Dissolved oxygen concentration in river sediment of the Lake Biwa tributaries, Japan |
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Authors: | Yoshihiro Yamada Yugo Mito Akitake Igeta Eitaro Wada |
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Institution: | (1) Faculty of Agriculture, Kagawa University, 2393 Ikenobe Miki-cho, Kita Kagawa, 761-0795, Japan;(2) The United Graduate School of Agricultural Sciences, Ehime University, 2393 Ikenobe Miki-cho, Kita Kagawa, 761-0795, Japan;(3) Present address: Department of Environmental Technology, Fukken Corporation, 2-10-11 Hikari, Higashi Hiroshima, 732-0052, Japan;(4) Research Institute for Humanity and Nature, 457-4 Motoyama Kamigamo, Kita-ku, Kyoto 603-8047, Japan;(5) Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama 236-0001, Japan |
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Abstract: | The dissolved oxygen concentration in the sediment pore water downstream of rivers in the Lake Biwa basin was measured, and
the factors affecting the dissolved oxygen concentration were analyzed. In August 2003, nine rivers (Sakai, Nakanoi, Hebisuna,
Anziki, Yasu, Echi, Ane, Oh, and Ohura) were surveyed. The dissolved oxygen was depleted in the sediment pore water of the
rivers with a high proportion of particles less than 250 μm in size. For these rivers, the difference between the dissolved
oxygen concentrations of the river surface water and the pore water was large, ranging from −9.54 to −5.26 mg L−1. It was found that the proportion of land turned to paddy fields has an effect on the percentage of the particles below 250 μm
(standard partial regression coefficient = 0.807, p = 0.023). These results suggest that, in the Lake Biwa basin, the sedimentation of the fine particles released from paddy
fields results in poor dissolved oxygen in the river sediment downstream. In addition, the water flow conditions in small-
and medium-scale rivers without headwaters also affect the sedimentation of suspended particles. |
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