Abstract

We investigated the forms and mobility of cadmium (Cd), lead (Pb) and zinc (Zn) in four contaminated and four non-contaminated surface soils, collected from different localities of Japan using a sequential extraction procedure. The total metal concentration in soils ranged from 0.69 to 12.5 for Cd, 19 to 359 for Pb and 90 to 704 mg kg^-1 for Zn. The metal concentration in the contaminated soils was higher by 5 to 18 fold than in non-contaminated soils. Cadmium in the contaminated soils was dominantly associated with the exchangeable fraction (28 to 48%), while in non-contaminated soils; the residual fraction was the dominant one (29 to 32%). The major proportion of Pb (34 to 53%) and Zn (41 to 64%) was associated in the residual fraction. The mobility factor (MF ═ (F1 to F3/F1 to F6) × 100) among the metals was the highest for Cd (43%), and the lowest for Pb (11%).  For all metals, the MF was several fold higher (Cd and Zn was 5 fold, and Pb was 2 fold) in the contaminated soils than in the non-contaminated soils. Higher mobility of metals in the contaminated soils may create a health risk by increasing their accumulation in the field crops.

Key words: Heavy metals, mobility, source, mining industries.We investigated the forms and mobility of cadmium (Cd), lead (Pb) and zinc (Zn) in four contaminated and four non-contaminated surface soils, collected from different localities of Japan using a sequential extraction procedure. The total metal concentration in soils ranged from 0.69 to 12.5 for Cd, 19 to 359 for Pb and 90 to 704 mg kg^-1 for Zn. The metal concentration in the contaminated soils was higher by 5 to 18 fold than in non-contaminated soils. Cadmium in the contaminated soils was dominantly associated with the exchangeable fraction (28 to 48%), while in non-contaminated soils; the residual fraction was the dominant one (29 to 32%). The major proportion of Pb (34 to 53%) and Zn (41 to 64%) was associated in the residual fraction. The mobility factor (MF ═ (F1 to F3/F1 to F6) × 100) among the metals was the highest for Cd (43%), and the lowest for Pb (11%).  For all metals, the MF was several fold higher (Cd and Zn was 5 fold, and Pb was 2 fold) in the contaminated soils than in the non-contaminated soils. Higher mobility of metals in the contaminated soils may create a health risk by increasing their accumulation in the field crops.

Key words: Heavy metals, mobility, source, mining industries.