Relationships between soil chemical properties and rare earth element concentrations in the aboveground biomass of a tropical herbaceous plant

The geochemical behavior of rare earth elements (REE) has been mainly investigated in geological systems where they represent the best proxies for processes occurring at the interface between different media. REE concentrations, normalized with respect to the upper continental crust, were used to assess their behavior. In this study, REE geochemical behavior was investigated in plant shoots of a facultative metallophyte naturally growing in Katanga (Democratic Republic of Congo). Anisopappus chinensis and rooting zone soil samples (n=80) were collected in four natural sites with contrasting pedogeological environments (e.g., parent rock type, pH, organic matter content) and highly variable REE contents. Soil and plant REE concentrations and chemical soil factors were was analyzed by ICP-MS, to examine relationships between soil factor and REE accumulation in plants. REE uptake by plants was primarily correlated with their concentrations and/or their speciation in the soil as previously shown in the literature. Results of this study show that REE patterns in shoots are relatively flat whereas soils are enriched in middle REE. The geochemical behavior of REE illustrates that metals accumulation in aerial parts of A. chinensis is most probably driven by mechanisms involving REE complexation processes in the rhizosphere.