Atmospheric measurements of naturally occurring radionuclides 210Pb and 7Be were conducted at ground level in the Okinawa Islands. Weekly data collected from Okinawa-jima over a seven-year period from 2004 to 2011 and Kume-jima and Minamidaito-jima over a two-year period from 2008 to 2010 are presented and discussed. The monthly averaged activity concentrations of 210Pb at three sites showed a ”one-peak” seasonal variation ―the maximum peak appeared from autumn to spring― and 7Be showed a pattern similar to that of 210Pb. Activity concentrations of 210Pb and 7Be at Okinawa Islands ranged from 0.06 to 1.98 mBq/m3 with a mean of 0.80 mBq/m3 and from 1.45 to 15.1 mBq/m3 with a mean of 8.47 mBq/m3, respectively. Activity concentrations of both radionuclides at Kume-jima and Minamidaito-jima were almost the same as at Okinawa-jima. It is suggested that the relatively higher activity concentrations of both radionuclides in winter observed at the present three sites are affected by the air mass from the inland area of the Asian Continent.
We analyzed the sulfur isotope ratio(δ34S) of sulfate in aerosols collected at Naha, Japan. The results are summarized as follows: ・Sea salt particles contributed to the aerosol mass concentrations. ・Volatile organic sulfur oxides from the sea were contributed to atmospheric non‐sea salt sulfate concentration in summer season. ・Continental anthropogenic sulfur oxides were contributed to atmospheric non‐sea salt sulfate concentration in winter season.
In order to understand the mechanism of beach-to-beach variations in dose rates, measurements at 35 sand beaches were carried out along the Enshu-nada coast(a total of 140km). The sand samples were collected at 10 beaches to obtain the concentrations of potassium, uranium and thorium by means of Ge(Li) spectroscopy. Factors affecting the variation in dose rates were discussed, incorporating these data with data of coastal sea-bottom sediments taken by the Geological Survey of Japan.Two-dimensional measurements were performed at 50 locations each in two beaches near the Tenryu river mouth to know within-beach variations in detail. Contour maps of the data revealed a considerable regularity.It was found from simple analyses of the data collected in this work that the dose rate levels at beaches are affected by the distance from the river mouth, erosion or sedimentation of beach, and depth distribution of seawater.
At the end of the 20th century, the accelerating expansion of the universe was discovered. The cosmological term, which was introduced by Einstein and abandoned later by himself, attracts much attention recently for that reason. The cosmological term is unnatural in a theoretical viewpoint, and the idea of dark energy, which is a generalization of the cosmological term, was introduced and investigated. At the moment, theoretical understanding of the dark energy is fairly poor, and much observational data are required. In this article, recent research for the dark energy is reviewed.
Iron is one of the major constituents of the earth's crust and is commonly contained in various geochemical and environmental samples such as rocks, soils and sediments. Since iron exists in various chemical states according to the ambient environment, it may serve as a probe for monitoring the chemical changes taking place in the environment and/or for estimating the origin of iron containing samples. In this paper, I introduce the application of 57Fe Mössbauer spectroscopy to the sediments under hypoxia in Tokyo bay, the Antarctic Ocean sediments and the deep‐sea pelagic cherts in order to estimate the sedimentation environments.