... F2fraction of Ni, Pb, Cu, and Cd, 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,F3of Zn and ... * and NS indicate significance at P = 0.01, 0.05 and non-significant difference between pairs, respectively.3.3. Effect of metal spiking and incubation on chemical pools Heavy metal spiking and ... affinity of copper and lead for organic ligands [23].The changes in per cent fractions of heavy metals ex-tracted in 1M CaCl2 and 0.005 M DTPA (pH 7.3) uponmetal spiking and incubation are depicted...