| 1. |
- Björk, Mats, 1960-, et al.
(author)
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Methane emissions from macrophyte beach wrack on Baltic seashores
- 2023
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In: Ambio. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 52:1, s. 171-181
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Journal article (peer-reviewed)abstract
- Beach wrack of marine macrophytes is a natural component of many beaches. To test if such wrack emits the potent greenhouse gas methane, field measurements were made at different seasons on beach wrack depositions of different ages, exposure, and distance from the water. Methane emissions varied greatly, from 0 to 176 mg CH4-C m−2 day−1, with a clear positive correlation between emission and temperature. Dry wrack had lower emissions than wet. Using temperature data from 2016 to 2020, seasonal changes in fluxes were calculated for a natural wrack accumulation area. Such calculated average emissions were close to zero during winter, but peaked in summer, with very high emissions when daily temperatures exceeded 20 °C. We conclude that waterlogged beach wrack significantly contributes to greenhouse gas emissions and that emissions might drastically increase with increasing global temperatures. When beach wrack is collected into heaps away from the water, the emissions are however close to zero.
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| 2. |
- Oni, Stephen, et al.
(author)
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Local- and landscape-scale impacts of clear-cuts and climate change on surface water dissolved organic carbon in boreal forests
- 2015
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In: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 120:11, s. 2402-2426
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Journal article (peer-reviewed)abstract
- Forest harvesting and climate change may significantly increase concentrations and fluxes of dissolved organic carbon (DOC) in boreal surface waters. However, the likely magnitude of any effect will vary depending on the landscape-element type and spatial scale. We used a chain of hydrological, empirical, and process-based biogeochemical models coupled to an ensemble of downscaled Regional Climate Model experiments to develop scenario storylines for local- and landscape-scale effects of forest harvesting and climate change on surface water DOC concentrations and fluxes. Local-scale runoff, soil temperature, and DOC dynamics were simulated for a range of forest and wetland landscape-element types and at the larger landscape scale. The results indicated that climate change will likely lead to greater winter flows and earlier, smaller spring peaks. Both forest harvesting and climate change scenarios resulted in large increases in summer and autumn runoff and higher DOC fluxes. Forest harvesting effects were clearly apparent at local scales. While at the landscape scale, approximately 1 mg L−1 (or 10%) of the DOC in surface waters can be attributed to clear-cuts, both climate change and intensified forestry can each increase DOC concentrations by another 1 mg L−1 in the future, which is less than that seen in many waterbodies recovering from acidification. These effects of forestry and climate change on surface water DOC concentrations are additive at a landscape scale but not at the local scale, where a range of landscape-element specific responses were observed.
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| 3. |
- Weis, Franz A., et al.
(author)
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Magmatic water contents determined through clinopyroxene : Examples from the Western Canary Islands, Spain
- 2015
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In: Geochemistry Geophysics Geosystems. - 1525-2027. ; 16:7, s. 2127-2146
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Journal article (peer-reviewed)abstract
- Water is a key parameter in magma genesis, magma evolution, and resulting eruption styles, because it controls the density, the viscosity, as well as the melting and crystallization behavior of a melt. The parental water content of a magma is usually measured through melt inclusions in minerals such as olivine, a method which may be hampered, however, by the lack of melt inclusions suitable for analysis, or postentrapment changes in their water content. An alternative way to reconstruct the water content of a magma is to use nominally anhydrous minerals (NAMs), such as pyroxene, which take up low concentrations of hydrogen as a function of the magma's water content. During magma degassing and eruption, however, NAMs may dehydrate. We therefore tested a method to reconstruct the water contents of dehydrated clinopyroxene phenocrysts from the Western Canary islands (n=28) through rehydration experiments followed by infrared and Mossbauer spectroscopy. Employing currently available crystal/melt partitioning data, the results of the experiments were used to calculate parental water contents of 0.710.07 to 1.490.15 wt % H2O for Western Canary magmas during clinopyroxene crystallization at upper mantle conditions. This H2O range is in agreement with calculated water contents using plagioclase-liquid-hygrometry, and with previously published data for mafic lavas from the Canary Islands and comparable ocean island systems elsewhere. Utilizing NAMs in combination with hydrogen treatment can therefore serve as a proxy for pre-eruptive H2O contents, which we anticipate becoming a useful method applicable to mafic rocks where pyroxene is the main phenocryst phase.
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| 4. |
- Erlandsson, M., et al.
