Study on biogeochemical cycle of iodine using speciation analysis of iodine isotopes

2023 Fiscal Year Research-status Report

• Project/Area Number: 23KF0210
• Research Institution: The University of Tokyo
• Principal Investigator: 松崎 浩之 東京大学, 総合研究博物館, 教授 (60313194)
• Co-Investigator(Kenkyū-buntansha): QI YUANZHI 東京大学, 総合研究博物館, 外国人特別研究員
• Project Period (FY): 2023-11-15 – 2026-03-31
• Keywords: Iodine-129 / Marin iodine cycle / Pacific Ocean / Arctic Ocean / 加速器質量分析

Outline of Annual Research Achievements

Over the past six months, I authored a paper which was subsequently submitted to the esteemed international journal, Geochimica et Cosmochimica Acta. This paper, now under review, has recently completed the revision process following feedback that required moderate adjustments. The focal point of this study is the utilization of iodine-129 as a tracer to explore the iodine cycle within the Arctic Ocean - an area of emerging interest due to its sensitive ecological balance and the implications of trace elements on its environment. In addition to my publication efforts, I participated in the 24th AMS symposium of Japan (JAMS-24). At this symposium, I presented my research on the iodine cycle, specifically through the speciation analysis of iodine-129. This presentation allowed me to discuss the novel methodologies and findings of my research with peers and experts in the field, contributing to a broader understanding and generating valuable discourse on marine biogeochemical cycles.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

In recent months, my research has advanced significantly through both fieldwork and laboratory analyses. I participated in the Pacific research cruise (MR23-07), during which I successfully collected eight depth profiles of various iodine species in the latitude range of 20°N to 60°N, encompassing both isotopes, 129I and 127I, in seawater. The total seawater sample number was 130. Additional seawater samples were also obtained during an expedition to the Arctic Ocean (MR23-06C), with total seawater sample number of 88.
Following these expeditions, I have completed all preliminary sample treatments for the seawater collected during both MR23-07 and MR23-06C cruises. The analytical phase has progressed, with the speciation analysis of 127I now fully completed. Currently, the speciation analysis of 129I is underway. This work is critical as it contributes to understanding the distribution and transformation of iodine isotopes in diverse marine environments, thereby enhancing our knowledge of biogeochemical cycles in these crucial regions.

Strategy for Future Research Activity

Moving forward, I am committed to completing the measurement of iodine-129 in samples collected from the MR23-07 and MR23-06C cruises using accelerator mass spectrometry. Upon the completion of these measurements, I will focus on the analysis and interpretation of the data. The results will be meticulously collated and prepared for dissemination through scholarly articles aimed at publication in high-impact journals. This will contribute significantly to the scientific community's knowledge of marine iodine cycles and their environmental implications.
In the upcoming year, I plan to further expand my research horizons by participating in another expedition, this time targeting the tropical Pacific. This will provide a unique comparative analysis between different oceanic regions. Additionally, I intend to conduct sediment experiments and simulation studies to achieve a more comprehensive understanding of the iodine cycle.

Causes of Carryover

Firstly, the paperwork was the main activity in the year. Secondly, the relevant experimental things (apparatus and chemicals) are carefully examined in the year. To make sure our research goes smoothly, we need to buy the right sampling tools and high-quality chemicals for our experiments. These are important to help us collect accurate data from seawater samples. Furthermore, to foster collaboration and share our findings with both domestic and international peers, participation in significant scientific conferences is vital.
We plan to attend prominent conferences such as The Japan Society of Applied Physics (JSAP) meeting and the International Accelerator Mass Spectrometry Conference (AMS-16). These events not only offer platforms for disseminating our research but also provide opportunities for engaging with other experts in the field, thereby enhancing our understanding and potentially leading to collaboration with other researchers.