{"created":"2023-07-27T06:44:30.671632+00:00","id":34761,"links":{},"metadata":{"_buckets":{"deposit":"efec0e9f-1af8-43a5-9baa-3d54137f7514"},"_deposit":{"created_by":3,"id":"34761","owners":[3],"pid":{"revision_id":0,"type":"depid","value":"34761"},"status":"published"},"_oai":{"id":"oai:kanazawa-u.repo.nii.ac.jp:00034761","sets":["2812:2813:2828"]},"author_link":["14986","2968"],"item_9_biblio_info_8":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"2006-03-01","bibliographicIssueDateType":"Issued"},"bibliographicPageStart":"12p.","bibliographicVolumeNumber":"2004-2005","bibliographic_titles":[{"bibliographic_title":"平成17(2005)年度科学研究費補助金 基盤研究(C) 研究報告書"},{"bibliographic_title":"2005 Fiscal Year Final Research Report","bibliographic_titleLang":"en"}]}]},"item_9_creator_33":{"attribute_name":"著者別表示","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{}],"nameIdentifiers":[{},{},{}]}]},"item_9_description_21":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"湖底堆積物は、過去における流域の変動や湖内での生物生産に絡む物理、化学、生物的変動の記録を化石として保存している。本研究では、天然放射性のウラン(U)・トリウム(Th)に着目し、それらの同位体測定を実施して、堆積挙動から周辺の古環境解明への基礎検討を行なった。Uは、集水域の砕屑物と湖内の懸濁物などに溶存Uが吸着して堆積物に移行する。一方、Thはその殆どが砕屑物由来である。それ故、Uについての2成分は、気候変動(環境変動)によってその割合が変化することが予想でき、詳細に検討することで環境・気候変動の指標になりうると考えられる。本研究は、バイカル湖の中央で採取した長さ12m(約25万年をカバー)のコアー試料を中心にして、U・Th同位体を他の物理・化学的パラメーター(粒径、組成など)と共に測定し、以下のことを明らかにした。 (1)U濃度の深度分布は氷期、間氷期の指標である珪藻Bio-Siの変動と相関し、湿潤で暖か時期に濃度が高く、この時期の指標になりうることを見い出した。 (2)Thは、Uと比べて変動が少なく、集水域から流入する砕屑物量の変動の指標として有効であるが分かった。 (3)湖底堆積物のUについて吸着成分と砕屑物由来のUを識別することが、環境変動解析に非常に有効である事を見いだし、さらに吸着成分のU-234/U-238比の減少より堆積速度を約4cm/kyを推定した。 (4)また、Th-230/U-238(Th-230/U-234)比による堆積年代測定法も検討した。この方法は、炭酸塩やサンゴなど、取り込み後のUの閉鎖系が成り立ち、かつ初期にThを取り込まない試料に最適であるが、堆積物にもある仮定のもとで適用可能であることが示唆された。 (5)全体として、U, Th濃度およびそれらの放射能比の変動は、バイカル湖の気候変動解析の一つの有効な指標になりうることを示した。","subitem_description_type":"Abstract"},{"subitem_description":"The core VER98st.6 taken from the northern part of the Academician Ridge of the Lake Baikal, Siberia, was measured for U and Th isotopes (U-238, U-234, Th-232 and Th-230). Physical and chemical parameters such median grain size and Bio-Si content were also measured. By using the orbital tuning method based on the median grain size fluctuation, the sediment core covers the last two to four interglacial stages, ca.20 ky and is characterized by low sedimentation rate, ca.4.7 cm/ky. The concentration of U-238 fluctuates by a factor of 4,ranging from 50 to 200 Bq/kg. The U-238 concentration displays the higher values during the warm intervals, accompanied by high accumulation of Bio-Si, and the lower values during the cold intervals. The variation of U-234/U-238 ratios is similar to the variation of U-238 concentrations throughout the core. The Th-232 concentration varies in a narrow range, only by a factor of 2. The low Th-232 contents characterize the diatom-rich intervals during the warm intervals. The profile of Th-232 flux correlates well with that of mineral flux, indicating that Th is a proxy for terrestrial materials. The discrimination of the U-238 into the authigenic and terrigenous U-238 fractions reveals that the authigenic