Heavy Metal Polluted Soils: Effect on Plants and Bioremediation Methods Generally, a plant can be called a hyperaccumulator if it meets the following criteria: (i) the concentration of metal in the shoot must be higher than 0.1% for Al, As, Co, Cr, Cu, Ni, and Se, higher than 0.01% for Cd, and higher than 1.0% for Zn []; (ii) the ratio of7, ]. …Web