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Mochizuki, Akihito; Sasamoto, Hiroshi; Ikigaki, Kayoko*
no journal, ,
Convenient characterization methods available to small volume of samples were applied to groundwater and surface water in the Horonobe area, Hokkaido, to characterize dissolved organic matter (DOM) including humic substances. 3D-fluorescense spectrum obtained from small volume of groundwater was similar to those from isolated humic substances, and showed little variation with depth. However, the peak position of spectrum for surface water was different from those for groundwater. Gel permeation chromatography showed that DOM in groundwater mainly consists of humic substances with molecule weight of approximately 1,200
2,000 Da, and that the molecule weight decreases with depth. These results were consistent with the characteristics of isolated humic substances. Ion chromatography revealed that low molecule weight organic matter was minor component of DOM in the groundwater, which was consistent with the result of gel permeation chromatography.
Cs concentrations in east Japanese riversTsuji, Hideki*; Ishii, Yumiko*; Hayashi, Seiji*; Shin, M.*; Taniguchi, Keisuke*; Arai, Hirotsugu*; Kurihara, Momo*; Yasutaka, Tetsuo*; Kuramoto, Takayuki*; Nakanishi, Takahiro; et al.
no journal, ,
Controlling factor of dissolved Cs concentrations in 66 in East Japan rivers was investigated. Dissolved Cs concentrations decreased by one order of magnitude between 2012 and 2017. Normalized dissolved Cs concentrations correlated well with building area ratios. Topographic wetness index generally predicted dissolved Cs concentrations. The high concentration of dissolved Cs in urban area cannot be explained by water quality condition.
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.
Watanabe, Takahiro; Nara, Fumiko*; Ueki, Tadamasa*; Tsuchiya, Noriyoshi*
no journal, ,
The identification of past tsunami deposits is important task for the risk assessment of major subduction zone earthquakes. Geological investigation now requires more reliable and precise identification of tsunami deposits and reconstructions of inundation limits than before. A tsunami deposit is preliminarily identified as an exotic layer within deposits that settled out in calm environments. The exotic deposit is then characterized using multiple criteria such as the lateral extent of the layer, changes in grain size, sedimentological features, and micropaleontology. Among the criteria, geochemical analysis is used to estimate the source of the sediments. Here, we tested inorganic geochemical analyses of the paleo tsunami deposits using XGT.