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Volume 46, Issue 2
Displaying 1-8 of 8 articles from this issue
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Takejiro TAKAMATSU, Renpei NAKATA, Tomio YOSHIDA, Munetsugu KAWASHIMA1985 Volume 46 Issue 2 Pages 93-99
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThree sediment cores were collected from Lake Biwa, and analysed for their dimethylarsinate (DMA), monomethylarsonate (MMA), and inorganic arsenic (I-As) content. The analytical technique used included solvent extraction, anion-exchange chromatography, and final determination of arsenic by flameless atomic absorption spectrophotometry. The sediment was found to contain trace levels of DMA (undetectable-24.7 μg·kg-1) and MMA (20.8-44.1 μg·kg-1) in addition to I-As which tended to be present in the greatest amount. The depth profiles of DMA, MMA, and I-As were also analysed in detail.View full abstractDownload PDF (1014K) -
Hiroshi SATO, Shigeru KUMANO1985 Volume 46 Issue 2 Pages 100-106
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe diatoms in core sediments from Loc. 3 were analyzed to clarify the paleoenvironmental changes of Lake Kamo-ko during the last 6, 000 years. Diatoms were grouped into three ecological categories; marine, brackish and freshwater. Based on the ecological spectra of the diatoms, the sediments were divided into five diatom zones. The results are discussed with reference to Holocene sea-level changes as follows : Marine Diatom Zone 1 (MD-1) is characterized by marine species Diploneis novae seelandiae indicating that this site might have had a wide channel with the sea at the time of Holocene transgression. Transitional Zone 2 (Tr-2) is dominated by marine diatoms and freshwater ones alternately. Freshwater Diatom Zone 2 (FD-2) is characterized by freshwater planktonic species Melosira italica suggesting that sedimentation took place under standing-water conditions such as a freshwater lake. This may reflect the small regression at c.a. 4, 500 yBP. Marine Diatom Zone 2 (MD-2), first reported here, is dominated by marine species Diploneis suborbicularis and Nitzschia granulata, and may reflect the small transgression at c.a. 3, 000 yBP. Transitional Zone 4 (Tr-4) is considered to reflect the process of emergence at this site.View full abstractDownload PDF (1145K) -
Hideo NISHIDA, Fumi TADA, Shizuo SUZUKI1985 Volume 46 Issue 2 Pages 107-114
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSBottom mud was collected from the upper and lower streams of 91 rivers in Japan to determine the distribution of Al, Fe, and Mn extracted HNO3-H2O2 and 0.5 N HCl. The concentrations of Al, Fe, and Mn extracted by HNO3-H2O2 ranged from 2, 900 to 67, 000 mg·kg-1, from 1, 500 to 57, 300 mg·kg-1, and from 23 to 861 mg·kg-1 of dry mud, respectively. About 95% of all samples contained 0.5 N HCl soluble Al of less than 5, 000 mg·kg-1 and their concentrations corresponded to about 10% of HNO3-H2O2 soluble Al. No difference between the upper and lower streams in the distribution of 0.5 N HCl soluble Al could be observed. About 90% of the samples from the upper stream and 35% of the samples from the lower stream contained 0.5 N HCl soluble Fe of less than 5, 000 mg·kg-1. A soluble Fe in 0.5 N HCl increased in the lower stream. The concentration of 0.5 N HCl soluble Mn was less than 300 mg·kg-1 in almost all rivers, and the average concentrations decreased slightly in the lower stream. The variation coefficients of these three metals extracted by HNO3-H2O2 and 0.5 N HCl were smaller than those of trace metals.View full abstractDownload PDF (1161K) -
Takejiro TAKAMATSU, Munetsugu KAWASHIMA, Rokuji MATSUSHITA, Mutsuo KOY ...1985 Volume 46 Issue 2 Pages 115-127
