Fixation Of Heavy Metals In Plant’s Roots

The contamination of heavy metals is more and more serious. However, their removal isless effective under near neutral conditions and at low concentrations. The main reason is thatthe key species possessing a strong fixation of heavy metals are not found. In order to find outthe key species possessing a strong fixation of heavy metals and the relevant species assistingin the fixation, a novel method was proposed that plants were cultivated in aheavy-metal-containing aqueous solution, their roots’were compelled to accumulate theheavy metals, and then the chemical elements and their content in the roots were analyzed.And sedimentation and adsorption experiments were followed to confirm the speculatedspecies.It is observed that the contents of phosphorus and calcium were increased as lead inplant’s roots （Hylotelephium spectabile （Bor.） H. Ohba） was accumulated. By sedimentationand adsorption experiments, it is confirmed that the fixation of lead by plant’s roots are viathe formation of lead-containing phosphate, and the presence of calcium can accelerate thisprocess.The fixation of cadmium and environmental cadmium content were positivelycorrelated. The fixation of cadmium were positively correlated to duration under Cd stress.The fixation of cadmium of Hylotelephium spectabile （Bor.） H. Ohba is via PO₄-Cd.The fixation of chromium of Hylotelephium spectabile （Bor.） H. Ohba is mainly viaCr（Ⅲ） confimed by XPS. The presence of iron can reduce Cr（Ⅵ） to Cr（Ⅲ）. The fixation ofchromium in Hylotelephium spectabile （Bor.） H. Ohba is mainly via chromic hydroxide. Thepresence of calcium and magnesium can accelerate this process.The fixation of arsenic of Hylotelephium spectabile （Bor.） H. Ohba is mainly via As（Ⅲ）confimed by XPS. The fixation of arsenic in Hylotelephium spectabile （Bor.） H. Ohba is viaAs-CO₃-Cu. The presence of iron can accelerate this process.The fixation of mercury of Hylotelephium spectabile （Bor.） H. Ohba is Hg（Ⅱ） confimedby XPS. The fixation of mercury in Hylotelephium spectabile （Bor.） H. Ohba is via theformation of mercuric-sulfide-containing compounds.