Use of elemental sulphur to enhance a cadmium solubilization and its vegetative removal from contaminated soil

To a soil artificially contaminated with cadmium, orthorhombic sulphur flower and a hydrophillic microbially produced elemental sulphur were added to induce the soil acidification. The soil was incubated in pots under open-sky conditions. pH, sulphate, and cadmium solubility were recorded in time. Soil acidification with microbially produced sulphur proceeded without any delay and at considerably higher rates, compared to the sulphur flower. Cadmium solubilization was solely controlled by the soil pH during the experiments. Similar experiments with cultivation of common mustard (Sinapis alba, cultivar JARA) were performed, evaluating both changes of cadmium solubilization and uptake by biomass. Cadmium concentration in shoots increased with decreasing pH. However, biomass was negatively affected by the decreasing pH. Combining these two effects, a pH-optimum for maximum cadmium removal from the soil by plants was found at pH = 5-5.5.