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Composting animal manure is one of feasible treatments that reserves some portion of nutrients of manure. Although the application of compost to arable land has many advantages, the repeated cultivation of the agriculture land will accumulate the level of heavy metals in the soil which is potentially harmful to people and animals. Therefore it is important to know the characteristics concentration and species of heavy metals in a variety of chemical forms than just total content of the metal. Because the metals in different forms have different mobilities and bioavailabilites. The aim of this study was to examine the total content and the chemical forms of the heavy metals; Cr, Ni, Cu, Zn, As, Cd and Pb in the animal manure composed with sawdust or rice hull as a bulking agent. A total of 75 compost samples were collected throughout the country and classified into the three groups in accordance with the characteristics of raw materials; swine manure, poultry manure, and mixed(swine＋poultry＋cattle)manure. The compost samples were analyzed for total metal content and fractionated by sequential chemical extractions to estimate the quantities of metals: exchangeable, adsorbed, organically bound, carbonate and residual. The results showed that the heavy metal concentrations in all compost samples were lower than the maximum acceptable limits by the Korea Compost Quality Standards. The concentrations of heavy metals in the swine manure compost were higher than those of both the poultry and the mixed manure compost except for Cr, Zn and Cu concentrations of three different compost ranged from 157 to 839 ㎎ Zn/㎏ DM(dry matter) and from 47 to 457㎎ Cu/㎏ DM, depending on the composition of animal manures. The predominant forms for extracted metals were Cr, Ni, Zn, As and Pb, residual; Cu, organic; and Cd, carbonate. The results suggested that the legal standards for composts should be reexamined to revise the criteria on the total metal content as well as metal speciation.
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