| 1. |
- Sun, Xiaole, 1983-, et al.
(författare)
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Stable silicon isotope analysis on nanomole quantities using MC-ICP-MS with a hexapole gas-collision cell
- 2010
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 25:2, s. 156-162
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate in this study that a single focusing multiple collector inductively coupled plasma massspectrometer (MC-ICP-MS) equipped with a hexapole gas-collision cell (GV-instrument Isoprobe) canprecisely determine the d29Si (2S.D., 0.2&) using a total Si consumption of less than 14 nmole (390 ngSi). Testing and evaluation of background, rinse time, and major matrix effects have been performed ina systematic way to establish a procedure to measure d29Si in small quantities. Chemical purificationprior to analysis is required to remove potential interferences. For data collected during a four-yearperiod, the average d29Si value of IRMM-018 relative to NBS-28 was found to be 0.95& (n ¼ 23,2S.D. 0.16&) with a 95% confidence interval (0.95 0.028&). The mean d29Si value of the Big-Batchstandard was found to be 5.50& (n ¼ 6, 2S.D. 0.26&). Although determination of the d30Simeasurements is not possible, with our current instrument we demonstrate that this system providesa fast and long-term reliable method for the analysis of d29Si in purified samples with low Siconcentration (18 mM Si).
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| 2. |
- Österblom, Henrik, et al.
(författare)
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Modeling Social—Ecological Scenarios in Marine Systems
- 2013
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Ingår i: BioScience. - : Oxford University Press (OUP). - 0006-3568 .- 1525-3244. ; 63:9, s. 735-744
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Tidskriftsartikel (refereegranskat)abstract
- Human activities have substantial impacts on marine ecosystems, including rapid regime shifts with large consequences for human well-being. We highlight the use of model-based scenarios as a scientific tool for adaptive stewardship in the face of such consequences. The natural sciences have a long history of developing scenarios but rarely with an in-depth understanding of factors influencing human actions. Social scientists have traditionally investigated human behavior, but scholars often argue that behavior is too complex to be repre-ented by broad generalizations useful for models and scenarios. We address this scientific divide with a framework for integrated marine social ecological scenarios, combining quantitative process-based models from the biogeochemical and ecological disciplines with qualitative studies on governance and social change. The aim is to develop policy-relevant scenarios based on an in-depth empirical understanding from both the natural and the social sciences, thereby contributing to adaptive stewardship of marine social-ecological systems.
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| 3. |
- Alling, Vanja, et al.
(författare)
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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
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Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 95, s. 143-159
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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.
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| 4. |
- Alling, Vanja, et al.
(författare)
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Non-conservative behavior of dissolved organic carbon across the Laptev and East Siberian Seas
- 2010
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 24, s. GB4033-
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to have a strong effect on the Eastern Siberian Arctic Shelf (ESAS) region, which includes 40% of the Arctic shelves and comprises the Laptev and East Siberian seas. The largest organic carbon pool, the dissolved organic carbon (DOC), may change significantly due to changes in both riverine inputs and transformation rates; however, the present DOC inventories and transformation patterns are poorly understood. Using samples from the International Siberian Shelf Study 2008, this study examines for the first time DOC removal in Arctic shelf waters with residence times that range from months to years. Removals of up to 10%–20% were found in the Lena River estuary, consistent with earlier studies in this area, where surface waters were shown to have a residence time of approximately 2 months. In contrast, the DOC concentrations showed a strong nonconservative pattern in areas with freshwater residence times of several years. The average losses of DOC were estimated to be 30%–50% during mixing along the shelf, corresponding to a first-order removal rate constant of 0.3 yr−1. These data provide the first observational evidence for losses of DOC in the Arctic shelf seas, and the calculated DOC deficit reflects DOC losses that are higher than recent model estimates for the region. Overall, a large proportion of riverine DOC is removed from the surface waters across the Arctic shelves. Such significant losses must be included in models of the carbon cycle for the Arctic Ocean, especially since the breakdown of terrestrial DOC to CO2 in Arctic shelf seas may constitute a positive feedback mechanism for Arctic climate warming. These data also provide a baseline for considering the effects of future changes in carbon fluxes, as the vast northern carbon-rich permafrost areas draining into the Arctic are affected by global warming.
