309 research outputs found
Organic matter composition of polygon-patterned tundra in the Thule area (NW Greenland)
No full textThis thesis on organic matter composition of polygon-patterned tundra in the Thule are in
Northwestern Greenland is based on analysis of a permafrost core obtained during an expedition of
the Danish NOW project in August 2015. In the ice-sheet marginal coastal area in NW Greenland,
Holocene ice-wedge polygons developed under permafrost conditions. The ice-wedge growth in
accumulating peats linked to the presence of local sea bird colonies is the topic of this thesis. It was
found that in the study area there is a high presence of nitrogen within the soil as well as very high
ice content, linking to the syngenetic freezing and permafrost aggradation. The samples obtained
from the core were processed in the laboratory and analyzed for ice content, age of the core, carbon
and nitrogen content, threshold of organic carbon and isotopic abundance ratios of total organic
carbon and total nitrogen. Analytical results show a quite steady content of all of these features with
some exceptions at different depths for each parameter. It was also found that there had to be a
change in permafrost aggradation and peat accumulation approx. 3000 years BP (before present,
meaning before 1950) as the accumulation rate drops at this point in time. The great impact of the
bird colonies on this specific permafrost formation is reflected as the high nitrogen values indicate
that the birds’ droppings were the original source of organic matter to decompose, allowing for
vegetation growth and permafrost soil development. Temporary changes found in isotopic ratios
within soil carbon may give a hint on bird colony evolution in the Thule area and the development
towards the current state of the little auks’ colony momentary inhabiting the study area of GL-3
Total mercury content of terrestrial Arctic soils exposed to different degrees of large ungulate activity
No full textThis dataset contains total mercury (THg) values for terrestrial Arctic and subarctic sites exposed to different degrees of grazing, indicated by numbers in the site names where 1 expresses an exclosure site. Samples collected from Siberia (CH19) include active layer and permafrost samples, while the remaining samples, taken from Finland, were collected from sites without permafrost influence but soil winter freezing from the surface.
Total mercury was measured at Alfred Wegener Institute's Permafrost Research section in Potsdam, Germany, using a Direct Mercury Analyzer (Milestone Slr DMA-80) on freeze-dried and homogenized sample material. Measurements were conducted as double measurements, using 50 mg of sample for each run, and results were compared to measurements of various standardized material. If the detection limit was not reached, double measurement was repeated with 200 mg of sample mass for each run.
Further data on these samples are published in separate datasets:
Siberia: https://doi.org/10.1594/PANGAEA.933446
Finland (reindeer summer ranges and reference sites): https://doi.org/10.1594/PANGAEA.941930
Finland (reindeer winter ranges): https://doi.org/10.1594/PANGAEA.95247
Does Large Herbivore Activity influence Mercury levels in Arctic Soils?
No full textMercury (Hg), a neurotoxic pollutant of global significance, is stored in high amounts in Arctic grounds, while its deposition in the Arctic further increases. With climate change inducing accelerated permafrost thaw as well as shortened freezing seasons in seasonal frozen ground, this could lead to the rerelease of Hg into the environment. For this reason, this study addressed the question of whether differences in activity by large herbivores might correlate with differences in soil mercury content in Arctic ground, due to the ground-cooling effects attributed to the animals. Therefore, soil cores from north-eastern Siberia (permafrost soil) and northern Finland (seasonally frozen soil) from sites with different grazing intensities were analyzed and compared for their mercury concentration. Additionally, depth trends of the cores regarding their mercury content, as well as possible correlations with other variables (total organic carbon, absolute water content and mean grain size) were examined. For a merged data set, grazing intensity did not show a significant correlation with mercury content in the soil, while a decrease with depth was detectable for most cores, which was attributed to decreasing surface influence and the associated input of mercury through the atmosphere, vegetation, animal dung and flooding. Total organic carbon showed the most relevant and highest correlation on the mercury content, due to the adsorbing property of organic matter. A separate consideration of the permafrost ground in Siberia and the seasonally frozen ground in Finland showed clear differences in regard to the influence of herbivore activity. While the animals did not show an effect on the concentration of mercury in seasonally frozen ground, the Siberian permafrost sites showed a clear variation in their mercury concentration between grazed and ungrazed sites. In contrast, a difference between sites with existing grazing but of varying intensity was less pronounced. A cause of this phenomenon was presumed in insufficiently diverse animal density, insufficient sample size, prevailing vegetation, as well as occasional flooding. Nevertheless, the samples from Siberia showed a positive correlation between grazing intensity and mercury, indicating that with higher herbivore activity mercury levels increase and suggesting a more effective fixation of the pollutant in permafrost soil
Does Large Herbivore Activity influence Mercury levels in Arctic Soils?
