Int. J. Environ. Res. Public Health 2009, 6 2405 Results from this study therefore suggest that temperature changes could have influenced the degradation of the existing organo-metallic complex, leading to the increased release or desorption of the metals from the solid to liquid phase. The negative correlations between Zn and temperature regime obtained in this study showed that Zn-organometallic complex could have been the most stable relative to that formed by Cu, Cd and Pb under the experimental conditions but more studies on temperature effect on the stability of the complexes formed between these metals and the compost derived humic acids are needed for confirmation. Water-extractable trace metal is the most active form, considered to be highly available for plant uptake, implying a potential for contamination of food chain, surface water and ground water [3]. Fortunately, in practice, less than 10% of water-soluble metal fraction relative to the total metal concentration in the bulk compost was obtained for the 4 metals at up to a temperature of 80 °C, suggesting that the composted organic wastes demonstrated potential for slow metal release. However, results from simulation models, which stand for the potential effects at such gradual temperature changes at unit interval of 0.1 °C, showed the possibility of a release beyond 10% with time. Temperature induced water extractability of heavy metals from soil amendments such as compost means more metal transport to nearby water bodies, endangering aquatic lives (fish, benthic organisms, plankton and microbial lives) and a risk to the entire ecosystem. By controlling the quality of the feedstock utilized in composting, the metal concentrations of the finished composts could be reduced, thus, alleviating possible adverse effect of global warming on agriculture. This is very important in the developing nations where wastes are not separated at source and there are no established guidelines on compost production and application. 5. Conclusions References The study showed that increasing temperature can potentially lead to increased water extraction of heavy metal from composted organic wastes utilized in land applications but some metals could exhibit some degree of stability to temperature variations. Effects of temperature changes on water extractability of these metals were found to be dependent on metal type, nature of compost and to some extent preparation procedure. Further studies on temperature effects on metal desorption from humic acid-metal complexes, correlation studies between temperature induced water-trace metal extractability and bioavailability are recommended. 1. 2. 3. 4. Garg, S.K. Environmental Engineering, vol. II: Sewage Disposal and Air Pollution Engineering; Khanna Publishers: New Delhi, India, 1979; pp. 749-764. Uberoi, N.K. Environmental Management, 2nd ed.; Excel Books: New Delhi, India, 2003; pp. 85-98. He, X.; Traina, S.J.; Logan, T.J. Chemical properties of municipal solid waste composts. J. Environ. Qual. 1992, 21, 318-329. Barker, A.V.; Gretchen, M.B. Bioremediation of heavy metals and organic toxicant by composting. Sci. Word J. 2002, 2, 407-420.