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| 5. |
- Alling, Vanja, 1978-
(författare)
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Terrestrial organic carbon dynamics in Arctic coastal areas : budgets and multiple stable isotope approaches
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Arctic rivers transport 31-42 Tg organic carbon (OC) each year to the Arctic Ocean, which is equal to 10% of the global riverine OC discharge. Since the Arctic Ocean only holds approximately 1% of the global ocean volume, the influence of terrestrially derived organic carbon (OCter) in the Arctic Ocean is relatively high. Despite the global importance of this region the behavior of the, by far largest fraction of the OCter, the dissolved organic carbon (DOC) in Arctic and sub-arctic estuaries is still a matter of debate. This thesis describes data originating from field cruises in Arctic and sub-arctic estuaries and coastal areas with the aim to improve the understanding of the fate of OCter in these areas, with specific focus on DOC. All presented studies indicate that DOCter and terrestrially derived particulate organic carbon (POCter) are subjected to substantial degradation in high-latitude estuaries, as shown by the non-conservative behavior of DOC in the East Siberian Arctic Shelf Seas (ESAS) (paper I) and the even more rapid degradation of POC in the same region (paper II). The removals of OCter in Arctic shelf seas were further supported by multiple isotope studies (paper III and IV), which showed that a use of 13C/12C in both OC and DIC, together with 34S/32S is a powerful tool to describe the sources and fate of OCter in estuaries and coastal seas. High-latitude estuaries play a key role in the coupling between terrestrial and marine carbon pools. In contrast to the general perception, this thesis shows that they are not only transportation areas for DOCter from rivers to the ocean, but are also active sites for transformation, degradation and sedimentation of DOCter, as well as for POCter. In a rapidly changing climate, the importance of these areas for the coupling between inorganic and organic carbon pools cannot be underestimated.
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| 6. |
- Alling, Vanja, 1978-, et al.
(författare)
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Tracing terrestrial organic matter by delta34S and delta13C signatures in a subarctic estuary
- 2008
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 53:6, s. 2594-2602
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Tidskriftsartikel (refereegranskat)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 34S and 13C 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 (34SDOS) have twice the range between terrestrial and marine end members compared to the stable isotope signatures for dissolved organic carbon (13CDOC); 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 13CDOC and 34SDOS signatures and applying fixed C: S ratios for riverine and marine end members to convert S isotope signatures into DOC concentrations. The 34SDOS signature of the riverine end member was +7.02‰, and the mean signatures from Bothnian Bay, Bothnian Sea, and Baltic proper were +10.27, +12.51, and +13.67‰, respectively, showing an increasing marine signal southwards (34SDOS marine end member 5 18.1‰). 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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| 7. |
- Andersen, Hans Estrup, et al.
(författare)
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Identifying Hot Spots of Agricultural Nitrogen Loss Within the Baltic Sea Drainage Basin
- 2016
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Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 227:1
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural management practices are among the major drivers of agricultural nitrogen (N) loss. Legislation and management incentives for measures to mitigate N loss should eventually be carried out at the individual farm level. Consequently, an appropriate scale to simulate N loss from a scientific perspective should be at the farm scale. A data set of more than 4000 agricultural fields with combinations of climate, soils and agricultural management which overall describes the variations found in the Baltic Sea drainage basin was constructed. The soil-vegetation-atmosphere model Daisy (Hansen et al. 2012) was used to simulate N loss from the root zone of all agricultural fields in the data set. From the data set of Daisy simulations, we identified the most important drivers for N loss by multiple regression statistics and developed a statistical N loss model. By applying this model to a basin-wide data set on climate, soils and agricultural management at a 10 x 10 km scale, we were able to calculate root-zone N losses from the entire Baltic Sea drainage basin and identify N loss hot spots in a consistent way and at a level of detail not hitherto seen for this area. Further, the root-zone N loss model was coupled to estimates of nitrogen retention in catchments separated into retention in groundwater and retention in surface waters allowing calculation of the coastal N loading.
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| 8. |
- Anderson, Leif G, 1951, et al.
