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Rare earth elements as micropollutants


The dissemination of high-tech metals in the environment is on the rise. Dr. Michael Bau, Professor of Geosciences at Jacobs University Bremen, and his Ph.D. student, Gila Merschel, published a study, showing that anthropogenic rare earth elements can enter the food chain.

Downstream from the city of Worms, the Rhine River is contaminated with lanthanum and samarium. Both metals are rare earth elements and are used in the production of catalysts for crude oil processing. Until now, it was unclear whether these anthropogenic rare earths are incorporated and accumulated by aquatic organisms. In a novel study, Michael Bau and Gila Merschel have detected these high-tech metals in mussel shells, the first time this has ever been shown.

"We sampled mussel shells at nine different locations along the Rhine River between Lake Constance and the Dutch border. In all shells sampled downstream of Worms, we found unusually high concentrations of lanthanum and samarium", reports Dr. Bau. "This proves the bioavailability of these elements, meaning that they are taken up from the water by animals and microorganisms."

Little is known about the long-term effects of rare earth elements on humans and particularly on children and pregnant women. Hence, further studies are needed to clarify whether these high-tech metals are also accumulated by fish which are caught for human consumption by professional and recreational fishermen. However, Bau and Merschel point out that at the levels measured these metals pose a potential hazard only in the immediate vicinity of the discharge point north of Worms where the concentration of lanthanum in Rhine River water is the highest.

Another rare earth element that is a known microcontaminant of nearly all rivers in Germany is gadolinium. The presence of high levels of this element stems from contrast agents used during magnetic resonance imaging in medical diagnostics. These contrast agents cannot be removed in waste water treatment plants and are released with their clear-water effluent into rivers and lakes. However, in mussel shells from the Rhine and Weser rivers, the Jacobs University geochemists have not been able to detect this anthropogenic gadolinium, indicating that in contrast to anthropogenic lanthanum and samarium this metal is not bioavailable.

Almost everywhere in the world the levels of high-tech metals in the environment are strongly increasing. As part of the EU-funded CLIM-AMAZON project, Bau and Merschel discovered that Lake Paranoá, an artificial lake used for recreation in Brasil's capital Brasilia, is widely contaminated with anthropogenic gadolinium. Together with Bachelor student Linda Baldewein, and colleagues of the University of Brasilia, the Bremen scientists provided the first evidence of the presence of this particular high-tech metal in lakes and rivers in South America.

"Our results suggest that similar to anthropogenic gadolinium, other waste water-derived xenobiotics, such as pharmaceutical residues, could enter the lake in the future", says Merschel. "At this point, this is not an issue, but our observation is relevant, as it is currently discussed whether Lake Paranoá could serve as a drinking water reservoir in the future." The joint research project with the University of Brasilia is part of a larger cooperation between Jacobs University and Brazil in the field of Earth and Environmental Sciences (EES). Besides research projects in Brasilia and along the Amazon River, this collaboration also includes a student exchange, as well as the joint supervision of doctoral students.

» Original Publication

Source: Jacobs University