Functions of organic matter in polluted soils: The effect of organic amendments on phytoavailability of heavy metals

The usefulness of organic matter contained in brown coal, brown coal-derived preparations and farmyard manure was studied as a factor decreasing the uptake of heavy metals by plants and/or their migration within groundwater by immobilizing them in soil. A conceptual model was developed for soil as a protective barrier against heavy metals uptake by plants and/or migration towards groundwater. Organic amendments to reduce immobilisation and thus the bioavailability of heavy metals in soils were tested in field stone pots. The phytoavailability of tested heavy metals was the lowest when a brown-coal derived preparation was used as an organic amendment, as indicated by the lowest bio-accumulation index (BI) of: 0.24 for Cd (winter wheat grain), 0.021 for Pb (winter wheat straw), and 0.48 for Zn (spinach).