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Fricke K.,Federal Institute of Hydrology | Baschek B.,Federal Institute of Hydrology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

Water temperature influences physical and chemical parameters of rivers and streams and is an important parameter for water quality. It is a crucial factor for the existence and the growth of animal and plant species in the river ecosystem. The aim of the research project "Remote sensing of water surface temperature" at the Federal Institute of Hydrology (BfG), Germany, is to supplement point measurements of water temperature with remote sensing methodology. The research area investigated here is the Upper and Middle Rhine River, where continuous measurements of water temperature are already available for several water quality monitoring stations. Satellite imagery is used to complement these point measurements and to generate longitudinal temperature profiles for a better systematic understanding of the changes in river temperature along its course. Several products for sea surface temperature derived from radiances in the thermal infrared are available, but for water temperature from rivers less research has been carried out. Problems arise from the characteristics of the river valley and morphology and the proximity to the riverbank. Depending on the river width, a certain spatial resolution of the satellite images is necessary to allow for an accurate identification of the river surface and the calculation of water temperature. The bands from the Landsat ETM+ sensor in the thermal infrared region offer a possibility to extract the river surface temperatures (RST) of a sufficiently wide river such as the Rhine. Additionally, problems such as cloud cover, shadowing effects, georeferencing errors, different emissivity of water and land, scattering of thermal radiation, adjacency and mixed pixel effects had to be accounted for and their effects on the radiance temperatures will be discussed. For this purpose, several temperature data sets derived from radiance and in situ measurements were com- pared. The observed radiance temperatures are strongly influenced by the atmosphere. Without atmospheric correction, the absolute mean difference between RST and in situ measurements was 1.1°C with a standard devi- ation of 1.3°C. Thus, a correction of atmospheric influences on radiances measured at the top of the atmosphere was necessary and two different methods for atmospheric correction (ATCOR2 and the Atmospheric Correction Parameter Calculator) were applied. The correction results showed that for both methods, the correct choice of atmospheric profiles is very important. With the calculator, an absolute mean difference of 0.8 ± 1.0°C and with the selected overall best scenes, an absolute mean difference of 0.5 ± 0.7°C was achieved. The selected corrected RST can be used to interpolate between in situ measurements available only for a limited number of points along the river course and longitudinal example profiles of the surface water temperature in the Upper and Middle Rhine could be calculated for different seasons. On the basis of these profiles, the increasing temperature gradient along the Upper Rhine could be identified and the possibility to detect heat or cooling discharge from tributaries and other sources is evaluated. © 2013 SPIE.

Lindim C.,Federal Institute of Hydrology
Ecological Modelling | Year: 2015

The Lower Havel is an eutrophicated river-lake system where the filter feeder Dreissena polymorpha (zebra mussel) are ubiquitous. Zebra mussels are known to efficiently reduce phytoplankton and increase soluble nutrients and water transparency in waterbodies but their impacts in the ecology of the Lower Havel are unknown. To address this matter, a zebra mussel submodel was integrated in the water quality model QSim to simulate its impacts. The model simulated adequately water quality trends over time and space. The simulation results show that the mussels can potentially reduce yearly Chl-a biomass by 39%, with the higher impacts taking place during summertime. Nutrient recycling by the zebra mussels is responsible for a yearly increase of 19% in ammonium and of 5% in phosphorus in the lake water. © 2015 Elsevier B.V.

Fabricius A.-L.,Federal Institute of Hydrology | Duester L.,Federal Institute of Hydrology | Meermann B.,Federal Institute of Hydrology | Ternes T.A.,Federal Institute of Hydrology
Analytical and Bioanalytical Chemistry | Year: 2014

