Edafología. Volumen 7-3. Septiembre 2000. pág 113-120.
The assessment of soil pollution and adoption of aceptable standards for permissible heavy metals levels in soils, are the key to the protection of ecological function of soils and for the sustainable agriculture.
For agricultural soils from Community of Madrid, four classes of contaminated soils are distinguished: Class 1, Soils uncontaminated; Class 2, Soils slightly contaminated; Class 3, Soils moderately contaminated; Class 4 - Soils heavily contaminated.
The "background" values for each heavy metal, were obtained using the classes 1 and 2 mean concentration. Reference values (VIEA- Values) for metals were calculated as follows:
Background values + 2 times standard deviation.
In order to formulate a toxicity risk assessment the heavy metal bioavailable contents were determined. For each class of contaminated soil, bioavailable values for the maximum addition of heavy metals and greater available percentage were obtained.
Key words: Soil quality, heavy metal, reference values.