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Berlin Environmental Atlas

01.11 Criteria for the Evaluation of the Soil Functions (Editin 2006)

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01.11.10 Binding Power for Heavy Metals

Description

The binding of heavy metals is accomplished by means of the adsorption of humins, clay minerals and sesquioxides. The solubility of heavy metals is dependent on their total content, and on the pH value of the soil solution. The solubility of heavy-metal compounds generally increases with increasing acidification. This is connected with the fact that the metals tend to form stable oxides at higher pH values, or to enter into not easily dissoluble compounds, e.g. PbCaCO3, through precipitation.
Relative binding power of heavy metals is used as one critiera for Filter and Buffer function.
Some of heavy metals are bind quite differently (DVWK 1988). ). Cadmium relatively dissolve quickly and spread as background load in Berlin.That's why recommended method from Hamburg Senate department of Health and Environment (2003) power of binding of easily dissolved cadmium would be used as binding power for heavy metal.

Methodology

Blume and Brümmer (1987-1991) found a concept to judge the sensitivity against metal load that is now used for allover Berlin. Principle of Progonosis is that relative binding power of some metal dependens on Ph value of soluble soil solution, based on condition of sand soil with week binding power and poorly humus Higher humus, clay and ironhydroxide enhances binding power and vice versa.The calculation is valid till 1 m depth. So here stepwise evalution for topsoil and subsoil dependent on ph value of humus and clay contents was determined, that's how it gives the sum of binding power BSSM. This value could be further corrected by coarse soil , horizontal depth and this value could be between 0 to 5, nothing to very high binding power for heavy metal.

Table 1: Evaluation of the Relative Binding Power of Heavy Metals
Step of binding power for heavy metal Designation
0 none
1 very low
2 low
3 medium
4 high
5 very high
Table 1: Evaluation of the Relative Binding Power of Heavy Metals in Dependence on pH Value Humus and Clay Contents, Coarse Soil and Horizontal Depth (Blume and Brümmer 1987, 1991)

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