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  • Kolditz, O  (172)
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  • 1
    In: PLoS ONE, 2015, Vol.10(4)
    Description: Background To achieve more realistic simulations, meteorologists develop and use models with increasing spatial and temporal resolution. The analyzing, comparing, and visualizing of resulting simulations becomes more and more challenging due to the growing amounts and multifaceted character of the data. Various data sources, numerous variables and multiple simulations lead to a complex database. Although a variety of software exists suited for the visualization of meteorological data, none of them fulfills all of the typical domain-specific requirements: support for quasi-standard data formats and different grid types, standard visualization techniques for scalar and vector data, visualization of the context (e.g., topography) and other static data, support for multiple presentation devices used in modern sciences (e.g., virtual reality), a user-friendly interface, and suitability for cooperative work. Methods and Results Instead of attempting to develop yet another new visualization system to fulfill all possible needs in this application domain, our approach is to provide a flexible workflow that combines different existing state-of-the-art visualization software components in order to hide the complexity of 3D data visualization tools from the end user. To complete the workflow and to enable the domain scientists to interactively visualize their data without advanced skills in 3D visualization systems, we developed a lightweight custom visualization application (MEVA - multifaceted environmental data visualization application) that supports the most relevant visualization and interaction techniques and can be easily deployed. Specifically, our workflow combines a variety of different data abstraction methods provided by a state-of-the-art 3D visualization application with the interaction and presentation features of a computer-games engine. Our customized application includes solutions for the analysis of multirun data, specifically with respect to data uncertainty and differences between simulation runs. In an iterative development process, our easy-to-use application was developed in close cooperation with meteorologists and visualization experts. The usability of the application has been validated with user tests. We report on how this application supports the users to prove and disprove existing hypotheses and discover new insights. In addition, the application has been used at public events to communicate research results.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 2
    Language: English
    In: Water Research, 01 January 2016, Vol.88, pp.199-206
    Description: Microscale zero valent iron (mZVI) is a promising material for in-situ contaminated groundwater remediation. However, its usefulness has been usually inhibited by mZVI particles' low mobility in saturated porous media for sedimentation and deposition. In our study, laboratory experiments, including sedimentation studies, rheological measurements and transport tests, were conducted to investigate the feasibility of xanthan gum (XG) being used as a coating agent for mZVI particle stabilization. In addition, the effects of XG concentration, flow rate, grain diameter and water chemistry on XG-coated mZVI (XG-mZVI) particle mobility were explored by analyzing its breakthrough curves and retention profiles. It was demonstrated that XG worked efficiently to enhance the suspension stability and mobility of mZVI particles through the porous media as a shear thinning fluid, especially at a higher concentration level (3 g/L). The results of the column study showed that the mobility of XG-mZVI particles increased with an increasing flow rate and larger grain diameter. At the highest flow rate (2.30 × 10  m/s) within the coarsest porous media (0.8–1.2 mm), 86.52% of the XG-mZVI flowed through the column. At the lowest flow rate (0.97 × 10  m/s) within the finest porous media (0.3–0.6 mm), the retention was dramatically strengthened, with only 48.22% of the particles flowing through the column. The XG-mZVI particles appeared to be easily trapped at the beginning of the column especially at a low flow rate. In terms of two representative water chemistry parameters (ion strength and pH value), no significant influence on XG-mZVI particle mobility was observed. The experimental results suggested that straining was the primary mechanism of XG-mZVI retention under saturated condition. Given the above results, the specific site-related conditions should be taken into consideration for the design of a successful delivery system to achieve a compromise between maximizing the radius of influence of the injection and minimizing the injection pressure.
    Keywords: Xanthan Gum (Xg) ; Microscale Zero Valent Iron (Mzvi) ; Transport ; Porous Media ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 3
    Language: English
    In: Science of the Total Environment, 15 December 2017, Vol.605-606, pp.598-609
    Description: The main objective of this study is to quantify the groundwater contamination risk of Songhua River Basin by applying a novel approach of integrating public datasets, web services and numerical modelling techniques. To our knowledge, this study is the first to establish groundwater risk maps for the entire Songhua River Basin, one of the largest and most contamination-endangered river basins in China. Index-based groundwater risk maps were created with GIS tools at a spatial resolution of 30 arc sec by combining the results of groundwater vulnerability and hazard assessment. Groundwater vulnerability was evaluated using the DRASTIC index method based on public datasets at the highest available resolution in combination with numerical groundwater modelling. As a novel approach to overcome data scarcity at large scales, a web mapping service based data query was applied to obtain an inventory for potential hazardous sites within the basin. The groundwater risk assessment demonstrated that 〈 1% of Songhua River Basin is at high or very high contamination risk. These areas were mainly located in the vast plain areas with hotspots particularly in the Changchun metropolitan area. Moreover, groundwater levels and pollution point sources were found to play a significantly larger impact in assessing these areas than originally assumed by the index scheme. Moderate contamination risk was assigned to 27% of the aquifers, predominantly associated with less densely populated agricultural areas. However, the majority of aquifer area in the sparsely populated mountain ranges displayed low groundwater contamination risk. Sensitivity analysis demonstrated that this novel method is valid for regional assessments of groundwater contamination risk. Despite limitations in resolution and input data consistency, the obtained groundwater contamination risk maps will be beneficial for regional and local decision-making processes with regard to groundwater protection measures, particularly if other data availability is limited.
