Ulrike Werban

A field investigation on transport of carbon-supported nanoscale zero-valent iron (nZVI) in groundwater.

The application of nanoscale zero-valent iron (nZVI) for subsurface remediation of groundwater contaminants is a promising new technology, which can be understood as alternative to the permeable reactive barrier technique using granular iron. Dechlorination of organic contaminants by zero-valent iron seems promising. Currently, one limitation to widespread deployment is the fast agglomeration and sedimentation of nZVI in colloidal suspensions, even more so when in soils and sediments, which limits the applicability for the treatment of sources and plumes of contamination. Colloid-supported nZVI shows promising characteristics to overcome these limitations. Mobility of Carbo-Iron Colloids (CIC) - a newly developed composite material based on finely ground activated carbon as a carrier for nZVI - was tested in a field application: In this study, a horizontal dipole flow field was established between two wells separated by 5.3m in a confined, natural aquifer. The injection/extraction rate was 500L/h. Approximately 1.2kg of CIC was suspended with the polyanionic stabilizer carboxymethyl cellulose. The suspension was introduced into the aquifer at the injection well. Breakthrough of CIC was observed visually and based on total particle and iron concentrations detected in samples from the extraction well. Filtration of water samples revealed a particle breakthrough of about 12% of the amount introduced. This demonstrates high mobility of CIC particles and we suggest that nZVI carried on CIC can be used for contaminant plume remediation by in-situ formation of reactive barriers.

The Bode hydrological observatory: a platform for integrated, interdisciplinary hydro-ecological research within the TERENO Harz/Central German Lowland Observatory

This article provides an overview about the Bode River catchment that was selected as the hydrological observatory and main region for hydro-ecological research within the TERrestrial ENvironmental Observatories Harz/Central German Lowland Observatory. It first provides information about the general characteristics of the catchment including climate, geology, soils, land use, water quality and aquatic ecology, followed by the description of the interdisciplinary research framework and the monitoring concept with the main components of the multi-scale and multi-temporal monitoring infrastructure. It also shows examples of interdisciplinary research projects aiming to advance the understanding of complex hydrological processes under natural and anthropogenic forcings and their interactions in a catchment context. The overview is complemented with research work conducted at a number of intensive research sites, each focusing on a particular functional zone or specific components and processes of the hydro-ecological system.

Hydro-, bio-geophysics

The global increase in demand for water, the dominant agent in all biological processes, calls for sustainable management of water catchments and better understanding of water and solute movement. At Kiel, we have started joint studies with eight European partners in such disciplines as botany, agronomy, and hydrology (projects “WATERUSE” and “GeoModel”) to develop integrated techniques to quantify water flow through the soil-plant-atmosphere-continuum that will be adequate for use in heterogeneous stands in dry regions. To develop novel integrated hydro-/biogeophysical 3D techniques with high resolution, we erected a unique, full-scale tank analog (3 m × 5 m × 2 m and named GeoModel) at the Kiel campus for controlled experiments on simulated soil models in their natural scale. It forms a bridge between scaled laboratory models (typically 1 m3) and field surveys (several km3) that takes advantage of both. GeoModel is used to study the static water content and dynamic flow in soils and plants using infiltr...

Noninvasive characterization of the Trecate (Italy) crude-oil contaminated site: links between contamination and geophysical signals

