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• 1
Article
Language: English
In: Environmental Earth Sciences, 2014, Vol.72(5), pp.1357-1366
Description: Landslide activity is largely controlled by changes in soil properties, particularly soil moisture and the corresponding changes in pore pressure within the vadose zone. While knowledge of changes in soil conditions is of utmost importance for the prediction of landslides, it is difficult to obtain reliable information on the field scale. A possibility of filling that information gap is the monitoring of changes in soil properties by time-lapse electromagnetic induction (EMI) data. Given the relative stability of soil properties, changes in apparent electric conductivity (ECa) are mainly related to changes in soil water content and its mineralization. Thus, we use time-lapse ECa data over a nine-month period from different investigation depths (0.75, 1.5, 3, and 6 m) to separate areas with different temporal behavior of soil properties. However, working with time-lapse EMI data raised the comparability problem since the recoded ECa is also affected by several day-specific survey conditions (e.g., instrument temperature, operator). Consequently, the reproducibility of accurate ECa measurements is difficult due to potential dynamic shifts which hinders a direct comparing. We introduce in this study a straightforward method for comparability of ECa values from different time steps by normalization of data ranges assuming that the majority of shifts of measured data originate from field calibration. We identify the intensity of spatial changes by means of the standard deviation (SD) as an indication for the intensity of soil properties variability. To obtain the temporal changes and its progression over time, we separate the dynamic signal from the background. A two-layer system could be identified: one shallow more dynamic layer with an east–west-oriented structure and a deeper, more stationary layer with a north–south-oriented structure. The ECa dynamics of the shallow layer is related to the altitude ( R 2  = 0.84) while the deeper dynamics follow a different regime. The decreasing of ECa dynamics with depth was consistent with the decreasing of SWC dynamics observed by previous studies.
Keywords: EMI time-lapse monitoring and normalization ; ECa calibration issues ; Landslide monitoring ; Proximal soil sensing
ISSN: 1866-6280
E-ISSN: 1866-6299
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• 2
Article
Language: English
In: Environmental Earth Sciences, 2011, Vol.63(6), pp.1239-1249
Description: The present work focuses on approaches for the characterization of subsurface contamination, which need to be reliable and cost-effective, particularly for extended and remote areas aimed at being redeveloped. Requirements are discussed with respect to specific conditions at megasites, in order to enable site valorization. In a case study, two approaches are compared, comprising (1) conventional site investigation based on historical surveys and concentration measurements at monitoring wells installed in areas suspected of being polluted and (2) the use of direct push (DP) methods covering the complete area. The DP investigation provided information on the contamination distribution and yielded also important information on hydraulic conditions. Statistical analysis of the results applying indicator kriging revealed that the conventional approach is markedly risky when decision-making relies solely on historical and sparse data. The DP campaign remarkably reduced the uncertainty concerning the estimated occurrence of polluted groundwater at the whole site. Furthermore, monitoring measurements are analyzed showing the possible importance of temporal variability. Taking economical consideration into account, DP-based groundwater screening is recommended to obtain either first or complementary information on the entire site. Based on these data, also locations for a long-term monitoring could be selected if temporal variability is assumed relevant.
Keywords: Groundwater contamination ; Direct-push ; Screening ; Monitoring ; Megasite
ISSN: 1866-6280
E-ISSN: 1866-6299
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• 3
Article
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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• 4
Article
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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• 5
Article
Language: English
In: Environmental Earth Sciences, 2016, Vol.75(23), pp.1-15
Description: Many hydrological, environmental, or engineering exploration tasks require predicting spatially continuous scenarios of sparsely measured borehole logging data. We present a methodology to probabilistically predict such scenarios constrained by ill-posed geophysical tomography. Our approach allows for transducing tomographic reconstruction ambiguity into the probabilistic prediction of spatially continuous target parameter scenarios. It is even applicable to data sets where petrophysical relations in the survey area are non-unique, i.e., different facies related petrophysical relations may be present. We employ static two-layer artificial neural networks (ANNs) for prediction and additionally evaluate, whether the training performance of the ANNs can be used to rank geophysical tomograms, which are mathematically equal reconstructions of physical parameter distributions in the ground. We illustrate our methodology using a realistic synthetic database for maximal control about the prediction performance and ranking potential of the approach. For doing so, we try to link geophysical radar and seismic tomography as input parameters to porosity of the ground as target parameter of ANN. However, the approach is flexible and can cope with any combination of geophysical tomograms and hydrologic, environmental or engineering target parameters. Ranking of equivalent geophysical tomograms based on additional borehole logging data is found to be generally possible, but risks remain that the ranking based on the ANN training performance does not fully coincide with the closeness of geophysical tomograms to ground truth. Since geophysical field data sets do usually not offer control options similar to those used in our synthetic database, we do not recommend the utilization of recurrent ANNs to learn weights for the individual geophysical tomograms used in the prediction procedure.