    Keywords: Groundwater Contamination Risk ; Hazard ; Intrinsic Vulnerability ; Drastic ; Model Sensitivity ; Songhua River Basin ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: Journal of Environmental Management, 01 March 2015, Vol.150, pp.420-426
    Description: This report focuses on the enhancement in trichloroethylene (TCE) removal from contaminated groundwater using xanthan gum (XG)-modified, microscale, zero-valent iron (mZVI). Compared with bare mZVI, XG-coated mZVI increased the TCE removal efficiency by 30.37% over a 480-h experimental period. Because the TCE removal is attributed to both sorption and reduction processes, the contributions from sorption and reduction were separately investigated to determine the mechanism of XG on TCE removal using mZVI. The results showed that the TCE sorption capacity of mZVI was lower in the presence of XG, whereas the TCE reduction capacity was significantly increased. The FTIR spectra confirmed that XG, which is rich in hydrophilic functional groups, was adsorbed onto the iron surface through intermolecular hydrogen bonds, which competitively repelled the sorption and mass transfer of TCE toward reactive sites. The variations in the pH, Eh, and Fe concentration as functions of the reaction time were recorded and indicated that XG buffered the solution pH, inhibited surface passivation, and promoted TCE reduction by mZVI. Overall, the XG-modified mZVI was considered to be potentially effective for the remediation of TCE contaminated groundwater due to its high stability and dechlorination reactivity.
    Keywords: Microscale Zero-Valent Iron (Mzvi) ; Xanthan Gum (Xg) ; Trichloroethylene (Tce) ; Groundwater Pollution ; Environmental Sciences ; Economics
    ISSN: 0301-4797
    E-ISSN: 1095-8630
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  • 5
    Language: English
    In: Journal of Hydrology, January 2016, Vol.532, pp.90-101
    Description: Ground water flow systems of shallow sedimentary basins are studied in general by analyzing the fluid dynamics at the real world example of the Thuringian Basin. The impact of the permeability distribution and density differences on the flow velocity pattern, the salt concentration, and the temperature distribution is quantified by means of transient coupled simulations of fluid flow, heat, and mass transport processes. Simulations are performed with different permeabilities in the sedimentary layering and heterogeneous permeability distributions as well as with a non-constant fluid density. Three characteristic numbers are useful to describe the effects of permeability on the development of flow systems and subsurface transport: the relation of permeability between aquiclude and aquifer, the variance, and the correlation length of the log-normal permeability distribution. Density dependent flow due to temperature or concentration gradients is of minor importance for the distribution of the flow systems, but can lead to increased mixing dissolution of salt. Thermal convection is in general not present. The dominant driver of groundwater flow is the topography in combination with the permeability distribution. The results obtained for the Thuringian Basin give general insights into the dynamics of a small sedimentary basin due to the representative character of the basin structure as well as the transferability of the settings to other small sedimentary basins.
    Keywords: Subsurface Flow and Transport ; Fluid Dynamics in Sedimentary Basins ; Heterogeneity in Permeability ; Density Dependent Flow ; Thuringian Basin ; Opengeosys ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 6
    Language: English
    In: Environmental Earth Sciences, 2012, Vol.67(6), pp.1859-1859
    Description: Byline: Olaf Kolditz (1,2), Karsten Rink (1), Haibing Shao (1), Thomas Kalbacher (1), Ralf Kunkel (3), Steffen Zacharias (1), Peter Dietrich (1,4) Author Affiliation: (1) Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318, Leipzig, Germany (2) Applied Environmental Systems Analysis, Technische Universitat Dresden, 01062, Dresden, Germany (3) Forschungszentrum Juelich GmbH, 52425, Juelich, Germany (4) Environmental and Engineering Geophysics, Eberhard-Karls-University of Tubingen, Holderlinstrasse 12, 72074, Tubingen, Germany Article History: Registration Date: 27/08/2012 Online Date: 12/09/2012 Article note: The online version of the original article can be found under doi: 10.1007/s12665-012-1661-8. The online version of the original article can be found at http://dx.doi.org/10.1007/s12665-012-1661-8.
