Response of a River Catchment to Climatic Change: Application of Expanded Downscaling to Northern Germany

We used the technique of expanded General Circulation Model (GCM) downscalingto derive time series of daily weather for the analysis of potential climaticchange impact on a river catchment in Northern Germany. The derived timeseries was then fed into a spatially distributed hydrological model tosimulate various water balance components and river discharge. All componentsof this modelling approach are known to provide fairly accurate results undernormal (current) climatic conditions. Hydrological time series, theirstatistics and spatial patterns of various water balance components, resultingfrom a `business-as-usual' emission scenario, were analysed. The simulationresults showed that if everything apart from climate is held constant, asignificant increase in river discharge may be expected in the coming decadesas a consequence of increased rainfall amounts. Although the modellingapproach provides an operational way of performing watershed climate changeimpact studies, many uncertainties still have to be considered.     

Preparative isolation and characterization of heavy metal complexes from acid mine drainage and surface wastewater

A preparative method was developed to sample dissolved organic carbon (DOC) and heavy metals (Ni, Mn) from polluted surface waters. Main focus was set on the preparative production of freeze‐dried samples mainly composed of organic ligands from heavy metal complexes. First characterizations were done in the aqueous phase. Finally, freeze‐dried samples provide stable organic matter for multiple characterizations. Acid mine drainage of the former mining area of Ronneburg (Germany) hold elevated concentrations of heavy metals and low concentrations of DOC. Municipal wastewater, passing the spoil pile, held elevated concentrations of DOC and low concentrations of heavy metals. Dissolved components smaller than 0.45 μm and larger than 1 nm were concentrated by nanofiltration. Organic heavy metal complexes were isolated from this solution by size‐exclusion chromatography (SEC). Different size classes of molecules were collected from the column effluent, depending on their elution time, and were characterized by UV spectroscopy, ICP‐OES, and DOC measurements. All samples held organic heavy metal compounds with different retention times. The organic heavy metal complexes in acid mine drainage had higher retention times than complexes from municipal wastewater. Most interestingly, we found different affinities of heavy metals to different size classes of DOC. This affinity of the heavy metals differs with size and origin of the DOC.     

Statistische Untersuchungen für abhängige Beobachtungsmerkmale am Beispiel authigener Quarze

International Journal of Earth Sciences - Die dargestellten Regressions- und Korrelationsrechnungen ermöglichen eine Beurteilung von Beobachtungsmerkmalen hinsichtlich ihrer gegenseitigen...     

Variability of the Northern Annular Mode's signature in winter sea ice concentration

Historical winter sea ice concentration data are used to examine the relation between the Northern Annular Mode (NAM) and the sea ice concentration in the Nordic seas over the past 50 years. The well known basic response pattern of a seesaw between the Labrador Sea and the Greenland, Iceland and Barents seas is being reproduced. However, the response is not robust in the Greenland and Iceland seas. There the observed variability has a more complex relationship with surface temperatures and winds. We divide the sea ice response into three spectral bands: high (P< year), band (515 year) filtered NAM indices. This division is motivated by the expected slow response of the ocean circulation which might play a significant role in the Greenland and Iceland seas. The response to the NAM is also examined separately for the periods before and after 1976 to identify variations due to the relocation of the northern centre of the North Atlantic Oscillation.     

From streambed temperature measurements to spatial‐temporal flux quantification: using the LPML method to study groundwater–surface water interaction

Knowledge on groundwater–surface water interaction and especially on exchange fluxes between streams and aquifers is an important prerequisite for the study of transport and fate of contaminants and nutrients in the hyporheic zone. One possibility to quantify groundwater–surface water exchange fluxes is by using heat as an environmlental tracer. Modern field equipment including multilevel temperature sticks and the novel open‐source analysis tool LPML make this technique ever more attractive. The recently developed LPML method solves the one‐dimensional fluid flow and heat transport equation by combining a local polynomial method with a maximum likelihood estimator. In this study, we apply the LPML method on field data to quantify the spatial and temporal variability of vertical fluxes and their uncertainties from temperature–time series measured in a Belgian lowland stream. Over several months, temperature data were collected with multilevel temperature sticks at the streambed top and at six depths for a small stream section. Long‐term estimates show a range from gaining fluxes of ?291 mm day^?1 to loosing fluxes of 12 mm day^?1; average seasonal fluxes ranged from ?138 mm day^?1 in winter to ?16 mm day^?1 in summer. With our analyses, we could determine a high spatial and temporal variability of vertical exchange fluxes for the investigated stream section. Such spatial and temporal variability should be taken into account in biogeochemical cycling of carbon, nutrients and metals and in fate analysis of contaminant plumes. In general, the stream section was gaining during most of the observation period. Two short‐term high stream stage events, seemingly caused by blockage of the stream outlet, led to a change in flow direction from gaining to losing conditions. We also found more discharge occurring at the outer stream bank than at the inner one indicating a local flow‐through system. With the conducted analyses, we were able to advance our understanding of the regional groundwater flow system. Copyright © 2015 John Wiley & Sons, Ltd.