The characterization of contaminated sites can benefit from the supplementation of direct investigations with a set of less invasive and more extensive measurements. A combination of geophysical methods and direct push techniques for contaminated land characterization has been proposed within the EU FP7 project ModelPROBE and the affiliated project SoilCAM. In this paper, we present results of the investigations conducted at the Trecate field site (NW Italy), which was affected in 1994 by crude oil contamination. The less invasive investigations include ground-penetrating radar (GPR), electrical resistivity tomography (ERT), and electromagnetic induction (EMI) surveys, together with direct push sampling and soil electrical conductivity (EC) logs. Many of the geophysical measurements were conducted in time-lapse mode in order to separate static and dynamic signals, the latter being linked to strong seasonal changes in water table elevations. The main challenge was to extract significant geophysical signals linked to contamination from the mix of geological and hydrological signals present at the site. The most significant aspects of this characterization are: (a) the geometrical link between the distribution of contamination and the site’s heterogeneity, with particular regard to the presence of less permeable layers, as evidenced by the extensive surface geophysical measurements; and (b) the link between contamination and specific geophysical signals, particularly evident from cross-hole measurements. The extensive work conducted at the Trecate site shows how a combination of direct (e.g., chemical) and indirect (e.g., geophysical) investigations can lead to a comprehensive and solid understanding of a contaminated site’s mechanisms.

Correlation of electrical resistivity, electrical conductivity and soil parameters at a long-term fertilization experiment

Geophysical methods are progressive, non-destructive but indirect techniques for characterization of soil properties and mapping of soil heterogeneities. Geophysical surveys for soil mapping lead generally to ambiguous results since geophysical parameters are influenced by several soil properties, e.g., organic content, clay content and bulk density. The investigations presented here focus on the effect of different stages of organic content on DC-geoelectrics and electromagnetic induction (EMI) at a long-term fertilization experiment. This experiment gives, after 105 years running, an excellent opportunity to study the correlations between electrical resistivity, apparent electrical conductivity and soil parameters. Results from DC-geoelectrical measurements (profile length 80–160 m, electrode distance 0.5 m) twice, in August after harvest and in January during black fallow period, are presented. Additionally electromagnetical investigations were conducted in January. Correlations of resistivity and carbon input into the soil are significant and very strong; especially in January with r = –0.89 but contradictive in summer and winter. The analysis of resistivity and apparent electrical conductivity is critical since bulk density and water storage capacity is influenced by fertilization and plant growth. Interpretation of a combination of DC-geoelectrics and electromagnetical techniques on agricultural areas has to be done with respect to management aspects.

Near-surface seismic traveltime tomography using a direct-push source and surface-planted geophones

Information about seismic velocity distribution in heterogeneous near-surface sedimentary deposits is essential for a variety of environmental and engineering geophysical applications. We have evaluated the suitability of the minimally invasive direct-push technology for near-surface seismic traveltime tomography. Geophones placed at the surface and a seismic source installed temporarily in the subsurface by direct-push technology quickly acquire reversed multioffset vertical seismic profiles (VSPs). The first-arrival traveltimes of these data were used to reconstruct the 2D seismic velocity distribution tomographically. After testing this approach on synthetic data, we applied it to field data collected over alluvial deposits in a former river floodplain. The resulting velocity model contains information about high- and low-velocity anomalies and offers a significantly deeper penetration depth than conventional refraction tomography using surface-planted sources and receivers at the investigated site. A combination of refraction seismic and direct-push data increases resolution capabilities in the unsaturated zone and enables reliable reconstruction of velocity variations in near-surface unconsolidated sediments. The final velocity model structurally matches the results of cone-penetration tests and natural gamma-radiation data acquired along the profile. The suitability of multiple rapidly acquired reverse VSP surveys for 2D tomographic velocity imaging of near-surface unconsolidated sediments was explored.

Are Earth Sciences lagging behind in data integration methodologies

This article reflects discussions German and South African Earth scientists, statisticians and risk analysts had on occasion of two bilateral workshops on Data Integration Technologies for Earth System Modelling and Resource Management. The workshops were held in October 2012 at Leipzig, Germany, and April 2013 at Pretoria, South Africa, and were attended by about 70 researchers, practitioners and data managers of both countries. Both events were arranged as part of the South African-German Year of Science 2012/2013. The South African National Research Foundation (NRF, UID 81579) has supported the two workshops as part of the South African–German Year of Science activities 2012/2013 established by the German Federal Ministry of Education and Research and the South African Department of Science and Technology.

