Japanese Journal of Limnology (Rikusuigaku Zasshi)
Online ISSN : 1882-4897
Print ISSN : 0021-5104
ISSN-L : 0021-5104
Volume 38, Issue 3
Displaying 1-4 of 4 articles from this issue
  • Hideaki NAKATA, Ren KUWABARA
    1977 Volume 38 Issue 3 Pages 75-89
    Published: July 30, 1977
    Released on J-STAGE: October 21, 2009
    JOURNAL FREE ACCESS
    The release of iron and manganese in hypolimnion water from bottom sediments was observed in Lake Shinsei, Kanagawa Pref., in 1973. Its mechanism and the conditions of the releasing process were investigated by using of laboratory experiments. The results were summarized as follows :
    1) The hypolimnion water of Lake Shinsei has been stable under conditions of water temperature 8°12°C, pH 6.77.0, and DO 0.00mg/l in the period ranging from the end of May to the beginning of November. In the period, total iron increased rapidly from the beginning of July and manganese from the beginning of September toward the beginning of November. These concentrations attain to the maximum, total iron 18mg/l, and manganese 6.9mg/l, respectively, in the beginning of November. Accompanying with these increases, the nutrients, conductivity, and total alkalinity simultaneously increased to the maximum at the same time, COD also increased from 3mg/l in May to the maximum, 910mg/l in the beginning of November. Redox potential conversely decreased from October to the beginning of November to the level of 0.100.15V accompanying with the slight increase between the end of May and the beginning of August. The condition which caused the release of iron and manganese was considered to be the fact that the bottom sediments had become anaerobic and eutrophic.
    2) Laboratory experiments under anaerobic condition suggested that the high concentrations of these elements emerged in combination with the formation of chelated substances of the elements with tannin and the decrease of redox potential caused by the microbiological reduction process.
    3) The increase of total iron and redox potential in the hypolimnion water from July to August suggests that the release of iron from the mud has been affected by the chelation of iron with an organic substance such as tannin which derives from decayed wood on the bottom. The abrupt increase of manganese from September to the beginning of November supposes the influence of some reductive substances released from the mud, since the decline of redox potential and the increase of COD were observed in the same period.
    4) In company with the disappearance of thermocline in the beginning of December, the concentration of iron and manganese in the hypolimnion water decreased rapidly to less than 0.1mg/l. These phenomena would be caused by accelerating of oxidation of the hypolimnion water due to the increase of dissolved oxygen and the dilution with epilimnion water in that period of overturn.
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  • Yasuhiko TEZUKA
    1977 Volume 38 Issue 3 Pages 90-93
    Published: July 30, 1977
    Released on J-STAGE: October 21, 2009
    JOURNAL FREE ACCESS
    The standing crop of Scenedesmus obliquus grown under continuous culture condition with a specific growth rate of about 1.0/day was determined for different concentrations of mineral nutrients. The concentrations of carbon, nitrogen and phosphorus to maintain chlorophyll a concentration at a level of 10μg/l that corresponds roughly to the minimum chlorophyll concentration in eutrophic lakes were suggested to be about 500, 100 and 2.5μg/l, respectively.
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  • Ryoshi ISHIWATARI, Nobuki TAKAMATSU, Tomoko ISHIBASHI
    1977 Volume 38 Issue 3 Pages 94-99
    Published: July 30, 1977
    Released on J-STAGE: October 21, 2009
    JOURNAL FREE ACCESS
    A density gradient centrifugation method by using Thoulet's liquid (HgI2/KI : density 1.92.4g/cm3) was applied for separating autochthonous and allochthonous materials in lacustrine sediments.
    The measurement of density distribution of sediment samples showed that a sediment sample can be divided into three main fractions in terms of density : Fraction 1 (density : <1.9g/cm3), which consists of wood, leaf fragments and sometimes phytoplanktons (nearly living?); Fraction 2 (density : 1.92.2g/cm3), which is predominantly composed of diatoms whose organic constituents seem to have been considerably lost; Fraction 3 (density : >2.2g/cm3), which consists of microscopically shapeless materials with a much lesser amount of diatoms. The former materials are probably flocks of clay minerals and chemical deposits.
    It was shown that the vertical change of carbon/nitrogen ratio in sediment of Lake Yunoko is closely related with that of relative amounts of the three fractions with different density. The weight percentage of autochthonous materials in the total was estimated to be 80 and 22 for the near surface sediment sample of Lakes Haruna and Aoki-ko, respectively.
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  • II. Ammonium Nitrogen in Dissolved and Adsorbed Form in the Sediments
    Kokichi KAMIYAMA, Setsuo OKUDA, Akira KAWAI
    1977 Volume 38 Issue 3 Pages 100-106
    Published: July 30, 1977
    Released on J-STAGE: October 21, 2009
    JOURNAL FREE ACCESS
    Ammonium nitrogen in bottom sediments may be classified into two types, one dissolved in interstitial water and the other adsorbed on the mud particles. In order to clarify the movement of ammonium nitrogen in the sediments and then to estimate its release rate into the overlying water, the basic behaviour of ammonium nitrogen in the interstitial water of the sediments should be investigated. The present experiments were carried out employing the mud samples collected from Akanoi Bay in Lake Biwa. The concentration of ammonium nitrogen in interstitial water was found to be in equilibrium with the amount of ammonium nitrogen adsorbed on the mud particles and a change in the former was observed to bring about adsorption or desorption of ammonium nitrogen onto or from the mud particles. The equilibrium was attained almost immediately and was affected by the temperature of the mud sample. The adsorption or the desorption in mud particles - interstitial water system should be taken into consideration in order to apply the diffusion process and to clarify the movement of ammonium nitrogen in the bottom sediments.
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