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  • 1.
    Björkvald, Louise
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Buffam, Ishi
    Laudon, Hjalmar
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Hydrogeochemistry of Fe and Mn in small boreal streams: The role of seasonality, landscape type and scale2008Inngår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, Vol. 72, nr 12, s. 2789-2804Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stream water from a stream network of 15 small boreal catchments (0.03–67 km2) in northern Sweden was analyzed for unfiltered (total) and filtered (<0.4 μm) concentrations of iron (Fetot and Fe<0.4) and manganese (Mntot and Mn<0.4). The purpose was to investigate the temporal and spatial dynamics of Fe, Mn and dissolved organic carbon (DOC) as influenced by snow melt driven spring floods and landscape properties, in particular the proportion of wetland area. During spring flood, concentrations of Fetot, Fe<0.4, Mntot, Mn<0.4 and DOC increased in streams with forested catchments (<2% wetland area). In catchments with high coverage of wetlands (>30% wetland area) the opposite behavior was observed. The hydrogeochemistry of Fe was highly dependent on wetlands as shown by the strong positive correlation of the Fetot/Altot ratio with wetland coverage (r2 = 0.89, p < 0.001). Furthermore, PCA analysis showed that at base flow Fetot and Fe<0.4 were positively associated with wetlands and DOC, whereas they were not associated during peak flow at spring flood. The temporal variation of Fe was likely related to varying hydrological pathways. At peak discharge Fetot was associated with variables like silt coverage, which highlights the importance of particulates during high discharge events. For Mn there was no significant correlation with wetlands, instead, PCA analysis showed that during spring flood Mn was apparently more dependent on the supply of minerogenic particulates from silt deposits on the stream banks of some of the streams. The influence of minerogenic particulates on the concentration of, in particular, Mn was greatest in the larger, lower gradient streams, characterized by silt deposits in the near-stream zone. In the small forested streams underlain by till, DOC was of greater importance for the observed concentrations, as indicated by the positive correlation of both Fetot and Fe<0.4 with DOC (r2 = 0.77 and r2 = 0.76, p < 0.001) at the smallest headwater forest site. In conclusion, wetland area and DOC were important for Fe concentrations in this boreal stream network, whereas silt deposits strongly influenced Mn concentrations. This study highlights the importance of studying stream water chemistry from a landscape perspective in order to address future environmental issues concerning mobility of Fe, Mn and associated trace metals.

  • 2.
    Björkvald, Louise
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi. Geokemi.
    Laudon, Hjalmar
    Borg, Hans
    Institutionen för tillämpad miljövetenskap (ITM).
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Trace metals and sulphur isotopes in samll boreal streams: the influence of landscape type2008Inngår i: 2008 Ocean Sciences Meeting: From the watershed to the global ocean, 2008, s. 1-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The transport of trace metals (TM) and dissolved organic carbon (DOC) from headwater streams to the sea is influenced by various landscape elements. Our focus was to investigate the influence of major landscape elements on observed concentrations of dissolved metals (e.g. As, Cd, Co, Fe, Pb), DOC, sulphate, and sulphur isotope composition in streams, north- eastern Sweden, a coastal region characterized by peat wetlands and coniferous forests.

    Stream water samples collected from 10 streams (0.13 to 67 km2) in a boreal stream network reveal that landscape type (i.e. coverage of wetland and forest) is significant for river chemistry. Streams with different catchment characteristics responded differently to hydrological episodes. In forested streams, concentrations of TM, Fe and DOC increased, while they decreased in wetland influenced streams. Furthermore, Fe and Pb correlated positively with wetland coverage. Moreover, significantly lower average sulphate concentrations, but higher isotope values, were observed in wetland streams.

    This study emphasises the importance of understanding stream water chemistry from a landscape perspective in order to identify potential environments where climate change may induce enhanced metal mobilization in the future.

  • 3. Giesler, R
    et al.
    Björkvald, Louise
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Laudon, H
    Mörth, Carl-Magnus
    Stockholms universitet, Stockholm Resilience Centre.
    Spatial and seasonal variations in stream water d34S-dssiolved organic matter in Northern Sweden2009Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, nr 2, s. 447-452Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The discharge of terrestrial dissolved organic matter (DOM) by streams is an important cross-system linkage that strongly influences downstream aquatic ecosystems. Isotopic tracers are important tools that can help to unravel the source of DOM from different terrestrial compartments in the landscape. Here we demonstrate the spatial and seasonal variation of delta S-34 of DOM in 70 boreal streams to test if the tracer could provide new insights into the origin of DOM. We found large spatial and seasonal variations in stream water delta S-34-DOM values ranging from -5.2 parts per thousand to + 9.6 parts per thousand with an average of +4.0 +/- 0.6 (N=62; average and 95% confidence interval). Large seasonal variations were found in stream water delta S-34-DOM values: for example, a shift of more than 10 parts per thousand during the spring snowmelt in a wetland-dominated stream. Spatial differences were also observed during the winter base flow with higher delta S-34-DOM values in the fourth-order Krycklan stream at the outlet of the 68 km(2) compared to the small (<1 km(2)) headwater streams. Our data clearly show that the delta S-34-DOM values have the potential to be used as a tracer to identify and generate new insights about terrestrial DOM sources in the boreal landscape.

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