... 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 ... dissolution of sample residue in HF–HClO4(residual fraction,) and also 1M CaCl2 and 0.005 M DTPA extractableheavy metals in sewage sludge. Metal spiking and incubation decreased pH and easily ... in case of Pb, Cu, and Cd, into F2fraction in case of Ni, Cd, Pb, and Cu and invariably increased theF1fraction (water soluble and exchangeable form) of all thetested heavy metals.Heavy...