Lead and cadmium soil contamination in Berlin varies considerably, particularly in allotment garden, agricultural, sewage farms, and forests. The number and distribution of measuring points for these areas give representative values. Other areas were tested with a much lesser test density. These surveys give only an initial overview of contamination degrees and distribution.
Tab. 3: Lead and Cadmium Levels in Soil in Various Use Categories
[Table is also available as Excel-File (MS-Excel is required).]
Allotment Gardens and Yards
The topsoil of allotment gardens everywhere is considerably contaminated with lead and cadmium. Both the 50th percentile value as well as the average value exceed greatly natural soil values - and that in areas where heavy metals can be absorbed by food crops. This was demonstrated by the Berlin Heavy Metal Measurement Survey analysis of food crops (cf. Map 01.03.3). In some cases, both elements were present at such levels that health risks incurred by direct contact with soil could not be ruled out.
Contaminated allotment gardens are found in all parts of the city, most heavily in the inner city. Lead levels show a more clear gradient than cadmium levels. There are considerable contamination level differences within a single area of gardens, sometimes even within a single garden.
The measurement values of differentiated follow-up tests of 1,600 allotment gardens conducted in 1989 and 1990 are not depicted in the map for graphic reasons. The values found at these sites are given in Table 3.
House yards are less contaminated. Levels exceeding index values were determined at few locations.
Agriculture and Horticulture
The majority of tested agricultural areas are considered only slightly contaminated. More than 50% of tested areas show levels within natural ranges for lead and cadmium. There is a clear regional differentiation of contamination. Cadmium levels exceeding applicable index values were found almost only in sites around the Gatow sewage farms. Lead levels are high here too, although few locations exceeded the index values. Soil contamination correlated with contamination of food and feed crops, also unusually high here (cf. Map 01.03.3).
High heavy metal levels were also found in green spaces in northwest Berlin and in Lübars, due to larger amounts of humus and its greater capability for binding heavy metals.
Horticultural businesses did not exceed soil index values. Determined lead and cadmium levels were in the range of natural levels.
Particularly high cadmium contamination was found in almost all soils of former or still functioning sewage farms in Berlin and its vicinity (cf. Map 01.10). The sewage farms in southern Berlin are more heavily contaminated than those in Gatow or northeast Berlin. There are great pollution gradations within single sewage farms. Soil contamination in the great majority of former sewage field areas, mainly used today for agricultural purposes, lead to the expectation of disturbing cadmium levels in the crops cultivated here. Contamination in crops cultivated on sewage farms have been determined. (cf. Map 03.03.3, Grün et al. 1990).
Lead is also accumulated in higher concentrations in sewage field soils, but concentrations remain under applicable index values. The homogeneous pollution levels determined in the test areas indicate that untested areas will have comparable heavy metal concentrations.
Forests and Green Spaces
High lead and cadmium levels were found in almost all forest topsoils. These values were, as a rule, under those found in areas for heavier anthropogenic (human) use (cf. Tab. 3). Heavy metal concentrations in organic horizon (not depicted) are usually higher than in mineral topsoil.
Contamination in depicted green spaces and other uses cannot be interpreted in context because of their wide heterogeneity. The inner city again shows higher contamination. Contamination levels in Schöneweide document the range of variation possible in inner-city areas.
Some playgrounds are contaminated with heavy metals. Some contamination levels were so high that health risks caused by direct contact with the soil cannot be ruled out.