    Keywords: Geophysics -- Models;
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 7
    Language: English
    In: Environmental Earth Sciences, 2012, Vol.66(4), pp.1279-1284
    Description: Byline: Olaf Kolditz (1,2), Karsten Rink (1), Haibing Shao (1), Thomas Kalbacher (1), Steffen Zacharias (1), Peter Dietrich (1,3) Author Affiliation: (1) Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318, Leipzig, Germany (2) Applied Environmental Systems Analysis, Technische Universitat Dresden, 01062, Dresden, Germany (3) Environmental and Engineering Geophysics, Eberhard-Karls-University of Tubingen, Holderlinstrasse 12, 72074, Tubingen, Germany Article History: Registration Date: 27/03/2012 Online Date: 19/04/2012 Article note: A German-wide Earth observation network, TERENO, was launched 3 years ago by the Helmholtz Association and now brings together climate and environmental research from the Alps to the Baltic coast. UFZ researchers from the Department of Environmental Informatics, Karsten Rink, Haibing Shao, Thomas Kalbacher, and Olaf Kolditz together with colleagues from the Department of Monitoring and Exploration Technologies, Steffen Zacharias and Peter Dietrich outline how their collaborative work embarks on new paths with this long-term environmental observation system. Dr. Olaf Kolditz heads UFZ's Department of Environmental Informatics and chairs the Department of Applied Environmental Systems Analysis at Technical University of Dresden. Dr. Peter Dietrich heads UFZ's Department of Monitoring und Exploration Technologies and is also the Professor for Environmental and Engineering Geophysics at the Eberhard-Karls-University of Tubingen.
    Keywords: Geophysics;
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 8
    Language: English
    In: Water Research, 01 September 2016, Vol.100, pp.80-87
    Description: Application of microscale zero-valent iron (mZVI) is a promising technology for in-situ contaminated groundwater remediation; however, its longevity is negatively impacted by surface passivation, especially in saline groundwater. In this study, the aging behavior of mZVI particles was investigated in three media (milli-Q water, fresh groundwater and saline groundwater) using batch experiments to evaluate their potential corrosion and passivation performance under different field conditions. The results indicated that mZVI was reactive for 0–7 days of exposure to water and then gradually lost H -generating capacity over the next hundred days in all of the tested media. In comparison, mZVI in saline groundwater exhibited the fastest corrosion rate during the early phase (0–7 d), followed by the sharpest kinetic constant decline in the latter phases. The SEM-EDS and XPS analyses demonstrated that in the saline groundwater, a thin and compact oxide film was immediately formed on the surface and significantly shielded the iron reactive site. Nevertheless, in fresh groundwater and milli-Q water, a passive layer composed of loosely and unevenly distributed precipitates slowly formed, with abundant reactive sites available to support continuous iron corrosion. These findings provide insight into the molecular-scale mechanism that governs mZVI passivation and provide implications for long-term mZVI application in saline contaminated groundwater.
    Keywords: Microscale Zero-Valent Iron (Mzvi) ; Aging ; Passivation ; Hydrogen Production ; Saline Groundwater ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 9
    Language: English
    In: Journal of Hydrology, August 2017, Vol.551, pp.648-659
    Description: Application of numerical models is a common method to assess groundwater resources. The versatility of these models allows consideration of different levels of complexity, but the accuracy of the outcomes hinges upon a proper description of the system behaviour. In seawater intrusion assessment, the implementation of the sea-side boundary condition is of particular importance. We evaluate the influence of the slope of the sea-side boundary on the simulation results of seawater intrusion in a freshwater aquifer by employing a series of slope variations together with a sensitivity analysis by varying additional sensitive parameters (freshwater inflow and longitudinal and transverse dispersivities). Model results reveal a multi-dimensional dependence of the investigated variables with an increasing relevance of the sea-side boundary slope for seawater intrusion (decrease of up to 32%), submarine groundwater discharge zone (reduction of up to 55%), and turnover times (increase of up to 730%) with increasing freshwater inflow or dispersivity values.
    Keywords: Saltwater Intrusion ; Coastal Aquifers ; Numerical Investigation ; Sea-Side Boundary Condition ; Submarine Groundwater Discharge ; Residence Times ; Opengeosys ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 10
    Language: English
    In: Environmental Earth Sciences, 2015, Vol.73(11), pp.6727-6732
    Description: Byline: Olaf Kolditz (1,2,3), Heping Xie (4), Zhengmeng Hou (5,6,7), Patrick Were (5), Hongwei Zhou (8) Author Affiliation: (1) Helmholtz Centre for Environmental Research UFZ, Permoserstra[sz]e 15, 04318, Leipzig, Germany (2) Technische Universitat Dresden, Helmholtzstra[sz]e 10, 01062, Dresden, Germany (3) Sino-German Research Centre for Environmental Information Science (RCEIS), Permoserstra[sz]e 15, 04318, Leipzig, Germany (4) Sichuan University, 610064, Chengdu, China (5) Energy Research Center of Lower Saxony (EFZN), Clausthal University of Technology, Am Stollen 19, 38640, Goslar , Germany (6) Sino-German Energy Research Center, Sichuan University, 610064, Chengdu, China (7) Institute of Petroleum Engineering, Clausthal University of Technology, Agricolastra[sz]e 10, 38678, Clausthal-Zellerfeld, Germany (8) State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xueyuan Road D11, 100083, Haidian, Beijing, China Article History: Registration Date: 16/04/2015 Received Date: 08/04/2015 Accepted Date: 15/04/2015 Online Date: 25/04/2015
    Keywords: Computer Storage Device Industry;
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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