No abstract

SummaryUrban areas -Zusammenfassung are expanding rapidly. Therefore the interest in soil science activities on urban and industrial sites grows. The paper gives an overview of the research and mapping activities in Germany. A model of soils in urban ecosystems shows the relationships of development of soils and soil quality to land use. The water rcgime of soils is influenced by the charactenstics of urbnn landscape and sealing. Of special interest are the typical substrates. Some properties of soils which develop on tipped substrates of natural material are discussed. Of importance are technological substrates as ruhhle, ash. slag. waste material and sludges in urban environments. Roposals of classification of urban and industrial soils are pmsented. For proper use by thc municipal authorities availability and application of information on urban soils must be a part of resswh.

The share of urban population of the world is expected to reach 75% by around 2050. The need to offer within the cities soil services rose awareness of keeping soil functions in cities. Parallel to strong growth of cities some cities are shrinking. In cope with this, working groups (WG) of urban soils have been established (AK Stadtboeden1987, Germany, ICOMANTH 1995, USA, and internationally the IUSS WG US/SUITMA 1998 (Urban Soils/Soils of Urban, Industrial, Traffic, Mining and Military Areas)).The first attempts at urban soil surveys involved municipal waters and sewers in the USA in the 1970s. In the 1990s, the soils of about 15 cities were mapped, totally or in part, in Germany, and in the USA in Baltimore, and recently in New York. But at all times the soil pollution was a main interest of urban soil investigation. Urban soils are characterized by their particular use on which first attempts of soil classification are based. As knowledge about soil morphology and soil composition increased, soil survey concepts were developed. These concepts take into account relicts of the original, natural soils, as well as new, man-modified and man-made materials. At least in humid climate Regosols, as well as other urban soils such as Carbonatosols, Dialeimmasols, Intrusols, Reductosols and Acid Sulfuric Soils, can develop within 25 years or less. Technosols as soils from man-made materials are already included in the WRB. Besides pollution, a major feature of urban soils is soil sealing by construction. This restricts the availability of soils for urban greenery and other functions. Some particular problems of urban soils are high stone content, high differences of bulk density, shape of particles and soil structure performance. This lowers the quality of soils to fulfill functions. Specific methods are necessary to determine many urban soil characteristics. Specific instructions have been developed for soil and soil sealing surveys, and stormwater infiltration. However, for other cases, feasible methods are still missing. The European Commission's "Thematic Strategy of Soil Protection" did raise political awareness of urban soils, with a main focus on sealing.

Sealing implies separation of soils from the atmosphere and above-ground biosphere by impermeable layers. Sealing has a strong impact on soils. The degree of sealing is related to the type of land use and to the population density. Sealed areas are still increasing, and it is often the most fertile soils which are sealed. The negative effects of sealing are partial or total loss of soils, e.g. for plant production and habitats, and an increase in floods, as well as an increase in health and social costs. On the other hand, sealed areas contribute hugely to the gross national product of a country. The most effective contributions for reducing soil sealing are expected to come from the engineering sciences. Other contributions could be made by the economic and social sciences. It is also important to address the problem at a political level, e.g. by passing an international convention to prevent soil consumption. Despite all these problems, soils can still exist underneath sealed areas. Their properties can be used to mitigate the negative effects of sealing.

No abstract