Toxicological effects of rare earth elements to photosynthetic organisms

Rare earth elements (REEs) have become a key component in many technological applications. Due to the rapid increase in their use, the potential environmental exposure has also expanded. However, the effects on the ecosystem have not been yet thoroughly evaluated, leaving many knowledge gaps. To evaluate the effects of REEs, a set of experiments with acute and chronic exposure were performed on photosynthetic organisms. The effects of acute exposure of four elements (cerium, gadolinium, lanthanum and neodymium) in two set upsexperimental scenarios with different pH values (6 and 4), was evaluated on three testing species: Raphidocelis subcapitata, Lepidium sativum and Vicia faba. In the rResults obtained in the acute exposure, a higher toxicity at pH 4 was observedindicated higher toxicity levels, which could be explained by a higher bioavailability of the elements. From the relative calculated median effective concentrations (EC50s), R. subcapitata was the most sensitive species, followed by L. sativum and lastly, V. faba. Further investigations focused on , the chronic exposure of lanthanum and cerium was evaluated on Raphidocelis subcapitata. After a 28 days exposure, results showed a growth inhibition effects effect and increasing a bioaccumulation (from day 7 to 28) with effect at the end of the test. Moreover, endpoints regardedfluctuating values of the relative as biomarkers of stress (ROS, CAT, and SOD)., fluctuated during the sampling days during the exposure (day 7, 14, 21 and 28).