... F3frac-tion of Pb, Cu, and Cd, F4or reducible fraction of Ni, Cu, and Cd and residual fraction of Zn and Pb, but decreased F2fraction of Zn,F3 of Zn and Ni, F4fraction of Zn and F5fraction of ... concentration of heavy metals in F2 and F1fractions [19]. This might be ascribed to the presence of unoxidized organic matter and the higher pH value of unspiked sludge.G. Kandpal et al./ Journal of ... exchangeable form) of all thetested heavy metals. Heavy metal spiking and incubation significantly in-creased 1 M CaCl2extractable content (water soluble and exchangeable) of all heavy metals in sludge...