U-238 fraction is very low during the periods of glacial intervals, especially being almost zero during MIS 6. The authigenic U in sediments is candidate for the climate-sensitive processes. Based on the U-234-U-238 and Th-230-U-238 dating methods using the estimated authigenic U-238, U-234 and Th-230 contents in sediments during the warm intervals, mean sedimentation rates are independently estimated as 3.84±0.43 and 4.71±0.21 cm/ky respectively. These rates are close to a mean rate of 4.7 cm/ky calculated by the orbital tuning method.","subitem_description_type":"Abstract"}]},"item_9_description_22":{"attribute_name":"内容記述","attribute_value_mlt":[{"subitem_description":"研究課題/領域番号:16510005, 研究期間(年度):2004–2005","subitem_description_type":"Other"},{"subitem_description":"出典：「湖底堆積物中のウラン・トリウム同位体変動と古環境解析の基礎研究」研究成果報告書　課題番号16510005\n  (KAKEN：科学研究費助成事業データベース（国立情報学研究所）)\n　　　本文データは著者版報告書より作成","subitem_description_type":"Other"}]},"item_9_publisher_17":{"attribute_name":"公開者","attribute_value_mlt":[{"subitem_publisher":"金沢大学自然計測応用研究センター"}]},"item_9_relation_28":{"attribute_name":"関連URI","attribute_value_mlt":[{"subitem_relation_type_id":{"subitem_relation_type_id_text":"https://kaken.nii.ac.jp/search/?qm=10121295","subitem_relation_type_select":"URI"}},{"subitem_relation_type_id":{"subitem_relation_type_id_text":"https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16510005/","subitem_relation_type_select":"URI"}},{"subitem_relation_type_id":{"subitem_relation_type_id_text":"https://kaken.nii.ac.jp/report/KAKENHI-PROJECT-16510005/165100052005kenkyu_seika_hokoku_gaiyo/","subitem_relation_type_select":"URI"}}]},"item_9_version_type_25":{"attribute_name":"著者版フラグ","attribute_value_mlt":[{"subitem_version_resource":"http://purl.org/coar/version/c_ab4af688f83e57aa","subitem_version_type":"AM"}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2017-10-05"}],"displaytype":"detail","filename":"OC-PR-YAMAMOTO-M-kaken 2006-12p.pdf","filesize":[{"value":"1.3 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"OC-PR-YAMAMOTO-M-kaken 2006-12p.pdf","url":"https://kanazawa-u.repo.nii.ac.jp/record/34761/files/OC-PR-YAMAMOTO-M-kaken 2006-12p.pdf"},"version_id":"ced800fc-4bb5-4850-8da3-f03b6b18e24c"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"jpn"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"research report","resourceuri":"http://purl.org/coar/resource_type/c_18ws"}]},"item_title":"湖底堆積物中のウラン・トリウム同位体変動と古環境解析の基礎研究","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"湖底堆積物中のウラン・トリウム同位体変動と古環境解析の基礎研究"},{"subitem_title":"Fundamental studies on variations of uranium and thorium isotopes in Lake bottom sediment core and their application to the paleoenvironmetal changes","subitem_title_language":"en"}]},"item_type_id":"9","owner":"3","path":["2828"],"pubdate":{"attribute_name":"公開日","attribute_value":"2017-10-05"},"publish_date":"2017-10-05","publish_status":"0","recid":"34761","relation_version_is_last":true,"title":["湖底堆積物中のウラン・トリウム同位体変動と古環境解析の基礎研究"],"weko_creator_id":"3","weko_shared_id":3},"updated":"2023-07-27T14:32:12.246318+00:00"}