A laboratory experiment was conducted to study the effect of metal spiking and incubation on some properties and sequentially extractable chemical pools of some heavy metals (F-1; two extractions with 0.1 M Sr(NO3)(2); F-2, one extraction with 1 M NaOAc (pH 5.0); F-3, three extractions with 5% NaOCl (pH 8.5) at 90-95degreesC; F-4, three extractions with 0.2 M oxalic acid + 0.2 M ammonium oxalate + 0.1 M ascorbic acid (pH 3.0); and F-5, dissolution of sample residue in HF-HClO4 (residual fraction) and also 1 M CaCl2 and 0.005 M DTPA extractable heavy metals in sewage sludge. Metal spiking and incubation decreased pH and easily oxidizable organic C content of sludge but increased electrical conductivity. Metal spiking and incubation increased F-1 fraction of all heavy metals, F-2 fraction of Ni, Pb, Cu, and Cd, F-3 fraction of Pb, Cu, and Cd, F-4 or reducible fraction of Ni, Cu, and Cd and residual fraction of Zn and Pb, but decreased F-2 fraction of Zn, F-3 of Zn and Ni, F-4 fraction of Zn: and F-5 fraction of Ni, Cu, and Cd. Metal spiking and incubation increased 1 M CaCl2 and 0:005 M DTPA extractable amounts of all heavy metals in sludge except for 0.005 M DTPA extractable Zn, which registered only very marginal decrease. (C) 2003 Published by Elsevier B.V.