Toxic effects of rare earth elements (cerium, europium, and neodymium) on radish, tomato, and durum wheat
Rare earth elements (REEs), or rare earth metals, are a group of 17 elements including the lanthanide series, yttrium and scandium. They occur naturally together in mineral deposits, have similar properties, and are being used at increasing rates in new technology. At low REE concentrations in soils, plant growth stimulation has been identified; however, at higher concentrations, toxicity has been determined for some REEs. Toxic effect concentrations (shoot/root length, and shoot biomass) for radish, tomato and durum wheat were determined for three REEs: cerium, neodymium, and europium. A hormetic response was not characterized by any of the data, however many endpoints displayed thresholds. Overall, effect concentrations (EC25) ranged from 900-7600 mg/kg; these were higher than those reported in previous literature, likely due to low bioaccessibility of REEs in the highly organic soil. Internal tissue concentrations might therefore be a better predictor of toxicity.