| 61. |
- Rämö, Robert, et al.
(författare)
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Sediment Remediation Using Activated Carbon: Effects of Sorbent Particle Size and Resuspension on Sequestration of Metals and Organic Contaminants.
- 2022
-
Ingår i: Environmental toxicology and chemistry. - : Wiley. - 1552-8618 .- 0730-7268. ; 41:4, s. 1096-1110
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Tidskriftsartikel (refereegranskat)abstract
- Thin-layer capping using activated carbon (AC) has been described as a cost-effective in situ sediment remediation method for organic contaminants. In this study, we compare the capping efficiency of powdered AC (PAC) against granular AC (GAC) using contaminated sediment from Oskarshamn harbor, Sweden. The effects of resuspension on contaminant retention and cap integrity were also studied. Intact sediment cores were collected from the outer harbor and brought to the laboratory. Three thin-layer caps, consisting of PAC or GAC mixed with clay, or clay only, were added to the sediment surface. Resuspension was created using a motor-driven paddle to simulate propeller wash from ship traffic. Passive samplers were placed in the sediment and in the water column to measure the sediment-to-water release of PAHs, PCBs, and metals. Our results show that a thin-layer cap with PAC reduced sediment-to-water fluxes of PCBs by 57 % under static conditions and 91 % under resuspension. Thin-layer capping with GAC was less effective than PAC, but reduced fluxes of high-molecular weight PAHs. Thin-layer capping with AC was less effective in retaining metals, except for Cd, which release was significantly reduced by PAC. Resuspension generally decreased water concentrations of dissolved cationic metals, perhaps due to sorption to suspended sediment particles. Sediment resuspension in treatments without capping increased fluxes of PCBs with log Kow > 7 and PAHs with log Kow 5 6, but resuspension reduced PCB and PAH fluxes through the PAC thin-layer cap. Overall, PAC performed better than GAC, but adverse effects on the benthic community and transport of PAC to non-target areas are drawbacks that favor the use of GAC. This article is protected by copyright. All rights reserved.© 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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| 62. |
- Hetzinger, S., et al.
(författare)
-
High-resolution analysis of trace elements in crustose coralline algae from the North Atlantic and North Pacific by laser ablation ICP-MS
- 2011
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Ingår i: Palaeogeography Palaeoclimatology Palaeoecology. - 0031-0182. ; 302:1-2, s. 81-94
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the trace elemental composition in the skeleta of two specimens of attached-living coralline algae of the species Clathromorphum compactum from the North Atlantic (Newfoundland) and Clathromorphum nereostratum from the North Pacific/Bering Sea region (Amchitka Island, Aleutians). Samples were analyzed using Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (IA-ICP-MS) yielding for the first time continuous individual trace elemental records of up to 69 years in length. The resulting algal Mg/Ca, Sr/Ca, U/Ca, and Ba/Ca ratios are reproducible within individual sample specimens. Algal Mg/Ca ratios were additionally validated by electron microprobe analyses (Amchitka sample). Algal Sr/Ca, U/Ca, and Ba/Ca ratios were compared to algal Mg/Ca ratios, which previously have been shown to reliably record sea surface temperature (SST). Ratios of Sr/Ca from both Clathromorphum species show a strong positive correlation to temperature-dependent Mg/Ca ratios, implying that seawater temperature plays an important role in the incorporation of Sr into algal calcite. Linear Sr/Ca-SST regressions have provided positive, but weaker relationships as compared to Mg/Ca-SST relationships. Both, algal Mg/Ca and Sr/Ca display clear seasonal cycles. Inverse correlations were found between algal Mg/Ca and U/Ca, Ba/Ca, and correlations to SST are weaker than between Mg/Ca, Sr/Ca and SST. This suggests that the incorporation of U and Ba is influenced by other factors aside from temperature. (C) 2010 Elsevier B.V. All rights reserved.
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| 63. |
- Hylén, Astrid, 1991, et al.
