... 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 ... F4fraction in case of Pb, Cu, and Cd, into F2fractionin case of Ni, Cd, Pb, and Cu and invariably increased the F1fraction (water soluble and exchangeable form) of all the tested heavy metals.Heavy ... bio-oxidation of organiccarbon and consequent acidification effected release of Ni,Cu, and Cd from F5(residual fraction), of Ni and Zn fromF3fraction, of Zn from F4 and F2fractions from...