CHELATING RESIN MEMBRANE METHOD FOR ESTIMATION OF SOIL CADMIUM PHYTOAVAILABILITY

A metal chelating exchange resin membrane was used to extract soil cadmium (Cd) and to evaluate die plant uptake of Cd from soils. Eight soils with widely varying properties and Cd levels were tested. Soil suspensions (4 g in 40 mL deionized water) were equilibrated with 5 cm2 Ca-Chelex membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd of the soils were correlated with Cd uptake by young wheat seedlings grown in these soils and compared with soil Cd extracted by several commonly used chemical extractants. The amounts of Cd extracted by the Ca-Chelex membrane from all tested soils were correlated with those absorbed by young wheat seedlings or those extracted by the tested chemical extractants. The Ca-Chelex membrane extractable Cd of the soil, however, had the strongest correlation with plant uptake Cd. It was demonstrated that the Ca-Chelex membrane extraction is an appropriate method in estimating Cd phytoavailability of soil and is applicable to a wide range of soils.