Water quality of Japanese rivers and its variation duriag these several decades by the change of cultural, industrial and hydrological systems

以J. Kobayashi（1961）研究的河流为基础，对北海道至鹿儿岛地区133条河流的水质进行了调查。通过对比Kobayashi和我们的研究结果，讨论了20世纪50年代至今河流水质的长期变化、各河流水质的区域特征以及影响它们的流域水文因素。在此基础上，我们总结如下。由于人为输入，Cl浓度显著升高，Ca、Mg、Na和K浓度略有下降。SO_4浓度受罗勒燃料燃烧的影响也显著升高，P浓度升高，但受人类活动影响不大。与上述元素相反，Si浓度在许多河流中呈下降趋势。讨论了流域各种水文特征对Si减少的影响。流域蓄水能力越大，Si浓度越低，表明Si浓度的降低受流域水库建设的影响较大。本研究调查了冈山县北部刚建成的大津湖河段的筑坝工程对河段水质的影响。我们没有观察到湖及其下游硅浓度的显著下降。使安静这湖是存在于最上层的吉井河的一部分,并不是由于低浓度的生物生产P在河流和湖泊水域这些结果表明,如果积累溶解在湖水在大坝底部沉积物受P和N的输入的分水岭,其积累可能是高度活跃在一个大坝下方的一条河。研究了湖底水质变化对湖泊沉积物中氧离子、钒酸盐和磷酸盐的溶解作用。天然湖和人工湖的溶解度受底水水质变化和水沙界面化学成分分布过程的影响较大。少

Based on the rivers studied by J. Kobayashi (1961), we surveyed water quality of 133 rivers from Hokkaido to Kagoshima areas. By comparing the results of Kobayashi and us, we discussed long term change of water quality of rivers from 1950s to present, regional characteristics of present water quality in respective rivers and the hydrological factors in the watershed affecting them. We concluded the followings based on such discussions. By anthropogenic input, Cl concentration increased heavily and Ca, Mg, Na and K concentrations inc eased slightly. The concentration of SO_4 also increased heavily by the effect from the combustion of basil fuel Increase of P concentration was observed but was not affected severely by human activities.In contrast to the above elements, Si concentration decreased in many rivers. We discussed the effects of various hydrological characteristics in their watersheds on Si decrease. The more the water-reserving capacity in the watershed is, the more the Si con … More centration decreased This result suggests that its decrease was greatly affected by the construction of water reservoirs in the watershed.We investigated the effect of a dam construction on the water quality of a river in Lake Okutsu which was recently constructed in northern part of Okayama Prefecture. We could not observe a remarkable decrease of Si concentration in the lake and its lower reaches, becalm this lake is existed at the most upper part of Yoshii River and was not biologically productive due to a low concentration of P in the river and lake waters These results indicate that accumulation of Si dissolved in the lake water into the bottom sediment in a dam is influenced by the input of P and N from its watershed and that its accumulation is possible to be highly active in a dam at the lower part of a river.We also investigated the dissolution of oxyanions, vanadate and phosphate, from lake sediments by the change of water quality in bottom waters. In both of natural and artificial lakes, their dissolution was greatly affected by the changes of water qualitiy in bottom waters and distribution process of chemical components at the water/sediment interface. Less