FACTORS AFFECTING BIOAVAILABILITY OF HEAVY METAL IN RHIZOSPHERE OF SCIRPUS MARIQUETER
海三菱藨草(Scirpus mariqueter)根际沉积物中重金属生物有效性的影响因素

A three-year successive field investigation and laboratory analysis were conducted for factors affecting bioavailability of heavy metal (Cu, Zn, Pb and Cd ) in rhizosphere of Scirpus mariqueter. The factors include plant growth season, pH, phosphorus, Eh and dissolved oxygen. Results indicate that season alternation affects the bioavailability; and the exchangeable contents of Cu and Pb are higher in spring-summer with higher bioavailability accordingly, but lower in autumn and winter with lower bioavailability. Particularly, the combination of carbonate and ferro-manganese oxides contents of Cu and Pb is also higher, indicative of potential bioavailability. However, the content of exchangeable Zn is low but the organic-bounded and residues that account for its low bioavailability. For Cd, mostly it is in the residue of no bioavailability. In spring and summer with the increase of pH, both the exchangeable and the ferro-manganese oxides increased, while the organic-bounded and the carbonate decreased, which improved their bioavailabilities. Furthermore, in autumn and winter, the scenario is opposite to that of spring and summer. Inorganic phosphorus affect directivity the bioavailability in spring and summer, resulting in decrease of pH because of inorganic phosphorus decline. The bioavailability of heavy metal decreased with the increase in Eh and dissolved oxygen.