Secrets of the subsurface

The condition of ecosystems and biodiversity also depends on the availability and quality of water. Human intervention and natural processes affect an ecosystem's water and matter cycles. For example, the quality and availability of water in river catchment areas can be changed by nutrient discharges from farming an agriculture, pollutant input from contaminated sites, and changes to the natural course of surface waters. Sustainable farming therefore needs to build on a sound knowledge and understanding of the interactions taking place in the water and matter balance of ecosystems. These interactions remain inadequately understood to this very day. Reasons for this include the fact that it is still only partly possible to reliably record matter and water fluxes. This means that it is also difficult to design sustainable land use and water management measures and to make any predictions. To counter these challenges, the Helmholtz Centre for Environmental Research - UFZ created the research platform MOSAIC to investigate, monitor and control ecosystems. MOSAIC stands for "Model Drive Site Assessment, Information and Control", thereby expressing that it not only aims for model-based subsurface investigations but also that the data can be used to control environmental processes. By combining and developing technologies from the fields of drilling, measurement and analytical techniques, MOSAIC makes it possible to perform field-scale studies of a new quality in terms of the efficiency and speed of high-resolution investigations of complex subsurface structures. MOSAIC helps in developing methods for decision-support and process control that also meet the relevant legal frameworks. "However, it's not just about a specific technology, we also aim to intelligently combine and advance various technologies. Because each method has its advantages and disadvantages," says Dr. Ulrike Werban, a junior scientist working at the UFZ. This is why the Helmholtz researchers are also working on a combination of direct-push technologies - a comparatively new field - and geophysical methods. This novel approach raises the quality of the results and substantially accelerates the investigations. In fact, MOSAIC not only serves interdisciplinary research, but also technology transfer, for example, by putting new monitoring and exploration technologies into practice. A UFZ pilot project is being carried out in the Jahna flood plain near Riesa, Saxony, to determine groundwater quality. Directpush equipment is being used to measure depth profiles of concentrations of selected substances in the groundwater.

This enables the scientists to examine the subsurface much faster and cheaper than with conventional drilling methods. Although an extensive network of groundwater monitoring wells exists in Saxony, the new method enables a much closer look at the particular problems there. And this is necessary because the EU Water Framework Directive requires measures to be drawn up by 2009 for water bodies affected by quality problems.

The pilot project is only one of many applications. Regardless of whether it's dealing with volatile hydrocarbons near Vienna or of precisely localising a benzene plume beneath a former refinery plant, the direct-push technology has proven itself in various UFZ campaigns over recent months. But the technology also opens up completely new opportunities for biologists and soil scientists for examining dykes, including flood protection measures. So, the researchers meanwhile spend a lot of time on the road with their equipment, so as to fill in the remaining white areas on the maps of the subsurface.