Investigation of potential anthropogenic pollution of rare metals in Tama River followed by establishment of a comprehensive multielement analysis of major-to-ultratrace elements in river water and sewage treatment effluent.

In this study, comprehensive multi-element analysis of at least 53 elements, including 40 rare metals, in river water at all points from upstream to the estuary in urban rivers and sewage treatment effluent was established using three analytical methods of ICP-MS, chelating solid-phase extraction (SPE)/ICP-MS, and reflux-type heating acid decomposition/chelating SPE/ICP-MS. Recoveries of some elements for sewage treatment effluent in chelating SPE were improved by being combined with reflux-type heating acid decomposition, because organic substances, such as EDTA, in sewage treatment effluent could be effectively decomposed. In particular, the reflux-type heating acid decomposition/chelating SPE/ICP-MS method enabled the determination of Co, In, Eu, Pr, Sm, Tb, and Tm, which had been difficult to determine in chelating SPE/ICP-MS without this decomposition procedure. A potential anthropogenic pollution (PAP) of rare metals in Tama River was investigated by the established analytical methods. As a result, 25 elements in river water samples from the inflow area of sewage treatment effluent were several to several dozen times higher than those in the clean area. In particular, the concentrations of Mn, Co, Ni, Ge, Rb, Mo, Cs, Gd, and Pt increased by more than one order of magnitude compared to the river water from clean area. These elements were suggested to be PAP. The concentrations of Gd in the effluents from five sewage treatment plants ranged from 60 to 120 ng L-1, 40 to 80 times higher than those in clean river water, and all sewage treatment plants effluents showed the definite elevation of Gd concentrations. This indicates that MRI contrast agent leakage is occurring in all sewage treatment effluents. In addition, concentrations of 16 rare metal elements (Li, B, Ti, Cr, Mn, Ni, Ga, Ge, Se, Rb, Mo, In, Cs, Ba, W, and Pt) in all sewage treatment effluents were higher than those in clean river water, suggesting that many rare metal elements may be PAP. In the river water after the merging of sewage treatment effluent, the concentrations of Gd and In were higher than the reported values about 20 years ago.

Potential Anthropogenic Pollution of High-technology Metals with a Focus on Rare Earth Elements in Environmental Water.

In recent years, the utilization of high-technology metals such as rare earth elements (REEs), which exist in extremely low quantities in the Earth, has rapidly increased with the development of new types of industrial materials and pharmaceutical products. This review provides an overview of a new type of potential anthropogenic pollution caused by high-technology metals, with a focus on REEs released into environmental waters from waste treatment plants. In this paper, potential anthropogenic pollution was defined as pollution caused by metals gradually enriched in the environment by human activity, although standard and guideline concentrations of these elements are not regulated by environmental quality standards for water pollution. We review the analytical methods of REEs and the potential anthropogenic pollution of REEs with a focus on Gd, from the viewpoints of a comparison of the degree of Gd anomaly, chemical speciation, ecotoxicology, and bioaccessibility. Moreover, we also highlight the comprehensive analysis based on multielement analysis of high-technology metals as well as REEs for the further screening for potential anthropogenic pollution.