| 1. |
- Martin, Tina, et al.
(författare)
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Examining biofilm growth and metabolism of Escherichia coli at laboratory scale using geoelectrical methods
- 2023
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Ingår i: Vatten: tidskrift för vattenvård /Journal of Water Management and research. - 0042-2886. ; :1-2, s. 71-90
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- To link geophysical field data to specific biological phenomena, controlled laboratory experiments are needed for the understanding of the response of geophysical parameters to changes in biological conditions. In this study, suspensions of bacteria were mixed with sand to create a biofilm growing on a surface and these mixtures were monitored using the geoelectrical spectral induced polarization method (SIP). The beginning growth of the biofilm was confirmed by scanning electron microscopy and the amount of bacteria in liquid and sand estimated using culture and DNA based methods (i.e. qPCR, quantitative polymerase chain reaction). While changes in SIP signal could not be clearly related to microbial activity, fluctuations in the phase shift were concomitant with the detection of two unidentified metabolites in the liquid extracted from the sand. These metabolites were only detected when the biofilm was produced under oxygen limiting conditions. Even though the experimental design was not optimal for the SIP measurements, the results support the idea that these measurements are not measuring cell mass but are influenced by the presence of smaller charged molecules that may be produced as microbial metabolites. As microbial metabolites would change in the field during bioremediation, this method could be applied for this type of monitoring.
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| 2. |
- Nivorlis, Aristeidis, et al.
(författare)
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Multidisciplinary monitoring of an in-situ remediation test of chlorinated solvents
- 2024
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Ingår i: Science of the Total Environment. - 0048-9697. ; 922
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Tidskriftsartikel (refereegranskat)abstract
- Pollutions on and within the underground poses risks for groundwater contamination and is a widespread global problem. Common remediation methods based on digging and removal can be expensive and have limitations, while in-situ remediation is an attractive alternative. However, there is a need to develop tools to monitor the effectiveness both in terms of the successful injection of remediation fluids but also the effectiveness of the treatment, i.e., degree of degradation/removal of the pollutants and possible metabolites. This paper presents a methodology for monitoring the changes following an in-situ remediation treatment of a site contaminated with chlorinated solvents. The methodology consists of two different methods, where Direct Current resistivity and time-domain Induced Polarization (DCIP) was used to acquire daily data and geochemical analyses on water samples were collected approximately every three months. The geophysical results provide insights on how the injected fluids are spreading and assist in acquiring a better understanding of the geological and hydrogeological system. On the other hand, the geochemical sampling enhances our knowledge about the hydrochemistry of the system and the concentration of the pollutants. Our research highlights the challenges of monitoring in-situ bioremediation experiments in complex environments and in cases where pollutants are situated in low hydraulic conductivity formations. The joint interpretation of the data shows the importance of an interdisciplinary approach to understand complex systems.
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| 3. |
- 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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| 4. |
- Åkesson, Sofia
(författare)
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Chlorinated aliphatic hydrocarbons; an interdisciplinary study of degradation and distribution in complex environments
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis degradation of chlorinated solvents, e.g., tetrachloroethene (perchloroethylene [PCE]), has been examined, both natural occurring degradation and in situ remediation strategies. The projects included have focused on two field sites of former dry-cleaning facilities, which are contaminated with PCE in both the groundwater and the sediments. One site had only been exposed to natural degradation, whereas the other site has been targeted for enhanced in situ remediation, both abiotic and biotic. The aim of this thesis was to characterize the subsurface conditions and monitor changes at contaminated site with an interdisciplinary approach. The data included within the studies are contaminant concentrations, major and minor ions concentrations, Compound Specific Isotope Analysis (CSIA) of carbon, and DNA analysis describing microbial content. At the site with natural degradation geoelectrical resistivity and chargeability measurements were also performed. In addition, a laboratory study has been conducted to link microbial growth and activity to geoelectrical signals.The studies have shown that changes in geological setting with shifts in hydrogeological properties, i.e., transition units, proved to be important features associated with more efficient degradation. The transitions units showed larger variations in microbial communities, compared to the aquifer material. The microbial communities were similar when comparing samples from the sediment and the groundwater; however, more of the microbes associated with dechlorination were found in the sediment samples. Correlation between the amount of microbes and resistivity was possible, while the chargeability could only indicate to arise due to by-products. During monitoring of enhanced biodegradation PCE’s metabolites were needed to be included when evaluating the CSIA data, but for the natural degradation it was not required. Since the location of transition units has been shown to be an important hydrogeological setting, both with regards to localization of the contaminant and as a preferred environment for the microbial communities, high quality data of the geological conditions are required from contaminated sites to capture changes in the settings. The sediment matrix should be investigated during in situ bioremediations to fully examine the microbial communities and to be able to evaluate the degradation effect. The interdisciplinary approach made it possible to challenge the limitation of commercially available analysis and state-of-the-art methods, and have contribute to more nuanced interpretations and evaluations of the complexities at contaminated sites.
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