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Leaching Potential of Heavy Metals, Nitrogen, and Phosphate from Compost-Amended Media

Compost Science & Utilization, (2007), Vol. 15, No. 1, 29-33

Y.P. Xia1, P.J. Stoffella (2,) Z.L. He (2), M.K. Zhang (3), D.V. Calvert (2), X. E. Yang (3) and S.B. Wilson (2)
1. Department of Horticulture, College of Agriculture and Biotechnology,
Zhejiang University, Hangzhou, China
2. University of Florida, Institute of Food and Agricultural Sciences, Indian River Research & Education Center, Fort Pierce, Florida
3. Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Natural Resource and Environmental Science, Zhejiang University, Hangzhou, China

Leaching potential of nutrients and heavy metals was evaluated from a peat-based medium (containing 70% peat, 20% perlite, and 10% vermiculite) amended with varying proportions (0%, 25%, 50%, 75%, or 100%) of compost (biosolids and yard waste, 1:1 by weight). The compost contained small amounts of Zn, Cu, Pb, and Cd. However, the leachate fractions of Zn, Cu, Pb, and Cd in compost accounted for only 0.19%, 0.23%, 0.05%, and 0.27%, respectively of the total concentrations. Except for Cu, the concentrations of Zn, Pb, and Cd were higher in the leachates of peat-based medium than the compost amended media. The concentrations of Cd and Pb in the first leachate of the peat-based medium exceeded the drinking water standards (USEPA 1989). However, the concentrations of Cd, Cr, Cu, and Pb in all the compost amended media were below the limit of the drinking water standards. The concentrations of total P and PO4-P in leachates increased with increasing proportion of compost in the media. Concentration of NO3-N in the first leachate was high and decreased in the subsequent leachings for all the compost amended media. These results suggested that the biosolids-yard waste compost may be a safe and acceptable replacement or partial replacement to peat-based medium without increased leachability of nutrients and heavy metals.