Phytoremediation of cadmium by rice in low-level of Cd contaminated paddy field

Phytoremediation using hyperaccumulator wild plants has been proposed as a promising, environmentally-friendly, low-cost technology for decontaminating toxic metals from soil. However, it may be difficult to use hyperaccumulator wild plants for practical phytoremediation of Cd-contaminated paddy fields because of their several drawbacks. Several rice varieties that accumulate high-Cd in their shoots have been found. To select rice variety practicable for phytoremediation of low-Cd-contaminated paddy field, we examined the decrease effect of Cd concentration in soil and brown rice of food rice variety by phytoremediation using six rice varieties. Six rice varieties (Kusayutaka, LAC23, Milyang 23, Habataki, Moretsu, and IR8) were planted for 3 years in Andosol, in which plow layer contained 0.44-0.50mg Cd kg^<-1> extracted with 0.1mol L^<-1> HCl (1:5 w/v). The order of the shoot Cd uptakes by these rice varieties was as follows: Kusayutaka<LAC23<Milyang 23<Habataki<Moretsu<IR8. IR8 absorbed 158g Cd ha^<-1> in its shoot from soil by 3-year phytoremediation. Soil Cd concentration in the IR8 plot has been decreased from 0.48mg Cd kg^<-1> to 0.33mg Cd kg^<-1>. Cd concentrations in brown rice of food rice variety (Koshihikahi) grown after the phytoremediation by IR8, Habataki and Moretsu were lower than those by Kusayutaka and LAC23. Judging from these results, we conclude that IR8 is the most promising in the six varieties for phytoremediation of Cd from paddy fields contaminated with relatively low Cd concentration