Mineralogical and chemical properties and lability of cadmium in some soils from Japan and Vietnam

We collected five Japanese and six Vietnamese soil samples that were polluted with cadmium (Cd) and analyzed them for chemical and mineralogical properties as well as for extractability of Cd in water, 0.01 mol L ^-1 CaCl ₂, 0.1 and 6 mol L ^-1 HCl. The total Cd content was in a range from 3 to 16 mg kg ^-1 for the Japanese samples and 0.5 to 1.1 mg kg ^-1 for Vietnamese samples. The soil samples had mixed clay mineralogy containing both the 1:1 and 2:1 type layer silicate minerals. We noticed no simple relationships among the mode of extractability in four different solutions and soil properties including clay mineralogy. The only exception was the relationship between the effective cation exchange capacity (ECEC) and the extractability for the Japanese samples. The regression analyses suggested that more Cd tends to reside on cation exchange sites of layer silicate minerals as ECEC increases but it does not results in increase of the extractability in the dilute CaCl ₂ solution.