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The ocean is a huge reservoir of dissolved organic carbon that contains almost the same amount of carbon in the atmosphere. Radiocarbon signatures of dissolved organic carbon (DO $^{14}$ C) in seawater can provide useful information on how organic carbon is produced, transported, and ultimately sequestered in the ocean's interior. In order to measure radiocarbon contents of seawater samples, they should be processed with a specific preparation system consists of the custom quartz reactor, dedicated vacuum line and UV lamp followed by radiocarbon counting with an accelerator mass spectrometer. As the first step of the study, we developed the irradiation procedure using a low-pressure Hg lamp and an oxidation catalyst. We present here not only how the system is progressing but also what radiocarbon study in the central Pacific Ocean means for better understanding of oceanic carbon cycle.

Oral presentation

Improvement of an analysis system of dissolved organic radiocarbon in seawater

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.

Oral presentation

Modeling of Eu $^{3+}$ binding by dissolved organic matters in groundwater

Terashima, Motoki; Saito, Takumi*; Akagi, Yosuke*; Endo, Takashi*

no journal, ,

no abstracts in English

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Determination of humic substances in deep groundwater from sedimentary formations by the carbon concentration-based DAX-8 resin isolation technique

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The Transfer capability of long-lived chernobyl radionuclides from surface soil to river water in dissolved forms

Characteristics of the fluorescent substances in the Yodo river system by three-dimensional excitation emission matrix spectroscopy

Migration behavior of Eu(III) in sandy soil in the presence of dissolved organic materials

Water chemistry in Kuji River; Its spatial and seasonal variations in major ions and organic substances

Improvement of photochemical extraction system for radiocarbon study of dissolved organic carbon in the central Pacific Ocean

Improvement of an analysis system of dissolved organic radiocarbon in seawater

Modeling of Eu $^{3+}$ binding by dissolved organic matters in groundwater