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Otosaka, Shigeyoshi*; Jeon, H.*; Hou, Y.*; Watanabe, Takahiro; Aze, Takahiro*; Miyairi, Yosuke*; Yokoyama, Yusuke*; Ogawa, Hiroshi*
Nuclear Instruments and Methods in Physics Research B, 527, p.1 - 6, 2022/09
Times Cited Count：0 Percentile：0.02(Instruments & Instrumentation)The measurement the radiocarbon of dissolved organic matter (DO
C) in seawater can provide information about a timescale of the dynamics of dissolved organic matter as well as about its sources in the ocean. Due to the low DOC concentration in seawater, in spite of the development of accelerator mass spectrometry, a relatively large volume of seawater (
1 L) is required for that analysis. In addition, complicated processing such as UV irradiation that emits high heat is required. In this study, we have developed a safer and easier method to analyze DOC in seawater than the conventional method. A particularly significant change was the adoption of a low-pressure mercury lamp in the decomposition system, which enabled direct decomposition of organic matter at lower temperatures. We also propose a method to quantitatively evaluate the accuracy of this system by analyzing simulated seawater consists of a soluble reference material of organic matter and sodium chloride. This method is expected to be applied not only to carbon isotope ratio analysis but also to analysis of trace elements and isotopes of various dissolved organic substances.
Jeon, H.; Otosaka, Shigeyoshi; Watanabe, Takahiro; Aze, Takahiro*; Miyairi, Yosuke*; Yokoyama, Yusuke*; Ogawa, Hiroshi*
no journal, ,
Measurements of the dissolved organic radio carbon (DOC-14) are expected to broaden our perspective on the role of DOC in the marine carbon cycle. Although the authors had succeeded in the DOC-14 analysis in seawater, it was necessary to use a large preprocessing apparatus, and the analysis has not been applied widely. We here report on the improvements to make this system safer and easier to handle. Following the previous method, DOC-14 in seawater was extracted as carbon dioxide by irradiating ultraviolet (UV), purified in a vacuum line, and the C-14 isotopic ratio was analysed with an accelerator mass spectrometer. As a major improvement, low-pressure mercury lamp which can irradiate UV of short wavelength (172 nm and 185 nm) suitable for decomposition of organic matter was used as UV source. By this improvement, the temperature increase in sample during processing was greatly reduced, and the size of the irradiation reactor was reduced to about half.
