| 1. |
- McCallum, James L., et al.
(författare)
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A Numerical Stream Transport Modeling Approach Including Multiple Conceptualizations of Hyporheic Exchange and Spatial Variability to Assess Contaminant Removal
- 2020
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 56:3
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanisms and controls on contaminant removal in streams is essential in managing human and ecosystem health. The hyporheic zone (HZ) plays a key role in the removal of contaminants from streams. Often, tracer tests are implemented in conjunction with measurements of compounds to assess the removal rates of contaminants in streams. The predicted removal rates largely rely on the estimated hyporheic residence time, and hence, the chosen conceptual model of hyporheic exchange flows (HEFs) will influence the predicted removal rate. Despite this, different HEF models are generally not considered when assessing contaminant removal rates. In this paper, we present a numerical modeling approach for interpreting tracer tests to determine contaminant removal rates that allows for multiple conceptual models of HEF to be considered. We demonstrate this method by interpreting data from a conservative tracer test in conjunction with grab samples of trace organic compounds using two commonly used models of HEF: one that assumes first-order exchange between the stream and the HZ and one that considers a power law weighting of first-order exchange coefficients. For the three degrading compounds measured, guanylurea, valsartan, and diclofenac, we observed that the power law model consistently predicted higher removal rates in the stream compared to the first-order model. Variations were also observed between the removal rates estimated in the HZ. Our results highlight the importance of considering multiple conceptualizations of the HEF when assessing contaminant removal rates.
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| 2. |
- Posselt, Malte, et al.
(författare)
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Bacterial Diversity Controls Transformation of Wastewater-Derived Organic Contaminants in River-Simulating Flumes
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:9, s. 5467-5479
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Tidskriftsartikel (refereegranskat)abstract
- Hyporheic zones are the water-saturated flow-through subsurfaces of rivers which are characterized by the simultaneous occurrence of multiple physical, biological, and chemical processes. Two factors playing a role in the hyporheic attenuation of organic contaminants are sediment bedforms (a major driver of hyporheic exchange) and the composition of the sediment microbial community. How these factors act on the diverse range of organic contaminants encountered downstream from wastewater treatment plants is not well understood. To address this knowledge gap, we investigated dissipation half-lives (DT50s) of 31 substances (mainly pharmaceuticals) under different combinations of bacterial diversity and bedform-induced hyporheic flow using 20 recirculating flumes in a central composite face factorial design. By combining small-volume pore water sampling, targeted analysis, and suspect screening, along with quantitative real-time PCR and time-resolved amplicon Illumina MiSeq sequencing, we determined a comprehensive set of DT50s, associated bacterial communities, and microbial transformation products. The resulting DT50s of parent compounds ranged from 0.5 (fluoxetine) to 306 days (carbamazepine), with 20 substances responding significantly to bacterial diversity and four to both diversity and hyporheic flow. Bacterial taxa that were associated with biodegradation included Acidobacteria (groups 6, 17, and 22), Actinobacteria (Nocardioides and Illumatobacter), Bacteroidetes (Terrimonas and Flavobacterium) and diverse Proteobacteria (Pseudomonadaceae, Sphingomonadaceae, and Xanthomonadaceae). Notable were the formation of valsartan acid from irbesartan and valsartan, the persistence of N-desmethylvenlafaxine across all treatments, and the identification of biuret as a novel transformation product of metformin. Twelve additional target transformation products were identified, which were persistent in either pore or surface water of at least one treatment, indicating their environmental relevance.
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| 3. |
- Posselt, Malte, 1987-
(författare)
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Transformation of Micropollutants in the Hyporheic Zone
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hyporheic zones (HZs) are reactive transition regions between rivers and aquifers which are thought to play an important role in the attenuation of micropollutants. Micropollutants are chemical substances such as pharmaceuticals, industrial chemicals or personal care products that are found in trace concentrations in the environment and that can be harmful to organisms. This thesis aimed to narrow the knowledge gap on the environmental fate of wastewater-derived polar organic micropollutants in the aquatic environment, with a specific emphasis on the hyporheic zone.In Paper I an efficient workflow was developed for the in-situ characterization of polar organic micropollutants and their transformation products (TPs) in the hyporheic zone at high spatial and temporal resolution and with minimal disturbance of natural flow paths. A low volume sampling device was combined with a newly developed high throughput-direct injection-UHPLC-MS/MS method. Application in the field revealed significant differences in micropollutant concentrations that varied over small time- and spatial scales. In Paper II the results of a comprehensive field study performed in the urban lowland river Erpe in Berlin, Germany, are presented. The work provided data on in-situ attenuation behavior of 24 micropollutants and TPs, along with novel insights into the spatially- and temporally varying environmental factors which play a major role in controlling in-stream attenuation of micropollutants. Paper III describes a novel, multi-flume experiment designed to investigate the influence of hyporheic exchange flow and sediment bacterial diversity on dissipation half-lives of 31 micropollutants and associated TPs. Attenuation and transformation of most substances increased significantly with bacterial diversity; fewer compounds responded to both bacterial diversity and hyporheic exchange flow. In addition to the discovery of several novel TPs, a number of bacterial strains were identified that might be associated with micropollutant degradation. In Paper IV the fate of metformin in the hyporheic zone was examined using large-scale (100m) recirculating flumes to perform realistic yet well-controlled experiments. In addition to determining dissipation half-lives in surface and pore water, the formation of novel TPs was investigated via suspect screening and bacterial communities were characterized using microbiological analyses. Data from these experiments indicate that dunes and macrophytes promote hyporheic exchange flow and create reactive environments with steep and varying biogeochemical gradients, which enhanced the degradation of metformin.Collectively, the fate of 33 parent compounds and 37 transformation products was assessed in field and mesocosm experiments described in this thesis. Additionally, 29 suspected TPs were tentatively identified. Higher bacterial diversity in the hyporheic zone and more intense hyporheic exchange flows significantly enhanced biodegradation of organic micropollutants. A number of known and novel TPs were discovered under diverse conditions, many of which showed signs of environmental persistence, providing further evidence for inclusion of TPs in contaminant risk assessments and regulatory frameworks. This work highlights the importance of considering both small- and reach-scale temporal and spatial variability for a mechanistic understanding of attenuation in in-stream studies.