(författare)
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Enhanced benthic nitrous oxide and ammonium production after natural oxygenation of long-term anoxic sediments
- 2022
-
Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 67:2, s. 419-433
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Tidskriftsartikel (refereegranskat)abstract
- Coastal and shelf sediments are central in the global nitrogen (N) cycle as important sites for the removal offixed N. However, this ecosystem service can be hampered by ongoing deoxygenation in many coastal areas.Natural reoxygenation could reinstate anoxic sediments as sites wherefixed N is removed efficiently. To investi-gate this further, we studied benthic N cycling in previously long-term anoxic sediments, following a largeintrusion of oxygenated water to the Baltic Sea. During three campaigns in 2016–2018, we measured in situsediment–waterfluxes of ammonium (NHþ4), nitrate (NO3), oxygen (O2), dissolved inorganic carbon, and NO3reduction processes using benthic chamber landers. Sediment microprofiles of O2, nitrous oxide (N2O), andhydrogen sulfide were measured in sediment cores. At a permanently oxic station, denitrification to N2was themain NO3reduction process. Benthic N2O production appeared to be linked to nitrification, although no netN2Ofluxes from the sediment were detected. At newly oxygenated sites, dissimilatory NO3reduction to NHþ4comprised almost half of the total NO3reduction. At these stations, the removal offixed N was inefficient dueto high effluxes of NHþ4. Sedimentary N2O production was associated with incomplete denitrification, account-ing for 41–88% of the total denitrification rate. Microprofiling revealed algae aggregates as potential hotspots ofseafloor N2O production. Our results show that transient oxygenation of euxinic systems initiates benthic NO3reduction, but may not lead to efficient sedimentary removal offixed N. Instead, recycling of N compounds ispromoted, which may accelerate the return to anoxia.
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| 64. |
- Kylander, Malin E., et al.
(författare)
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Potentials and problems of building detailed dust records using peat archives : An example from Store Mosse (the "Great Bog"), Sweden
- 2016
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533 .- 0046-564X. ; 190, s. 156-174
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Tidskriftsartikel (refereegranskat)abstract
- Mineral dust deposition is a process often overlooked in northern mid-latitudes, despite its potential effects on ecosystems. These areas are often peat-rich, providing ample material for the reconstruction of past changes in atmospheric deposition. The highly organic (up to 99% in some cases) matrix of atmospherically fed mires, however, makes studying the actual dust particles (grain size, mineralogy) challenging. Here we explore some of the potentials and problems of using geochemical data from conservative, lithogenic elements (Al, Ga, Rb, Sc, Y, Zr, Th, Ti and REE) to build detailed dust records by using an example from the 8900-yr peat sequence from Store Mosse (the "Great Bog"), which is the largest mire complex in the boreo-nemoral region of southern Sweden. The four dust events recorded at this site were elementally distinct, suggesting different dominant mineral hosts. The oldest and longest event (6385-5300 cal yr BP) sees a clear signal of clay input but with increasing contributions of mica, feldspar and middle-REE- rich phosphate minerals over time. These clays are likely transported from a long-distance source (< 100 km). While dust deposition was reduced during the second event (5300-4370 cal yr BP), this is the most distinct in terms of its source character with [Eu/Eu*] UCC revealing the input of plagioclase feldspar from a local source, possibly active during this stormier period. The third (2380- 2200 cal yr BP) and fourth (1275-1080 cal yr BP) events are much shorter in duration and the presence of clays and heavy minerals is inferred. Elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element. The broad changes in major mineral hosts, grain size, source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern Europe. The two most recent dust events are much shorter in duration, which in combination with evidence of their local and regional character, may explain why they have not been seen elsewhere.
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| 65. |
- Kylander, Malin E., 1977-, et al.
