ABSTRACT
The composting process could decrease the bioavailability of heavy metals. The study on bioavailability of heavy metals provides more important evidence in determining the toxicity of metals. A repeating application of compost having high concentration of metals to land can increase metals concentration in the soil even if the heavy-metal concentrations in composting are far below the regulation standard. The bioavailability of metals is considered one of the most critical issues in agricultural studies. The fraction of heavy metals was increased moderately with the degradation of organic matter, whereas the water solubility of metals was decreased due to the changes of ionic and oxidizing conditions of the composting environment at the end of the composting process. The diethylene triamine pentracetic acid (DTPA) extractability of metals may characterize a complementary methodology to check the availability of metals in the soil and sludge-amended soil to plant uptake.
