and/or intervention limits set by international regulatory agencies. In particular, high As concentrations in water (up to 2900 mu g L- 1) and sediment (up to 900 mg kg(-1)) are of concern. There is large variability in trace element concentrations, implying that both physical (grain size) and chemical factors (pH, secondary phases as sulfides, Al-oxides or clay minerals) play an important role in their distribution. The low PH keeps the trace elements dissolved, and they are transported farther downstream. Trace element partition coefficients are low (log K-d = 0.3-4.3), and saturation indices calculated with PHREEQC are < 0 for common oxide and sulfidic minerals. The sediment and soil samples indicate an enhanced pollution index (up to 17), and high enrichment factors for trace elements (As up to 38,300; Zn up to 800). Finally, leaves collected from different plant types indicate bioaccumulation of several elements (As, Al, Cu, Fe and Zn). However, some of the plants growing in this area (e.g., Salix, Equisetum) are generally resistant to metal toxicity, and hence, liming and phytoremediation could be considered as potential on-site remediation methods.
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| 4. |
- Biswas, Ashis, et al.
(author)
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Hydrogeochemical contrast between brown and grey sand aquifers in shallow depth of Bengal Basin : consequences for sustainable drinking water supply
- 2012
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 431, s. 402-412
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Journal article (peer-reviewed)abstract
- Delineation of safe aquifer(s) that can be targeted by cheap drilling technology for tubewell (TW) installation becomes highly imperative to ensure access to safe and sustainable drinking water sources for the arsenic (As) affected population in Bengal Basin. This study investigates the potentiality of brown sand aquifers (BSA) as a safe drinking water source by characterizing its hydrogeochemical contrast to grey sand aquifers (GSA) within shallow depth (<70 m) over an area of 100 km(2) in Chakdaha Block of Nadia district, West Bengal, India. The results indicate that despite close similarity in major ion composition, the redox condition is markedly different in groundwater of the two studied aquifers. The redox condition in the BSA is delineated to be Mn oxy-hydroxide reducing, not sufficiently lowered for As mobilization into groundwater. In contrast, the enrichments of NH4+, PO43-, Fe and As along with lower Eh in groundwater of GSA reflect reductive dis-solution of Fe oxy-hydroxide coupled to microbially mediated oxidation of organic matter as the prevailing redox process causing As mobilization into groundwater of this aquifer type. In some portions of GSA the redox status even has reached to the stage of SO42- reduction, which to some extent might sequester dissolved As from groundwater by co-precipitation with authigenic pyrite. Despite having low concentration of As in groundwater of the BSA the concentration of Mn often exceeds the drinking water guidelines, which warrants rigorous assessment of attendant health risk for Mn prior to considering mass scale exploitation of the BSA for possible sustainable drinking water supply.
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| 5. |
- Dunca, Elena, et al.
(author)
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Using ocean quahog (Arctica islandica) shells to reconstruct palaeoenvironment in A-resund, Kattegat and Skagerrak, Sweden
- 2009
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In: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 98:1, s. 3-17
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Journal article (other academic/artistic)abstract
- Shells of Arctica islandica collected between 1884 and 2004 from A-resund, Kattegat and Skagerrak (Swedish West Coast) were used to monitor local climate variations and the influence of human activities on the local environment. For this purpose, we analysed the growth, structure and chemical composition of these shells and compared them with shells collected from Kiel Bay, Norway and Iceland. The growth rate of the studied shells registers an NAO periodicity of ca 8 years. However, the observed signal is weak because of other environmental interferences that are either of natural or anthropogenic origin. For example, the oxygen isotope ratios show temperature fluctuation, but also the influx of low salinity water. Higher contents of S, N, Cu, Zn, As, Cd and P in shell portions formed during the last century are related to human activities such as mining and industrial development. Our study indicates that in order to use Arctica shells as archives of climate change it is necessary to study the full range of environmental data that is recorded in the shells by using a multi element and isotope approach in combination with different analytical techniques including investigation of growth rates and shell structure.
