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| 2. |
- Björkvald, Louise, et al.
(författare)
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Influence of landscape type on trace metals in small boreal catchments
- 2007
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Ingår i: Geochimica et cosmochimica acta 71 (15) A95 Suppl. S. Aug 2007. ; , s. A95-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We studied temporal and spatial variations of trace metal (TM) concentrations (As, Cd, Co, Cr, Cu, Ge, La, Ni, Pb, Rb, Sc, and Y) in stream water and their correlation with catchment properties (i.e. coverage of wetland and forest), but also with Fe and Mn. During 2004 and 2005 water samples were collected from 10 streams (0.13 km2 to 67 km2) in the Krycklan Catchment Study, a boreal stream network in northern Sweden. Since spring snowmelt is the most important hydrological event, the monthly sampling was intensified during spring flood (April-May) when samples were collected every second day. Total and dissolved (<0.4µm) concentrations of Fe and Mn were determined by ICP-OES. Dissolved concentrations of TM were determined by ICP-MS.Preliminary results show a seasonal variation for all TM, in particular during spring flood. In forested catchments most TM concentrations increased at spring flood, but for Rb and Sc a decrease was observed. Conversely, in wetland influenced catchments the opposite seasonal variation was observed, i.e. concentrations of all TM decreased by a factor of 2 to 3. The seasonal variation of Fe shows a similar pattern to many TM, due to the association of TM to Fe oxyhydroxides. In particular, Fe correlates significantly with Cr and Pb in a forested headwater stream (r2=0.77 and r2=0.71, respectively, p<0.05). In the wetland headwater stream similar correlations between Fe and TM are found, but DOC also correlates significantly with As, Cd, Ni, and Pb (r2=0.92, p<0.05).A significant negative correlation (p<0.05) was observed between coverage of wetlands and average concentrations of Cr, Cu, Ge, Ni, Sc and Y. The results indicate that wetlands act as sinks for these elements. Alternatively, there is a source limitation in wetlands and that increased concentrations during base flow are due to mineral groundwater influence. Positive correlation with wetland coverage was only observed for Pb (r2=0.79, p<0.05), indicating that wetlands acts as a source for this element. Sulfate concentrations correlated negatively (r2=0.97, p<0.05) with increasing coverage of wetlands, which highlights the importance of sulfate reduction within wetland areas.This study emphasizes the importance of considering stream water chemistry from a landscape perspective.
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- Björkvald, Louise, et al.
(författare)
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Trace metals and sulphur isotopes in samll boreal streams: the influence of landscape type
- 2008
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Ingår i: 2008 Ocean Sciences Meeting. ; , s. 1-
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 4. |
- Grabs, Thomas, et al.
(författare)
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Modelling spatial patterns of saturated areas: a comparison of the topographic wetness index and a distributed model
- 2007
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Ingår i: Geophysical Research Abstracts. - : European Geoscience Union. ; , s. vol 9-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The spatial distribution of saturated areas within a catchment is a key factor to understanding and predicting hydrological response and stream water quality at the catchment scale. The topographic wetness index (TWI, ln(a/tan(beta))) is a widely used measure for assessing the spatial distribution of wetness conditions and only requires distributed elevation data as input. The predicted pattern is constant in time because the index is a static representation of the landscape. In this study we examined the predictions of saturated areas using this static topographic wetness index and compared the spatial predictions with temporally aggregated simulations of a distributed hydrological model. The model was calibrated against discharge measured at the outlet and at two internal points of a small forested catchment in northern Sweden. After calibration the model was applied to a larger 68 km2 catchment which included the subcatchment used for calibration. The dynamic groundwater level simulations of this model were temporally aggregated into dynamic indices. These indices were compared to the static topographic wetness index (TWI). We used the ability to spatially predict the occurrence of wetlands as a validation of the static and dynamic indices. First results indicate that the dynamic approach is superior to the static TWI.
