A comparison between heavy metals released from soil and its efficient speciation extracted by sequential extraction procedure

A simulating experiment was carried out on the interaction between natural precipitation and soil. The results demonstrated that the contents of heavy metals (V, Co, Cr, and Ni) released from soil into the solution under Earth's surface conditions are higher than the contents of those metals bonded to exchangeable species, which were extracted by sequential extraction procedure recommended by Tessier and others in 1979. It is demonstrated that the metals bonded to other 3 species (carbonate, Fe-Mn oxide, and organic matter) except those bonded to the exchangeable species in efficient speciation can be released under the Earth's surface conditions, when pH=4 in the reaction system, and the higher correlation coefficient indicated that the concentrations of heavy metals released from soil into the solution vary approximately with reaction time in terms of index regulations.