| 1. |
- Kylander, Malin, 1977-, et al.
(author)
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A novel geochemical approach to paleorecords of dust deposition and effective humidity: 8500 years of peat accumulation at Store Mosse (the "Great Bog") , Sweden )
- 2013
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 69, s. 69-82
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Journal article (peer-reviewed)abstract
- Both bog surface wetness and atmospheric dust deposition are intricately linked to changes in the hydrological cycle and pairing these types of records at the same site provides complementary information. Here a peat core from Store Mosse in southern Sweden covering the last 8500 years was used to make a high-resolution paleoclimate reconstruction based on a combination of bog development, colourimetric humification and inorganic geochemistry data. The coupling of Principal Component Analysis with changepoint modelling allowed for precise linking of changes in bog surface wetness and dust deposition records.A long-term trend towards warm (and possibly wet) conditions starts ca 8150 cal yr BP and culminates with the most pronounced conditions from 6900 to 6600 cal yr BP. The most significant arid period at Store Mosse occurred between 6500 and 5600 cal yr BP during which dust deposition was significantly higher. Wetter conditions dominate from 5500 to 4980 cal yr BP as the transition from the Hypsithermal and into the Neoglacial is made. After a shift to drier conditions, humification enters a more stable period that lasts from 4525 until 3200 cal yr BP. It is during this time that the first possible anthropogenic dust signals occur at ca 4200 cal yr BP. From 3200 cal yr BP to present humification generally shows a long-term decline moving towards wetter conditions. The main exceptions are during the transition from the Neoglacial to Roman Warm Period which is registered as a significantly wetter period and two dry periods recorded 2365 to 2155 cal yr BP and 1275–1105 cal yr BP. In general, the observed changes agree well with regional records of effective humidity and temperature. The high temporal resolution of the Store Mosse record reveals that palaeoclimatic change over the last 8500 years in southern Sweden has had a complex and variable structure.
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| 2. |
- Sun, Xiaole, 1983-, et al.
(author)
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Climate Dependent Diatom Production is Preserved in Biogenic Si Isotope Signatures
- 2011
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In: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 8:11, s. 3491-3499
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Journal article (peer-reviewed)abstract
- The aim of this study was to reconstruct diatom production in the subarctic northern tip of the Baltic Sea, Bothnian Bay, based on down-core analysis of Si isotopes in biogenic silica (BSi). Dating of the sediment showed that the samples covered the period 1820 to 2000. The sediment core record can be divided into two periods, an unperturbed period from 1820 to 1950 and a second period affected by human activities (from 1950 to 2000). This has been observed elsewhere in the Baltic Sea. The shift in the sediment core record after 1950 is likely caused by large scale damming of rivers. Diatom production was inferred from the Si isotope composition which ranged between δ30Si −0.18‰ and +0.58‰ in BSi, and assuming fractionation patterns due to the Raleigh distillation, the production was shown to be correlated with air and water temperature, which in turn were correlated with the mixed layer (ML) depth. The sedimentary record showed that the deeper ML depth observed in colder years resulted in less production of diatoms. Pelagic investigations in the 1990's have clearly shown that diatom production in the Baltic Sea is controlled by the ML depth. Especially after cold winters and deep water mixing, diatom production was limited and dissolved silicate (DSi) concentrations were not depleted in the water column after the spring bloom. Our method corroborates these findings and offers a new method to estimate diatom production over much longer periods of time in diatom dominated aquatic systems, i.e. a large part of the world's ocean and coastal seas.
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| 3. |
- Klaminder, Jonatan, et al.
(author)
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Carbon mineralization and pyrite oxidation in groundwater : Importance for silicate weathering in boreal forest soils and stream base-flow chemistry
- 2011
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In: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 26:3, s. 319-324
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Journal article (peer-reviewed)abstract
- What role does mineralized organic C and sulfide oxidation play in weathering of silicate minerals in deep groundwater aquifers? In this study, how H(2)CO(3), produced as a result of mineralization of organic matter during groundwater transport, affects silicate weathering in the saturated zone of the mineral soil along a 70 m-long boreal hillslope is demonstrated. Stream water measurements of base cations and delta(18)O are included to determine the importance of the deep groundwater system for downstream surface water. The results suggest that H2CO3 generated from organic compounds being mineralized during the lateral transport stimulates weathering at depths between 0.5 and 3 m in the soil. This finding is indicated by progressively increasing concentrations of base cations-, silica- and inorganic C (IC) in the groundwater along the hillslope that co-occur with decreasing organic C (OC) concentrations. Protons derived from sulfide oxidation appear to be an additional driver of the weathering process as indicated by a buildup of SO(4)(2-) in the groundwater during lateral transport and a delta(34)S parts per thousand value of +0.26-3.76 parts per thousand in the deep groundwater indicating S inputs from pyrite. The two identified active acids in the deep groundwater are likely to control the base-flow chemistry of streams draining larger catchments (>1 km(2)) as evident by delta(18)O signatures and base cation concentrations that overlap with that of the groundwater.
