Simultaneous realization of cadmium bioavailability reduction and spinach growth promotion in acidic soils with calcined oyster shells and dolomite

Abstract Cheap and widely available calcium‐based materials have gained popularity for remediating cadmium‐contaminated soils, but their potential to address cadmium (Cd) toxicity in acidic soils remains deeply understudied. The current study investigated the effects of calcined oyster shells (COS) and dolomite (DM), applied at a rate of 30 g kg −1 , on Cd availability and its accumulation in spinach plants in acidic Cd‐contaminated soils (Cd concentration: 4.42 mg kg −1 ). Additionally, the influence of active aluminium (Al) on Cd bioavailability and plant Cd accumulation was examined. The application of COS and DM led to a reduction in diethylenetriaminepentaacetic acid extracted Cd (DTPA‐Cd) of 42.1% and 28.6%, respectively. Furthermore, the COS and DM positively increased soil pH (2.48 and 1.81 units), electrical conductivity (89.4% and 28.1%), organic matter content (17.2% and 11.9%) and available phosphorus (37.7% and 6.39%) and decreased soil exchangeable Al 3+ (100% and 83.9%). As a result of amending with COS and DM, the Cd concentration (81.0%–82.9%) and bioaccumulation factor (78.8%–80.2%) in spinach plants were significantly decreased ( p < .05). The presence of exchangeable Al 3+ in the soil showed only a weak influence on plant Cd accumulation. The COS and DM also induced 8.65 times and 5.42 times greater spinach fresh matter yield compared with the control. In conclusion, the application of COS and DM as amendments in Cd‐polluted acidic soils holds great promise. The COS has greater prospects for immobilizing Cd, promoting plant biomass and producing plants with lesser Cd concentrations in acidic soils. This work offers a new strategy by adopting wide‐resource and cost‐effective mineral materials for sustainable environmental management.