(författare)
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Storm chasing : Tracking Holocene storminess in southern Sweden using mineral proxies from inland and coastal peat bogs
- 2023
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 299, s. 107854-
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Tidskriftsartikel (refereegranskat)abstract
- Severe extratropical winter storms are a recurrent feature of the European climate and cause widespread socioeconomic losses. Due to insufficient long-term data, it remains unclear whether storminess has shown a notable response to changes in external forcing over the past millennia, which impacts our ability to project future storminess in a changing climate. Reconstructing past storm variability is essential to improving our understanding of storms on these longer, missing timescales. Peat sequences from coastal ombrotrophic bogs are increasingly used for this purpose, where greater quantities of coarser grained beach sand are deposited by strong winds during storm events. Moving inland however, storm intensity decreases, as does sand availability, muting potential paleostorm signals in bogs. We circumvent these issues by taking the innovative approach of using mid-infrared (MIR) spectral data, supported by elemental information, from the inorganic fraction of Store Mosse Dune South (SMDS), a 5000-year-old sequence from a large peatland located in southern Sweden. We infer past changes in mineral composition and thereby, the grain size of the deposited material. The record is dominated by quartz, whose coarse nature was confirmed through analyses of potential local source sediments. This was supported by further mineralogical and elemental proxies of atmospheric input. Comparison of SMDS with within-bog and regionally relevant records showed that there is a difference in proxy and site response to what should be similar timing in shifts in storminess over the-100 km transect considered. We suggest the construction of regional storm stacks, built here by applying changepoint modelling to four transect sites jointly. This modelling approach has the effect of reinforcing signals in common while reducing the influence of random noise. The resulting Southern Sweden-Storm Stack dates stormier periods to 4495-4290, 3880-3790, 2885-2855, 2300-2005, 1175-1065 and 715-425 cal yr BP. By comparing with a newly constructed Western Scotland-Storm Stack and proximal dune records, we argue that regional storm stacks allow us to better compare past storminess over wider areas, gauge storm track movements and by extension, increase our understanding of the drivers of storminess on centennial to millennial timescales.
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| 66. |
- Lundin, Erik J, et al.
(författare)
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Is the subarctic landscape still a carbon sink? : Evidence from a detailed catchment balance
- 2016
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 43:5, s. 1988-1995
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming raises the question whether high-latitude landscape still function as net carbon (C) sinks. By compiling an integrated C balance for an intensely studied subarctic catchment, we show that this catchment's C balance is not likely to be a strong current sink of C, a commonly held assumption. In fact, it is more plausible (71% probability) that the studied catchment functions as a C source (-1120gCm(-2)yr(-1)). Analyses of individual fluxes indicate that soil and aquatic C losses offset C sequestering in other landscape components (e.g., peatlands and aboveground forest biomass). Our results stress the importance of fully integrated catchment C balance estimates and highlight the importance of upland soils and their interaction with the aquatic network for the catchment C balance.
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| 67. |
- Löfgren, Johan, 1983, et al.
(författare)
-
Sea Level Monitoring Using a GNSS-Based Tide Gauge
- 2009
-
Ingår i: 2nd International Colloquium - Scientific and Fundamental Aspects of the Galileo Programme, 14 - 16 October 2009, Padua, Italy.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Global climate change is believed to result in the melting of large masses of ice in Polar Regions, bringing freshwater into the ocean, and changing the sea level. The traditional way to measure the sea level, by tide gauges, results in measurements relative to the Earth’s crust. However, in order to fully understand the sea level changes, absolute measurements (change in sea level in relation to the Earth’s center of gravity) are necessary, in particular in regions affected by post-glacial uplift, e.g., Fennoscandia. Satellite techniques, e.g., GNSS can be used to determine the motion of the Earth’s crust in relation to the center of gravity. By measuring reflected GNSS-signals from the sea surface, information of the sea level change can be obtained. Therefore a GNSS-based tide gauge is proposed.The proposed GNSS-based tide gauge installation consists of two antennas, one zenith looking right hand circular polarized (RHCP) and one nadir looking left hand circular polarized (LHCP), mounted back-to-back on a beam over the ocean. The RHCP antenna receives the GNSS-signals directly, whereas the LHCP antenna receives the signals reflected from the sea surface. Because of the additional path delay of the reflected signal, the LHCP antenna will appear to be a virtual GNSS-antenna located below