Influence of pH on copper and zinc uptake by soil clays

Abstract

Nine soil clays were isolated from a wide range of soil horizons in New South Wales, and after minerological characterization, the adsorptive behaviour of the NH4+ form of the organic-free material was examined. The amount of copper and zinc sorbed increased with pH and, prior to precipitation of hydroxy species material, differences in pH-dependent capacity were discernible, reflecting differences in clay composition. Uptake at a fixed pH (5) did not always vary with concentration in accordance with Langmuir isotherms. Calculated parameters for amenable systems were similar to those observed by other workers, but capacities at a fixed pH proved to be less informative than pH dependence curves. The implications of the data for availability of the metal ions in the environment have been considered.