iSOIL: An EU Project to Integrate Geophysics, Digital Soil Mapping, and Soil Science

The Thematic Strategy for Soil Protection, prepared by the European Commission in 2006, concluded that soil degradation is a significant problem in Europe. Degradation is driven or exacerbated by human activity and has a direct impact on water and air quality, biodiversity, climate, and the quality of (human) life. High-resolution soil property maps are a major prerequisite for the specific protection of soil functions and the restoration of degraded soils, as well as for sustainable land use and water and environmental management. To generate such maps, a combination of digital soil mapping approaches and remote and proximal soil sensing techniques is most promising. However, a feasible and reliable combination of these technologies for the investigation of large areas (e.g. catchments and landscapes) and the assessment of soil degradation threats is still missing. There is insufficient dissemination – to relevant authorities as well as prospective users – of knowledge on digital soil mapping and proximal soil sensing from the scientific community. As a consequence, there is inadequate standardisation of the techniques. In this chapter we present the EU project iSOIL, which is funded within the 7th Framework Program of the European Commission. iSOIL focuses on improving and developing fast and reliable mapping of soil properties, soil functions, and soil degradation threats. This requires the improvement and integration of advanced soil sampling approaches, geophysical and spectroscopic measurement techniques, as well as pedometric and pedophysical approaches. Another important aspect of the project is the sustainable dissemination of the technologies and the concepts developed. For this purpose, guidelines for soil mapping on different scales, and using various methods for field measurements, will be written. Outcomes of the project’s measurements will be implemented in national and European soil databases. The present state of knowledge and future perspectives will be communicated to authorities, providers of technologies (e.g. small and medium enterprises), and end-users.

River water infiltration enhances denitrification efficiency in riparian groundwater

Nitrate contamination in ground- and surface water is a persistent problem in countries with intense agriculture. The transition zone between rivers and their riparian aquifers, where river water and groundwater interact, may play an important role in mediating nitrate exports, as it can facilitate intensive denitrification, which permanently removes nitrate from the aquatic system. However, the in-situ factors controlling riparian denitrification are not fully understood, as they are often strongly linked and their effects superimpose each other. In this study, we present the evaluation of hydrochemical and isotopic data from a 2-year sampling period of river water and groundwater in the riparian zone along a 3rd order river in Central Germany. Based on bi- and multivariate statistics (Spearmans rank correlation and partial least squares regression) we can show, that highest rates for oxygen consumption and denitrification in the riparian aquifer occur where the fraction of infiltrated river water and at the same time groundwater temperature, are high. River discharge and depth to groundwater are additional explanatory variables for those reaction rates, but of minor importance. Our data and analyses suggest that at locations in the riparian aquifer, which show significant river water infiltration, heterotrophic microbial reactions in the riparian zone may be fueled by bioavailable organic carbon derived from the river water. We conclude that interactions between rivers and riparian groundwater are likely to be a key control of nitrate removal and should be considered as a measure to mitigate high nitrate exports from agricultural catchments.

Reliability of MASW profiling in near-surface applications

Pseudo-2D surface wave profiling (MASW) has become a powerful state-of-the-art tool for the characterization of near-surface features in recent years. The rapid gathering and interpretation of surface wave data, i.e. Rayleigh waves, that this method offers is applicable to many investigations and environments. However, most studies only perform unidirectional active surface wave profiling, i.e. without data evaluation by measuring the same profile in the opposite direction. Uncertainties arising from using the MASW method are connected to the one-dimensional inversion of a two-dimensional subsurface. Moreover, the occurence of lateral inhomogeneities and dipping layers distort the flat-layered 1D assumption used in surface wave inversion. In this study, we present data from two different MASW surveys. For both locations, we reveal shot-geometrical effects and prove the necessity of bidirectional profiling, especially since these check shots can be implemented with only little extra effort. The results of this investigation show that, in general, more attention should be paid to data evaluation.