(author)
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Spatial and temporal variations of base cation release from chemical weathering on a hillslope scale
- 2016
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In: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 441, s. 1-13
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Journal article (peer-reviewed)abstract
- Cation release rates to catchment runoff from chemical weathering were assessed using an integrated catchment model that included the soil's unsaturated, saturated and riparian zones. In-situ mineral dissolution rates were calculated in these zones as a function of pH, aluminum and dissolved organic carbon (DOC) concentrations along a hillslope in Northern Sweden where soil water was monitored over nine years. Three independent sets of mineral dissolution equations of varying complexity were used: PROFILE, Transition-State Theory (TST), and the Palandri & Kharaka database. Normalization of the rate-coefficients was necessary to compare the equations, as published rate-coefficients gave base cation release rates differing by several orders of magnitude. After normalizing the TST- and Palandri & Kharaka-rate coefficients to match the base cation release rates calculated from the PROFILE-equations, calculated Ca2 + and Mg2 + release rates are consistent with mass balance calculations, whereas those of Na+ and K+ are overestimated. Our calculations further indicate that a significant proportion of base cations are released from the organic soils in the near-stream zone, in part due to its finer texture. Of the three sets of rate equations, the base cation release rates calculated from the normalized TST-equations were more variable than those calculated using the other two sets of equations, both spatially and temporally, due to its higher sensitivity to pH. In contrast, the normalized Palandri & Kharaka-equations were more sensitive to variations in soil temperature.
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| 5. |
- Teutschbein, Claudia, 1985-, et al.
(author)
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Future Riverine Inorganic Nitrogen Load to the Baltic Sea From Sweden : An Ensemble Approach to Assessing Climate Change Effects
- 2017
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In: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 31:11, s. 1674-1701
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Journal article (peer-reviewed)abstract
- The dramatic increase of bioreactive nitrogen entering the Earth’s ecosystems continues toattract growing attention. Increasingly large quantities of inorganic nitrogen are flushed from land towater, accelerating freshwater, and marine eutrophication. Multiple, interacting, and potentiallycountervailing drivers control the future hydrologic export of inorganic nitrogen. In this paper, we attempt toresolve these land-water interactions across boreal/hemiboreal Sweden in the face of a changing climatewith help of a versatile modeling framework to maximize the information value of existing measurementtime series. We combined 6,962 spatially distributed water chemistry observations spread over 31 years withdaily streamflow and air temperature records. An ensemble of climate model projections, hydrologicalsimulations, and several parameter parsimonious regression models was employed to project future riverineinorganic nitrogen dynamics across Sweden. The median predicted increase in total inorganic nitrogenexport from Sweden (2061–2090) due to climate change was 14% (interquartile range 0–29%), based on theensemble of 7,500 different predictions for each study site. The overall export as well as the seasonal patternof inorganic nitrogen loads in a future climate are mostly influenced by longer growing seasons and morewinter flow, which offset the expected decline in spring flood. The predicted increase in inorganic nitrogenloading due to climate change means that the political efforts for reducing anthropogenic nitrogen inputsneed to be increased if ambitions for reducing the eutrophication of the Baltic Sea are to be achieved.
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| 6. |
- Winterdahl, Mattias, et al.
(author)
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Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites
- 2011
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In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:8, s. 920-930
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Journal article (peer-reviewed)abstract
- Short-term variability in stream water dissolved organic carbon (DOC) concentrations is controlled by hydrology, climate and atmospheric deposition. Using the Riparian flow-concentration Integration Model (RIM), we evaluated factors controlling stream water DOC in the Swedish Integrated Monitoring (IM) catchments by separating out hydrological effects on stream DOC dynamics. Model residuals were correlated with climate and deposition-related drivers. DOC was most strongly correlated to water flow in the northern catchment (Gammtratten). The southern Aneboda and Kindla catchments had pronounced seasonal DOC signals, which correlated weakly to flow. DOC concentrations at GAyenrdsjon increased, potentially in response to declining acid deposition. Soil temperature correlated strongly with model residuals at all sites. Incorporating soil temperature in RIM improved model performance substantially (20-62% lower median absolute error). According to the simulations, the RIM conceptualization of riparian processes explains between 36% (Kindla) and 61% (Aneboda) of the DOC dynamics at the IM sites.
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| 7. |
- Hawkes, Jeffrey A., et al.