No full textMercury (Hg), a neurotoxic pollutant of global significance, is stored in high amounts in Arctic grounds, while its deposition in the Arctic further increases. With climate change inducing accelerated permafrost thaw as well as shortened freezing seasons in seasonal frozen ground, this could lead to the rerelease of Hg into the environment. For this reason, this study addressed the question of whether differences in activity by large herbivores might correlate with differences in soil mercury content in Arctic ground, due to the ground-cooling effects attributed to the animals. Therefore, soil cores from north-eastern Siberia (permafrost soil) and northern Finland (seasonally frozen soil) from sites with different grazing intensities were analyzed and compared for their mercury concentration. Additionally, depth trends of the cores regarding their mercury content, as well as possible correlations with other variables (total organic carbon, absolute water content and mean grain size) were examined. For a merged data set, grazing intensity did not show a significant correlation with mercury content in the soil, while a decrease with depth was detectable for most cores, which was attributed to decreasing surface influence and the associated input of mercury through the atmosphere, vegetation, animal dung and flooding. Total organic carbon showed the most relevant and highest correlation on the mercury content, due to the adsorbing property of organic matter. A separate consideration of the permafrost ground in Siberia and the seasonally frozen ground in Finland showed clear differences in regard to the influence of herbivore activity. While the animals did not show an effect on the concentration of mercury in seasonally frozen ground, the Siberian permafrost sites showed a clear variation in their mercury concentration between grazed and ungrazed sites. In contrast, a difference between sites with existing grazing but of varying intensity was less pronounced. A cause of this phenomenon was presumed in insufficiently diverse animal density, insufficient sample size, prevailing vegetation, as well as occasional flooding. Nevertheless, the samples from Siberia showed a positive correlation between grazing intensity and mercury, indicating that with higher herbivore activity mercury levels increase and suggesting a more effective fixation of the pollutant in permafrost soil
Review: Doing educational research : a guide for first time researchers
No full textTitle: Doing Educational Research : a guide for first time researchers
Author/Editor: Clive Opie
Publisher: Sage Publications
Publication Date: 2004
ISBN: Paperback 0761970029
Price: £18.99
Reviewed by: Torben Steeg, Independent D&T Consultan
Visual Author-ship: Creativity and Intentionality in Media
No full textBook review of Torben Grodal (ed.): Visual Author-ship: Creativity and Intentionality in Media Northern Lights, vol. 3, 2004, Museum Tusculanum Press/University of Copenhage
Organic Matter Characteristics in a Changing Permafrost Environment: Yukechi Alas Landscape, Central Yakutia
No full textWith alarmingly fast climate change on global scale, the origin of carbon emissions is becoming more important. Permafrost as one of the largest terrestrial natural storages is among the most relevant carbon sinks that might become a carbon source as air temperatures and snowfall are increasing. This study examines the Yukechi Alas area (N 61.76495° / E 130.46664°), a landscape in Central Yakutia, located on the Abalakh terrace in the Lena-Aldan interfluve). Two drilling cores from different ground types were taken. The comparison of the both cores used in this study also gives insights into the development of permafrost carbon storage. One is a Yedoma core, consisting of material accumulated and syngenetically frozen during the late Pleistocene. The second core was taken from an adjacent alas basin. Alas deposits in this area are altered Yedoma deposits thawed and subsided after lake formation. Both cores cover a timespan of approximately 50 000 years. The cores were analysed for ice content, total carbon and total nitrogen content, total organic carbon content, stable oxygen and hydrogen isotopes, stable carbon isotopes, mass specific magnetic susceptibility and grain size distribution, and were dated using radiocarbon measurements. The laboratory analyses revealed some interesting features that are quite uncommon for Yedoma deposits globally but have been found in Central Yakutia before. The most astonishing finding is the lack of carbon over several meters depth, found in both cores. While in the alas core this could hint on deep thawing during lake-covered stages and large talik formation, and hence decomposition, the same finding in the Yedoma core indicate sediment input of organic-poor material. Water isotope data derived from pore ice show a permanently frozen state of the lower core parts and only represent