Cadmium Adsorption by Soils and Uptake by Plants as Affected by Soil Chemical Properties

The quantity of Cd 2+ adsorbed by soils from the northeastern USA was measured at a given equilibrium concentration (10 −5 M ) of the metal in soil solution. This “retention capacity” was strongly related by a linear function to the exchangeable Ca 2+ content of the soils. In addition, Cd 2+ uptake by corn plants grown in these soils amended with 1‐µg Cd 2+ /g of soil was measured and found to be related to the retention capacity of the soil for Cd 2+ by a curvilinear function. Although organic matter and clay in soil were able to limit Cd 2+ uptake by the plants, the best soil indicators of Cd 2+ availability were the retention capacity and exchangeable base (mainly Ca 2+ ) content. The ability of exchangeable bases to account for most of the variability in Cd 2+ adsorption by the soils as well as uptake by the plants is attributed to the important role of Cd 2+ ‐Ca 2+ exchange reactions in the soil.