(författare)
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Shelf-Basin interaction along the East Siberian Sea
- 2017
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Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 13:2, s. 349-363
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Tidskriftsartikel (refereegranskat)abstract
- Extensive biogeochemical transformation of organic matter takes place in the shallow continental shelf seas of Siberia. This, in combination with brine production from sea-ice formation, results in cold bottom waters with relatively high salinity and nutrient concentrations, as well as low oxygen and pH levels. Data from the SWERUS-C3 expedition with icebreaker Oden, from July to September 2014, show the distribution of such nutrient-rich, cold bottom waters along the continental margin from about 140 to 180 degrees E. The water with maximum nutrient concentration, classically named the upper halocline, is absent over the Lomonosov Ridge at 140 degrees E, while it appears in the Makarov Basin at 150 degrees E and intensifies further eastwards. At the intercept between the Mendeleev Ridge and the East Siberian continental shelf slope, the nutrient maximum is still intense, but distributed across a larger depth interval. The nutrient-rich water is found here at salinities of up to similar to 34.5, i.e. in the water classically named lower halocline. East of 170 degrees E transient tracers show significantly less ventilated waters below about 150 m water depth. This likely results from a local isolation of waters over the Chukchi Abyssal Plain as the boundary current from the west is steered away from this area by the bathymetry of the Mendeleev Ridge. The water with salinities of similar to 34.5 has high nutrients and low oxygen concentrations as well as low pH, typically indicating decay of organic matter. A deficit in nitrate relative to phosphate suggests that this process partly occurs under hypoxia. We conclude that the high nutrient water with salinity similar to 34.5 are formed on the shelf slope in the Mendeleev Ridge region from interior basin water that is trapped for enough time to attain its signature through interaction with the sediment.
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| 9. |
- Andrén, Margareta, et al.
(författare)
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Coupling between mineral reactions, chemical changes in groundwater, and earthquakes in Iceland
- 2016
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Ingår i: Journal of Geophysical Research - Solid Earth. - 2169-9313 .- 2169-9356. ; 121:4, s. 2315-2337
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Tidskriftsartikel (refereegranskat)abstract
- Chemical analysis of groundwater samples collected from a borehole at Hafralækur, northernIceland, from October 2008 to June 2015 revealed (1) a long-term decrease in concentration of Si and Naand (2) an abrupt increase in concentration of Na before each of two consecutive M > 5 earthquakes whichoccurred in 2012 and 2013, both 76 km from Hafralækur. Based on a geochemical (major elements and stableisotopes), petrological, and mineralogical study of drill cuttings taken from an adjacent borehole, we areable to show that (1) the long-term decrease in concentration of Si and Na was caused by constant volumereplacement of labradorite by analcime coupled with precipitation of zeolites in vesicles and along fracturesand (2) the abrupt increase of Na concentration before the first earthquake records a switchover tononstoichiometric dissolution of analcime with preferential release of Na into groundwater. We attributedecay of the Na peaks, which followed and coincided with each earthquake to uptake of Na along fracturedor porous boundaries between labradorite and analcime crystals. Possible causes of these Na peaks are anincrease of reactive surface area caused by fracturing or a shift from chemical equilibrium caused by mixingbetween groundwater components. Both could have been triggered by preseismic dilation, which was alsoinferred in a previous study by Skelton et al. (2014). The mechanism behind preseismic dilation so far from thefocus of an earthquake remains unknown.
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| 10. |
- Aullón Alcaine, Anna, et al.
(författare)
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Geogenic arsenic and fluoride in shallow aquifers of northeastern La Pampa, Argentina : mobility constraints
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- High concentrations of geogenic arsenic (As) and fluoride (F-) in groundwater have been reported at elevated concentrations in different parts of the Chaco-Pampean Plain, in Argentina, where more than 2 million people may be exposed to high levels of these toxic elements through drinking water. Groundwater from the shallow aquifer is far exceeding the permissible WHO Standard limits of 10 μg/L for As and 1.5 mg/L for fluoride, as well as the Argentinean Standard limit of 50 μg/L for As. Geogenic As results due to the weathering of ash originated by volcanic eruptions from the Andean Cordillera and transported by wind and deposited along with the sediments and also as discrete layers and lenses over large geographical area containing around 90% of rhyolitic glass. Groundwater is hosted in a sandy silty interconnected system of aquifers and aquitards within the The Pampean aquifer. A total of 44 groundwater samples were collected from the shallow aquifers in NE of La Pampa province. Two rural areas covering an area of 600km2 in Quemú Quemú (QQ) and 300km2 in Intendente Alvear (IA) were investigated in the present study. Groundwater was circum-neutral to alkaline (pH 7.43-9.18), predominantly oxidizing (Eh ~0.24 V) with widely variable EC range (456-11,400 μS/cm). The major cation dissolved in groundwater was Na+, while the predominant anions were HCO3-, Cl- and SO42-, respectively. Water type in QQ was mostly Na-HCO3- while in IA, the composition differed between Na-HCO3- and Na-Cl-SO42- water types. Groundwater composition showed high degree of mineralization and high salinity evidenced by high EC. In discharge areas, high evaporation rates result in high salinity of shallow groundwater and visible salts incrustations on the surface of the lakes. Elevated concentrations of NO3- and PO43- observed in some wells indicated possible anthropogenic contamination. Total As concentration in groundwater from QQ ranged from 5.58 to 535 μg/L, where 94% of the wells exceeded the WHO standard limit for safe drinking water of 10 μg/L, and 56% of the wells exceeded the old Argentine standard limit of 50 μg/L. F- concentrations revealed heterogeneity and high concentrations in some wells (0.5-14.2 mg/L), 78% of samples in QQ study area exceeded the WHO standard limit of 1.5 mg/L. Under oxidizing conditions and neutral to alkaline pH, arsenate (AsV) species predominated, mainly in HAsO42- forms. As "hotspots" indicated locally contamination and correlated positively with F-, HCO3-, B and V and showed negative correlation with salinity, dissolved Fe, Al and Mn. The mechanisms involved in the mobilization of As in the shallow aquifers are controlled by the rise of pH, variations in Eh conditions and the presence of competitor ions (HCO3-, PO43-, Si, V oxyanions). Geochemical processes like adsorption/desorption, precipitation/dissolution and redox reactions may trigger to As mobilization in the shallow aquifers of La Pampa region.
