諏訪湖の汚染とけん濁物質ならびに溶存物質との関係 : 現状と経年変化 : 諏訪湖陸水学資料III

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  • PRESENT STATUS AND RECENT TREND OF APPARENT EUTROPHICATION AND POLLUTION OF WATER IN LAKE SUWA WITH SPECIAL REFERENCES TO THEIR RELATIONS TO THE AMOUNTS OF SUSPENDED AND DISSOLVED SUBSTANCES : MATERIALS FOR THE LIMNOLOGY OF LAKE SUWA, III
  • 諏訪湖の汚染とけん濁物質ならびに溶存物質との関係 現状と経年変化(諏訪湖陸水学資料-3-)
  • スワコ ノ オセン ト ケンダク ブッシツ ナラビニ ヨウゾン ブッシツ ト ノ カンケイ ゲンジョウ ト ケイネン ヘンカ スワコ リクスイ ガクシリョウ 3

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1. Lakeside people say that Lake Suwa has recently become badly polluted. To prove this limnologically some observations were made three times in 1966 concerning the turbidity and the amounts of suspended and dissolved matters. The results were compared with those obtained in the past. 2. The waters in the littoral region of urban areas become so heavily stained with the rapid growth of population and by the extension of industrialization that the values of transparency by Secchi's disc are even less than 50cm. The values in the pelagic zone, however, have decreased but very slightly during the course from 1904 to 1966. 3. The dissolved matters together with the colloidal ones in the lake are exceedingly larger in total amount than that of the suspended solids occupying about 80〜90 percent of the total residue on evaporation. They only show slight increase in the course of years in the pelagic waters, while in the littoral regions there is a surplus of substances in solution accruing from the towns. 4. The suspended solids are composed mainly of organic constituents occupying about 60-80 percent of the total weight. They are at present about five to 15 times as much as those in the years before 1950 either in total amount or in the amount of organic ingredients. 5. The lake water becomes almost colorless and transparent by filtration through any filtering material. So the recent striking pollution in the eyes of the people is no doubt principally due to the marked increase of substances in suspension. 6. Among the suspended solids, the most important factor that makes the water opaque to light is cnsidered to be the prosperous occurence of plankton organisms. The results of analysis show that the contents of nitrogen and phosphorus in the lake water have recently increased very much with years as the essential nutrients for plant organisms. This is caused by the increased discharge of municipal wastes and by the yearly accumulation of organic constituents generated from decomposition of dead bodies of plankton and hydrophytes. 7. In addition to the above the remarkable floating of bottom sediments on windy days is also responsible for the turbidity of the lake. In recent years the lake has become shallow and the bottom oozy by the continual addition of decaying materials.

収録刊行物

  • 日本生態学会誌

    日本生態学会誌 18 (4), 167-171, 1968

    一般社団法人 日本生態学会

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