precipitation water very close to the surface. Therefore, it is unlikely that strong organic matter decomposition took place in this Yedoma core. Also, these core parts consist of more coarse material. Fine sand is found here instead of the silty material that makes up most of the cores. This change in material input was dated to a timespan between 39 000 and 18 000 years before present. During this time, climate experienced variations on a global as well as on a regional scale, which could have influenced the availability of liquid water as well as thaw depth and wind regimes. Especially the changes in wind direction and velocity are likely to have influenced the material composition. The sandy material found is not originating from surrounding areas but could be transported over greater distances. These findings indicate that Yedoma might be more heterogeneous on a global scale than previously thought, making it important to further study Yedoma deposits. Both general carbon content as well as carbon vulnerability, for example due to alternating sediment characteristics within a Yedoma deposit, might be very different. It can be assumed that, before thermokarst processes occured, the core drilled within the alas basin had quite similar characteristics as the Yedoma core. This indicates possible developing characteristics of Yedoma deposits during ongoing climate change. A possible reason for this is increasing lake formation in Arctic areas due to warming air temperatures, which in turn can lead to further carbon release with further permafrost thaw, enhancing a positive feedback cycle in Northern permafrost areas
Permafrost carbon stabilisation by recreating a herbivore-driven ecosystem
No full textWith Arctic ground as a huge and temperature-sensitive carbon reservoir, maintaining low ground temperatures and frozen conditions to prevent further carbon emissions that contrib-ute to global climate warming is a key element in humankind’s fight to maintain habitable con-ditions on earth. Former studies showed that during the late Pleistocene, Arctic ground condi-tions were generally colder and more stable as the result of an ecosystem dominated by large herbivorous mammals and vast extents of graminoid vegetation – the mammoth steppe. Characterised by high plant productivity (grassland) and low ground insulation due to animal-caused compression and removal of snow, this ecosystem enabled deep permafrost aggrad-ation. Now, with tundra and shrub vegetation common in the terrestrial Arctic, these effects are not in place anymore. However, it appears to be possible to recreate this ecosystem local-ly by artificially increasing animal numbers, and hence keep Arctic ground cold to reduce or-ganic matter decomposition and carbon release into the atmosphere. By measuring thaw depth, total organic carbon and total nitrogen content, stable carbon iso-tope ratio, radiocarbon age, n-alkane and alcohol characteristics and assessing dominant vegetation types along grazing intensity transects in two contrasting Arctic areas, it was found that recreating conditions locally, similar to the mammoth steppe, seems to be possible. For permafrost-affected soil, it was shown that intensive grazing in direct comparison to non-grazed areas reduces active layer depth and leads to higher TOC contents in the active layer soil. For soil only frozen on top in winter, an increase of TOC with grazing intensity could not be found, most likely because of confounding factors such as vertical water and carbon movement, which is not possible with an impermeable layer in permafrost. In both areas, high animal activity led to a vegetation transformation towards species-poor graminoid-dominated landscapes with less shrubs. Lipid biomarker analysis revealed that, even though the available organic material is different between the study areas, in both permafrost-affected and sea-sonally frozen soils the organic material in sites affected by high animal activity was less de-composed than under less intensive grazing pressure. In conclusion, high animal activity af-fects decomposition processes in Arctic soils and the ground thermal regime, visible from reduced active layer depth in permafrost areas. Therefore, grazing management might be utilised to locally stabilise permafrost and reduce Arctic carbon emissions in the future, but is likely not scalable to the entire permafrost region
n-Alkane characteristics of Arctic soils, comparing different large herbivore grazing intensities under permafrost and non-permafrost conditions
No full textThese data originate from soil samples collected on several field campaigns, aiming at identifying impacts of large herbivore activity on soil carbon storage and degradation in permafrost (northeastern Siberia (68.51 °N, 161.50 °E); campaign in July 2019) and seasonally frozen Arctic ground (northern Finland (69.15 °N, 27.00 °E); campaigns in September 2020 and June 2022).