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| 11. |
- Aullón Alcaine, Anna, et al.
(författare)
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Hydrogeochemical controls on the mobility of arsenic, fluoride and other geogenic co-contaminants in the shallow aquifers of northeastern La Pampa Province in Argentina
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 715
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Tidskriftsartikel (refereegranskat)abstract
- Elevated Arsenic (As) and Fluoride (F) concentrations in groundwater have been studied in the shallow aquifers of northeastern of La Pampa province, in the Chaco-Pampean plain, Argentina. The source of As and co-contaminants is mainly geogenic, from the weathering of volcanic ash and loess (rhyolitic glass) that erupted from the Andean volcanic range. In this study we have assessed the groundwater quality in two semi-arid areas of La Pampa. We have also identified the spatial distribution of As and co-contaminants in groundwater and determined the major factors controlling the mobilization of As in the shallow aquifers. The groundwater samples were circum-neutral to alkaline (7.4 to 92), oxidizing (Eh similar to 0.24 V) and characterized by high salinity (EC = 456-11,400 mu S/cm) and Na+-HCO3- water types in recharge areas. Carbonate concretions ("tosca") were abundant in the upper layers of the shallow aquifer. The concentration of total As (5.6 to 535 mu g/L) and F (0.5 to 14.2 mg/L) were heterogeneous and exceeded the recommended WHO Guidelines and the Argentine Standards for drinking water. The predominant As species were arsenate As(V) oxyanions, determined by thermodynamic calculations. Arsenic was positively correlated with bicarbonate (HCO3-), fluoride (F), boron (B) and vanadium (V), but negatively correlated with iron (Fe), aluminium (Al), and manganese (Mn), which were present in low concentrations. The highest amount of As in sediments was from the surface of the dry lake. The mechanisms for As mobilization are associated with multiple factors: geochemical reactions, hydrogeological characteristics of the local aquifer and climatic factors. Desorption of As(V) at high pH, and ion competition for adsorption sites are considered the principal mechanisms for As mobilization in the shallow aquifers. In addition, the long-term consumption of the groundwater could pose a threat for the health of the local community and low cost remediation techniques are required to improve the drinking water quality.