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| 6. |
- Laudon, Hjalmar
(författare)
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Bacterial utilization of imported organic material in three small nested humic lakes
- 2010
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Ingår i: Verhandlungen / Internationale Vereinigung Für Theoretische Und Angewandte Limnologie. - 0368-0770. ; 30, s. 1393-
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Konferensbidrag (refereegranskat)abstract
- Lakes import organic carbon in the form of dissolved humic substances and other terrigenous compounds. This allochthonous organic carbon is consumed by heterotrophic bacteria, with significant consequences for the biostructure and energy pathways of freshwater ecosystems (JANSSON et al. 2007). Laboratory studies generally show that a minor share of terrigenous material (similar to 10 %) is available to bacterial consumption on short term scales (weeks) and that the degradation thereafter proceeds at slow rates (TRANVIK 1998). Although natural exposure to solar UV radiation may increase the availability (LINDELL et al. 1995, TRANVIK 1998), it is not certain that this can compensate the loss of bioavailable carbon from bacterial consumption. We hypothesized that as allochthonous organic carbon is processed and aged during its residence time in lakes, its potential to support bacterial growth, both in terms of rates and efficiency, decreases successively. We employed a short term (12 day) bioassay approach to study 3 small nested lakes in Northern Sweden, almost entirely dominated by allochthonous organic carbon. The first 2 lakes drained almost directly into the third, making it possible to examine a downstream gradient from inlet to outlet and from lake to lake.
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| 8. |
- Laudon, Hjalmar, et al.
(författare)
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The Krycklan Catchment Study, Sweden: A field based experimental platform for linking small-scale process understanding to landscape patterns
- 2007
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Krycklan Catchment Study (KCS) (http://ccrew.sek.slu.se/krycklan), is a multiscale experimental catchment located in the boreal region of northern Sweden. The catchment is extensively instrumented for hydrological and biogeochemical research, including 15 permanent gauging stations, ranging from 3 ha to 6700 ha in size, intensively sampled and continuously monitored to quantify temporal and spatial variations in water chemistry and discharge. An additional 90 locations are sampled occasionally for water chemistry at different runoff stages. The multi-investigator KCS has been developed to provide a direct insight into the governing hydrological and biogeochemical processes at a range of catchment scales and consists at present of over 30 separate projects. Its location within an established Experimental Forest provides a comprehensive instrumental infrastructure, long-term climate monitoring facilities and a small research catchment where process-based hillslope, hydrological and biogeochemical research has been conducted for three decades. Recently two new major investments are being implemented. The first includes a Riparian Observatory with over 200 soil lysimeters in the riparian zone. The second investment is the use of laserscanning (LIDAR) which makes KCS one of the first large-scale research catchments where high-resolution elevation and ground cover data are available for hydrological and water quality modeling.
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| 9. |
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| 10. |
- Nathanson, Marcus, 1955-, et al.
(författare)
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Using LiDAR data to define stream flow rating curves
- 2012
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Konferensbidrag (refereegranskat)abstract
- In remote locations, it is difficult to obtain stream flow information because of the difficulty making sufficient dis- charge measurements. In this study we investigate the feasibility to constrain a fluid mechanics-based flow model for defining stream flow rating curves with remotely sensed topographic data from airborne LiDAR scanning. A near infrared (NIR) LiDAR scan was carried out for an 8-m wide channel in northern Sweden. The topographic information from this NIR LiDAR scan along the 90-m surveyed reach was used to define channel geometry above the water surface. To fill in the channel bed topography below the water surface we used a detailed ground survey to create a hybrid model for comparison to a simple assumption of a flat bottom channel. Based on the boundaries of confidence intervals calculated from the direct measurements, we show that for the channel considered the sim- ple flat bottom assumption performs just as well as the hybrid model with regards to estimating direct discharge measurements. The mismatch between the two models was greatest at low flows and may be associated with unre- solved submerged bed topography. This deficiency, while rather small, could potentially be remedied by scanning during periods of low flow, or use other techniques such as multi-frequency bathymetric LiDAR or passive optical remote sensing that offer alternative ways for generating the necessary topographic information.
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