电感耦合等离子体质谱联用技术在稀土元素物源指示研究中的应用进展

A Review of Research Progress on Provenance Indication of Rare Earth Elements by Inductively Coupled Plasma-Mass Spectrometry Hyphenated Techniques

稀土元素(REEs)不仅是重要的战略资源,而且因其特有的地球化学属性,在追踪岩石、矿物、沉积物等物质的来源方面具有重要研究意义。近年来,随着REEs在现代社会的广泛应用,人为源REEs作为潜在新兴污染物,在自然环境中的出现频率及浓度水平明显提高。然而,相比于地质源REEs,目前关于人为源REEs研究相对较少,且受检测技术的制约直接测定人为源REEs较为困难。随着仪器分析技术的发展,高选择性的离子色谱(IC)分离技术与高灵敏的电感耦合等离子体质谱(ICP-MS)技术的联用在人为源REEs分析中发挥了重要作用,该技术的元素形态分析能力使其成为人为源REEs分析的重要研究工具之一。ICP-MS及其联用技术等高精度分析技术发展,使REEs物源指示方面的研究取得革命性突破。本文系统阐述了REEs分异特征、同位素分馏、赋存形态等地球化学特征在识别物质来源、解析关键过程、示踪环境行为等方面的研究进展,主要包括:(1)REEs配分模式、同位素分异特征在传统物源指示方面有着广泛应用,研究主要基于REEs丰度或同位素分馏信息,结合相关数理统计模型,完成岩石、矿物等物质的溯源研究;(2)REEs形态特征能够为指示人类活动提供重要依据,譬如,由于使用的核磁共振钆对比剂(GBCAs)种类存在地域差异,人为源REEs赋存形态在不同地区也存在明显的不同,德国等地区自然水体中大环型GBCAs检出率较高,线型检出率较低。在此基础上,系统回顾了ICP-MS及其联用技术在REEs物源示踪研究中的相关应用进程,归纳总结了REEs在追踪物质来源、指示人类活动方面的主要研究情况,对REEs物源示踪研究发展前景作了展望。在这些分析技术中,激光剥蚀多接收等离子体质谱技术(LA-MC-ICP-MS)可以原位获得样品内部REEs同位素组成的空间分布信息;基于亲水离子色谱-电感耦合等离子体质谱联用技术(HILIC-ICP-MS)的形态分析方法可为人为源REEs研究提供“多维”数据。针对目前技术方法体系存在的不足,本文提出了开发快速便携分析技术、整合多维信息进行示踪研究、综合考虑人类活动影响的研究展望。

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.