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| 12. |
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| 13. |
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| 14. |
- Bauer, Susanne
(författare)
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Dissolved and suspended transport of tungsten, molybdenum, and vanadium in natural waters
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Some transition metals and metalloids occur primarily as oxyanions in natural waters including antimony, arsenic, chromium, molybdenum, tungsten and vanadium. These oxyanions can pass through cell walls along the same pathways as phosphate or sulfate. Some of these oxyanions are essential for life, but in high concentrations they become all toxic. Recent studies showed that tungsten probably is posing a risk to human health. The growing use of tungsten in industrial and military applications probably leads to an increased release of tungsten to the environment. It has also been shown that the use of studded winter tires in Sweden significantly increases tungsten concentrations in road runoff. Still, little is known about the geochemical cycling of tungsten in the environment as it has been considered to be a more or less inert element. Only a few studies deal with tungsten in natural waters. For example, for the Baltic Sea no concentration data have been published before this work and data on the suspended particulate fraction of tungsten in terrestrial and marine waters are scarce.This thesis contributes to the understanding of the distribution and behavior of tungsten, molybdenum and vanadium in natural waters under changing redox conditions, varying pH and different seasons. Particular attention is paid to the suspended particulate fraction of these elements, which is often neglected even though it can be of great importance. Tungsten, molybdenum and vanadium primarily occur as oxyanions in solution and can be adsorbed to particles, which determines their mobility.Molybdenum usually is very mobile, while vanadium has a tendency to adsorb to iron oxyhydroxides or to form organic complexes. Tungsten has many similarities with molybdenum, but it seems to be less mobile than molybdenum in natural waters.Tungsten and molybdenum have a similar abundance in the upper continental crust, but in the ocean molybdenum is almost 2000 times more abundant. A strong fractionation of these two elements occurs from land to the ocean, indicating a removal of W during mixing of river and seawater.This study comprises data from small streams in the boreal landscape of northern Sweden, major rivers (Kalix River and Råne River) and their estuaries discharging into the Baltic Sea. In the marine environment, sediment cores from the Bothnian Bay and water profiles at the stratified Landsort Deep have been studied. Apart from the spatial distribution, the temporal behavior of tungsten, molybdenum, and vanadium in was investigated. In the boreal environment snowmelt is playing a major role for their transport.All water samples were filtered through 0.22 pore size filters to define dissolved and suspended particulate fractions. The particulate fraction of all studied elements increases from streams to rivers. Especially during spring flood, particle transport becomes even more important. About 80% tungsten, 70% vanadium and 30% molybdenum occur in the particulate fraction during this event. During estuarine mixing, tungsten and molybdenum are released from the particles again. However, vanadium seems to be removed in both fractions, probably due to a different adsorption behavior. In the dissolved fraction molybdenum increased and vanadium decreased from land to the sea, while tungsten showed small variation in all surface waters.All three elements are affected by manganese redox cycling at the transition zone between oxic and sulfidic water at the Landsort Deep in the Baltic Sea. Adsorption of these oxyanions to the freshly formed manganese oxides plays an important role for their transport to the sulfidic zone. In contrast to molybdenum, dissolved tungsten is accumulated in the sulfidic environment. There is no effective removal mechanisms like for molybdenum, which is adsorbed to sulfides. Also in the sediment, redox cycling of manganese and iron affects the distribution of tungsten and molybdenum close to the water-sediment interface.
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| 15. |
- Berggren, Ann-Marie, et al.
(författare)
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Variability of Be-10 and delta O-18 in snow pits from Greenland and a surface traverse from Antarctica
- 2013
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 294, s. 568-572
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Tidskriftsartikel (refereegranskat)abstract
- To examine temporal variability of Be-10 in glacial ice, we sampled snow to a depth of 160 cm at the NEEM (North Greenland Eemian Ice Drilling) drilling site in Greenland. The samples span three years between the summers of 2006 and 2009. At the same time, spatial variability of Be-10 in glacial ice was explored through collection of the upper similar to 5 cm of surface snow in Antarctica during part of the Swedish-Japanese traverse from Svea to Syowa station during the austral summer in 2007-2008. The results of the Greenlandic 1 Be snow suggested variable concentrations that apparently do not clearly reflect the seasonal change as indicated by the delta O-18 data. The Be-10 concentration variability most likely reflects also effects of aerosol loading and deposition pathways, possibly in combination with post-depositional processes. The Antarctic traverse data expose a negative correlation between Be-10 and delta O-18, while there are weaker but still significant correlations to altitude and distance to the coast (approximated by the distance to the 70th latitude). These relationships indicate that geographical factors, mainly the proximity to the coast, may strongly affect 1 Be concentrations in snow in Queen Maud Land, Antarctica.
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| 16. |
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| 17. |
- Björkvald, Louise, et al.
