琵琶湖における水質変動 : II.南湖表層水におけるCOD,SS,リン,窒素およびクロロフィルaの季節変化再溶出と酸化還元サイクル

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Chemical components in the surface water were surveyed monthly from April, 1981 to January, 1983 in and around the dredged area of the southern basin of Lake Biwa. COD(T), SS and total phosphorus increased according to the growth of phytoplankton, as indicated by the increase of chlorophyll a concentration during the period late summer-autumn. During this time the total nitrogen concentration remained almost constant. Particulate COD, obtained as the difference between total COD and COD (F) in the filtered sample, and presumably due to phytoplankton, reached 65 % of total COD in September, 1981, when the largest total COD was recorded. The regression line was obtained between the concentrations of particulate phosphorus and chlorophyll a, passed through the origin with a slope of 1 (w/w). The concentration of soluble reactive phosphorus (SRP) in the lake water was very low throughout the year, but was hiqher in the rivers flowing into the lake. The reason for the low concentration of SRP in the lake water could be that phosphate, the greater part of SRP, was incorporated into growing phytoplankton during the period summer-autumn and was therefore present as particulate phosphorus, while in winter, most of the phosphate was precipitated by inorganic reactions such as adsorption onto clay minerals and ferric hydroxide. Seasonal changes of total nitrogen were small but there was substantial conversion between dissolved inorganic (DIN), dissolved organic and particulate forms. Disappearance of DIN in the summer season may to suggest a limitation by DIN to the growth of phytoplankton, provided that the availability of phosphorus inside the cells of the phytoplankton is sufficient for growth.
滋賀大学の論文
1984-03-10

琵琶湖における水質変動 : II.南湖表層水におけるCOD,SS,リン,窒素およびクロロフィルaの季節変化再溶出と酸化還元サイクル

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