the sea surface. When the sea level changes, the path delay of the reflected signal changes, thus the LHCP antenna will appear to be in a new position. The vertical position change corresponds to twice the sea level change, and therefore monitors sea level changes.Multiple satellites with different elevation and azimuth angles are observed each epoch and will give rise to reflected signals with different incidence angles from different directions. This means that the estimated sea level change can not be considered to originate from one specific point on the surface, but rather represents the change of an average surface formed by the reflection points.An experimental setup was installed in December 2008 over the ocean at Onsala Space Observatory (OSO) at the west coast of Sweden. Data was collected during three days using two Leica GRX1200+ receivers (one for the direct and one for the reflected signal). The receivers recorded 40 hours of continuous 20Hz data. The signal-to-noise ratio (SNR) as determined by the two receivers was used as a first data quality check. On average the SNR difference between the directly received and the reflected signals was less than 3dB.The data was analyzed using an in-house developed software in MATLAB. Solutions were made using L1 phase delays for relative positioning. Two approaches to estimate the vertical difference between the RHCP and the LHCP antenna were tested: hourly estimates of the vertical difference, and high-rate estimates of the vertical difference. For the hourly estimates 40 hours of continuous 1Hz data (reduced for faster processing using the TEQC software) were used. Each solution was made using 20 minutes of data every full hour, solving for differences in the local vertical components together with receiver clock and phase ambiguities differences for each epoch.The solution for the high-rate vertical component was made in two steps. First, the phase ambiguity differences were determined. This was done using equally distributed short intervals of ~1 second (21 epochs) from ~20 minutes of 20Hz data, solving for difference in phase ambiguities and receiver clocks every epoch together with differences in vertical coordinate for each short interval. The processing was done based on the assumptions that the sea surface does not change significantly during ~1 second and that the satellite geometry changes considerably in ~20 minutes. Second, the differences in phase ambiguities were rounded to the nearest integer and inserted as known values for a reprocessing of the 20Hz data. In this reprocessing the receiver clock parameters were estimated every epoch and the vertical coordinate difference with different time resolutions (e.g. 0.05s, 1s, 30s).The resulting time-series for the sea level change from the hourly solutions were compared to data from two traditional tide gauges operated by the Swedish Meteorological and Hydrological Institute at Ringhals and Göteborg, about 18 km south of and 33 km north of OSO, respectively. The GNSS-derived sea level change resembles reasonably well the independently observed sea level change. This indicates that the GNSS-tide gauge gives valuable results for sea level monitoring. Furthermore, the use of the high-rate GNSS-receivers additionally allows a flexible time resolution for sea level monitoring.
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| 68. |
- Maskenskaya, Olga M., et al.
(författare)
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Source and character of syntaxial hydrothermal calcite veins in Paleoproterozoic crystalline rocks revealed by fine-scale investigations
- 2014
-
Ingår i: Geofluids. - : Wiley. - 1468-8115 .- 1468-8123. ; 14:4, s. 495-511
-
Tidskriftsartikel (refereegranskat)abstract
- Calcite veins in Paleoproterozoic granitoids on the Baltic Shield are the focus of this study. These veins are distinguished by their monomineralic character, unusual thickness and closeness to Neoproterozoic dolerite dykes and therefore have drawn attention. The aim of this study was to define the source of these veins and to unravel their isotopic and chemical nature by carrying out fine-scale studies. Seven calcite veins covering a depth interval of 50-420m below the ground surface and composed of breccias or crack-sealed fillings typically expressing syntaxial growth were sampled and analysed for a variety of physicochemical variables: homogenization temperature (T-h) and salinity of fluid inclusions, and stable isotopes (Sr-87/Sr-86, C-13/C-12, O-18/O-16), trace-element concentrations (Fe, Mn, Mg, Sr, rare earth elements) and cathodoluminescence (CL) of the solid phase. The fluid-inclusion data show that the calcites were precipitated mainly from relatively low-temperature (T-h=73-106 degrees C) brines (13.4-24.5wt.% CaCl2), and the Sr-87/Sr-86 is more radiogenic than expected for Rb-poor minerals precipitated from Neoproterozoic fluids. These features, together with the distribution of C-13 and O-18 values, provide evidence that the calcite veins are not genetic with the nearby Neoproterozoic dolerite dykes, but are of Paleozoic age and were precipitated from warm brines expressing a rather large variability in salinity. Whereas the isotopic and chemical variables express rather constant average values among the individual veins, they vary considerably on fine-scale across individual veins. This has implications for understanding processes causing calcite-rich veins to form and capture trace metals in crystalline bedrock settings.
