In areas like Salinas Valley, California, the soils are naturally rich in the element cadmium. Leafy vegetables grown in these soils can take up the cadmium and become harmful to humans. What to do? The solution goes back to the soil. Adrian Paul, a former researcher now working in the Sustainable Mineral Institute in Brisbane, Australia, is working to find which soil additives work best.
Cadmium appears in very low levels or in forms that prevent contamination in soils across the world. However some soils, like those in this California study, naturally have more than others. It can result from the erosion of local rock formations. In some instances, it's present due to human activity. Metal processing, fertilizer or fossil fuel combustion, for example, can leave cadmium behind.
Paul worked with four additives: zinc and manganese salts, limestone, and biosolids compost. (Biosolids are nutrient-rich organic materials from sewage processed at a treatment facility. They are typically used to improve soil's physical and chemical characteristics and fertilize the soil).