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Showing 1 to 8 of 8 (0.041 seconds)Spelling suggestions: "subject:"permafrost than"" "subject:"permafrost thai""
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Investigation of Microbial Community Structure and Functional Groups from Thawing Permafrost Peat IncubationsCrossen, Kelsey B. January 2017 (has links)
No description available.
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Geochemical Controls over Phosphorus Bioavailability as a Function of Redox Sensitive Iron OxidesMaximilian, Barczok R. 21 July 2022 (has links)
No description available.
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| 3 |
Effect of Permafrost Thaw Slumps on Benthic Invertebrates and on Concentrations of Persistent Organic Pollutants in Lakes of the Mackenzie Delta Uplands, NTRebecca, D'Onofrio January 2014 (has links)
Permafrost thaw slumping along lakeshores in lakes of the Mackenzie Delta Uplands, NT is known to alter water chemistry significantly. Its impact on benthic communities and persistent organic pollutant (POP) behaviour in lakes is not known. Benthic invertebrate communities responded to slumps through changes to community composition and size spectra. Larger taxa tended to dominate in lakes with slumps. Variability in biomass size spectra was related to total dissolved nitrogen concentration and slump size. Concentrations of POPs in Gammarus were negatively correlated with total phosphorus and positively correlated with the percentage of the catchment slumped. Lakes with slumps generally had higher mean concentrations of POPs in Gammarus (ex. ΣPCBsDisturbed = 27.54 ng/g lipid, ΣPCBsUndisturbed = 16.97 ng/g lipid; ΣDDT Disturbed =18.47 ng/g lipid and ΣDDTUndisturbed =10.86 ng/g lipid). Benthic invertebrate biomass was also negatively correlated with concentrations of contaminants in Gammarus, supporting the biomass dilution hypothesis. Thaw slumps have large enough impacts on the physico-chemical characteristics of lakes that they alter benthic invertebrate community composition and size-structure, and contaminant concentrations in Gammarus.
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The potential disturbance of the 210Pb profile in peat cores by roots and the implications for 210Pb dating.Spjut, Nora January 2020 (has links)
At this moment there is a gap in information regarding the affect roots might have on 210Pb distribution in peat cores and in turn the obtained chronologies by 210Pb dating. Therefore, four peat cores were collected from the snow manipulation study site within the mire complex Storflaket (68°20048″N, 18°58016″E). Two cores from snow fence plots, which has experienced root growth due to permafrost thaw, and 2 cores from control plots. 210Pb distribution and the provided 210Pb chronologies were then compared with root content within and between the cores. In two of the cores (C5 and SF2) did subsurface peaks in the 210Pb activity profile follow the distribution profile of the dwarf shrub roots. The same pattern was not seen with Eriophorum roots. This indicates that presence of dwarf root with their shallow and horizontally growth can affect the 210Pb profile by horizontal translocation of 210Pb. The chronologies obtained by the CF:CS and CRS dating models could not be validated for the C5 core which suggest that dwarf shrub roots also can affect the 21oPb dating.
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| 5 |
The potential disturbance of the 210Pb profile in peat cores by roots and the implications for 210Pb dating.Spjut, Nora January 2020 (has links)
At this moment there is a gap in information regarding the affect roots might have on 210Pb distribution in peat cores and in turn the obtained chronologies by 210Pb dating. Therefore, four peat cores were collected from the snow manipulation study site within the mire complex Storflaket (68°20048″N, 18°58016″E). Two cores from snow fence plots, which has experienced root growth due to permafrost thaw, and 2 cores from control plots. 210Pb distribution and the provided 210Pb chronologies were then compared with root content within and between the cores. In two of the cores (C5 and SF2) did subsurface peaks in the 210Pb activity profile follow the distribution profile of the dwarf shrub roots. The same pattern was not seen with Eriophorum roots. This indicates that presence of dwarf root with their shallow and horizontally growth can affect the 210Pb profile by horizontal translocation of 210Pb. The chronologies obtained by the CF:CS and CRS dating models could not be validated for the C5 core which suggest that dwarf shrub roots also can affect the 21oPb dating.
