Björn Kluge

Metal leaching in a highway embankment on field and laboratory scale

Increasing worldwide motor vehicle traffic leads to the question of the possible environmental consequences. This paper aims to analyse metal leaching in a highway embankment using both field and laboratory experiments. Soil, soil solution and road runoff were collected along one of the oldest highways in the world to characterize leaching of the metals Cd, Cr, Cu, Ni, Pb and Zn. Batch, column and adsorption experiments were carried out to study the reliability and transferability of laboratory approaches. Depending on the element, the ratio of particle-bound metals in road runoff varied between 15-90%. Metal levels in embankment soils were significantly higher compared to a reference site in a forest at 800 m distance (up a factor of 30). High metal concentrations in soil solution at 50 cm soil depth were not a direct result of road runoff but rather of elevated concentrations in the soil matrix. The use of batch S4 elution was found to be the best overall laboratory method to predict soil solution concentrations in field. Adsorption experiments showed a relative increase in retention capacity in roadside soil of up to a factor of 20 after nearly 100 years of operation. The input of alkaline dust and organic carbon into roadside soils increases its retention capacity in the long term.

Urban Soils in the Vadose Zone

Between the soggy ceiling of the ground water aquifer and the uppermost interface of earth and air is the unsaturated space of soil particles and pores invisible to most surface dwellers – the vadose zone. In cities, this space can be frozen in time under buildings and sidewalks, and contaminated with various kinds and concentrations of polluting substances. With more than 50% of the world’s population living in cities as of 2007, research on the composition, function and dynamics of urban soils is of utmost importance for urban ecological questions as well as the for the wellbeing of city dwellers world wide. Even before the 50% demographic benchmark, interest in anthropogenic soils began stirring in Germany in the 1970s in Berlin and Essen (Burghardt 1995; Blume 1975). At that time, research concerns revolved around the proper classification of soils in urban areas and the dilemma of restoring and re-using former industrial sites. From the 1980s until the beginning of the 1990s, pollution of urban soils with organic and inorganic contaminants became the focus of many studies (Thornton 1991; Lux 1993; Radtke et al. 1997). Since then, research on urban soils has substantially broadened. The BMBF (Federal Ministry of Education and Research) project “Evaluation of Urban Soils” from 1993 to 1996, for example, included groundbreaking work on the chemical, physical and biological properties of anthropogenic soils, involving major soil science institutions from the universities of Kiel, Essen, Hohenheim, Halle, Rostock and Berlin. Results are presented in Blume and Schleuss (1997).

From a stinking wastewater disposal field toward a recreation area—the story of an unconventional soil remediation in Berlin, Germany

PurposeWastewater irrigation is still a common practice in many cities worldwide. After ending the wastewater irrigation, the question arises as to how the highly polluted areas can be reused. Mostly, the remediation costs for liming or adding synthetic soil conditioners are too high for decision makers, often leading to unattractive wastelands in neighboring suburbs. This story shows how part of a former wastewater disposal field in Berlin (Germany) was remediated by adding and mixing loam-rich glacial until excavated from subway construction work. The remediation led to long-term improvements of soil and landscape, which nowadays is an attractive forested recreation area. Part of this landscape is used as an ecological lab for research, art, and education.Materials and methodsThe article summarizes the results of soil analysis of the contamination status and remediation technique over the last 2 decades. We collected and reevaluated historical data, research results, technical reports, and graphic materials concerning the wastewater disposal field in Berlin, Germany.Results and discussionThe remediation concept without adding any synthetic substances was a successful soft technology leading to (i) a reduction of the long-term groundwater risk, (ii) an immobilization of the trace element concentration in the soil solution, and (iii) a reduction of the metal uptake by plants. Remediation led to much better conditions for plant growth, soil fauna, and microbiological activity, which improved the environment in a sustainable way. The implementation of a new landscape concept combining ecology, culture, and art totally changed the character of the landscape from former stinking wastewater fields to present-day attractive sites that can be used for many purposes.ConclusionsThe remediation of the former wastewater disposal fields, using natural glacial till materials rich in clay and silt, became a “story of success.” However, a remediation project of this type and scope only becomes reality if all responsible actors in society participate continuously. We conclude that stakeholders should not focus only on remediation costs but also on the benefits for society: reclaiming waste sites significantly improves our well-being.