Uptake of heavy metals by plants from highly contaminated soils

In a field trial with application of highly contaminated sewage sludge on a sandy soil five levels of heavy metal contamination were installed. Eight field crops and three vegetables were grown during twelve years on this trial. Plant growth and yields were not impaired by the treatments not even at the highest level of contamination (808 mg/kg Pb, 40 mg/kg Cd). The ZEBS-values (limiting values for human food) were not exceeded by lead even on the highest level, however they were exceeded by cadmium already on the lowest level. The limiting value for animal food was not exceeded by lead, by cadmium however it was exceeded in all treatments in the leaves of sugar beets and only in the highest level of contamination in red clover and oats. Spring rye, spring barley, corn and potatoes always remained below the limiting values. Constant logarithmic relations were found between the content of heavy metals in plants and in soils. The contents in plants increased approximately at the amount as the logarithm of the contents in soils did. This relation can be used for the prediction of the content of plants growing on soils with different degrees of contamination. The experiment has demonstrated that highly contaminated soils do not necessarily need to be excluded from agricultural use.