Suche
Anzeige der Treffer 121-130 von 254
Bereiche und Sammlungen, die Ihrer Suche entsprechen.
In this appendix, the interested reader can learn further information about the comparison and evaluation of the identified maturity models. In addition, the three questionnaires used in the case study that was conducted are shown.
Stable isotope analysis is widely used in environmental tracer studies, e.g. for groundwater flow and discharge quantification. In this context, this study presents an inexpensive approach for the combined use of deuterium (2H) and oxygen-18 (18O) as active semiartificial groundwater tracers by a direct injection of snowmelt into aquifers. This dual isotope approach takes advantage of isotope signature differences between typical groundwater and precipitation water. Aim of this study is the experimental demonstration on laboratory- and field-scale. For this, two column flow experiments were performed using δ2H and δ18O values of snowmelt for breakthrough detection. The differences of the isotope signature between the snowmelt and groundwater were ∆(δ2H) ≈ 61.0 ‰ and ∆(δ18O) ≈ 8.2 ‰. Breakthrough was observed to be almost congruent to a sodium chloride tracer, indicating conservative transport. The low electrical conductivity (EC) of snowmelt (45 µS/cm, i.e. ∆EC ≈ 486 µS/cm to groundwater) was used as an additional easy-to-measure breakthrough indicator. However, the snowmelt EC breakthrough suffered from a slight retardation due to ion exchange. Based on these results, a push-drift-pull tracer test with snowmelt, additionally labeled with uranine, was realized at the field site Pirna, Germany. In the pull phase, a significant isotopic depletion was observed with peak differences of ∆Peak(δ2H) ≈ 24.2 ‰ and ∆Peak(δ18O) ≈ 3.2 ‰, which equals approx. 40 % of the initial difference. The isotope breakthrough was observed to be almost the same as the breakthrough of uranine indicating conservative behavior, while EC breakthrough was affected by ion exchange again.
Replikationsdaten für die Publikation "The dirty work of boundary maintenance: Der Topos der sicheren Grenzen im neurechten Diskurs"
Marine-terminating outlet glaciers experience a combination of seasonal and climate-driven change. Nearby glaciers exhibit very different retreat and advance behavior despite being situated in similar climatic conditions. This highlights the demand to essentially improve our understanding of the driving mechanisms and to provide a basis for parameterizations of oceanic forcing that are fed into mass-loss projections. Temporal changes of glacial flow velocities are presumably linked to the evolution of the subglacial hydrological system. Depending on the type of subglacial system, the temporal acceleration of the glacier is represented by different characteristics. While this is typically investigated only along a central flow line, the spatial distribution contains more information on the cause of the acceleration. In a similar way, the spatial pattern of acceleration due to changes at the calving front is likely driven by upstream propagation of changes in stresses. Hence, understanding the mechanisms in detail requires an analysis of different physical variables in high temporal and spatial resolution and combination with ice modelling. With the new generation of satellites the era of big data has started in glaciology, and new efficient methods to analyze change patterns are required.