Validated and easily applicable analytical tools are required to develop and implement regulatory frameworks and an appropriate risk assessment for engineered nanoparticles (ENPs). Concerning metal-based ENPs, two main aspects are the quantification of the absolute mass concentration and of the "dissolved" fraction in, e.g., (eco)toxicity and environmental studies. To provide information on preparative aspects and on potential uncertainties, preferably simple off-line methods were compared to determine (1) the total concentration of suspensions of five metal-based ENP materials (Ag, TiO2, CeO2, ZnO, and Au; two sizes), and (2) six methods to quantify the "dissolved" fraction of an Ag ENP suspension. Focusing on inductively coupled plasma-mass spectrometry, the total concentration of the ENP suspensions was determined by direct measurement, after acidification and after microwave-assisted digestion. Except for Au 10 nm, the total concentrations determined by direct measurements were clearly lower than those measured after digestion (between 61.1 % for Au 200 nm and 93.7 % for ZnO). In general, acidified suspensions delivered better recoveries from 89.3 % (ZnO) to 99.3 % (Ag). For the quantification of dissolved fractions two filtration methods (ultrafiltration and tangential flow filtration), centrifugation and ion selective electrode were mainly appropriate with certain limitations, while dialysis and cloud point extraction cannot be recommended. With respect to precision, time consumption, applicability, as well as to economic demands, ultrafiltration in combination with microwave digestion was identified as best practice. © Springer-Verlag Berlin Heidelberg 2013.

Grabs W.,Federal Institute of Hydrology | Moser H.,International Commission for the Hydrology of the Rhine Basin
Water Policy | Year: 2015

This paper describes methods and processes to link policy development to the implementation of those policies in actionable implementation plans. It is shown that policies can only be implemented effectively if they are embedded in a legal framework that is designed to facilitate achievement of the policy objectives. The paper shows different levels of policy making and decision support for the development of policies at different levels, ranging from the level of Federal States in Germany to policy development and implementation at the European level as part of the European Framework Directive. Using the Elbe River as a case study, the paper shows the need to anchor regional, transboundary and state level policies to mandated national institutions. A key lesson learnt from the Elbe River Basin is that policy integration is of utmost importance. The paper also demonstrates that a balance needs to be reached with regard to structural and nonstructural measures in flood risk management to arrive at a truly integrated flood risk management strategy and its implementation. The development of research policies on the basis of sound science is indispensable in support of policy development and its implementation. © IWA Publishing 2015.

Krausse T.,TU Dresden | Cullmann J.,Federal Institute of Hydrology
Hydrology and Earth System Sciences | Year: 2012

The development of methods for estimating the parameters of hydrologic models considering uncertainties has been of high interest in hydrologic research over the last years. In particular methods which understand the estimation of hydrologic model parameters as a geometric search of a set of robust performing parameter vectors by application of the concept of data depth found growing research interest. Bárdossy and Singh (2008) presented a first Robust Parameter Estimation Method (ROPE) and applied it for the calibration of a conceptual rainfall-runoff model with daily time step. The basic idea of this algorithm is to identify a set of model parameter vectors with high model performance called good parameters and subsequently generate a set of parameter vectors with high data depth with respect to the first set. Both steps are repeated iteratively until a stopping criterion is met. The results estimated in this case study show the high potential of the principle of data depth to be used for the estimation of hydrologic model parameters. In this paper we present some further developments that address the most important shortcomings of the original ROPE approach. We developed a stratified depth based sampling approach that improves the sampling from non-elliptic and multi-modal distributions. It provides a higher efficiency for the sampling of deep points in parameter spaces with higher dimensionality. Another modification addresses the problem of a too strong shrinking of the estimated set of robust parameter vectors that might lead to overfitting for model calibration with a small amount of calibration data. This contradicts the principle of robustness. Therefore, we suggest to split the available calibration data into two sets and use one set to control the overfitting. All modifications were implemented into a further developed ROPE approach that is called Advanced Robust Parameter Estimation (AROPE). However, in this approach the estimation of the good parameters is still based on an ineffective Monte Carlo approach. Therefore we developed another approach called ROPE with Particle Swarm Optimisation (ROPE-PSO) that substitutes the Monte Carlo approach with a more effective and efficient approach based on Particle Swarm Optimisation. Two case studies demonstrate the improvements of the developed algorithms when compared with the first ROPE approach and two other classical optimisation approaches calibrating a process oriented hydrologic model with hourly time step. The focus of both case studies is on modelling flood events in a small catchment characterised by extreme process dynamics. The calibration problem was repeated with higher dimensionality considering the uncertainty in the soil hydraulic parameters and another conceptual parameter of the soil module. We discuss the estimated results and propose further possibilities in order to apply ROPE as a well-founded parameter estimation and uncertainty analysis tool. © Author(s) 2012.