(author)
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Regional diversity of complex dissolved organic matter across forested hemiboreal headwater streams
- 2018
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Journal article (peer-reviewed)abstract
- Dissolved organic matter (DOM) from soils enters the aquatic environment via headwater streams. Thereafter, it is gradually transformed, removed by sedimentation, and mineralised. Due to the proximity to the terrestrial source and short water residence time, the extent of transformation is minimal in headwaters. DOM has variable composition across inland waters, but the amount of variability in the terrestrial end member is unknown. This gap in knowledge is crucial considering the potential impact large variability would have on modelling DOM degradation. Here, we used a novel liquid chromatography –mass spectrometry method to characterise DOM in 74 randomly selected, forested headwater streams in an 87,000 km2 region of southeast Sweden. We found a large degree of sample similarity across this region, with Bray-Curtis dissimilarity values averaging 8.4 ± 3.0% (mean ± SD). The identified variability could be reduced to two principle coordinates, correlating to varying groundwater flow-paths and regional mean temperature. Our results indicate that despite reproducible effects of groundwater geochemistry and climate, the composition of DOM is remarkably similar across catchments already as it leaves the terrestrial environment, rather than becoming homogeneous as different headwaters and sub-catchments mix.
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| 8. |
- Zhang, Yi Ge, et al.
(author)
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Refining the alkenone-pCO2 method II : Towards resolving the physiological parameter ‘b’
- 2020
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In: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 281, s. 118-134
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Journal article (peer-reviewed)abstract
- Haptophyte algal biomarkers called alkenones are widely used to reconstruct atmospheric CO2 in Earth’s Cenozoic history. This method is based on the notion that the algal carbon isotope fractionation during photosynthesis, as represented by ep37:2, is a function of seawater CO2 concentration and algal physiology. Constraining the algal physiological parameter, known as the ‘b’ term, is the key for successful applications of the alkenone-CO2 method. Using sensitivity analyses, we show that the growth rate (µ), cell size (r), and membrane permeability (P) are the most important variables to determine b. For all life on Earth, body size is a key factor that regulates metabolic rates. Exploiting the interdependence between phytoplankton cell size and growth rate, and specifically, the r – µ relationship for coccolithophores, we show that the length of fossil coccoliths (Lcoccolith) produced by ancient alkenone-synthesizers can be used to estimate r and therefore µ. Combining our new Lcoccolith data and published ep37:2 from the South China Sea Site MD01-2392, existing results from ODP Site 925, and ice core CO2, we determined the cell membrane permeability (P = 5.09 10-5 m s-1) for the Pleistocene community employing a bootstrap resampling technique. These new methods of constraining r, µ and P, combined with proxy-derived temperature (T), led us to rebuild b as a variable for each sample individually, which is subsequently used for alkenone-CO2 calculations. Application of this approach established pCO2 of the last 3 glacial-interglacial cycles, which turns out to be comparable with the ice core data in both the amplitude of changes and absolute values. It also reconciles the published Eocene – Oligocene alkenone-CO2 data which showed large geographical differences, with the new estimates much more consistent among different sites, and in line with other proxy-based results and ice sheet model predictions.
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| 9. |
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| 10. |
- Schutz, Johanna, et al.
(author)
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A newly developed injection method for aluminum treatment in eutrophic lakes: : Effects on water quality and phosphorus binding efficiency
- 2017
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In: Lake and reservoir management. - : TAYLOR & FRANCIS INC. - 1040-2381 .- 2151-5530. ; 33:2, s. 152-162
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Journal article (peer-reviewed)abstract
- Application of aluminum (Al) salts has been used to reduce phosphorus (P) concentrations in lakes since the 1960s. Al is typically applied to the water column where Al-hydroxides form, settle to the sediment surface, and bind P in sediment. Al can be transported to other, non-target areas of the lake, however, potentially limiting treatment effectiveness. To alleviate this problem, a new method has been developed in which the Al salt is injected directly into the sediment as a liquid. In this study, the binding efficiency and application costs were calculated for 2 lakes in Sweden that received injection applications of polyaluminum chloride (PAC). Binding efficiency was similar to previous water column applications, implying there is little difference between the 2 application methods. Other factors, however, such as dissolved organic matter and type of Al salt used (PAC vs. Al sulfate), can also affect binding efficiency. Thus, Al injection may have improved the amount of P bound per unit Al in the study lakes given the in-lake conditions and Al salt used. Treatment cost (cost per kilogram of P bound to Al) for the injection method compared to previous water column treatments was somewhat higher due to increased costs for buffered PAC and time needed for application. Both mobile sediment P and internal loading remained reduced compared to pre-treatment conditions, showing that the Al injection treatments continued to control sediment P release. More study is needed, however, to determine the relative effectiveness of this method in different types of lakes.
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