de Campos Francisco Ferreira, Enzweiler Jacinta
Institute of Geosciences, University of Campinas, UNICAMP, C.P. 6152, CEP 13083-970, Campinas, SP, Brazil.
Geological Survey of Brazil, Rua Costa 55, CEP 01304-010, São Paulo, SP, Brazil.
Environ Monit Assess. 2016 May;188(5):281. doi: 10.1007/s10661-016-5282-7. Epub 2016 Apr 11.
The concentrations of rare earth elements (REE), measured in water samples from Atibaia River and its tributary Anhumas Creek, Brazil, present excess of dissolved gadolinium. Such anthropogenic anomalies of Gd in water, already described in other parts of the world, result from the use of stable and soluble Gd chelates as contrast agents in magnetic resonance imaging. Atibaia River constitutes the main water supply of Campinas Metropolitan area, and its basin receives wastewater effluents. The REE concentrations in water samples were determined in 0.22-μm pore size filtered samples, without and after preconcentration by solid-phase extraction with bis-(2-ethyl-hexyl)-phosphate. This preconcentration method was unable to retain the anthropogenic Gd quantitatively. The probable reason is that the Gd chelates dissociate slowly in acidic media to produce the free ion that is retained by the phosphate ester. Strong correlations between Gd and constituents or parameters associated with effluents confirmed the source of most Gd in water samples as anthropogenic. The shale-normalized REE patterns of Atibaia River and Anhumas Creek water samples showed light and heavy REE enrichment trends, respectively. Also, positive Ce anomalies in many Atibaia River samples, as well as the strong correlations of the REE (except Gd) with terrigenous elements, imply that inorganic colloidal particles contributed to the REE measured values.
在巴西阿蒂巴亚河及其支流安胡马斯溪的水样中测得的稀土元素（REE）浓度显示，溶解钆含量超标。这种水中钆的人为异常现象在世界其他地区已有报道，是由于在磁共振成像中使用稳定且可溶的钆螯合物作为造影剂所致。阿蒂巴亚河是坎皮纳斯大都市区的主要水源，其流域接收废水排放。水样中的REE浓度是在孔径为0.22μm的过滤样品中测定的，未进行预浓缩以及经过用磷酸二（2-乙基己基）酯进行固相萃取预浓缩之后。这种预浓缩方法无法定量保留人为来源的钆。可能的原因是钆螯合物在酸性介质中缓慢解离，产生被磷酸酯保留的游离离子。钆与与废水相关的成分或参数之间的强相关性证实了水样中大多数钆的来源是人为的。阿蒂巴亚河和安胡马斯溪水样的页岩标准化REE模式分别显示出轻稀土和重稀土富集趋势。此外，许多阿蒂巴亚河样品中存在正铈异常，以及REE（钆除外）与陆源元素的强相关性，这意味着无机胶体颗粒对测得的REE值有贡献。
