Wheat straw biochar reduces environmental cadmium bioavailability

Cadmium contamination in waters and soils can lead to food chain accumulation and ultimately deterioration in human health; means for reducing bioavailable Cd are desperately required, and biochars may play a role. Long-term (240 d) lab incubation experiments were utilized to explain wheat straw-derived biochar effects on Cd sorption and decreasing Cd bioavailability in soils and solutions (0, 5, and 15% biochar as wt:wt or wt:vol, respectively), and to identify Cd forms present using both the European Community Bureau of Reference (BCR) chemical sequential extraction procedure and synchrotron-based X-ray absorption spectroscopy (XAS). Biochar Cd removal was up to ~90% from Cd-containing solutions and contaminated soil as compared to the control. Based on the wet chemical sequential extraction procedure in conjunction with XAS, biochar application promoted the formation of (oxy)hydroxide, carbonate, and organically bound Cd phases. As a material, biochar may be promoted as a tool for reducing and removing bioavailable Cd from contaminated waters and soils. Thus, biochar may play a role in reducing Cd bioaccumulation, trophic transfer, and improving environmental quality and human health. •Batch experiments, BCR procedure, and XAS for biochar-Cd sorption identification.•Quantified biochar-Cd sorption mechanisms.•Biochar-Cd sorption reduced Cd bioavailability.•Insoluble precipitates and, over time, organically complexed Cd phases formed.•Biochar can reduce Cd bioavailability in heavily contaminated soils/waters.