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| 4. |
- Lidman, Fredrik, et al.
(author)
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Selenium Dynamics in Boreal Streams : The Role of Wetlands and Changing Groundwater Tables
- 2011
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 45:7, s. 2677-2683
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Journal article (peer-reviewed)abstract
- The concentrations of selenium in 10 catchments of a stream network in northern Sweden were monitored over two years, yielding almost 350 observations of selenium concentrations in streamwater. The export of selenium was found to be systematically greater from forests than from mires. Accounting for atmospheric deposition, which was monitored over four years, there was a net accumulation of selenium in mires, while the export from forest soils was approximately equal to the atmospheric deposition. In forest dominated catchments the concentrations of selenium oscillated rapidly back and forth from high to low levels during spring floods. High selenium concentrations coincided with rising groundwater tables in the riparian forest soils, while low selenium concentrations were associated with receding groundwater. Thermodynamic modeling indicated that precipitation of elemental selenium would occur under reducing conditions in the riparian soils. Since changes in the redox conditions are likely to occur near the transition from the unsaturated to the saturated zone, it is hypothesized that the transport of selenium from forest soils to streams is controlled by redox reactions in riparian soils.
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| 5. |
- Giesler, Reiner, et al.
(author)
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Spatiotemporal variations of pCO(2) and delta C-13-DIC in subarctic streams in northern Sweden
- 2013
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In: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 27:1, s. 176-186
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Journal article (peer-reviewed)abstract
- Current predictions of climate-related changes in high-latitude environments suggest major effects on the C export in streams and rivers. To what extent this will also affect the stream water CO2 concentrations is poorly understood. In this study we examined the spatiotemporal variation in partial pressure of CO2 (pCO(2)) and in stable isotopic composition of dissolved inorganic carbon (delta C-13-DIC) in subarctic streams in northern Sweden. The selected watersheds are characterized by large variations in high-latitude boreal forest and tundra and differences in bedrock. We found that all streams generally were supersaturated in pCO(2) with an average concentration of 850 mu atm. The variability in pCO(2) across streams was poorly related to vegetation cover, and carbonaceous bedrock influence was manifested in high DIC concentrations but not reflected in either stream pCO(2) or delta C-13-DIC. Stream water pCO(2) values were highest during winter base flow when we also observed the lowest delta C-13-DIC values, and this pattern is interpreted as a high contribution from CO2 from soil respiration. Summer base flow delta C-13-DIC values probably are more affected by in situ stream processes such as aquatic production/respiration and degassing. A challenge for further studies will be to disentangle the origin of stream water CO2 and quantify their relative importance.
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| 6. |
- Alling, Vanja, et al.
(author)
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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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In: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 95, s. 143-159
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Journal article (peer-reviewed)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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| 7. |
- Hong, Bongghi, et al.
(author)
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NANI/NAPI Calculator Toolbox Version 2.0 Documentation : Net Anthropogenic Nutrient Inputs in Baltic Sea Catchments
- 2011
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Reports (other academic/artistic)abstract
- The main objective of this work was to develop regional settings of the NANI budgeting tool that will address the significant variation in agricultural practices and resulting nutrient accountings among European countries. NANI (Net Anthropogenic Nitrogen Inputs), first introduced by Howarth et al. (1996), estimate the human‐induced nitrogen inputs to a watershed and have been shown to be a good predictor of riverine nitrogen export at a large scale, multi‐year average basis. NANI have been calculated as the sum of four major components: atmospheric N deposition, fertilizer N application, agricultural N fixation, and net food and feed imports, which in turn are composed of crop and animal N production (negative fluxes removing N from watersheds) and animal and human N consumption (positive fluxes adding N to watersheds). Assuming approximate steady-state behavior, riverine N export is a fixed proportion of net nitrogen inputs.Similar calculations can be made for phosphorus (P) inputs, though because atmospheric deposition of P is usually considered negligible and there is no analog in P for atmospheric fixation, the calculation of Net Anthropogenic Phosphorus Inputs (NAPI) reduces to accounting for P fertilizer and P in net food/feed terms. While this document is primarily concerned with calculating NANI, we also describe the data sources and assumptions used to make the parallel calculations of NAPI.Version 2.0 of the Toolbox described in this document is an improvement of version 1.0 developed for US watersheds (http://www.eeb.cornell.edu/biogeo/nanc/nani/nani.htm; Hong et al. 2011). Version 1.0 allows the user to calculate NANI in any area within the contiguous United States (e.g., watershed, county, etc.) from nationally available databases downloadable from the Internet. The toolbox consists of a set of tools that:(1) calculate the proportions of various regions (political or gridded) in which data are collected that fall into areas of interest such as watersheds (“NANI‐GIS tools”),(2) extract and organize relevant data downloaded from web‐based datasets to be used by the accounting tools (“NANI‐extraction tools”), and(3) calculate NANI, their components, and other relevant items such as animal excretion (“NANI-.