Issues

Centrifuges have been used for several decades to determine the unsaturated hydraulic conductivity

This study extensively investigated the effects of electrical conductivity, cable length, and dielectric dispersion on various time domain reflectometry apparent dielectric constants and the associated effective frequencies. The implications of these influencing factors on soil moisture content measurements and the

Hydraulic properties of intact, variously weathered granitic bedrock cores were measured in the laboratory. Effects of weathering on the hydraulic properties and modes of water flow through weathered bedrock were discussed based on the relationships between weathering degree and core-scale hydraulic properties, core shape, and in situ saturated hydraulic conductivity values.

Root Pu uptake and xylem transport was added to an existing reactive transport model to evaluate Pu

In a long-term tillage experiment, we used apparent electrical conductivity to define areas

Time domain reflectometry probes partially coated with high-dielectric material allows,

Following a conservative tracer in a heterogeneous vadose zone is challenging. To characterize the

First-order analysis was used to analyze the probability density function (PDF) of the logarithm

Water flow is not uniform in most soils. We compared dye-marked, high velocity zones with

There is great interest in the ability to relate hydraulic properties of unsaturated soils to their acoustic response. Compressional and shear wave velocities and their attenuations, soil water characteristic curves, and unsaturated hydraulic conductivity functions were determined for a full range of saturations for two soil types.

A series of detailed, intermediate-scale laboratory experiments, using unsaturated homogeneous and heterogeneous systems, was conducted to improve our understanding of energy balance issues related to soil desiccation. The experiments were subsequently simulated with the multifluid flow simulator STOMP, using independently obtained hydraulic and thermal porous medium properties. The injection of dry air proved to be an effective means for removing essentially all moisture from the test media.

A variety of characterization methods were used to derive conceptual understanding and estimates of hydraulic properties of a coarse alluvial gravel vadose zone. Three main types of material were observed—sandy gravels, open framework gravels, and sand lenses—each with differing hydraulic properties resulting in a highly heterogeneous profile.

This paper introduces the special section on research at the Agrosphere Institute, Forschungszentrum Juelich, Germany. It describes the impact of global change on soil and water resources and summarizes results obtained in the functional analysis of soils and sediments, the development of sensing methods, and in flow and transport modeling.

A binding study of nitrogen 15-labeled 2-aminobenzothiazole (ABT) and a soil humic acid in the presence of laccase was conducted. Different types of bindings could be identified through nitrogen-15 cross-polarization magic angle spinning spectroscopy and comparison with synthesized derivatives of the labeled ABT that simulated possible chemical bindings.

Solute displacement experiments with the antibiotic sulfadiazine (SDZ) and its main transformation products in pig manure were performed to investigate the influence of manure on SDZ transport. The fitting process revealed a high mobility of both SDZ and its transformation products.

Bromide was used in transient infiltration experiments in zero-potential lysimeters containing undisturbed soil and in the field. The transferability of the transport behavior between the two systems was investigated and the lateral mass redistribution regime was inferred from the spreading of the solute plume in the field.

A rural aquifer was screened for potential microbial activities using a functional gene microarray. Specific microbial atrazine degraders were detected even for conditions of minor levels of atrazine contamination (about 2 micrograms per liter). Microbial communities in these oligotrophic environments appear to be sensitive to relatively small quantities of contaminants.

We used 3-D time-lapse electrical resistivity tomography (ERT) to noninvasively characterize four solute transport experiments in an unsaturated soil column. We benchmarked ERT-derived apparent transport model parameters at different observation scales using the mass balance, TDR probes, and the effluent breakthrough curve.

We examined the transport characteristics of four tracer experiments in a large undisturbed soil column under different unsaturated hydraulic boundary conditions using 3-D electrical resistivity tomography (ERT). We compared the transport velocity patterns and derived the mixing regime. We introduced and applied a dispersivity up-scaling approach.

Fast field cycling NMR relaxometry ís used for the determination of distribution functions of spin-lattice relaxation time in saturated samples of sand, sand-loam and silt-loam soils. Estimates of pore size distribution for these samples were obtained by normalizing the spin-lattice relaxation time distribution functions on the specific surface area.

We use full-waveform, integrated hydrogeophysical inversion of time-lapse, off-ground GPR data to remotely estimate the unsaturated hydraulic properties of a sand under laboratory conditions. The results suggest that the proposed method is promising for mapping the shallow soil hydraulic properties at the field scale with a high spatial resolution.

Hybrid wireless soil moisture networks like the novel SoilNet use a mixture of underground devices each wired to several soil sensors and aboveground router devices. In this study we developed a semi-empirical model to demonstrate that in the case of a 5 cm soil layer data communication over longer distances for most soil conditions is possible.

Measuring representative average field-scale fluxes of soil heterotrophic respiration with a chamber method is delicate. We investigated the underlying spatial patterns of respiration as related to soil water contents and temperatures and present a method that facilitates determination of an optimum sampling setup.

Multistep outflow experiments were performed to estimate soil hydraulic properties as well as carbon dioxide production parameters using the SOILCO2/RothC model. The results indicate that the control parameters of the soil water reduction function can be estimated accurately only if carbon rate constants are adjusted simultaneously with the control parameters.

In this study, different microscopic modeling approaches were assessed that consider soil hydraulic effects around roots in a three-dimensional, macroscopic, soil-root water flow model. Results showed that local soil hydraulic effects should be considered in soils where their hydraulic properties are lower than root hydraulic properties.

The study showed that local inverse modeling approaches may result in erroneous parameter uncertainty estimations. Additionally, the advantages of multiobjective inverse modeling are highlighted compared with a sequential single-objective approach. The study was based on observed pesticide leaching lysimeter data; however, conclusions may be extrapolated to a wider range of vadose zone modeling work.

Roots need to stay in close contact with the soil to take up water. During drought, roots may lose contact due to shrinkage, thereby reducing the capacity for water uptake and limiting water loss from the soil. When water becomes available again, contacts are restored due to root swelling. These dynamics were observed by means of x-ray computed tomography.

An improved tension infiltrometer for field use, where both water level measurement in the reservoir and tension settings can be automated, was developed. The use of this automated system allows replicated measurements to be taken under the exact same tension with very little operator intervention other than for refilling the reservoir.