Uptake of iron cyanide complexes into willow trees

The uptake of iron cyanide into willows was studied. Trees were grown in solutions with Prussian blue, ferricyanide, or ferrocyanide. Iron cyanide speciation in solution was determined by HPLC during the experiment. Total cyanide and total iron in solution and trees were measured at the end of the experiments. Ferrocyanide wasthe dominating species in most solutions at the end. Ferricyanide was preferably taken up from solutions. Between 20 and 83% of the cyanide was lost from the solutions, and up to 28% could be recovered from the plants, mainly from roots. Cyanide could also be detected in stems and leaves of most exposed trees. Uptake was increased when no other nitrogen source but cyanide was present in solutions. Iron contents in exposed trees, compared to controls, increased significantly. The ratio of iron to cyanide remained rather stable in solution, but changed to higher values inside the plants. This indicates that iron and cyanide were taken up together as a complex, which was dissolved inside plants, and then cyanide was metabolized. No toxic effects could be seen. The study shows that trees can take up and metabolize iron cyanide complexes, making phytoremediation of iron cyanide waste a feasible option.