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Nara, Fumiko*; Watanabe, Takahiro; Matsunaka, Tetsuya*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Seto, Koji*; Yamada, Kazuyoshi*; Yasuda, Yoshinori*
Palaeogeography, Palaeoclimatology, Palaeoecology, 592, p.110907_1 - 110907_11, 2022/04
Times Cited Count：2 Percentile：28.09(Geography, Physical)Radiocarbon dating, tephrochronology, and geochemical signatures such as bromine (Br), iodine (I), total sulfur (TS), total organic carbon (TOC), and total nitrogen (TN) in a continuous sediment core (OG12-2) were applied to estimate past salinity change on the Lake Ogawara, Pacific coast of northeast Japan. Since the Lake Ogawara was the inner bay of the Pacific Ocean and became the brackish lake in the late Holocene, clarifying the past salinity change on the lake Ogawara could give us important insight into the past sea level changes of the Pacific Ocean. The core OG12-2 has two tephra layers, the Towada eruption and the Changbaishan eruption (B-Tm: AD 946). The age model for the core OG12-2 was established using the radiocarbon measurements of the plant residues in the core, also was constrained by the B-Tm tephra. Depletions of marine-derived elements (Br, I, and TS), from 88.4 to 64.2 mg/kg, 20.0 to 14.1 mg/kg, and 3.1 to 1.1 mass %, respectively, were observed in the layers with 2200-2000 cal BP. These results indicate paleosalinity changes from saline (inner bay) to brackish conditions within Lake Ogawara caused by sea level fluctuations during the late Holocene.
Watanabe, Takahiro; Ishii, Chikako; Ishizaka, Chika; Niwa, Masakazu; Shimada, Koji; Sawai, Yuki*; Tsuchiya, Noriyoshi*; Matsunaka, Tetsuya*; Ochiai, Shinya*; Nara, Fumiko*
Journal of Mineralogical and Petrological Sciences, 116(3), p.140 - 158, 2021/00
Times Cited Count：5 Percentile：51.59(Mineralogy)A portable energy dispersive X-ray fluorescence spectrometer (potable XRF) can be an effective tool for detecting chemical elements in various materials, such as geological, and environmental samples. In this study, working curves were confirmed using reference materials, such as igneous rocks and other geochemical standards, distributed by national and international organizations. Subsequently, quantification and semi-quantification analyses were performed by the portable XRF for inorganic elements in (A) fault rocks, (B) lake sediments from the middle Japan, and (C) soils with paleotsunami deposits from the Pacific coast of northeast Japan. Twenty-four elements (Mg-U) in these geological samples were measured by potable XRF using our working curves. Measured values by the portable XRF of the samples were good agreement with the reported values in almost cases.
C activities in tree rings near the Fukushima Dai-ichi Nuclear Power PlantMatsunaka, Tetsuya*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Matsumura, Masumi*; Satou, Yukihiko; Shen, H.*; Sueki, Keisuke*; Matsuzaki, Hiroyuki*
Radiocarbon, 61(6), p.1633 - 1642, 2019/12
Times Cited Count：2 Percentile：11.66(Geochemistry & Geophysics)
Cl in soil near the Fukushima Dai-ichi Nuclear Power PlantOta, Yuki*; Sueki, Keisuke*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Matsunaka, Tetsuya*; Matsumura, Masumi*; Tosaki, Yuki*; Honda, Maki*; Hosoya, Seiji*; Takano, Kenta*; et al.
JAEA-Conf 2018-002, p.99 - 102, 2019/02
no abstracts in English
Matsunaka, Tetsuya*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Hosoya, Seiji*; Matsumura, Masumi*; Satou, Yukihiko; Shen, H.*; Sueki, Keisuke*
Nuclear Instruments and Methods in Physics Research B, 439, p.64 - 69, 2019/01
Times Cited Count：2 Percentile：23.19(Instruments & Instrumentation)no abstracts in English
Matsunaka, Tetsuya*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Hosoya, Seiji*; Matsumura, Masumi*; Sueki, Keisuke*; Satou, Yukihiko
Dai-19-Kai AMS Shimpojiumu, 2016-Nendo "Jumoku Nenrin" Kenkyukai Kyodo Kaisai Shimpojiumu Hokokushu, p.76 - 79, 2017/06
To evaluate the radiological impact of the atmospheric C discharge from the Tokai nuclear facilities, a 80-year-old Japanese pine tree from Tokai, 1.8 km south-southwest of the Tokai Nuclear Power Plants (Tokai NPP and Tokai-2 NPP) and 1.4 km North-Northwest of the Tokai Reprocessing Plant (Tokai RP), was cored and each annual ring was measured for C. The C specific activities varied from 232.8 Bq kg
C to 403.3Bq kg C in the tree rings formed during the periods 1954-2013. The specific activities in 1967-2010 are significantly elevated compared with the ambient background values, clearly indicating C discharges from the nuclear facilities during their normal operation. The excess C activities of 0.5-70.0 Bq kg C in 1970-2011 are positively correlated with the estimated annual C discharges of 0.1-1.2 TBq from Tokai NPP and Tokai-2 NPP with R
of 0.66 (n = 38). These activity values of 
70.0 Bq kg C were corresponding to an additional annual effective dose of 3.9 uSv via the food ingestion pathway in the study location.
