- 著者
- Hiroyuki OBANAWA Yuichi ONDA Hiromu MORIWAKI Yukinori MATSUKURA
- 出版者
- The Association of Japanese Geographers
- 雑誌
- 地理学評論 (ISSN:13479555)
- 巻号頁・発行日
- vol.78, no.12, pp.859-866, 2005-10-01 (Released:2008-12-25)
- 参考文献数
- 12
To examine running distance of debris flows occurring on the talus slopes, rainfall experiments were carried out. The quantity Vt is defined as the reciprocal of the threshold value of Lc/ Lt, at which debris flows just reach the bottom of the talus slope, where Lc is the horizontal length of the cliff and Lt is the horizontal length of the talus slope. The value of Vt is also a measure of the possibility of sedimentary outflow from the talus slope by debris flow. The value of Vt shows strong correlation with the hydraulic conductivity of talus sediment (K) and the rainfall intensity (Ir). The outflow of debris from the talus slope can be predicted using the values of Lc, Lt, K, and Ir.
- 著者
- AYA SAKAGUCHI AKINOBU KADOKURA PETER STEIER KAZUYA TANAKA YOSHIO TAKAHASHI HARUKA CHIGA AKIHITO MATSUSHIMA SATORU NAKASHIMA YUICHI ONDA
- 出版者
- GEOCHEMICAL SOCIETY OF JAPAN
- 雑誌
- GEOCHEMICAL JOURNAL (ISSN:00167002)
- 巻号頁・発行日
- vol.46, no.4, pp.355-360, 2012-08-20 (Released:2013-11-08)
- 参考文献数
- 26
- 被引用文献数
- 90 27
Concentrations of the radionuclides, U, Pu, and Cs were measured in water samples (10-20 L) to study analyte dispersion and migration following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. A total of 8 water samples including oceanic water and paddy-field water were collected in the vicinity of the plant. Determinations of U, Pu and Cs isotopes were performed by accelerator mass spectrometry (AMS), inductively coupled plasma mass spectrometry (ICP-MS), and γ-ray spectrometry. The 236U/238U atom ratio was in the range 1.83-8.20 × 10-9 for fresh water and around 0.57 × 10-9 for seawater while the concentration of 236U was about 104-105 and 106 atoms/kg, respectively. Plutonium (239,240Pu) was detected in one riverine sample and the marine samples at very low levels and with large uncertainty. The concentrations of 137Cs in fresh riverine samples were 0.02-0.46 Bq/kg which are more than three orders of magnitude larger than the global fallout level. As for seawater samples within 80 km offshore of the FDNPP, the concentrations of 137Cs were 10-20 times higher than that of the Japan Sea water. Also 134Cs and 137Cs were of similar concentrations in all samples. The results show that volatile and refractory nuclides such as Cs, U and Pu exist in the dissolved phase, which can be readily assimilated by plants/humans. However the environmental impact of Pu and U in the vicinity of the FDNPP is considered to be low in comparison to that of the volatile radionuclide Cs.