I think the following should be of interest in NZ based on the levels of Cd contamination in some of our soils. There are other similar research finding coming from China. I posted a link to a NZ PhD thesis on the contamination issue in April at the ABE FB page that fails to mention biochar as a potential solution.
The effect of several activated biochars on Cd immobilization and microbial community composition during in-situ remediation of heavy metal contaminated sediment
Chemical activation and microwave assisted activation were adopted to modify biochar. Activated biochars were characterized by SEM, BET, FTIR, XRD and XPS. Raw biochar, activated biochars and commercial activated carbon were compared as remediation strategies for sediment from the Xiangjiang River containing 14.70 mg/kg Cd. After the treatment by activated biochar, the overlying water and pore water concentration of Cd decreased by 71% and 49%, respectively. And the threat of heavy metal along with bioavailability of Cd was depressed. Moreover, the immobilsation of Cd in sediment was related to BET surface area and the content of oxygen containing functional groups of activated biochars. Furthermore, a PCR-DGGE-based experiment was performed for the detection of microbial community. The indigenous microbial community was affected and new microbial community appeared after treat by activated biochar. Activated biochar can be used as an inexpensive and efficient in situ remediation material of sediment containing metal.