The samples were collected in transects across grazing intensity gradients, spanning over 5 different intensities:
1 - no grazing / exclosure sites (Siberia: 23 years; Finland: 50 years)
2 - occasional animal migration (Siberia: year-round; Finland: seasonal)
3 - daily animal migration (Siberia: year-round; Finland: seasonal)
4 - high-frequency daily animal migration (Siberia: year-round; Finland: seasonal)
5 - pasture / supplementary feeding sites (Siberia: year-round; Finland: seasonal)
Samples cover different ground types and seasonalities, which are marked out in the site names:
B - drained thermokarst basin
U - Yedoma upland
P - peat
M - mineral soil (podsol)
E - exclosure (Finland-specific)
S - reindeer summer ranges
W - reindeer winter ranges
In this context, 'grazing' refers to any animal activity exerted by large herbivorous animals, including browsing, trampling and defecation.
Values were measured following the lab procedure after Jongejans et al. (2021):
1. Lipids were extracted from the freeze-dried and homogenised samples using accelerated solvent extraction (ASE). For this, we used a ThermoFisher Scientific Dionex ASE 350, equipped with dichloromethane / methanol (DCM / MeOH 99:1 v/v) as the solvent. Samples were hold in a static phase for 20 minutes (heating for 5 minutes to 75 °C a 5 MPa). Extracts were subsequently concentrated using a Genevac SP Scientific Rocket Synergy evaporator at 42 °C.
2. Internal standards for compound quantification (5α-androstane for n-alkanes, 5α-androstan-17-one for n-alcohols) were added.
3. Asphaltenes (n-hexane-insoluble compounds) were removed by asphaltene precipitation.
4. The remaining maltene fraction was separated by medium pressure liquid chromatography (MPLC) (Radke et al. 1980) into aliphatic, aromatic and NSO (nitrogen-, sulphur- and oxygen-containing) compounds.
5. The NSO fraction was afterwards separated into acidic and neutral polar compounds applying column separation. The acidic compounds were trapped by impregnating the column with potassium hydroxide before sample addition. After washing the neutral compounds off the column using DCM, a mixture of DCM / formic acid (98:2 v/v) was added to wash the acidic compounds off the column.
6. The neutral NSO fraction, containing n-alcohols, was silyllated by adding 100 µl DCM / MSTFA (N-Methyl-N-(trimethylsilyl)trifluoroacetamide; 50:50 v/v) and heating for 60 minutes at 75 °C.
7. For measurement, we used a Thermo Scientific ISQ 7000 Single Quadrupole Mass Spectrometer with a Thermo Scientific Trace 1310 Gas Chromatograph (capillary column from BPX5, 2 mm x 50 m, 0.25 mm) with a MS transfer line temperature of 320 °C. The ion source temperature was set to 300 °C with an ionisation energy of 70 eV at 50 µA. The scan was set to the full mass spectrum (m/z 50-600 Da, 2.5 scans / second).