‐accounting tools”).While attempting to apply version 1.0 of the toolbox to Baltic Sea catchments, we found that the calculation of NANI in Baltic Sea catchments is more challenging than in US watersheds, mainly for two reasons:• Watersheds span international boundaries. Significant variation in agricultural practices and resulting nutrient accountings among European countries exist. For example, a substantial gradient in agricultural practices is expected among the former EU countries, new EU member states with transitional economies, and Belarus and Russia.• Gaps and uncertainties in the available data are much greater than those in the US. In general, the problem of missing information is more severe for the transitional countries, Belarus, and Russia, requiring numerous assumptions and guesswork to be made to deal with the insufficient data issue.Version 2.0 of the Toolbox describe in this document has several modules and improvements added to version 1.0 (which assumes spatially uniform agricultural practices, i.e., fixed values for all the NANI parameters, supported by the availability of well‐established and standardized datasets) to address the above difficulties. These improvements include:• Allowing spatial variation of NANI parameters (in this example, country‐specific NANI parameters) (Sections 4, 5.1, and 5.2)• Distribution of regional data (e.g., country-level crop production) into smaller spatial units (e.g., grid cells containing crop area information) (Section 5.3)• Making post‐calculation adjustments and refinements by accepting auxiliary datasets and manual calculations from the user (Section 3) In the following sections we describe the calculation of NANI and their components in the Baltic Sea catchments, with details of data availability, input preparation, and step-by‐step procedure of the use of various tools, and provide some preliminary results. In addition, Appendix 1 described parameter values used to create NAPI estimates following an accounting methodology in parallel to that for NANI.
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| 8. |
- Lidman, Fredrik, et al.
(author)
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Metal transport in the boreal landscape : the role of wetlands and the affinity for organic matter
- 2014
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 48:7, s. 3783-3790
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Journal article (other academic/artistic)abstract
- Stream water concentrations of 13 major and trace elements (Al, Ba, Ca, Cr, Cu, La, Mg, Na,Ni, Si, Sr, U, Y) were used to estimate fluxes from 15 boreal catchments. All elementsdisplayed a significant negative correlation to the wetland coverage in each catchment, butthe influence of wetlands was stronger for organophilic metals. 73% of the spatialdifferences in the normalized element fluxes could be explained based only on the wetlandcoverage and the affinity for organic matter, which was quantified using thermodynamicmodeling. When restraining the analysis to the smaller streams (<10 km2) the explanatorypower increased to 88%. The results suggest that wetlands may decrease the fluxes ofmetals from boreal forests to downstream recipients by up to 40%. We suggest that thedecrease in element fluxes is caused by a combination of low weathering in peat soils andaccumulation of organophilic metals in peat. The model could not explain the spatial pattersfor some metals with low affinity for organic matter, some redox-sensitive metals and somemetals with exceptionally high atmospheric deposition, but the results still demonstrate thatwetlands play a crucial role for the biogeochemical cycling of metals in the boreal landscape.
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| 9. |
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| 10. |
- Sun, Xiaole, et al.
(author)
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Silicon isotope enrichment in diatoms during nutrient-limited blooms in a eutrophied river system
- 2013
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In: Journal of Geochemical Exploration. - : Elsevier BV. - 0375-6742 .- 1879-1689. ; 132, s. 173-180
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Journal article (peer-reviewed)abstract
- We examined the Si isotope fractionation by following a massive nutrient limited diatom bloom in a eutrophied natural system. The Oder River, which is a eutrophied river draining the western half of Poland and entering the southern Baltic Sea, exhibits diatom blooms that cause extreme Si isotope fractionation. The rapid nutrient depletion and fast BSi increase observed during the spring bloom suggest a closed system Rayleigh behavior for DSi and BSi in the river at certain time scales. A Si isotope fractionation factor ((30)epsilon(Dsi-Bsi)) of -1.6 +/- 0.31%. (2 sigma) is found based on observations between April and June, 2004. A very high delta Si-30 value of up to +3.05 parts per thousand. is measured in BSi derived from diatoms. This is about 2 times higher than previously recorded delta Si-30 in freshwater diatoms. The Rayleigh model used to predict the delta Si-30 values of DSi suggests that the initial value before the start of the diatom bloom is close to +2 parts per thousand, which is relatively higher than the previously reported values in other river water. This indicates that there is a biological control of the Si isotope compositions entering the river, probably caused by Si isotope fractionation during uptake of Si in phytoliths. Clearly, eutrophied rivers with enhanced diatom blooms deliver Si-30-enriched DSi and BSi to the coastal ocean, which can be used to trace the biogeochemistry of DSi/BSi in estuaries.
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