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A sediment trap experiment was conducted between August 2011 and July 2013 and sinking particles were collected at 100 km east of the Fukushima Daiichi Nuclear Power Plant. Particulate fluxes of radiocesium were mainly affected by two principal processes. One was a rapid sinking of radiocesium-bound particles (vertical mode). This mode was dominant especially in the early post-accident stage, and was presumed to establish the distribution of radiocesium in the offshore seabed. Another was the secondary transport of particles attributed to turbulence near the seabed and was observed in winter (lateral mode). Although the latter process would not drastically change the distribution of sedimentary radiocesium, attention should be paid as this key process redistributing the accident-derived radiocesium over a long duration.

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Three years passed from an accident of the Fukushima Daiichi Nuclear Power Plant that occurred in 2011. However, it is important to continue monitoring in environment in order to assess the current status of the nuclear reactor and and the contaminated water. We will show the data for the distributions of Sr-90 and Cs-137 in seawater near the power plant in 2013 and 2014.

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A large amount of radioisotopes have been emitted from the Fukushima Atomic Power Plant (I) damaged heavily by the Tsunami induced after the heavy earthquake on March 11, 2011. By analyses of radioactivity of atmospheric aerosols, surface soils and living plants, radionuclides and their respective amounts have been estimated. On the other hand, concerning radiocarbon (14C) emissions during the accident, 14C chemical compositions and their amounts have not been estimated. It is difficult to get 14C samples near the power plant, because the areas are restricted for normal persons. We have collected marine 14C samples from the seashore located 20-30 km south of the power plant in 2012. We also collected plant samples for 14C measurements at the Kanayagawa Campus of Fukushima University. Part of the samples measured for 14C so far indicate that evidences of 14C increase in environmental samples after the accident have not be certified.

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Monte Carlo radiation transport modeling is an indispensable tool for understanding the fate of radionuclides released into the environment after a nuclear accident. Radiation transport modeling is used to derive conversion factors for in air detector responses to ground contamination levels, and thus for quantifying the activity and distribution of radionuclides released to the environment. In the converse scenario, radiation transport modeling is used to predict future air dose rates upon separate modeling results for radionuclide movements and decay within the environment. We have studied the effect of land topography on air radiation dose levels across a range of heights from ground level to 300m using the PHITS Monte Carlo particle transport code. The geometries considered were a simple conical geometry, where the angle was varied to simulate locations from hilltops to valley bottoms, and angled ground at the intersection of two planes, where the land surface gradient changes uniformly perpendicular to a horizontal axis. Relationships between the air dose rate and the activity of radiocesium on the ground were derived for these geometries. The results show that air dose rates at large heights above the land surface are more strongly affected by land topography than dose rates measured close to the ground.

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The application of isotopic effects in the field of geochemistry has developed decades of fruitful experience where countless atoms, both light and heavy, have been used to trace the geochemical mechanisms operating in space and planetary systems. Among the different types of isotopic mechanisms operating in physical and chemical phenomena, light induced chemistry still lacks a general theory capable to explain isotopic effects that produces mass dependent and non-mass dependent effects.

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Uranium 236 is useful to estimate the origin of the uranium, i.e., whether it is natural or it is from nuclear fuel. Also, 236U/238U isotope system is expected to be new environmental tracer. For the detection of 236U with wide range of 236U/238U isotopic ratio, Accelerator Mass Spectrometry is needed. Thus the development 236U-AMS system was started at MALT, The University of Tokyo.

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Obervation of atmospheric environment at Mt. Tateyama and over Toyama Prefecture using a helicopter has been performed. Measrements of trace gases, aerosol particles, fog and precipitation chemistry were made. High concentrations of trans-boundary pollutants and Kosa particles have frequentry been detected.Fog water at Mt. Tateyama was highly acidified during the air mass was transported from the anthropogenic regions in the Asian continent. Acidic fogs contained high concentraions of sulfate and peroxides.Kosa particles were transported not only in spring but also in summer and autumn. The amounts of Kosa particles from the Asian continent during autumn seassons showed year to year variabilities.Measurements of peroxides in the upper atmosphere using a helicopter were performed in the summer and spring. The concentrations of atmospheric peroxides at high altitudes were higher than those near the ground. The concentrations of peroxides in the summer of 2013 were higher than those in the summer of 2012. These results were due to air pollutants might have been long-range transported from the Asian continent.

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The presentation will be in Japanese.

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The concentrations of B in the hydrothermal fluids from Okinawa Trough were higher than those from sediment-starved MOR, and the δ¹¹B showed ¹⁰B enrichments. A difference of δ¹¹B among Okinawa Trough hydrothermal fields was found; Yonaguni IV < Izena Caldron < Iheya North < Hatoma Knoll. The δ¹¹B in the hydrothermal fluids showed the strong correlation with the carbon isotopic ratios of methane (δ¹³C-CH₄) in the hydrothermal fluids, suggesting a large amount of sediment is distributed in recharge zone in Hatoma Knoll, and the B would be derived from the sediment at relatively low temperature. On the other hand, sediment is distributed in reaction zone beneath Yonaguni IV, and the B would be derived from the sediment at relatively high temperature.

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The similarities and the specificities between the diets of three Final Jomon sites of Tohoku Kamegaoka Culture were discussed based of chemistry perspectives. The lipid analysis, the compound specific isotope analysis and the N・C isotope analysis were applied to the excavated ceramics. As the results, the diet of two coastal sites including one salt-making site showed similarities of using marine food as well as terrestrial food. The usage of jar from the salt-making site was unknown, but lipid analysis implied that it was used in salt-making processes. The diet of inland site was suggested to be C3 plant with some terrestrial mammals.

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