Gold uptake by perennial ryegrass: the influence of humates on the cycling of gold in soils

An experiment in which perennial ryegrass (Lolium perenne L.) was grown in solution cultures containing various forms of radioactive gold (198Au) is described. Uptake of labelled Au from solutions containing either Au chloride or various Au-humic acid (HA) complexes is compared. In each case concentrations of Au in the plant roots were several fold higher than in the plant shoots. However, the Au concentration in roots from some of the Au-HA preparations was only about 5% of that from the Au-HA solutions. High voltage electrophoresis studies indicate the presence of several Au-HA complexes in the solution cultures. The relevance of these findings to the cycling of Au within soils is discussed.