Remediation of alkaline soil with heavy metal contamination using tourmaline as a novel amendment

Tourmaline, a novel mineral material, was utilized to remediate agricultural alkaline soil that had been subjected to heavy metals contamination. The results showed that tourmaline increased the maximum dry matter and total chlorophyll content of lettuce by 109.11% and 31.76%, respectively, and decreased the Cd and Cu content in lettuce shoots by up to 49.01% and 30.90%, respectively. DTPA-extractable metals and BCR results indicated that tourmaline could decrease the available heavy metal content and transform heavy metals into less toxic forms. Meanwhile, PCR
• DGGE results showed that tourmaline could increase indigenous microbial populations and increase Ca, Mg and K ion content. The increase in ion content of water-soluble nutrient elements, such as Ca and Mg, in soils where tourmaline was added indicates that an ion exchange mechanism is involved, providing nutrients for plant growth. Therefore, tourmaline could be used to remediate alkaline soils with historic heavy metal contamination.