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Seasonal permafrost subsidence monitoring in Tavvavuoma (Sweden) and Chersky (Russia) using Sentinel-1 data and the SBAS stacking techniqueRehn, Ida January 2022 (has links)
Permafrost deformation is expected to increase due to climatic perturbations such as amplified air and soil temperatures, resulting in permafrost thawing and subsequent subsidence. Palsas and peat plateaus are uplifted ice-rich peat mounds that experience permafrost subsidence. This is due to the uppermost layer of permafrost, known as the Active Layer (AL), that seasonally thaws and freezes. Interferometric Synthetic Aperture Radar (InSAR) is an interferometric stacking technique successfully applied over permafrost regions when monitoring ground subsidence. The Small Baseline Subset (SBAS) technique is based on interferograms produced by stacking Synthetic Aperture Radar (SAR) acquisitions with small normal baselines. In this study, seasonal Sentinel-1 SAR C-band data obtained during June, July, August and September (JJAS) was used to generate seasonal Line of Sight (LoS) deformation time series of palsas and peat plateaus in Tavvavuoma (Sweden) by using the SBAS technique. Chersky (Russia) has documented permafrost subsidence and was used as a reference site. Findings include that seasonal stacks with short normal baselines generated more robust results than inter-annual stacks with longer normal baselines and temporal data gaps. No instances of pronounced subsidence were reported during JJAS. Nevertheless, minor subsidence during the early season and negative development trends were identified in the Tavvavuoma 2020 andChersky 2020-2021 stacks, respectively. Increased subsidence during the mid-and late thaw season was detected. The SBAS technique performed better and resulted in less temporal and seasonal decorrelation in areas above the tree line (Tavvavuoma) compared to the lowlands in the forest-tundra (Chersky). The challenge lies in whether surface subsidence of palsas and peat plateaus in sporadic permafrost regions experience irreversible long-term changes or seasonally cyclic changes in the permafrost ground regime. Future studies are recommended to implement annual intervals, including winter images over Tavvavuoma.
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The Effects of Retrogressive Thaw Slump Development on Persistent Organic Pollutants in Lake Sediments of the Mackenzie River Delta Uplands, NT, CanadaEickmeyer, David 03 September 2013 (has links)
Using a comparative spatial and temporal analysis on sediment cores from 8 lakes in the Mackenzie River Delta uplands region, NT, Canada, this study assessed how persistent organic pollutant (POP) deposition to lake sediments was affected by: (1) the presence of retrogressive thaw slumps on lake shores; and (2) changes occurring with increased autochthonous primary productivity. POPs examined included polychlorinated biphenyls (PCBs), penta- and hexachlorobenzenes (CBzs), and dichlorodiphenyltrichloroethane and metabolites (DDTs). Surface sediments of slump-affected lakes contained higher total organic carbon (TOC)-normalized POP concentrations than nearby reference lakes unaffected by thaw slumps. Inorganic sedimentation rates were positively related to contaminant concentrations, suggesting that the influx of siliciclastic material reducing organic carbon in slump-affected lake water indirectly results in higher concentrations of POPs on sedimentary organic matter. This explanation was corroborated by an inverse relationship between sedimentary POP concentrations and TOC content of the lake water.
Deposition proxies of autochthonous carbon were not significantly correlated to POP fluxes of surface sediments, and historical profile fluctuations did not coincide with variation in POP deposition. Thus this study does not support the contention that algal-derived organic carbon increases the delivery of organic pollutants to sediments (the algal-scavenging hypothesis), as previously proposed for mercury. Higher POP concentrations observed in surface sediments of slump-affected lakes are best explained by simple solvent switching processes of hydrophobic contaminants onto a lower pool of available organic carbon when compared to neighbouring lakes unaffected by thaw slump development.
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| 8 |
The Effects of Retrogressive Thaw Slump Development on Persistent Organic Pollutants in Lake Sediments of the Mackenzie River Delta Uplands, NT, CanadaEickmeyer, David January 2013 (has links)
Using a comparative spatial and temporal analysis on sediment cores from 8 lakes in the Mackenzie River Delta uplands region, NT, Canada, this study assessed how persistent organic pollutant (POP) deposition to lake sediments was affected by: (1) the presence of retrogressive thaw slumps on lake shores; and (2) changes occurring with increased autochthonous primary productivity. POPs examined included polychlorinated biphenyls (PCBs), penta- and hexachlorobenzenes (CBzs), and dichlorodiphenyltrichloroethane and metabolites (DDTs). Surface sediments of slump-affected lakes contained higher total organic carbon (TOC)-normalized POP concentrations than nearby reference lakes unaffected by thaw slumps. Inorganic sedimentation rates were positively related to contaminant concentrations, suggesting that the influx of siliciclastic material reducing organic carbon in slump-affected lake water indirectly results in higher concentrations of POPs on sedimentary organic matter. This explanation was corroborated by an inverse relationship between sedimentary POP concentrations and TOC content of the lake water.
Deposition proxies of autochthonous carbon were not significantly correlated to POP fluxes of surface sediments, and historical profile fluctuations did not coincide with variation in POP deposition. Thus this study does not support the contention that algal-derived organic carbon increases the delivery of organic pollutants to sediments (the algal-scavenging hypothesis), as previously proposed for mercury. Higher POP concentrations observed in surface sediments of slump-affected lakes are best explained by simple solvent switching processes of hydrophobic contaminants onto a lower pool of available organic carbon when compared to neighbouring lakes unaffected by thaw slump development.
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