Meermann B.,Federal Institute of Hydrology
Analytical and Bioanalytical Chemistry | Year: 2015

Abstract Since its introduction in the early 1990s, the on-line coupling of field-flow fractionation to inductively coupled plasma-mass spectrometry (FFF/ICP-MS) has evolved from a "niche" method into an established technique, especially in the field of natural-colloid analysis. Around the turn of the millennium engineered nanomaterials became prominent in research as a result of new properties, and in recent years FFF/ICP-MS has been revealed to be a promising tool for their analysis. Given the beneficial properties of this technique (e.g., no stationary phase, high separation power, multi-elemental capabilities, and high sensitivity) further applications, especially in the field of biomolecule analysis, will be discovered in the near future, and FFF will evolve further as a complementary tool to well-established chromatographic techniques (e.g. high-performance liquid chromatography, size-exclusion chromatography). The focus of this article is on recent application trends of FFF/ICP-MS, revealing the applicability of this technique within several fields of research, especially natural colloids and engineered nanoparticles. Possible future application trends, based on the author's opinion, are outlined in the "Concluding remarks and outlook" section. © 2015 Springer-Verlag Berlin Heidelberg.

Hoffmann T.,Federal Institute of Hydrology | Hoffmann T.,University of Bonn
Earth-Science Reviews | Year: 2015

Growing empirical evidence shows that many geomorphic systems are in transient state or out of equilibrium with respect to the external driving forces. The transient state is often related to the (dis)connectivity of the many constituent parts of geomorphic systems as a result of sediment storage along the sediment flow path from its source to the final sink. The response time of geomorphic systems to external changes is thus dependent on the residence time of sediment in various storage compartments. Here, I present a mathematical concept based on reservoir theory to model residence time of sediment using millennial scale sediment budgets. The framework sheds light on the limitation of the sediment delivery ratio, which is often used as a measure of sediment connectivity in geomorphic systems, and provides analytical information on process type, pace of sediment flux and connectivity of storage compartments along the sediment cascade. The application of the reservoir theory to geomorphic systems under agricultural land use shows that sediment delivery ratios are linked to the virtual velocity of the eroded sediment, the time since the onset of agricultural land use and the size of the studied basins. With respect to the temporal evolution of sediment storages that temporarily remove sediment from the conveyor belt, the framework aims to estimate the sediment residence time in storages, which is linked to the effective time scale of disconnectivity. Reanalysis of a long-term empirical sediment budget from Central Europe reveals that the response to agricultural land use, which started ~5000yearsBP, is mainly buffered by the long residence time of sediment on hillslopes (in the order of 103years), which results in a delayed floodplain aggradation. Furthermore, the framework was applied to paraglacial mountain systems that inherit striking evidences of Pleistocene glacial erosion and still recover from the change from glacial to interglacial conditions as a consequence of the reduced lateral and longitudinal connectivity. I show that paraglacial response times of sediment flux in mountain headwater in the Canadian Rocky Mountains range in the order of 100-400ka. The results indicate that response times at the transition from glacial to interglacial conditions are much longer than the return interval of the major glaciations, causing a transient behavior of mountain headwater basins during interglacial periods. The presented reanalysis of millennial-scale sediment budgets of agricultural and mountain geosystems provides an integrative framework to link paleo-environmental reconstructions and the connectivity of transient geomorphic system to external changes. © 2015 Elsevier B.V.