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| 6. |
- Morth, Carl-Magnus, et al.
(author)
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Modeling riverine nutrient transport to the Baltic Sea : A large-scale approach
- 2007
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In: Ambio. - 0044-7447 .- 1654-7209. ; 36:02-Mar, s. 124-133
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Journal article (peer-reviewed)abstract
- We developed for the first time a catchment model simulating simultaneously the nutrient land-sea fluxes from all 105 major watersheds within the Baltic Sea drainage area. A consistent modeling approach to all these major watersheds, i.e., a consistent handling of water fluxes (hydrological simulations) and loading functions (emission data), will facilitate a comparison of riverine nutrient transport between Baltic Sea subbasins that differ substantially. Hot spots of riverine emissions, such as from the rivers Vistula, Oder, and Daugava or from the Danish coast, can be easily demonstrated and the comparison between these hot spots, and the relatively unperturbed rivers in the northern catchments show decisionmakers where remedial actions are most effective to improve the environmental state of the Baltic Sea, and, secondly, what percentage reduction of riverine nutrient loads is possible. The relative difference between measured and simulated fluxes during the validation period was generally small. The cumulative deviation (i.e., relative bias) [Sigma(Simulated - Measured)/Sigma Measured X 100 (%)] from monitored water and nutrient fluxes amounted to+8.2% for runoff, to-2.4% for dissolved inorganic nitrogen, to +5.1% for total nitrogen, to +13% for dissolved inorganic phosphorus and to +19% for total phosphorus. Moreover, the model suggests that point sources for total phosphorus compiled by existing pollution load compilations are underestimated because of inconsistencies in calculating effluent loads from municipalities.
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| 7. |
- Struyf, Eric, et al.
(author)
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An enormous amorphous silica stock in boreal wetlands
- 2010
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115, s. G04008-
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Journal article (peer-reviewed)abstract
- We investigated amorphous Si (ASi) in a boreal wetland in northern Sweden. We found enormous stocks of ASi in the upper soil layers (up to 11% of dry weight), in the form of diatom frustules and plant ASi. A consistent exponential decrease in ASi concentrations was observed with increasing depth in the soil profile. An inverse modeling approach shows that vegetation takes up a substantial part of weathered dissolved Si (DSi). Concurrent analysis of N and C indicates a faster turnover in and a higher leakage from the ASi pool. The magnitude of the biological buffering we observed is unprecedented and supports the emerging paradigm of the importance of biological uptake of DSi governing the export of DSi from terrestrial ecosystems. Our results complicate current models of silicate transport, highlighting the necessity to incorporate ecosystem biological buffering in our concept of Si biogeochemistry.
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| 8. |
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| 9. |
- Tollefsen, Elin, et al.
(author)
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Ikaite nucleation at 35 degrees C challenges the use of glendonite as a paleotemperature indicator
- 2020
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10
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Journal article (peer-reviewed)abstract
- Glendonites have been found worldwide in marine sediments from the Neoproterozoic Era to the Quaternary Period. The precursor of glendonite, ikaite (CaCO3 . 6H(2)O), is metastable and has only been observed in nature at temperatures <7 degrees C. Therefore, glendonites in the sedimentary record are commonly used as paleotemperature indicators. However, several laboratory experiments have shown that the mineral can nucleate at temperatures>7 degrees C. Here we investigate the nucleation range for ikaite as a function of temperature and pH. We found that ikaite precipitated at temperatures of at least 35 degrees C at pH 9.3 -10.3 from a mixture of natural seawater and sodium carbonate rich solution. At pH 9.3, we observed pseudomorphic replacement of ikaite by porous calcite during the duration of the experiment (c. 5hours). These results imply that ikaite can form at relatively high temperatures but will then be rapidly replaced by a calcite pseudomorph. This finding challenges the use of glendonites as paleotemperature indicators.
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