Distributions of dissolved rare earth elements and anthropogenic gadolinium in the Yeongil Bay, Korea

Recently, with the increasing demand for rare earth elements (REEs) in various high-tech industries, anthropogenic REEs has been released over the past few decades into the aquatic environments. Among the REEs, anthropogenic gadolinium (Gdanth) has been reported in urbanized areas as a result of magnetic resonance imaging (MRI). In this study, we collected water samples from the Yeongil Bay (YB), to investigate the distributions of dissolved REEs and Gdanth. The concentrations of dissolved REEs in the YB were gradually decreased as proximity to the sea. Significantly high concentrations of dissolved Gd (244.9 +/- 100.6 pM, n = 3) were observed at riverside sampling sites, which were about 18 times higher than those at other sampling sites (13.7 +/- 8.4 pM, n = 24). The Gd anomalies, which are defined by the ratio of the normalized measured concentration to theoretical concentration, also showed high values at riverside sampling sites (8.2 +/- 3.1, n=3), whereas other sampling sites were < 1.4. The calculated Gdanth showed a negative correlation with the salinity, indicating that Gdanth from the Hyeongsan River may be conservatively mixed. Concentration of Gdanth at zero salinity were estimated as 869 pM by extrapolation. Our results indicate that a considerable amount of Gdanth is being discharged into the YB. Thus, mid- and/or long-term monitoring of Gdanth would be needed because it could be a major concern in the future.