[H-TT16] Development and application of environmental traceability methods

[HTT16-15] Sub-micro level isotope analysis of sulfur to understand its biogeochemical and ecological cycles

*Nanako O. Ogawa¹, Toshihiro Yoshimura¹, Takeru Kochi^2,1, Junichiro Kuroda^2,1, Yoshinori Takano¹, Naohiko Ohkouchi¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:nano EA/IRMS, Sulfur Isotope Analysis, Sulfate, Anion Chromatography, Barite

The use of isotopic abundance ratios to trace and interpret the movement of materials has been widely recognized in various fields. In many cases, the breakthroughs in these studies have been accompanied by advances in analytical techniques, demonstrating the close interrelationship between the development of analytical methods and the progress of scientific research. This includes not only analytical instruments for isotope detection but also pre-processing techniques for preparing the target substances for isotope analysis. In the case of the biological element (CNSHO) isotope studies, the development of various on-line or off-line pretreatment techniques, from cryogenic isolation under vacuum conditions in the early days to carbonate devices, elemental analyzers, capillary gas chromatography, liquid chromatography, etc., has supported the progress of the research. The true potential of high-precision detection devices, such as isotope ratio mass spectrometers, is enhanced when coupled with excellent pre-processing methods, and these often serve as important catalysts for advancing science.
From this perspective, our research group has been developing ultra-sensitive isotope analysis techniques based on meticulous pre-processing methods. In this presentation, we will introduce the newly developed δ³⁴S analysis for trace amounts of sulfate and discuss its potential applications through some examples of environmental sample data. The anion chromatographic fraction collection method (ICFC method) detects and separates a few tens nmol of sulfate, and the micro-barite formation technique (μ-Barite method), which converts collected sulfate into barite crystals introduces 5-50 nmol of sulfur into an isotope analyzer without loss. Together with the already established nano EA/IRMS system, these techniques will broaden the scope of studies using δ³⁴S.
Although sulfur is present in the atmosphere and ocean in various forms and plays an important role in maintaining life, there remain many unexplored links between its isotopic characteristics and biogeochemical cycles. This presentation aims to discuss the technical details of our new method, its potential advantages, practical applications, and challenges to be overcome.