Yankuang ceshi (Jan 2023)
A Review of Research Progress on Provenance Indication of Rare Earth Elements by Inductively Coupled Plasma-Mass Spectrometry Hyphenated Techniques
Abstract
Rare earth elements (REEs) are not only important strategic resources, but also have important research significance in tracing the sources of rocks, minerals, sediments, and other materials due to their unique geochemical properties. In recent years, with the increasing use of REEs in modern society, anthropogenic REEs have attracted widespread attention from scholars at home and abroad through different pathways into environmental media such as the atmosphere, water and soil. Gadolinium (Gd), one of the most widely used REEs, is commonly used as Gd-based constrast agents (GBCAs). Since the application of GBCAs in the 1980s, their use has increased year by year. However, GBCAs are highly hydrophilic and stable, and they are difficult to remove in conventional wastewater treatment; the vast majority of them can directly enter urban and surrounding waters. Since Bau and Dulski first reported positive Gd anomalies in the Rhine River in Germany in 1996, anthropogenic Gd, an emerging contaminant, has now been detected in surface waters worldwide. However, there are relatively few studies on anthropogenic REEs, and the direct determination of them is difficult due to the constraints of detection techniques, and traditional methods for estimating anthropogenic REEs are inevitably subject to varying degrees of error.Since its introduction in the 1980s, inductively coupled plasma-mass spectrometry (ICP-MS) has shown great potential for trace multi-element analysis due to its high sensitivity, low detection limits and wide linearity range. The technique combines a plasma ion source with high ionization efficiency and a mass spectrometer with the advantages of high sensitivity, rapid multi-element detection and less mass interference compared to spectroscopy in a special interface, making it a highly efficient technique for simultaneous multi-element analysis. The development of high-precision ICP-MS and its coupling techniques, has led to a revolutionary breakthrough in the study of REEs provenance indication. The combination of highly selective separation techniques such as ion chromatography and highly sensitive ICP-MS has played an important role in the analysis of anthropogenic REEs, and the elemental speciation analysis capabilities of it make this one of the key research tools for the analysis of anthropogenic REEs.The progress of geochemical features of REEs such as isotopes in identifying material sources, resolving key processes and tracing environmental behavior, is summarized in this study, mainly including: (1)REEs fractionation patterns and isotopic features have been widely used in traditional provenance indication, and research is mainly based on REEs content or isotope information, combined with relevant mathematical and statistical models; (2) The speciation of REEs can provide an important basis for indicating anthropogenic activities, for example, due to the regional differences in the types of GBCAs used, there are obvious geographical differences in the speciation of anthropogenic REEs, with a high detection rate of macrocyclic GBCAs and a low detection rate of linear GBCAs in natural waters in regions such as Germany. On this basis, the application of ICP-MS and its coupling techniques in the source tracing of REEs is systematically reviewed, the main studies on REEs for tracing the sources of substances and indicating human activities are summarized, and the prospects for the development of source tracing of REEs are outlined. Among these analytical techniques, laser ablation multicollector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) can be used to obtain in-situ information on the spatial distribution of the isotopic composition of REEs within samples. Hydrophilic interaction liquid chromatography coupled to inductively coupled plasma-mass spectrometry (HILIC-ICP-MS) has become an important tool for the analysis of the speciation of anthropogenic REEs in waters.To address the shortcomings of the current technical approach, a research outlook for the development of rapid and portable analytical techniques, the integration of multidimensional information for tracer studies, and the integrated consideration of the effects of human activitiesis proposed. It is worth noting that the frequency and concentration levels of anthropogenic REEs in the natural environment have increased significantly, which may affect the distribution characteristics of geogenic REEs and thus reduce the accuracy of traditional source tracing studies. Therefore, future studies need to consider whether human activities in the vicinity have significantly influenced the study area before conducting conventional provenance indication analyses.
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