Three-step extraction procedure for determination of heavy metals availability to vegetables.

A three-step sequential extraction procedure was used to determine the concentration of heavy metal speciation forms in soil. The procedure allows one to identify the pool of heavy metals that can be potentially mobilised under changes in soil pH value or redox potential. It has been shown that similar portions of heavy metals are present in reducible, oxidisable and residual fractions. It was found that soil chemical properties significantly affected the distribution of heavy metals among different fractions and their uptake by vegetables. Cadmium was a dominant element which occurred in the exchangeable fraction-the most bioavailable and potentially toxic.