Berlin Environmental Atlas

01.03.1 Lead in Soils / 01.03.2 Cadmium in Soils

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Causes of Pollution


Causes of lead and cadmium soil contamination are mostly additives of contaminated materials (building rubble, cinders) some of which come from refuse dumps or industrial sites.

Such land fill is especially practiced in allotment gardens and house yards, green spaces and miscellaneous use areas. 115 allotment garden areas in West Berlin are on old deposit sites, old industrial sites, or suspected old contaminated sites. Conspicuous are large areas on the edge of West Berlin used today for allotment gardens (SenStadtUm 1991c). In the inner city there are large deposits of debris.
The highest heavy metal values are regularly found at these locations and are usually due to anthropogenic deposits. Significant contamination also appears in small areas, often from building activity or land-fill in gardens.

Soil conditioners

Considerable heavy metal deposits are also found in allotment gardens, house yards and green areas because of the use of contaminated compost and soil conditioners, especially from regular and long-term use. Contaminated composts at many locations were confirmed by the Berlin Heavy Metal Program. This is primarily caused by the composting of polluted waste (i.e., ash). The previously widely practiced use of contaminated sewage sludge compost (fertilizer) in allotment gardens, house yards and green spaces (used today only in small areas) contributed to soil contamination. Sewage farm sludge was used as soil conditioner for agricultural areas around the Gatow sewage farms.

Waste water

Soil contamination in current and former sewage farms is due to contaminants in their waste waters. The contaminant spectrum of waste water is reflected in the soil. Variations in pollutant level between different sewage farms and within individual sewage farms are due to the length and intensity of waste water flow and origin. It is assumed that pollutants in waste water and treatment intensity were previously significantly higher than at sewage farms in use today.

Variations of pollution within individual sewage farms are due to non-homogeneous use. Soil contamination decreases with the distance from the waste water discharge pipes. Especially high values are regularly found in sludge drying areas and sedimentation basins. These relationships are clearly seen in comparing contamination levels in the 01.10 Map of Use of Sewage Farms.

The lead and cadmium contamination around the Tiefwerder meadows exemplifies the effects of periodic flooding by contaminated surface waters.

Contamination of playgrounds is due to the use of contaminated surfacing and building materials, such as cinders and building rubble.

Inputs from the air

Airborne heavy metals also contaminate the soil. This influence is more clear for lead than cadmium because of the much greater amounts of lead. Soil in the inner city is more contaminated than soil at the edge of the city. The highest contamination is found in the vicinity of commercial emitters, but also directly next to heavily-traveled streets (cf. Map 01.03.3).

Forest contamination is almost entirely due to airborne pollutants. Pollutant sources cannot be clearly determined in gardens and agricultural areas, because of regular supplements of soil conditioners and other substances to the topsoil.

Table 4
Tab. 4: Input and Accumulation of Lead and Cadmium in the Soil

[Table is also available as Excel-File (MS-Excel is required).]

Overall View

The diversity of pollution and causes of contamination make it clear that the depicted lead and cadmium levels in topsoils at many locations illustrate only part of the entire contamination present. Many sites show contamination of other heavy metals, such as zinc, copper and chrome. The risk potential of soil is clearly higher at these sites. Sewage farms and old contaminated sites often had organic pollutants in relevant concentrations. It can be assumed that pollutants have been carried or washed into deeper soil levels at landfill sites, sewage farms, and sites where topsoils have low binding capacities.

It can also be assumed that comparable contaminant levels are present at the many sites not yet tested, particularly in East Berlin.

The Berlin Department of Urban Development and Environmental Protection is preparing possible action plans for reducing risks arising from soil contamination (cf. Tab. 2). But these can only be sensibly conceived after a thorough investigation of the causes of specific site contamination, and in consideration of the total spectrum of pollution. Additional information about soil characteristics is needed in some cases. This information would be given to users of those areas. Concrete safety or restoration measures have been initiated for particularly highly-contaminated playgrounds.

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