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| 4. |
- Ribbenstedt, Anton, et al.
(författare)
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In-plate toxicometabolomics of single zebrafish embryos
- 2020
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Ingår i: Molecular Omics. - : Royal Society of Chemistry (RSC). - 2515-4184. ; 16:3, s. 185-194
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Tidskriftsartikel (refereegranskat)abstract
- Toxicometabolomic studies involving zebrafish embryos have become increasingly popular for linking apical endpoints to biochemical perturbations as part of adverse outcome pathway determination. These experiments involve pooling embryos to generate sufficient biomass for metabolomic measurement, which adds both time and cost. To address this limitation, we developed a high-throughput toxicometabolomic assay involving single zebrafish embryos. Incubation, microscopy, embryo extraction, and instrumental metabolomic analysis were all performed in the same 96-well plate, following acquisition of conventional toxicological endpoints. The total time for the assay (including testing of 6 doses/n= 12 embryos per dose plus positive and negative controls, assessing conventional endpoints, instrumental analysis, data processing and multivariate statistics) is <14 days. Metabolomic perturbations at low dose were linked statistically to those observed at high dose and in the presence of an adverse effect, thereby contextualizing omic data amongst apical endpoints. Overall, this assay enables collection of high resolution metabolomic data in a high throughput manner, suitable for mode of action hypothesis generation in the context of pharmaceutical or toxicological screening.
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| 5. |
- Rutere, Cyrus, et al.
(författare)
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Fate of Trace Organic Compounds in Hyporheic Zone Sediments of Contrasting Organic Carbon Content and Impact on the Microbiome
- 2020
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- The organic carbon in streambed sediments drives multiple biogeochemical reactions, including the attenuation of organic micropollutants. An attenuation assay using sediment microcosms differing in the initial total organic carbon (TOC) revealed higher microbiome and sorption associated removal efficiencies of trace organic compounds (TrOCs) in the high-TOC compared to the low-TOC sediments. Overall, the combined microbial and sorption associated removal efficiencies of the micropollutants were generally higher than by sorption alone for all compounds tested except propranolol whose removal efficiency was similar via both mechanisms. Quantitative real-time PCR and time-resolved 16S rRNA gene amplicon sequencing revealed that higher bacterial abundance and diversity in the high-TOC sediments correlated with higher microbial removal efficiencies of most TrOCs. The bacterial community in the high-TOC sediment samples remained relatively stable against the stressor effects of TrOC amendment compared to the low-TOC sediment community that was characterized by a decline in the relative abundance of most phyla except Proteobacteria. Bacterial genera that were significantly more abundant in amended relative to unamended sediment samples and thus associated with biodegradation of the TrOCs included Xanthobacter, Hyphomicrobium, Novosphingobium, Reyranella and Terrimonas. The collective results indicated that the TOC content influences the microbial community dynamics and associated biotransformation of TrOCs as well as the sorption potential of the hyporheic zone sediments.
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| 6. |
- Rutere, Cyrus, et al.
(författare)
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Ibuprofen Degradation and Associated Bacterial Communities in Hyporheic Zone Sediments
- 2020
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Ingår i: Microorganisms. - : MDPI AG. - 2076-2607. ; 8:8
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Tidskriftsartikel (refereegranskat)abstract
- Ibuprofen, a non-steroidal anti-inflammatory pain reliever, is among pharmaceutical residues of environmental concern ubiquitously detected in wastewater effluents and receiving rivers. Thus, ibuprofen removal potentials and associated bacteria in the hyporheic zone sediments of an impacted river were investigated. Microbially mediated ibuprofen degradation was determined in oxic sediment microcosms amended with ibuprofen (5, 40, 200, and 400 µM), or ibuprofen and acetate, relative to an un-amended control. Ibuprofen was removed by the original sediment microbial community as well as in ibuprofen-enrichments obtained by re-feeding of ibuprofen. Here, 1-, 2-, 3-hydroxy- and carboxy-ibuprofen were the primary transformation products. Quantitative real-time PCR analysis revealed a significantly higher 16S rRNA abundance in ibuprofen-amended relative to un-amended incubations. Time-resolved microbial community dynamics evaluated by 16S rRNA gene and 16S rRNA analyses revealed many new ibuprofen responsive taxa of the Acidobacteria, Actinobacteria, Bacteroidetes, Gemmatimonadetes, Latescibacteria, and Proteobacteria. Two ibuprofen-degrading strains belonging to the genera Novosphingobium and Pseudomonas were isolated from the ibuprofen-enriched sediments, consuming 400 and 300 µM ibuprofen within three and eight days, respectively. The collective results indicated that the hyporheic zone sediments sustain an efficient biotic (micro-)pollutant degradation potential, and hitherto unknown microbial diversity associated with such (micro)pollutant removal.
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