Keywords: Geophysics ; Petrophysics ; Probabilistic prediction ; Tomography ; ANN ; Global search inversion
ISSN: 1866-6280
E-ISSN: 1866-6299
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• 6
Article
Language: German
In: Grundwasser, 2012, Vol.17(2), pp.105-111
Description: Korngrößenanalysen werden häufig für die hochauflösende Charakterisierung der räumlichen Variabilität von k f -Werten genutzt und sind somit Grundlage vieler hydrogeologischer Modellierungen. In Anbetracht der Vielzahl von Formeln zur Berechnung von k f -Werten auf Grundlage von Korngrößenanalysen existiert ein breites Spektrum an Literatur zur Evaluierung dieser Formeln, allerdings wurden bislang weder der Grad der Reproduzierbarkeit, noch die Auswirkungen der in der Praxis unvermeidbaren Messunsicherheit bei der Korngrößenanalyse auf die errechneten k f -Werte kritisch betrachtet. Die Auswertung verschiedener Ringanalysen in dieser Studie zeigt, dass die Messunsicherheit bei der Korngrößenanalyse zu deutlichen Unterschieden in den abgeleiteten wirksamen Korndurchmessern und in der Folge zu deutlichen Unterschieden in den berechneten -Werten führte, wobei sich die Messunterschiede in Abhängigkeit von der Zusammensetzung der analysierten Proben und dem gewählten wirksamen Korndurchmesser verschieden stark auswirken. Jedoch zeigte sich im direkten Vergleich hierzu, dass die Auswahl der Berechnungsgrundlage die auf Grundlage von Korngrößenanalysen berechneten -Werte deutlich stärker beeinflusst. Grain size analyses are often used for the high-resolution characterization of hydraulic conductivity () and its variation in space. Resulting values are then frequently used in hydrogeological modeling. In consideration of the variety of formulas to determine from grain size data, several publications exist that evaluate the performance of these formulas. However, neither the degree of reproducibility nor the effects of measuring inaccuracy on the determination of from grain size data has yet been evaluated. In this study, data from several ring analyses show that measuring inaccuracies during grain size analyses lead to strong differences in effective grain size diameters and hence, calculated values. The effects depend on the sample composition and the approach to determine the effective grain size diameter. However, a direct comparison between methods indicated that the variability of is mainly influenced by strong differences of estimates between formulas.
Keywords: Earth Sciences ; Hydrogeology ; Geoecology/Natural Processes ; Soil Science & Conservation ; Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution ; Geotechnical Engineering & Applied Earth Sciences ; Sieve Analyses ; Hydraulic Conductivity ; Site Characterization ; Grain Size Distribution ; Environmental Sciences ; Geography;
ISSN: 1430-483X
E-ISSN: 1432-1165
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• 7
Article
Language: English
In: Environmental Earth Sciences, 2016, Vol.75(11), pp.1-21
Description: Color data are a useful proxy for soil/sediment parameterization since they reflect material characteristics. We introduce direct push color logging for real-time and depth-resolved, in situ colorimetric record of colors in unconsolidated sediments in terrestrial environments. Until now, no routines exist on how to handle highly resolved (mm-scale) data. To develop such routine, we transform colorimetric data (CIE XYZ ) into color surrogates of selected color spaces (CIE xyZ , $${\text{CIE}}L^{*} a^{*} b^{*}$$ CIE L ∗ a ∗ b ∗ , $${\text{CIE}}L^{*} c^{*} h^{*}$$ CIE L ∗ c ∗ h ∗ , sRGB ). We obtain interpretable color logs over depth by filtering with Haar and Daublet4 wavelet functions. We verify the approach, according to repeatability of in situ sediment color measurements, with related lithological determination gathered by state-of-the-art direct push-based cone penetration testing and soil sampling data. The developed routine is appropriate for unambiguous transformation of color data into interpretable color surrogates and filtering small-scale variability. We observe that soil color logs are repeatable and proved to correlate with lithological/chemical changes. Thus, the technique allows enhanced profiling by means of providing a reproducible high-resolution parameter for analysis of soil/sediment characteristics. This opens potential new areas of application and new outputs for in situ-obtained colorimetric data in and beyond geotechnical site characterization.
