Hydraulic processes and properties of partially hydrophobic soils: The effect of water repellency on the characteristic curves estimated from dynamic flow experiments

Soil research done over the past decades, has proven that water repellent soils are widespread in all climates. In order to assess the effect of hydrophobicity in the estimated characteristic curves, inflow/outflow experiments were conducted in the laboratory for one soil and two artificial created hydrophobic mixtures. In the inflow/outflow experiments the pressure head at the bottom of the soil column was increased/decreased and the estimated curves were obtained by means of inverse modeling. Multistep inflow/outflow experiments were also conducted using ethanol instead of water in order to estimate the effect of liquid wetting properties on the estimated characteristic curves of the materials under study. The results have shown that the water retention functions and the unsaturated hydraulic conductivity functions estimated from the dynamic experiments are strongly dependent on the degree of hydrophobicity and the wetting/drying process

3D infiltration dynamics in an initially dry sandy soil: interactive soil hydraulic-geophysical interpretation

To assess water transport dynamics in a poorly structured homogeneous sandy soil, labour-intensive TDR and tensiometer measurements were conducted during a double tracer ponding experiment. Water transport was also observed by 3D-ERT measurements. The excavated soil profile showed a cone-shaped infiltration zone with depth, contrary to an expected tracer pattern in sand. Water content changes showed highest water contents at the wetting front, referred to as saturation overshoot. This non-monotonic pattern is likely to have been caused by reduced wettability of the soil material, which reduces capillary forces during the infiltration. Independent ERT-data showed the same infiltration pattern during ponding, but could not detect the saturation profile due to gradient smoothing during the inversion process

Kohlenstoffmineralisierung in Böden: Einfluss von Benetzungshemmung, Bodenstruktur und Benetzungsgeschichte

Der Einfluss von Bodenstruktur und Benetzungshemmung auf die Kohlenstoff-mineralisierung im Boden wurde anhand der CO2-Freisetzung von Stech-zylinderproben während eines Trocknungs-/Wiederbefeuchtungszyklus untersucht. Ergebnisse zeigen eine Reduktion der Kohlenstoffmineralisierung bedingt durch die Benetzungshemmung des Bodens. Diese variiert in Abhängigkeit vom Wassergehalt der Proben, der Zeit seit Befeuchtung der Proben und der Benetzungsgeschichte (Hysterese). Die Bodenstruktur zeigt einen messbaren Einfluss auf die Kohlenstoffmineralisierung. Allerdings konnte der Einfluss der Bodenstruktur auf die Kohlenstoff-mineralisierung aus messtechnischen Gründen nur bei Entwässerung gemessen werden

Neue Kennwerte für die Wasserbindung in Böden - Ergebnisse der Abstimmung zwischen dem Personenkreis Wasserhaushaltstabellen der Ad-hoc-AG Boden und dem DWA

Mit den vorliegenden Diagrammen und Tabellen liegen bundesweit abgestimmte Grundlagen für die Einschätzung des Wasser- und Lufthaushaltes von Böden vor. Die Werteschwankungen von Wasserge-halten in verschiedenen Porenbereichen des Bodens können über die graphische Datenauswertung auf der Basis des Korn-größendiagramms schlüssig abgebildet werden. Gegenüber der bodenkundlichen Kartieranleitung (Ad-hoc-AG Boden 2005) liegen folgende Änderungen bzw. Erweiterungen vor: - Schätzrahmen mit Werten für 5 Trockenrohdichten - Schätzrahmen mit Angaben für pF 2,5 - Schätzrahmen mit Angaben für die Frühjahrsfeuchte - Diagramme auf der Basis des Korngrößendreiecks - Erweiterung der Tabelle mit Zuschlägen in Abhängigkeit von der Humusstufe und Bodenart für pF 2,5 Schätzrahmen und Diagramme bieten ein aufeinander abgestimmtes Gesamtpaket für die feldbodenkundliche Arbeit

Hydraulic Modeling and in situ Electrical Resistivity Tomography to Analyze Ponded Infiltration into a Water Repellent Sand

Water repellency (WR) might affect the spatial and temporal dynamics of a wetting front during infiltration and redistribution in a way that is difficult to predict with standard approaches. Therefore, the objectives of this study were to simulate the wetting plume geometry with a three‐dimensional numerical model and to test whether electrical resistivity tomography (ERT) is able to illustrate the geometry under highly dynamic conditions. At our study site under agricultural use (Gleyic Podzol, groundwater affected), persistent WR in the subsoil to the 120‐cm depth was responsible for a conical plume geometry observed after ponded tracer application with Brilliant Blue (BB) and bromide. The process was invasively observed with hydraulic sensors. At the same time, ERT was used to monitor a second ponded infiltration event under equal boundary conditions at the same site. Numerical simulation of the process showed that hysteresis in the water retention curve is needed to describe the specific infiltration plume geometry correctly. The main wetting function was derived from scaling the main drying curve with measured contact angle data. A comparison of wetting front arrival times among the hydraulic model, sensors, and independent ERT observations indicates an overall good agreement and shows the usefulness of ERT measurements under highly dynamic in situ conditions. Our results confirm the need to include strong hysteresis effects scaled with independent contact angle data when simulating infiltration dynamics in a water repellent soil to avoid an underestimation of the wetting front arrival

The Role of Matric Potential, Solid Interfacial Chemistry, and Wettability on Isotopic Equilibrium Fractionation

