An integrated approach to safer plant production on metal contaminated soils using species selection and chemical immobilization

- Plant selection was crucial for avoiding metal contamination of medicinal plants.
- Application of soil immobilizing agents further decreased metal uptake.
- Combinations of immobilizing agents were most effective.
- Lime with compost decreased phytoavailability of Cd and Pb the most.
- such as Gypsum (a dissolved organic carbon coagulator) was also effective.

In order to examine the species specific accumulation of heavy metals in medicinal crops, seven different common medicinal plants were cultivated on a Cd (55 mg kg−1) and Pb (1283 mg kg−1) contaminated soil. Subsequently, the effect of various immobilizing agents, applied in isolation and in combination, on Cd and Pb uptake by two medicinal plant species was examined.Cadmium and Pb root concentrations in medicinal plants grown in the control soil varied between 0.5 and 2.6 mg kg−1 for Cd and 3.2 and 36.4 mg kg−1 for Pb. The highest accumulation occurred in Osterici Radix (Ostericum koreanum) and Ginger (Zingiber officinale) and the lowest in Yam (Dioscorea batatas). Application of immobilizing agents significantly reduced both Cd and Pb concentrations in all medicinal plants examined, where the most effective single immobilizing agent was lime fertilizer (LF). Application of combination treatments involving sorption agents such as compost together with lime further decreased Cd and Pb concentrations from 1.3 and 25.3 mg kg−1 to 0.2 and 4.3 mg kg−1, respectively, which was well below the corresponding WHO guidelines. Thus appropriate immobilizing agents in combination with species selection can be practically used for safer medicinal plant production.