3. Species bound to organic matter:- High amounts of Cu (up to 68 %) and also Ni, and Hg are bound to the organic matter.
4. Species in residual fraction:-The proportion of Fe (above 68 %) in the residual form of is much higher than the other elements. The order of element follows Fe>Cr>Ni> Mn>Cu. The weight of As and Zn in this fraction is relatively low.
In summary, Cu, Fe, Mn, and Pb are present mainly in the oxides fraction, Cu is bound to organic matter, while the main fraction for As & Cr is the residual. For all elements, an increase of the fraction bound to Fe/Mn oxides occurs with an increase of Fe and Mn content in soil.