Jewell K.S.,Federal Institute of Hydrology | Wick A.,Federal Institute of Hydrology | Ternes T.A.,Federal Institute of Hydrology
Water Research | Year: 2014

The transformation of selected phenolic substances was investigated during biological wastewater treatment. A main emphasis was put on the relevance of abiotic processes leading to toxic nitrophenolic transformation products (TPs). Due to their environmental relevance, the antiseptic ortho-phenylphenol (OPP), the plastics additive bisphenol A (BPA) and the psychoactive drug dextrorphan have been studied. Batch experiments confirmed that nitro- and nitroso-phenolic TPs can be formed under acidic conditions when nitrite is present. HNO2, N2O3 and NO and NO2 radicals are likely involved in the abiotic process. It was found that the process was promoted by the freezing of water samples, since this can lead to an unexpected pH drop. However, under conditions present at wastewater treatment plants (neutral pH, low nitrite concentrations), the formation of appreciable concentrations is rather unlikely through this process, since HNO2 concentrations are extremely low and NO and NO2 radicals will also react with other wastewater constituents. Thus, the transformation of phenolic substances such as OPP and BPA is mainly caused by biotic transformation. In addition to hydroxylation as a common reaction under aerobic conditions, the formation of sulfate conjugates was detected with the original compounds as well as with nitrophenolic TPs. Therefore, even when nitro-phenolic substances are formed it is likely that they are further transformed to sulfate conjugates. In raw wastewater and WWTP effluent nitrated BPA and NO2-dextrorphan were not detected. Only nitro-OPP was found in the influent of a WWTP with 2.3ng/L, but it was not identified in the WWTP effluents. The concentrations of dextrorphan increased slightly during WWTP passage, possibly due to the cleavage of the glucuronide-conjugate, its human metabolite form, or demethylation of the prodrug dextromethorphan. © 2013 Elsevier Ltd.

Schubert B.,Federal Institute of Hydrology | Heininger P.,Federal Institute of Hydrology | Keller M.,Federal Institute of Hydrology | Claus E.,Federal Institute of Hydrology | Ricking M.,Free University of Berlin
TrAC - Trends in Analytical Chemistry | Year: 2012

The Water Framework Directive (WFD) requires Member States of the European Union to achieve good status of all waters in 2015. The survey of chemical status focuses on checking compliance of the quality of water systems against environmental quality standards and temporal trend monitoring of contaminants in sediments and/or biota. As sediments appropriate for monitoring contaminants may not always be available, we discuss the use of suspended particulate matter (SPM) as an alternative. We describe and discuss differences in quality and quantity of sediments and SPM collected by different sampling techniques with regard to the respective advantages and drawbacks for various monitoring purposes. Often, both contaminant concentrations in sediments and in SPM may give the required information. However, selection of the technique applied for collecting SPM should take into consideration, inter alia, the purpose of the monitoring, as well as the hydrodynamic and morphological conditions of the area monitored. We illustrate general conclusions with field applications from the European rivers Rhine and Elbe. © 2012 Elsevier Ltd.

Meermann B.,University of Munster | Meermann B.,Federal Institute of Hydrology | Sperling M.,University of Munster | Sperling M.,European Virtual Institute for Speciation Analysis EVISA
Analytical and Bioanalytical Chemistry | Year: 2012

Method development and applications of hyphenated techniques as tools for speciation analysis of metalbased pharmaceuticals are summarized within this review. Advantages and limitations of the separation modes-highperformance liquid chromatography (HPLC), capillary electrophoresis (CE), and gas chromatography (GC)-as well as the detection modes-inductively coupled plasma-mass spectrometry (ICP-MS) and electrospray ionization-mass spectrometry (ESI-MS)-are discussed. ICP-MS detection is found to be advantageous for the quantification of drugs containing metals and other heteroatoms. The species-independent sensitivity and multielement capabilities of ICP-MS allow it to be used for quantification even when species-specific standards are not available, as well as to determine the stoichiometry in metallodrug-biomolecule interactions. Molecular information that is totally destroyed when ICP is applied as ionization source and is therefore not obtainable via ICP-MS detection can be accessed by the complementary technique of ESI-MS. Speciation analysis combining both elemental and molecular information is therefore a powerful tool for the analysis of metal-based pharmaceuticals and their metabolites in body fluids and other relevant matrices. © Springer-Verlag 2012.

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