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Search Results: Records 1-8 displayed on this page of 8
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Oral presentation

Characterizing the plastic-associated biofilms by a multi-isotope approach; Insight from visible plastics in two contrasting coastal areas of Japan

Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plastic debris in the aquatic environment receives special attention from scientific communities, whereas the radioactivity of environmental plastic and the dynamics of plastic-associated biofilm remain largely unknown. In this study, we addressed plastic-associated biofilms and bottom sediments from two contrasting coastal areas of Japan to elucidate their characteristics and interaction with radionuclides especially radiocesium ($$^{137}$$Cs) in the environment. We also explored stable isotope ($$^{13}$$C and $$^{15}$$N) signatures of the biofilm and sediment samples based on seasonal variations. Trace of $$^{137}$$Cs was observed in biofilm with an activity concentration of 292$$pm$$19.4 Bq kg$$^{-1}$$ biofilm (dw) which correspond to 1.15$$pm$$0.08 Bq kg$$^{-1}$$ plastic (dw).

Oral presentation

Gas phase reaction of trace iodine-129 for determination by ICP-DRC-MS/MS

Matsueda, Makoto; Aoki, Jo; Koarai, Kazuma; Terashima, Motoki; Takagai, Yoshitaka*

no journal, , 

Long half-life $$^{129}$$I have provided important information as a tracer to estimate the environmental behaviour of radioisotopes released from nuclear facilities. Inductively coupled plasma-mass spectrometry (ICP-MS) is capable of rapid data acquisition, but the application is limited caused by the main interferences at m/z 129 ($$^{127}$$IH$$_{2}$$$$^{+}$$ and $$^{129}$$Xe$$^{+}$$). It has been reported that $$^{129}$$Xe$$^{+}$$ can be removed by introducing O$$_{2}$$ gas into the reaction cell in an ICP-MS. Tandem mass spectrometry (ICP-MS/MS) has also made it possible to suppress the formation of $$^{127}$$IH$$_{2}$$$$^{+}$$. However, more precise removal of interferences is required to apply various environmental samples. In this study, the gas-phase reactions between $$^{129}$$I and interferents were investigated in a reaction cell of an ICP-MS/MS. The results showed that introducing an O$$_{2}$$-CO$$_{2}$$ gas mixture into the reaction cell reduced the background counts of m/z 129 to a minimum level.

Oral presentation

Investigation of factors controlling adsorption structures of cations on clay minerals based on EXAFS, HERFD-XANES, and ab initiocalculation

Yamaguchi, Akiko; Okumura, Masahiko; Takahashi, Yoshio*

no journal, , 

no abstracts in English

Oral presentation

Microscopic pore structure and macroscopic fluid flow-chemical transport in host rocks and barrier materials

Wang, Q. M.*; Hu, Q.*; Zhao, C.*; Zhang, T.*; Fukatsu, Yuta; Tachi, Yukio

no journal, , 

Oral presentation

Chemical equilibrium modelling of radiocesium elution from contaminated litter and its humus into water phase

Terashima, Motoki; Tagomori, Hisaya*; Watanabe, Yusuke; Sasaki, Yoshito

no journal, , 

Oral presentation

Super-hydrated kaolinite under high pressure; A Machine learning molecular dynamics study

Okumura, Masahiko; Kobayashi, Keita; Yamaguchi, Akiko

no journal, , 

Numerical simulation, specifically molecular dynamics (MD), is important for studying clay minerals. Classical molecular dynamics (CMD) and ab initio molecular dynamics (AIMD) are commonly used. CMD is less accurate but computationally efficient for large-scale simulations, whereas AIMD provides higher accuracy at a higher computational cost for precise evaluations. Machine learning molecular dynamics (MLMD) combines cost-effectiveness and accuracy by utilizing artificial neural networks trained on ab initio calculations. Super-hydrated kaolinite is an attractive clay mineral, which exhibits a thin water layer between layers and sheds light on extreme mineral-fluid interfaces under high pressure. The presentation will cover our results of the MLMD simulations for super-hydrated kaolinite with various properties, including hydroxyl group vibrations, water diffusion within interlayers, and other static and dynamic features of super-hydrated kaolinite.

Oral presentation

Improvement of the stability of IO$$_{3}$$$$^{-}$$, SeO$$_{3}$$$$^{2-}$$, and SeO$$_{4}$$$$^{2-}$$-coprecipitated barite after treatment with phosphate ions

Tokunaga, Kohei; Tanaka, Kazuya; Takahashi, Yoshio*; Kozai, Naofumi

no journal, , 

Oral presentation

Removal processes of dissolved elements in groundwater leached from waste by redox reaction

Watanabe, Yusuke; Terashima, Motoki; Matsueda, Makoto; Koarai, Kazuma; Aoki, Jo; Inoue, Junya

no journal, , 

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