Researchers conducted a pot experiment to test how phosphate rocks treated with oxalic acid can reduce cadmium (Cd) contamination in soil. They found that applying activated phosphate rocks decreased the amount of exchangeable Cd in the soil, with the most significant reduction seen with Baokang phosphate rock. Activated phosphate rocks were more effective than raw phosphate rocks in immobilizing Cd in contaminated soil, leading to lower Cd uptake by lettuce plants.