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Results 1-6 of 6 (Search time: 0.145 seconds).
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  • Numerical and Experimental Investigations of Cesium and Strontium Sorption and Transport in Agricultural Soils

    • Authors: Berns, A.E.;  Advisor: -;  Participants: Mehmood, K.; Flath, A.; Hofmann, D.; Jacques, D.; Sauter, M.; Vereecken, H.; Engelhardt, I. (2018)

  • We identified undefined cation exchange as the dominant sorption process for Sr2+, followed by surface complexation on organic matter. These process‐based analyses were the basis for field‐scale simulations to predict the leaching risk of Cs and Sr radionuclides in agricultural soils under humid climate conditions. For both soils and radionuclides, the distribution coefficients (Kd) varied distinctly with time in shallow layers due to changes in temperature, saturation, and the prevailing dominant sorption processes. During a 3‐yr‐simulation period, 137Cs+ migrated to depths of 3.6 cm (silty loam) and 7.6 cm (sandy loam), while 90Sr2+ migrated to depths of 15.6 cm (silty loam) and 23.6 cm (sandy loam) due to competitive sorption of infiltrating Ca2+ and Mg2+ ions reducing 90Sr2+ sor...
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  • Monitoring Hydrological Processes for Land and Water Resources Management in a Mediterranean Ecosystem: The Alento River Catchment Observatory

    • Authors: Romano, N.;  Advisor: -;  Participants: Nasta, P.; Bogena, H.; De Vita, P.; Stellato, L.; Vereecken, H. (2018)

  • Rainy seasons are likely to be characterized by intense storms that trigger floods, resulting in increasing damage severity. The negative effects of anthropogenic disturbance on hydrological ecosystem services can be tempered by demand‐side adaptation options and appropriate investments to ensure water supply under drought conditions. To shed light on some of the scientific challenges related to these issues, a critical zone observatory (CZO) has been established in the Alento River catchment. Although sampling campaigns and monitoring investigations have been performed in this area for >25 yr, a more systematic research program was recently started to take comprehensive measurements in representative subcatchments of the study area. These sites are instrumented with advanced ground...
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  • Characterizing Redox Potential Effects on Greenhouse Gas Emissions Induced by Water‐Level Changes

    • Authors: Wang, J.;  Advisor: -;  Participants: Bogena, H.R.; Vereecken, H.; Brüggemann, N. (2018)

  • The dynamics of redox potential were induced by changing the water‐table depth in a laboratory lysimeter. Before fertilization during saturated conditions, we found a clear negative correlation between redox potentials and N2O emission rates. After switching from saturated to unsaturated conditions, N2O emission quickly decreased, indicating denitrification as the main source of N2O. In contrast, the emissions of CO2 increased with increasing soil redox potentials. After fertilization, N2O emission peaked at high redox potential, suggesting nitrification as the main production pathway, which was confirmed by isotope analysis of N2O. We propose that redox potential measurements are a viable method for better understanding of the controlling factors of GHG emissions, for the different...
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  • Parameterization of Root Water Uptake Models Considering Dynamic Root Distributions and Water Uptake Compensation

    • Authors: Cai, C.;  Advisor: -;  Participants: Vanderborght, J.; Couvreur, V.; Mboh, C.M.; Vereecken, H. (2018)

  • These models were implemented in HYDRUS‐1D, and soil hydraulic parameters were optimized by inverse modeling using soil water content and potential measurements and observations of root distributions of winter wheat (Triticum aestivum L.) in horizontally installed rhizotubes. Soil moisture was equally well predicted by the three models, and the soil hydraulic parameters optimized by the models with compensation were comparable. The obtained RWU parameters of the Feddes–Jarvis model were consistent with data reported in the literature, although the pressure heads h3l and h3h for lower and higher transpirations rates, respectively, could not be uniquely identified. Response surfaces of the objective function showed that the root‐related parameters of the Couvreur model could be identi...
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  • Inverse Estimation of Soil Hydraulic and Transport Parameters of Layered Soils from Water Stable Isotope and Lysimeter Data

    • Authors: Groh, J.;  Advisor: -;  Participants: Stumpp, C.; Lücke, A.; Pütz, T.; Vanderborght, J.; Vereecken, H. (2018)

  • We used different optimization strategies to investigate which observation types are necessary for simultaneously estimating soil hydraulic and solute transport parameters. Combining water content, matric potential, and tracer (e.g., δ18O) data in one objective function (OF) was found to be the best strategy for estimating parameters that can simulate all observed water flow and solute transport variables. A sequential optimization, in which first an OF with only water flow variables and subsequently an OF with transport variables was optimized, performed slightly worse indicating that transport variables contained additional information for estimating soil hydraulic parameters. Hydraulic parameters that were obtained from optimizing OFs that used either water contents or matric pot...
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  • Magnetic Resonance Monitoring and Numerical Modeling of Soil Moisture during Evaporation

    • Authors: Merz, S.;  Advisor: -;  Participants: Balcom, B.J.; Enjilela, R.; Vanderborght, J.; Rothfuss, Y.; Vereecken, H.; Pohlmeier, A. (2018)

  • Evaporation from bare soil surfaces can be restrained to a great extent with the development of a dry layer at the soil surface where capillary hydraulic conductance ceases and water flow proceeds only by gas phase transport. Model calculations and preliminary experiments with model porous media have shown that this surface layer can be very thin. An accurate characterization of these processes is required, which is provided by noninvasive magnetic resonance (MR) methods. The evaporative drying of a silt loam and a sandy loam was monitored at high spatial resolution in laboratory experiments. The MR data were used to assess the performance of two numerical models: (i) the Richards equation, which considers isothermal liquid water flow, and (ii) a coupled soil water, heat, and vapor ...
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