(författare)
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Hydrogeochemistry of Fe and Mn in small boreal streams : The role of seasonality, landscape type and scale
- 2008
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 72:12, s. 2789-2804
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 18. |
- 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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| 19. |
- Björkvald, Louise, 1973-
(författare)
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Landscape hydrogeochemistry of Fe, Mn, S and trace elements (As, Co, Pb) in a boreal stream network
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The transport of elements by streams from headwater regions to the sea is influenced by landscape characteristics. This thesis focuses on the influence of landscape characteristics (e.g. proportion of wetland/forest coverage) on temporal and spatial variations of Fe, Mn, S and trace elements (As, Co, Pb) in streams located in northern Sweden, a boreal region characterized by coniferous forests and peat wetlands.Water samples from a network of 15 streams revealed a different hydrogeochemistry in forested catchments compared to wetland catchments. The temporal variation was dominated by spring flood, when concentrations of Fe, Mn and trace elements increased in forested headwaters. However, in streams of wetland catchments concentrations decreased, but Pb concentrations were higher in comparison to other streams. Both Fe and Pb showed positive correlations with wetland area, while Co correlated with forest coverage. The anthropogenic contribution of As and Pb appear to be larger than the supply from natural sources.During spring flood SO42- decreased in most streams, although concentrations increased in streams of wetland catchments. Concentrations of SO42- were higher in streams of forested catchments than in wetland dominated streams, the former being net exporters of S and the latter net accumulators. Isotope values of stream water SO42- (δ34SSO4) were close to that of precipitation during spring flood, indicating that the major source of S is from deposition. The results show that, although emissions of anthropogenic S have been reduced, there is still a strong influence of past and current S deposition on runoff in this region.In conclusion, wetlands are key areas for the hydrogeochemistry in this boreal landscape. The findings emphasize the importance of understanding stream water chemistry and element cycling from a landscape perspective. This may be important for predicting how boreal regions respond to environmental disturbances such as climate change.
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| 20. |
- Björkvald, Louise, et al.
(författare)
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Landscape variations in stream water SO42- and delta S-34(SO4) in a boreal stream network
- 2009
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 73:16, s. 4648-4660
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Tidskriftsartikel (refereegranskat)abstract
- Despite reduced anthropogenic deposition during the last decades, deposition sulphate may still play an important role in the biogeochemical cycles of S and many catchments may act as net sources of S that may remain for several decades. The aim of this study is to elucidate the temporal and spatial dynamics of both SO42- and delta S-34(SO4) in stream water from catchments with varying percentage of wetland and forest coverage and to determine their relative importance for catchment losses of S. Stream water samples were collected from 15 subcatchments ranging in size from 3 to 6780 ha, in a boreal stream network, northern Sweden. In forested catchments (2% wetland cover) S-SO42- concentrations in stream water averaged 1.7 mg L-1 whereas in wetland dominated catchments (30% wetland cover) the concentrations averaged 0.3 mg L-1. A significant negative relationship was observed between S-SO42- and percentage wetland coverage (r(2) = 0.77, p 0.001) and the annual export of stream water SO42- and wetland coverage (r(2) = 0.76 p 0.001). The percentage forest coverage was on the other hand positively related to stream water SO42- concentrations and the annual export of stream water SO42- (r(2) = 0.77 and r(2) = 0.79, respectively). The annual average delta S-34(SO4) value in wetland dominated streams was +7.6%omicron. and in streams of forested catchments +6.7%omicron. At spring flood the delta S-34(SO4) values decreased in all streams by 1%omicron to 5%omicron. The delta S-34(SO4) values in all streams were higher than the delta S-34(SO4) value of +4.7%omicron in precipitation (snow). The export of S ranged from 0.5 kg S ha(-1) yr(-1) (wetland headwater stream) to 3.8 kg S ha(-1) yr(-1) (forested headwater stream). With an average S deposition in open field of 1.3 kg S ha(-1) yr(-1) (2002-2006) the mass balance results in a net export of S from all catchments, except in catchments with 30% wetland. The high temporal and spatial resolution of this study demonstrates that the reducing environments of wetlands play a key role for the biogeochemistry of S in boreal landscapes and are net sinks of S. Forested areas, on the other hand were net sources of S.
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| 21. |
- 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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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Bohlin, Hanna, et al.
(författare)
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Point source influences on the carbon and nitrogen geochemistry of sediments in the Stockholm inner archipelago, Sweden
- 2006
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Ingår i: Science of the Total Environment. - : Elsevier B.V.. - 0048-9697 .- 1879-1026. ; 366:1, s. 337-349
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Tidskriftsartikel (refereegranskat)abstract
- This study reports analyses of carbon and nitrogen content, and δ15N and δ13C in sediments of the Höggarnsfjärden Bay near Stockholm. Samples have been taken upstream, near, and downstream of a point source of processed leach water from a garbage dump. The surface sediment at the upstream and downstream sites has δ15N and δ13C close to the expected background of the area, even though a contribution from the leach water can be observed downstream of the point source. The sediment close to the outflow is strongly influenced by the carbon and nitrogen in the leach water.
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