Environmental Assessments of Ariake Bay during the Past 100 Years Based on Marine Sediments
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- YOKOSE Hisayoshi
- Department of Earth Sciences, Faculty of Science, Kumamoto University
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- MOMOSHIMA Noriyuki
- Department of Environmental Science, Faculty of Science, Kumamoto University
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- MATSUOKA Kazumi
- Laboratory of Coastal Environmental Sciences, Faculty of Fisheries, Nagasaki University
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- HASE Yoshitaka
- Department of Earth Sciences, Faculty of Science, Kumamoto University
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- HONZA Eiichi
- Department of Earth Sciences, Faculty of Science, Kumamoto University
Bibliographic Information
- Other Title
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- 海底堆積物を用いた有明海100年変遷史の環境評価
- カイテイ タイセキブツ オ モチイタ アリアケカイ 100ネン ヘンセンシ ノ カンキョウ ヒョウカ
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Description
Submarine sediments in Ariake Bay, Kyushu Japan, were examined to assess geoenvironmental changes in the area. 6 core samples from representative stations (Stas. 1-6) were analyzed for 16 minor elements (S, Cl, Ba, Rb, Th, Nb, Zr, Y, Ga, V, Zn, Cu, Ni, Co, Cr, and Pb) using XRF. Based on measurements of 210Pb radioactivity, sedimentation rates at 2 stations, one off the Chikugo River (Sta. 2) and the other at the mouth of Isahaya Bay (Sta. 4), were calculated, respectively, at 0.24 cm/year and a maximum of 0.15 cm/year.<BR>The concentrations of heavy metals, such as Cr, Ni, Zn, and Pb, in the marine sediments are about one-third of those of the highly polluted marine sediments recorded in Tokyo Bay around 1970. The vertical profile of a minor element can be divided into an upper section and a lower section. The upper section indicates various gradual changes, but the lower section is almost constant. The boundaries between the sections roughly correspond to the beginning of the 20th century, based on the sedimentation rate.<BR>Zn and Pb in the submarine sediments can be useful indicators to trace suspended mud derived from the Chikugo River. The complementary relationship of the vertical profiles in the spatial distribution suggests that the continuous migration of the sedimentary province may be governed by the geometrical arrangement of the estuaries of major rivers and by the tidal circulation pattern in Ariake Bay. Probably, large dams built on the major rivers have hampered the sedimentation process dominated by traction flow and have decreased the maximum drainage speed. As a result, such processes have promoted the expansion of the muddy area in Ariake Bay.<BR>Planktonic dinoflagellata (Sta. 2) and diatom (Sta. 4) fossils were also analyzed. Assuming such sedimentation rates at the stations, marine phytoplanktons (Brigantedinium spp., Rhizosorenia spp. and Skeletonema costatum), which indicate eutrophication of the sea water, have increased in relative abundance during the past 10 years.
Journal
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- Journal of Geography (Chigaku Zasshi)
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Journal of Geography (Chigaku Zasshi) 114 (1), 1-20, 2005
Tokyo Geographical Society
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Keywords
Details 詳細情報について
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- CRID
- 1390282679206166400
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- NII Article ID
- 10017473576
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- NII Book ID
- AN00322536
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- COI
- 1:CAS:528:DC%2BD2MXktV2qu74%3D
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- ISSN
- 18840884
- 0022135X
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- NDL BIB ID
- 7315987
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- Text Lang
- ja
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- Data Source
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- JaLC
- IRDB
- NDL
- Crossref
- CiNii Articles
- KAKEN
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- Abstract License Flag
- Disallowed