碳酸盐碳氧同位素标准物质性状对分析和保存的影响  

Characteristics of Carbon and Oxygen Isotope Standard Materials of Carbonates and Their Effect on Isotope Analysis and Standard Preservation

作　　者：胡志中[1] 晏雄 王坤阳[1] 王冠 潘忠习[1] 杜谷[1] HU Zhi-zhong;YAN Xiong;WANG Kun-yang;WANG Guan;PAN Zhong-xi;DU Gu(Chengdu Center of Geological Survey,China Geological Survey,Chengdu 610081,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081

出　　处：《岩矿测试》2021年第4期476-490,共15页Rock and Mineral Analysis

摘　　要：碳酸盐物质碳氧同位素广泛应用于地质和气候环境研究,而标准物质是其分析的基准物质和数据比较的重要依据。不同标准物质性状存在差异,对于性状特点的了解,有助于标准的选择和使用、不均匀性的改善以及最佳实验条件的建立。本文采用X射线衍射(XRD)、光学显微镜及能谱扫描-电子显微镜(EDX-SEM)技术,从不同尺度对物源、粒径、颗粒形貌和结构,以及纯净程度等性状不同的碳酸盐碳氧同位素标准物质开展了观察和分析,并采用连续流磷酸法测定部分碳酸盐标准物质的δ^(13)C和δ^(18)O值,从而探讨其性状特点以及对分析和保存的影响。结果表明:天然碳酸盐标准物质普遍含有非碳酸钙成分,如少量石英;以及存在明显性状差异的颗粒,但总量较少。不同标准物质之间、标准物质颗粒之间也存在程度不同的粒径、形貌、微细结构和矿物组分等性状差异。实验测定了不同标准物质的δ^(13)C和δ^(18)O值,多数分析结果与推荐值吻合,其中IAEA-CO-8的δ^(13)C和δ^(18)O值标准偏差相比其他物质偏大,可能与该标准组成复杂且均一性较差有关,而NBS20的δ^(18)O值标准偏差相对偏大以及7902的δ^(18)O值与推荐值偏离较大,推测与其粉末状且组成颗粒细小的性状更容易受到空气中二氧化碳和水的影响有关。结合前人和本研究认为,在推荐使用量下天然碳酸盐标准物质性状对分析精准性造成的影响有限;而为了保证微量分析和研究的准确性,建议根据分析和研究目的,结合标准和物质的性状特点,有针对性地选择标准以及标准中的颗粒,同时粉末状且组成颗粒细小标准物质在制备和保存上需要更加注意。本研究补充和丰富了碳酸盐碳氧同位素标准物质的性状信息,有助于其更好地应用于微量碳酸盐碳氧同位素分析和研究,同时也为保存和制备提供参考。BACKGROUND:Carbon and oxygen isotopes in carbonates are commonly used in geology and climate studies.Reference materials for these isotopes are an important basis for analysis and data comparison.Understanding the differences in the characteristics of different standard materials is helpful for the selection and use of standards,improvement of heterogeneity,and establishment of optimal experimental conditions.OBJECTIVES:To investigate the influence of the characteristics of carbon and oxygen isotope standard materials of carbonates on isotope analysis and preservation of the standards.METHODS:In this study,X-ray diffraction(XRD),optical microscopy,and energy dispersive X-ray scanning electron microscopy(EDX-SEM)were used to analyze carbonate carbon and oxygen isotope reference materials with different properties,such as provenance,particle size,particle morphology and structure,and purity.Theδ^(13)C andδ^(18)O values of some carbonate reference materials were determined by the continuous flow phosphoric acid method to explore their characteristics and their influence on isotope analysis and standard preservation.RESULTS:Natural carbonate reference materials generally contain non-calcium carbonate components,such as small amounts of quartz and other particles with obvious differences in properties.There are also differences in particle size,morphology,microstructure,and mineral composition between different standard materials and between standard material particles.Theδ^(13)C andδ^(18)O values of different standard materials were determined,and most results were consistent with the recommended values.The standard deviations of theδ^(13)C andδ^(18)O values of IAEA-CO-8 were larger than those of other standard materials,which is attributable to their complex composition and homogeneity.The standard deviation of theδ^(18)O value of NBS20 was large,while theδ^(18)O value of 7902 deviated from the recommended value.It is inferred that their powdery and fine particles are more likely to be affected by carbon dio

关 键 词：碳酸盐 碳氧同位素 标准物质 矿物组成 性状 保存和制备 

分 类 号：O628[理学—有机化学]