Assessment of the Use of Natural Materials for the Remediation of Cadmium Soil Contamination

Rice plants accumulate cadmium (Cd(2+)) within the grain, increasing the danger of human exposure. Natural materials have been used in soil remediation, but few studies have examined the risks (based on the bioavailability of these metals to plants) of using these materials, so the practice remains controversial. In the present study, we evaluated the effectiveness of biochar produced from sugarcane bagasse, vermicompost (VC), vermicompost solid residue (VCR) and humin for remediation of Cd(2+)-contaminated soils. We characterized the interactions between these materials and Cd(2+) and evaluated their capacity to alter Cd(2+) availability to rice plants. Our results show that under the conditions in this study, biochar and humin were not effective for soil remediation. Although biochar had high Cd(2+) retention, it was associated with high Cd(2+) bioavailability and increased Cd(2+) accumulation in rice plants. VC and VCR had high Cd(2+) retention capacity as well as low Cd(2+) availability to plants. These characteristics were especially notable for VCR, which was most effective for soil remediation. The results of our study demonstrate that in the tested materials, the bioavailability of Cd(2+) to plants is related to their structural characteristics, which in turn determine their retention of Cd(2+).