Cadmium stabilization with nursery stocks through transplantation: a new approach to phytoremediation.

Disposal of heavy metal contaminated biomass after phytoremediation is still unfeasible. This paper presents a viable phyto-extraction approach in which metals in contaminated soils are stabilized by nursery stocks before transplantation for greening. In this respect, two pot-experiments are reported comparing seven nursery stocks species exposed to different Cd levels. The first experiment revealed that Cd was mainly stabilized in the roots of all species studied. Greater amounts of Cd were accumulated in the epidermis than cortex plus stele. Cupressus Blue Ice showed greatest tolerance to the 100 and 200 mg kg(-1) Cd stresses. The second experiment additionally evaluated the possible risk of Cd release after transplanting the Cd treated plants into uncontaminated soil. After 120 days of transplantation, the relatively trace amounts of Cd in the roots of Euonymus japonicus, Pittosporum tobira and C. Blue Ice had either been partially transferred into the shoots or released into the soil. The highest Cd concentration increase in bulk soil (0.428 mg kg(-1)), however, was much lower than the environmental quality standard for soils of China (1 mg kg(-1)). The potential effectiveness of this technique in the use of Cd-contaminated soil and further investigation needed in the field trials were also evaluated.