Salinity increases cadmium uptake by wheat and Swiss chard from soil amended with biosolids

Soil salinity has been shown to significantly increase cadmium (Cd) concent rations in crops grown on soils fertilised with phosphatic fertilisers cont aining Cd. However, the effect of soil salinity on plant availability of Cd derived from biosolids is unknown. This paper reports the influence of inc reasing chloride (Cl) (NaCl) concentrations in soil solution on the phytoav ailability of Cd in soils amended with biosolids (equivalent to 50 t/ha). W heat (Triticum aestivum cv. Halberd) and Swiss chard (Beta vulgaris cv. Foo dhook Giant) were grown in biosolids-amended soil and watered daily with a dilute NaCl solution (0-27.4 mM). After 30 days, plant shoots were analysed for Cd and soil solution was displaced. Major cations and anions in soil s olution were determined and Cd speciation was calculated with the computer program GEOCHEM-PC. Cadmium concentrations in soil solution and shoots of w heat and Swiss chard plants increased linearly with increasing Cl concentra tion in soil solution of the biosolids-amended soil. The activity of CdClspecies correlated best with the Cd uptake of both plant species. Increases in shoot Cd concentrations were unrelated or only weakly correlated to the activity of the free Cd2+ ion in solution. It was concluded that chloro-co mplexation of Cd increased the phytoavailability of Cd in biosolids-amended soil.