Distinct trophic transfer of rare earth elements in adjacent terrestrial and aquatic food webs

Growing demand and usage of rare earth elements (REEs) lead to significant pollution in wildlife, but trophic transfer of REEs in different food webs has not been well understood. In the present study, bioaccumulation and food web transfer of 16 REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc) were investigated in different terrestrial and aquatic species. Median concentrations of REEs in plant, invertebrate, fish, amphibian, reptile, bird, and vole samples were 488-6030, 296-2320, 123-598, 17.5-88.1, 88.0, 14.2-92.0, and 170 mu g/kg, respectively. The REE concentrations decreased as plants > invertebrates > fishes > amphibians and snakes > birds. The biomagnification factors (BMFs) and trophic biomagnification factors of most REEs were lower than 1, indicating trophic dilution of REEs. Most poikilotherms including fishes, amphibians, and snakes presented higher BMFs of REEs than homotherms including birds and voles (p < 0.05). Negative correlations were observed between REE concentrations and delta C-13 (p < 0.01), not delta N-15 (p > 0.05) in terrestrial organisms, while REE concentrations were negatively correlated with delta N-15 (p < 0.05), not delta C-13 (p > 0.05) in aquatic organisms. The result implies diet source and trophic level as key factors affecting the cycling of REEs in terrestrial and aquatic food webs, respectively.