Remediation Effect of Cd Amendments Evaluated by Tobacco Leaf Cd Depletion Rate and Remediation Marginal Efficiency

Cadmium (Cd) pollution in cropland is becoming an increasingly serious issue in China. In present, development of low cost, high efficiency, and going green and environmental protection remediation materials are critical in remediation of heavy metal polluted soils. In this study, two tobacco varieties (Yunyan87 and K326) were used, and Cd heavily polluted paddy soil in Hunan province were collected for pot experiment, for the sake of investigating remediation effect of different amendments on Cd heavily polluted soils. Remediation effect was evaluated by soil available Cd reduction rate, tobacco leaf Cd depletion rate (%), and remediation marginal efficiency (RME) (RME, defined as tobacco leaf Cd reduction rate based on 1500 yuan cost per hectare for the tested soils). The results indicated that:the Cd uptaken by tobacco was significantly reduced by the soil amendment applications (p<0.05). Compared with control (CK), soil available Cd reduced from 17.69% to 35.65%, Cd depletion rate of tobacco leaf was 25.08%-60.75%. The RME of four soil amendment ranged from 2.84% to 21.98%. As the soil amendment application concentration increases, the reduction rate of soil available Cd and tobacco leaf Cd increased significantly, while the RME showed a diminishing tendency. The RME of 1% soil amendment application was 69.42% and 152.73% higher than 2% and 4% applications respectively. RME aiming at K326 was 13.21% higher than Yunyan87. By considering soil available Cd reduction rate, tobacco leaf Cd depletion rate (%), and RME, the remediation effect of different amendments ordered as:biochar FB > Hydroxyapatite FP > rock foundation FA > clay mineral FS.