Removal of Prussian blue from contaminated soil in the rhizosphere of cyanogenic plants

The fate of radiolabeled cyanide in soil was investigated during exposure to cyanogenic plant species, sorghum (Sorghum bicolor var. P721) and flax (Linum usitassimum var. Omega-Gold), in fully-contained growth chambers. Labeled cyanide was subject to microbial transformation, assimilation by plant roots, incorporation and biodegradation in plant tissue. For this study, ¹⁴C-labeled cyanide was added to soil, and distribution of ¹⁴C activity was assessed before plant establishment and after harvest. After 3 months of plant growth, 7% of the ¹⁴C-labeled cyanide was converted to ¹⁴CO₂ with sorghum and 6% with flax, compared with only 2% conversion in unplanted soil. A small amount of unaltered cyanide was shown to be accumulated by the plants (≈140 mg cyanide/kg plant or <0.1% of the total). Results from this experiment demonstrate the potential of cyanogenic plants for use in phytoremediation of cyanide-contaminated soil.