Watanabe, Takahiro; Nara, Fumiko*; Matsunaka, Tetsuya*; Minoura, Koji*; Kakegawa, Takeshi*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Nakamura, Toshio*; Junbo, W.*; Liping, Z.*
no journal, ,
Understanding of past environmental and geochemical changes is significant issues to estimate global climate variation. Therefore, these changes have been studied by continuous terrestrial sediments. The high-time resolution past environmental changes, especially monsoon fluctuations, have been reported in previous studies using geochemical signatures in stalagmites from Asian caves. However, continuous climate records in Tibetan plateau have not yet been cleared, which a key area to understand mechanism of monsoon fluctuations. In this study, mean grain size and geochemical proxies from lake sediment cores from south Tibetan plateau were used for estimation of past monsoon changes during Holocene. Spectral analysis of the mean grain size in the Tibetan lake indicated 1000-1500 years climate cycles, which might be caused by the changes in solar activities. These monsoon fluctuations based on the mean grain size were also supported by geochemical proxies in this study.
Tomita, Ryohei*; Matsunaka, Tetsuya*; Honda, Maki*; Satou, Yukihiko; Matsumura, Masumi*; Takahashi, Tsutomu*; Sakaguchi, Aya*; Matsuzaki, Hiroyuki*; Sasa, Kimikazu*; Sueki, Keisuke*
no journal, ,
no abstracts in English
Cl in surface soils near the Fukushima Dai-ichi Nuclear Power Plant using accelerator mass spectrometryOta, Yuki*; Sueki, Keisuke*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Matsunaka, Tetsuya*; Matsumura, Masumi*; Tosaki, Yuki*; Hosoya, Seiji*; Takano, Kenta*; Ochiai, Yuta*; et al.
no journal, ,
no abstracts in English
Sb and 
I in radioactive particles derived from FDNPPMatsuo, Kazuki*; Sueki, Keisuke*; Satou, Yukihiko; Yoshikawa, Hideki; Minowa, Haruka*; Sasa, Kimikazu*; Matsunaka, Tetsuya*; Matsumura, Masumi*; Takahashi, Tsutomu*; Sakaguchi, Aya*
no journal, ,
no abstracts in English
Matsunaka, Tetsuya*; Goto, Akio*; Watanabe, Takahiro; Tsuchiya, Noriyoshi*; Sasa, Kimikazu*
no journal, ,
The volcanic activity has become higher at Zao volcano in Japan since January 2013 after the 2011 Tohoku Earthquake. Basic water quality of crater lake and geothermal area have been studied by Tohoku University since the water quality of hydrothermal system in volcano are correlating with volcanic activity. As a part of this investigation, we are trying to monitor the volcanic activity using iodine isotopic ratios at Zao volcano. In our previous study, iodine isotopic ratio in water collected in October 2013 from the crater lake at Zao volcano were 2.2
10
, which were affected by anthropogenic I. In terms of the global iodine cycle, chronologically-old iodine with low isotopic ratio was considered to be supplied into the crater lake and geothermal area from underground corresponding to the volcanic activity, resulting the decrease in iodine isotopic ratio of the crater lake. The iodine isotopic ratios of the crater lake increased from 2.210 to 5.610 during October 2013 to the middle of October 2014, then, abruptly decreased to 4.310
soon after the white turbidity in the lake. While the iodine isotopic ratios of the geothermal area decreased from 5.310 to 1.610 at August 2014 corresponding to increase of the volcanic earthquake. Further investigations are needed to discuss the relationship of changes in iodine isotopic ratio of the hydrothermal system and the volcanic activity at Zao volcano.
Nara, Fumiko*; Matsunaka, Tetsuya*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Watanabe, Takahiro; Yamada, Kazuyoshi*; Yasuda, Yoshinori*
no journal, ,
Lake Ogawara, which is the brackish lake in Aomori prefecture, northern Japan, has been formed by the sea level change. Although the lake formation period is roughly estimated at the late Jomon period, the precise formation period is still unclear. The Lake Ogawara formation is directly connected with the sea level change, therefore, determination of the precise formation period of the Lake Ogawara is very important to understand the sea level history during the Jomon period. In this study, we constructed the precise age model based on the radiocarbon (C-14) for the plant residues and total organic carbon (TOC), Cs-137, Pb-210 and tephra identify in the Lake Ogawara sediment core. Two visible tephras (the Baegdosan-Tomakomai: B-Tm and Towada carudera eruption: To-a) were observed in the sediment core. Since the absolute age of the Millennium Eruption (ME) of Changbaishan volcano is widely accepted as AD 946, the B-Tm tephra in the sediment core can be used as the precice chronological key bed layer. Age profile of the trace element (Br), which was derived from the sea water, in the core showed that the Lake Ogawara started to change to the brackish lake at around 2000 cal BP.