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| 69. |
- Metcalfe, Daniel B., et al.
(författare)
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Patchy field sampling biases understanding of climate change impacts across the Arctic
- 2018
-
Ingår i: Nature Ecology and Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 2:9, s. 1443-1448
-
Tidskriftsartikel (refereegranskat)abstract
- Effective societal responses to rapid climate change in the Arctic rely on an accurate representation of region-specific ecosystem properties and processes. However, this is limited by the scarcity and patchy distribution of field measurements. Here, we use a comprehensive, geo-referenced database of primary field measurements in 1,840 published studies across the Arctic to identify statistically significant spatial biases in field sampling and study citation across this globally important region. We find that 31% of all study citations are derived from sites located within 50 km of just two research sites: Toolik Lake in the USA and Abisko in Sweden. Furthermore, relatively colder, more rapidly warming and sparsely vegetated sites are under-sampled and under-recognized in terms of citations, particularly among microbiology-related studies. The poorly sampled and cited areas, mainly in the Canadian high-Arctic archipelago and the Arctic coastline of Russia, constitute a large fraction of the Arctic ice-free land area. Our results suggest that the current pattern of sampling and citation may bias the scientific consensuses that underpin attempts to accurately predict and effectively mitigate climate change in the region. Further work is required to increase both the quality and quantity of sampling, and incorporate existing literature from poorly cited areas to generate a more representative picture of Arctic climate change and its environmental impacts.
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| 70. |
- Mills, Gina, 1959, et al.
(författare)
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Tropospheric Ozone Assessment Report: Present-day tropospheric ozone distribution and trends relevant to vegetation
- 2018
-
Ingår i: Elementa-Science of the Anthropocene. - : University of California Press. - 2325-1026. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- This Tropospheric Ozone Assessment Report (TOAR) on the current state of knowledge of ozone metrics of relevance to vegetation (TOAR-Vegetation) reports on present-day global distribution of ozone at over 3300 vegetated sites and the long-term trends at nearly 1200 sites. TOAR-Vegetation focusses on three metrics over vegetation-relevant time-periods across major world climatic zones: M12, the mean ozone during 08:00-19:59; AOT40, the accumulation of hourly mean ozone values over 40 ppb during daylight hours, and W126 with stronger weighting to higher hourly mean values, accumulated during 08:00-19:59. Although the density of measurement stations is highly variable across regions, in general, the highest ozone values (mean, 2010-14) are in mid-latitudes of the northern hemisphere, including southern USA, the Mediterranean basin, northern India, north, north-west and east China, the Republic of Korea and Japan. The lowest metric values reported are in Australia, New Zealand, southern parts of South America and some northern parts of Europe, Canada and the USA. Regional-scale assessments showed, for example, significantly higher AOT40 and W126 values in East Asia (EAS) than Europe (EUR) in wheat growing areas (p < 0.05), but not in rice growing areas. In NAM, the dominant trend during 1995-2014 was a significant decrease in ozone, whilst in EUR it was no change and in EAS it was a significant increase. TOAR-Vegetation provides recommendations to facilitate a more complete global assessment of ozone impacts on vegetation in the future, including: an increase in monitoring of ozone and collation of field evidence of the damaging effects on vegetation; an investigation of the effects on peri-urban agriculture and in mountain/upland areas; inclusion of additional pollutant, meteorological and inlet height data in the TOAR dataset; where not already in existence, establishing new region-specific thresholds for vegetation damage and an innovative integration of observations and modelling including stomatal uptake of the pollutant.
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