| 1. |
- Åkesson, Sofia, et al.
(författare)
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Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach
- 2020
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Ingår i: Ambio: a Journal of the Human Environment. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 50, s. 1074-1088
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Tidskriftsartikel (refereegranskat)abstract
- A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity. This observation was confirmed by all methods and the examination of the impact of geological conditions on the biotransformation process was facilitated by the unique combination of the applied methods. There is thus significant benefit from deploying an extended array of methods for these investigations, with the potential to reduce costs involved in remediation of contaminated sediment and groundwater.
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| 2. |
- Barthel, Roland, 1967, et al.
(författare)
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Similarity-based approaches in hydrogeology: proposal of a new concept for data-scarce groundwater resource characterization and prediction
- 2021
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1435-0157 .- 1431-2174. ; 29:5, s. 1693-1709
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Tidskriftsartikel (refereegranskat)abstract
- A new concept is proposed for describing, analysing and predicting the dynamic behaviour of groundwater resources based on classification and similarity. The concept makes use of the ideas put forward by the “PUB” (predictions in ungauged basins) initiative in surface-water hydrology. One of the approaches developed in PUB uses the principle that similar catchments, exposed to similar weather conditions, will generate a similar discharge response at the catchment outlet. This way, models developed for well-observed catchments can be used to make predictions for ungauged catchments with similar properties (topography, land use, etc.). The concept proposed here applies the same idea to groundwater systems, with the goal to make predictions of the dynamic behaviour of groundwater in poorly observed systems using similarities to well-observed and understood systems. This paper gives an overview of the main ideas, the methodological background, the progress so far, and the challenges that the authors regard as most crucial for further development. One of the main goals of this article is thus to raise interest for this new concept within the groundwater community. There are a multitude of highly interesting aspects to investigate, and a community effort, as with PUB, is required. A second goal is to foster and exchange ideas between the groundwater and surface water research communities who, while often working on similar problems, have often missed the opportunity to learn from each other.
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| 3. |
- 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
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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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| 4. |
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| 5. |
- Aldenhoff, Wiebke, 1985, et al.
(författare)
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Comparison of ice/water classification in Fram Strait from C- and L-band SAR imagery
- 2018
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Ingår i: Annals of Glaciology. - : Cambridge University Press (CUP). - 0260-3055 .- 1727-5644. ; 59:76pt2, s. 112-123
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Tidskriftsartikel (refereegranskat)abstract
- In this paper an algorithm for ice/water classification of C- and L-band dual polarization synthetic aperture radar data is presented. A comparison of the two different frequencies is made in order to investigate the potential to improve classification results with multi-frequency data. The algorithm is based on backscatter intensities in co- and cross-polarization and autocorrelation as a texture feature. The mapping between image features and ice/water classification is made with a neural network. Accurate ice/water maps for both frequencies are produced by the algorithm and the results of two frequencies generally agree very well. Differences are found in the marginal ice zone, where the time difference between acquisitions causes motion of the ice pack. C-band reliably reproduces the outline of the ice edge, while L-band has its strengths for thin ice/calm water areas within the icepack. The classification shows good agreement with ice/water maps derived from met.no ice-charts and radiometer data from AMSR-2. Variations are found in the marginal ice zone where the generalization of the ice charts and lower accuracy of ice concentration from radiometer data introduce deviations. Usage of high-resolution dual frequency data could be beneficial for improving ice cover information for navigation and modelling.
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| 6. |
- Liu, Qianyun, et al.
(författare)
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Roadside assessment of a modern city bus fleet: Gaseous and particle emissions
- 2019
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Ingår i: Atmospheric Environment: X. - : Elsevier BV. - 2590-1621. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 The Authors In many cities worldwide, modern fleets have been introduced to reduce gaseous and particle emissions from city buses. To date, most emission studies are limited to a few vehicles, making a statistically significant assessment of control options difficult, especially under real-world driving conditions. Exhaust emissions of 234 individual city buses were measured under real-world stop-and-go traffic conditions at a bus stop in Gothenburg, Sweden. The buses comprised models fulfilling Euro III-VI and EEV (Enhanced Environmentally Friendly Vehicle) standards with different engine technologies, fuels, and exhaust after-treatment systems, and also included hybrid-electric buses (HEV). Both gaseous (NOx, CO, HC, and SO2) and size-resolved particle number (PN) and mass (PM) emission factors (EF) were calculated for vehicles using compressed natural gas (CNG), diesel (DSL), Rapeseed Methyl Ester (RME) and Hydro-treated Vegetable Oil (HVO) equipped with various after-treatment technologies, e.g., diesel particulate filter (DPF), selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) systems. The highest median EFPN was obtained from Euro VHEV-HVO-SCR buses (MdEFPN = 18×1014 # kg-1) when their combustion engines were used though 53% of their accelerations were below detection limits indicating the use of their electrical engine. The highest MdEFPM was obtained from the Euro V-DSL-SCR buses (MdEFPM = 150 mg kg-1) and the lowest from EEV-CNG buses (below detection threshold) and Euro VIHEV-HVO- SCR+EGR+DPF buses (MdEFPM = 19 mg kg-1). The highest MdEFNOx was obtained from the Euro V-RME-SCR (MdEFNOx = 30 g kg-1) and Euro VHEV-HVO-SCR buses (MdEFNOx = 24 g kg-1), and the lowest from CNG buses (MdEFNOx = 4.8 g kg-1) and Euro VIHEV-HVO-SCR+EGR+DPF buses (MdEFNOx = 7.4 g kg-1). Hybrid buses can give higher PN emissions compared to traditional diesel engines, likely due to downsized combustion engines. Replacing diesel by biodiesel fuel reduced MdEFPM significantly but increased MdEFNOx which may be due to the higher combustion temperature and oxygen contents of the fuel (for RME). Overall, the EEV-CNG buses performed the best regarding both the MdEF and low contribution to the high emitters. It was also found that a small (5%) proportion of the buses contributed significantly (14-30%) to the total emissions. Identification and monitoring the maintenance of the high emitters in the fleets should be considered for the improvement of air quality.