Keywords: Color logging tool ; In situ ; Soil color ; Direct push ; Colorimeter
ISSN: 1866-6280
E-ISSN: 1866-6299
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• 8
Article
Language: German
In: Grundwasser, 2011, Vol.16(4), pp.221-234
Description: Vor etwa zehn Jahren haben die sogenannten Direct-Push -Technologien in Deutschland als „neue“ Technik für die Erkundung des Untergrundes Einzug gehalten und werden seither vielfach in den verschiedensten Bereichen der Untergrunderkundung eingesetzt. Allerdings werden ihre Anwendungsmöglichkeiten noch zum Teil recht konträr diskutiert und eine gewisse Skepsis ist auch nach mehr als zehn Jahren Erfahrung in Deutschland geblieben. Bei genauerer Betrachtung der Anwendungsfelder dieser Technologie fällt auf, dass die Vielfältigkeit der Technologie zwar in einem zunehmenden Maße genutzt wird, in der „Praxis“ aber noch nicht vollständig angekommen zu sein scheint. Und dies obwohl die Technologie in ihrer einfachsten Art – nämlich in Form von Rammkernsondierungen – standardmäßig eingesetzt, aber das Potenzial der Methode nicht genutzt wird. Um diesem Defizit zu begegnen, zielt dieser Beitrag darauf ab, einen umfassenden Überblick über den Stand der Direct-Push -Technologie und deren vielfältigen Anwendungsmöglichkeiten und -limitierungen zu geben. About ten years ago, Direct Push technologies were introduced in Germany as a “new” tool for subsurface characterization. Ever since, they have been frequently used in various fields of site investigations. However, despite over ten years of experience, their application potential is often perceived with scepticism. Closer consideration of the range of applications of this method shows that the technology is indeed being increasingly used, even though it does not seem to be completely accepted in the “consulting world”. This is surprising as Direct Push is already used in Germany in its simplest form—i.e. by percussion coring—on a routine basis. Nonetheless, the full potential of Direct Push has not yet been exploited. This article aims to provide a comprehensive overview on the state of the art of this technology and its various application potentials and limitations.
Keywords: Direct Push ; Site characterization ; Sampling ; Direct sensing ; Subsurface investigation
ISSN: 1430-483X
E-ISSN: 1432-1165
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• 9
Article
Language: German
In: Grundwasser, 2013, Vol.18(1), pp.59-61
Keywords: Earth Sciences ; Hydrogeology ; Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution ; Geotechnical Engineering & Applied Earth Sciences ; Soil Science & Conservation ; Geoecology/Natural Processes ; Environmental Sciences ; Geography;
ISSN: 1430-483X
E-ISSN: 1432-1165
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• 10
Article
Language: English
In: Environmental Earth Sciences, 2013, Vol.69(2), pp.633-644
Description: River management and restoration measures are of increasing importance for integrated water resources management (IWRM) as well as for ecosystem services. However, often river management mainly considers engineering and construction aspects only and the hydrogeological settings as the properties and functions of ancient fluvial systems are neglected which often do not lead to the desired outcome. Knowledge of the distribution of sediment units could contribute to a more efficient restoration. In this study, we present two noninvasive approaches for delineation of fluvial sediment architecture that can form a basis for the restoration, particularly in areas where site disturbance is not permitted. We investigate the floodplain of a heavily modified low-mountain river in Switzerland using different hydrogeophysical methods. In the first approach, we use data from electromagnetic induction (EMI) with four different integral depths (0.75–6 m) and gamma-spectrometry as well as the elevation data as input for a K-means cluster algorithm. The generated cluster map of the surface combines the main characteristics from multilayered input data and delineates areas of varying soil properties. The resulting map provides an indication of areas with different sedimentary units. In the second approach, we develop a new iterative method for the generation of a geological structure model (GSM) by means of various EMI forward models. We vary the geological input parameters based on the measured data until the predicted EMI maps match the measured EMI values. Subsequently, we use the best matched input data for the GSM generation. The derived GSM provides a 3D delineation of possible ancient stream courses. A comparison with an independent ground penetrating radar (GPR) profile confirmed the delineations on the cluster map as well as the vertical changes of the GSM qualitatively. Thus, each of the approaches had the capacity for detecting sedimentary units with distinct hydraulic properties as an indication of former stream courses. The developed methodology presents a promising tool for the characterization of test sites with no additional subsurface information.
Keywords: ECa forward modelling ; Noninvasive methods ; 3D Geological structure model ; Channel restoration ; Sediment architecture ; EMI ; Cluster analysis ; Gamma-spectrometry ; GPR
ISSN: 1866-6280
E-ISSN: 1866-6299
Source: Springer Science & Business Media B.V.
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