Soil water stable isotopes are widely used for geo- and ecohydrological applications. However, the signature of the soil water isotopic composition in the environment depends on various factors. While recent work has shown matric potential effects on equilibrium fractionation, little work has examined other soil parameters concerning soil water energy status like the surface wettability, usually quantified in terms of contact angle. We simultaneously explored the role of matric potential, contact angle, and soil surface chemistry effects on the equilibrium fractionation factor during soil water evaporation. We present a simple laboratory experiment with four different soils of various textures. Subsamples of each texture class were treated with dichlorodimethylsilane to modify surface wetting properties. Additionally, we tested two natural soil samples to explore wettability effects. Samples were dried at temperatures between 40 and 550°C to produce chemically modified surface properties. All samples were spiked with water of known isotopic composition at different water contents. The isotopic signature was determined using the vapor-bag equilibration method. The matric potential of each sample was measured with a soil water potential meter, the contact angle was determined with the sessile drop method, and the surface chemistry by X-ray photoelectron spectroscopy. In addition to temperature and soil matric potential, the elemental composition has apparently some control on the equilibrium fractionation factor. Based on findings, we introduce a new soil water isotope retention characteristic approach to summarize how these factors (matric potential, contact angle, and soil surface chemistry) each control the equilibrium fractionation factor for O/O and H/H. Corresponding retention curve approach parameters are promising to be applied in the future to predict soil water fractionation effects under natural and non-stationary conditions

Reproducibility of the wet part of the soil water retention curve: a European interlaboratory comparison

The soil water retention curve (SWRC) is a key soil property required for predicting basic hydrological processes. The SWRC is often obtained in the laboratory with non-harmonized methods. Moreover, procedures associated with each method are not standardized. This can induce a lack of reproducibility between laboratories using different methods and procedures or using the same methods with different procedures. The goal of this study was to estimate the inter- and intralaboratory variability of the measurement of the wet part (from 10 to 300 hPa) of the SWRC. An interlaboratory comparison was carried out between 14 laboratories, using artificially constructed, porous reference samples that were transferred between laboratories according to a statistical design. The retention measurements were modelled by a series of linear mixed models using a Bayesian approach. This allowed the detection of sample-to-sample variability, interlaboratory variability, intralaboratory variability and the effects of sample changes between measurements. The greatest portion of the differences in the measurement of SWRCs was due to interlaboratory variability. The intralaboratory variability was highly variable depending on the laboratory. Some laboratories successfully reproduced the same SWRC on the same sample, while others did not. The mean intralaboratory variability over all laboratories was smaller than the mean interlaboratory variability. A possible explanation for these results is that all laboratories used slightly different methods and procedures. We believe that this result may be of great importance regarding the quality of SWRC databases built by pooling SWRCs obtained in different laboratories. The quality of pedotransfer functions or maps that might be derived is probably hampered by this inter- and intralaboratory variability. The way forward is that measurement procedures of the SWRC need to be harmonized and standardized

Reproducibility of the Wet Part of the Soil Water Retention Curve: A European Interlaboratory Comparison

Abstract. The soil water retention curve (SWRC) is a key soil property required for predicting basic hydrological processes. SWRC is often obtained in laboratory with non-harmonized methods. Moreover, procedures associated to each method are not standardized. This can induce a lack of reproducibility between laboratories using different methods and procedures or using the same methods with different procedures. The goal of this study was to estimate the inter/intralaboratory variability of the measurement of the wet part (from 10 to 300 hPa) of the SWRC. An interlaboratory comparison was conducted between 14 laboratories, using artificially constructed, porous and structured samples as references. The bulk densities of samples were different at the very beginning of the experiment. This resulted in a variability of retention properties between the samples, which was estimated by a linear mixed model with a "sample" random effect. Our estimate of inter/intralaboratory variability was therefore not affected by intrinsic differences between samples. The greatest portion of the differences in the measurement of SWRCs was due to interlaboratory variability. The intralaboratory variability was highly variable depending on the laboratory. Some laboratories successfully reproduced the same SWRC on the same sample, while others did not. The mean intralaboratory variability over all laboratories was smaller than the mean interlaboratory variability. A possible explanation for these results is that all laboratories used slightly different methods and procedures. We believe that this result may be of great importance regarding the quality of SWRC databases built by pooling SWRCs obtained in different laboratories. The quality of pedotransfer functions or maps that might be derived is probably hampered by this inter-/intralaboratory variability. The way forward is that measurement procedures of the SWRC need to be harmonized and standardized. </jats:p

All-trans retinoic acid as adjunct to intensive treatment in younger adult patients with acute myeloid leukemia: results of the randomized AMLSG 07-04 study

The aim of this clinical trial was to evaluate the impact of all-trans retinoic acid (ATRA) in combination with chemotherapy and to assess the NPM1 status as biomarker for ATRA therapy in younger adult patients (18-60 years) with acute myeloid leukemia (AML). Patients were randomized for intensive chemotherapy with or without open-label ATRA (45 mg/m(2), days 6-8; 15 mg/m(2), days 9-21). Two cycles of induction therapy were followed by risk-adapted consolidation with high-dose cytarabine or allogeneic hematopoietic cell transplantation. Due to the open label character of the study, analysis was performed on an intention-to-treat (ITT) and a per-protocol (PP) basis. One thousand one hundred patients were randomized (556, STANDARD; 544, ATRA) with 38 patients treated vice versa. Median follow-up for survival was 5.2 years. ITT analyses revealed no difference between ATRA and STANDARD for the total cohort and for the subset of NPM1-mutated AML with respect to event-free (EFS; p = 0.93, p = 0.17) and overall survival (OS; p = 0.24 and p = 0.32, respectively). Pre-specified PP analyses revealed better EFS in NPM1-mutated AML (p = 0.05) and better OS in the total cohort (p = 0.03). Explorative subgroup analyses on an ITT basis revealed better OS (p = 0.05) in ATRA for genetic low-risk patients according to ELN recommendations. The clinical trial is registered at clinicaltrialsregister.eu (EudraCT Number: 2004-004321-95)