Development of new geochemical tracer using stable and radiogenic cerium isotopes

利用稳定的放射性成因的Ce同位素，开发了一种新的岩石元素地球化学示踪剂，并将其应用于环境样品、河流和海水中。考察了热电离质谱双峰检测法和电感耦合等离子体质谱外标法。对于海水样品，由于在化学分离过程中对依赖质量的分馏进行了修正，因此双加标法更适合于环境样品。所需样本量为100 ng，分析误差为0.015%。采用所提出的方法对河流和海水进行分析。河口和表层海水样品具有明显的同位素分馏特征。这些差异被认为是取决于去除过程。Nd同位素分馏与Ce同位素分馏一致。这说明氧化还原过程对同位素分馏的影响较小。

New geochemical tracer for lithogenic elements was development by using stable and radiogenic cerium isotopes, and adopted to environmental sample, river and seawater. Double spike method using thermal ionization mass spectrometry and external standard method using MC-ICP-MS were examined. In order to seawater sample, double spike method was suitalbe for environmental sample, because of correction to mass dependent fractionation during chemical separation. Requied sample size was 100ng to achieve 0.015% of anaylytical error. Proposed method was adopted for analysis of river and seawater. Estuary and surface seawater samples showed distinct isotopic fractionation. These variations were though to be depends on the removal process. Nd isotopic fractionation was consistent with those of Ce. It suggested that influence of the redox process was relatively small to the isotopic fractionations.