Predicting plant uptake of cadmium: validated with long-term contaminated soils.

Cadmium accumulates in plant tissues at low soil loadings and is a concern for human health. Yet at higher levels it is also of concern for ecological receptors. We determined Cd partitioning constants for 41 soils to examine the role of soil properties controlling Cd partitioning and plant uptake. From a series of sorption and dose response studies, transfer functions were developed for predicting Cd uptake in Cucumis sativa L. (cucumber). The parameter log Kf was predicted with soil pHca, logCEC and log OC. Transfer of soil pore-water Cd2+ to shoots was described with a power function (R 2 = 0.73). The dataset was validated with 13 long-term contaminated soils (plus 2 control soils) ranging in Cd concentration from 0.2 to 300 mg kg-1. The series of equations predicting Cdshoot from pore-water Cd2+ were able to predict the measured data in the independent dataset (root mean square error = 2.2). The good relationship indicated that Cd uptake to cucumber shoots could be predicted with Cdpore and Cd2+ without other pore-water parameters such as pH or Ca2+. The approach may be adapted to a range of plant species.