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| 7. |
- Earon, Robert, et al.
(författare)
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Groundwater Resources Potential in Hard Rock Terrain : A Multivariate Approach
- 2014
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Ingår i: Ground Water. - : John Wiley & Sons. - 0017-467X .- 1745-6584.
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater resources are limited and difficult to predict in crystalline bedrock due to heterogeneity and anisotropy in rock fracture systems. Municipal-level governments often lack the resources for traditional hydrogeological tests when planning for sustainable use of water resources. A new methodology for assessing groundwater resources potential (GRP) based on geological and topographical factors using principal component analysis (PCA) and analysis of variance (ANOVA) was developed and tested. ANOVA results demonstrated statistically significant differences in classed variable groups as well as in classed GRP scores with regard to hydrogeological indicators, such as specific capacity (SC) and transmissivity. Results of PCA were used to govern the weight of the variables used in the prediction maps. GRP scores were able to identify 79% of wells in a verification dataset, which had SC values less than the total dataset median. GRP values showed statistically significant correlations using both parametric (using transformed datasets) and non-parametric methods. The method shows promise for municipal or regional level planning in crystalline terrains with high levels of heterogeneity and anisotropy as a hydrogeologically and statistically based tool to assist in assessing groundwater resources. The methodology is executed in a geographic information systems environment, and uses often readily available data, such as geological maps, feature maps and topography, and thus does not require expensive and time-consuming aquifer tests.
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| 8. |
- Löfgren, Johan, 1983, et al.
(författare)
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Sea Level Monitoring Using a GNSS-Based Tide Gauge
- 2009
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Ingår i: 2nd International Colloquium - Scientific and Fundamental Aspects of the Galileo Programme, 14 - 16 October 2009, Padua, Italy.
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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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| 9. |
- Lorenz, Henning, Dr. 1972-, et al.
(författare)
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COSC-2 – drilling the basal décollement and underlying margin of palaeocontinent Baltica in the Paleozoic Caledonide Orogen of Scandinavia
- 2022
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Ingår i: Scientific Drilling. - Göttingen : Copernicus Publications. - 1816-8957 .- 1816-3459. ; 30, s. 43-57
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Tidskriftsartikel (refereegranskat)abstract
- Abstract.The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project aims to characterise the structure and orogenic processes involved in a major collisional mountain belt by multidisciplinary geoscientific research. Located in western central Sweden, the project has drilled two fully cored deep boreholes into the bedrock of the deeply eroded Early Paleozoic Caledonide Orogen. COSC-1 (2014) drilled a subduction-related allochthon and the associated thrust zone. COSC-2 (2020, this paper) extends this section deeper through the underlying nappes (Lower Allochthon), the main Caledonian décollement, and the upper kilometre of basement rocks. COSC-2 targets include the characterisation of orogen-scale detachments, the impact of orogenesis on the basement below the detachment, and the Early Paleozoic palaeoenvironment on the outer margin of palaeocontinent Baltica. This is complemented by research on heat flow, groundwater flow, and the characterisation of the microbial community in the present hard rock environment of the relict mountain belt. COSC-2 successfully, and within budget, recovered a continuous drill core to 2276 m depth. The retrieved geological section is partially different from the expected geological section with respect to the depth to the main décollement and the expected rock types. Although the intensity of synsedimentary deformation in the rocks in the upper part of the drill core might impede the analysis of the Early Paleozoic palaeoenvironment, the superb quality of the drill core and the borehole will facilitate research on the remaining targets and beyond. Protocols for sampling in the hard rock environment and subsequent sample preservation were established for geomicrobiological research and rock mechanical testing. For the former, a sparse sample series along the entire drill core was taken, while the target of the latter was the décollement. COSC-2 was surveyed by a comprehensive post-drilling downhole logging campaign and a combined borehole/land seismic survey in autumn 2021. This paper provides an overview of the COSC-2 (International Continental Scientific Drilling Project – ICDP 5054_2_A and 5054_2_B boreholes) operations and preliminary results. It will be complemented by a detailed operational report and data publication.
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| 10. |
- Hobiger, Thomas, 1978, et al.
(författare)
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Software-Defined Radio Direct Correlation GNSS Reflectometry by Means of GLONASS
- 2016
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Ingår i: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. - 2151-1535 .- 1939-1404. ; 9:10, s. 4834-4842
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Tidskriftsartikel (refereegranskat)abstract
- Ground-based GNSS reflectometry (GNSS-R)systems can be realized by different means. The concept ofcorrelation between direct and reflected GNSS signals is basicallypossible with all GNSS systems. However, using signals fromthe Russian GLONASS system simplifies the signal processingso that software-defined radio (SDR) components can be usedat replace expensive hardware solutions. This paper discusseshow such a solution, called GLONASS-R, can be realized usingentirely off-the-shelf components. Field tests with such a systemdemonstrate the capability to monitor sea surface heights with aprecision of 3 cm or better even with a sampling rate of 1.5 Hz.The flexibility of a SDR and the simple concept of GLONASS-Rallow build such a system with low costs and adapt it to the needsof any ground-based GNSS-R problem.
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