8. Peaks were identified and quantified in relation to the added standards using the software Xcalibur.
The measurement results of n-alkanes and n-alcohols are given in µg/g(TOC) in reference to the organic carbon (OC) content of the sediment samples
n-alcohol characteristics of Arctic soils, comparing different large herbivore grazing intensities under permafrost and non-permafrost conditions
No full textThese data originate from soil samples collected on several field campaigns, aiming at identifying impacts of large herbivore activity on soil carbon storage and degradation in permafrost (northeastern Siberia (68.51 °N, 161.50 °E); campaign in July 2019) and seasonally frozen Arctic ground (northern Finland (69.15 °N, 27.00 °E); campaigns in September 2020 and June 2022).
The samples were collected in transects across grazing intensity gradients, spanning over 5 different intensities:
1 - no grazing / exclosure sites (Siberia: 23 years; Finland: 50 years)
2 - occasional animal migration (Siberia: year-round; Finland: seasonal)
3 - daily animal migration (Siberia: year-round; Finland: seasonal)
4 - high-frequency daily animal migration (Siberia: year-round; Finland: seasonal)
5 - pasture / supplementary feeding sites (Siberia: year-round; Finland: seasonal)
Samples cover different ground types and seasonalities, which are marked out in the site names:
B - drained thermokarst basin
U - Yedoma upland
P - peat
M - mineral soil (podsol)
E - exclosure (Finland-specific)
S - reindeer summer ranges
W - reindeer winter ranges
In this context, 'grazing' refers to any animal activity exerted by large herbivorous animals, including browsing, trampling and defecation.
Values were measured following the lab procedure after Jongejans et al. (2021):
1. Lipids were extracted from the freeze-dried and homogenised samples using accelerated solvent extraction (ASE). For this, we used a ThermoFisher Scientific Dionex ASE 350, equipped with dichloromethane / methanol (DCM / MeOH 99:1 v/v) as the solvent. Samples were hold in a static phase for 20 minutes (heating for 5 minutes to 75 °C a 5 MPa). Extracts were subsequently concentrated using a Genevac SP Scientific Rocket Synergy evaporator at 42 °C.
2. Internal standards for compound quantification (5α-androstane for n-alkanes, 5α-androstan-17-one for n-alcohols) were added.
3. Asphaltenes (n-hexane-insoluble compounds) were removed by asphaltene precipitation.
4. The remaining maltene fraction was separated by medium pressure liquid chromatography (MPLC) (Radke et al. 1980) into aliphatic, aromatic and NSO (nitrogen-, sulphur- and oxygen-containing) compounds.
5. The NSO fraction was afterwards separated into acidic and neutral polar compounds applying column separation. The acidic compounds were trapped by impregnating the column with potassium hydroxide before sample addition. After washing the neutral compounds off the column using DCM, a mixture of DCM / formic acid (98:2 v/v) was added to wash the acidic compounds off the column.
6. The neutral NSO fraction, containing n-alcohols, was silyllated by adding 100 µl DCM / MSTFA (N-Methyl-N-(trimethylsilyl)trifluoroacetamide; 50:50 v/v) and heating for 60 minutes at 75 °C.
7. For measurement, we used a Thermo Scientific ISQ 7000 Single Quadrupole Mass Spectrometer with a Thermo Scientific Trace 1310 Gas Chromatograph (capillary column from BPX5, 2 mm x 50 m, 0.25 mm) with a MS transfer line temperature of 320 °C. The ion source temperature was set to 300 °C with an ionisation energy of 70 eV at 50 µA. The scan was set to the full mass spectrum (m/z 50-600 Da, 2.5 scans / second).
8. Peaks were identified and quantified in relation to the added standards using the software Xcalibur.
The measurement results of n-alkanes and n-alcohols are given in µg/g(TOC) in reference to the organic carbon (OC) content of the sediment samples
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