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThirty sediment cores (30-40 cm in length), 47 Ekman dredge sediments, and Mn concretions were collected from Lake Biwa. The concentrations of 36 elements in the samples were determined by instrumental neutron activation, X-ray fluorescence, atomic absorption, and colorimetric analyses. The elements determined included Mn, P, As, Sb, Fe, Ni, Co, Zn, Cu, Pb, Hg, Cr, Ti, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Hf, La, Ce, Sm, Eu, Yb, Lu, U, Th, Au, Ta, Nd, Br and N. Based on statistical considerations and calculation of the concentration factors of the elements, the features of the elemental distribution in Lake Biwa sediment were determined. The main results are summarized as follows : (1) Concentrations of Mn and As were very high in the uppermost oxidized layer of the offshore sediment and Mn concretions. This resulted from the dissolution-deposition cycles of these elements within the sedimentary column and the bottom water. The fixation of As at the sediment surface is mainly attributed to the adsorption of arsenate onto Mn (II) -rich hydrous Mn (IV) oxide. (2) There were high concentrations of Zn, Cu, Pb and Hg in the recent sediments. Although the source of these elements is attributed to human activities, the individual distributions of Zn and Cu in the sediment may result from the deposition of metal-rich planktonic debris and subsequent degradation of the debris. (3) The orders of increasing concentrations of alkali metals and lanthanides in the sediment from the central region compared with the nearshore pediment were identical to the orders of increasing atomic numbers from Na to Cs and from La to Lu, respectively.View full abstractDownload PDF (1943K) -
In the Western Part of the Shimoina Area in Nagano PrefectureMotoshi TAKEMURA1985 Volume 46 Issue 2 Pages 128-134
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe chemical compositions of 56 different river waters were determined in the western part of the Shimoina area, Nagano Prefecture. Since the effect of human activities on water quality is negligible in these river waters, their chemical compositions would be controlled chiefly by chemical weathering of parent rocks.
The author has tried to classify the river waters from their chemical compositions, in relation to the interaction with parent rock in the area.
The results showed that the chemical composition of river waters in this area is clearly reflecting the nature of parent rock, and the river water quality can be classified into four groups according to the differences in geologic conditions.View full abstractDownload PDF (934K) -
Method and Some ResultsYasuaki OKUMURA, Shuichi ENDOH1985 Volume 46 Issue 2 Pages 135-142
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSA method of continuous measurements of lake currents and some results obtained in the north basin of Lake Biwa are presented. Two types of current meters were used, both being able to record the current speed and direction and equipped with either a water temperature sensor or a pressure sensor : one is an Aanderaa RCM-4 current meter and another one is a DCM-3B current meter manufactured at Osaka Electro-Communication University. Adopting the subsurface mooring buoy system, observations have been carried out at several locations in the northern part of the north basin of Lake Biwa, mainly in summer and winter since 1981.
Analysis of the current measurement data shows the following features of lake currents :
(1) In summer, when the lake water is stratified, a counter-clockwise gyre develops above the thermo cline. Surface currents are prominent and stable.
(2) In winter, when the lake water is not stratified, surface currents are weak and usually controlled by wind stresses over the lake, so that current directions are deflected to the right-hand side from down wind directions.
(3) Both in summer and winter, deep currents are, in general, very weak and have no stable directions. Sometimes, however, the current speed becomes greater than 10 cm·s-1 after a strong wind in summer.View full abstractDownload PDF (1279K) -
Ichiro AOKI1985 Volume 46 Issue 2 Pages 143-144
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe annual value of the transmission-diffusion summation S of solar radiation in the southern basin of Lake Biwa is calculated to be 0.91. It is assumed that this S value can also be applied to the northern basin. From the assumed S value and from global radiation G and the Angot value I in the northern basin, the ratio of diffuse radiation D to G in the northern basin is estimated. The value of the ratio D/G in the northern basin becomes 0.51, slightly smaller than that in the southern basin.
The ratio D/I in the southern basin is 0.20. If the ratio D/I in the southern basin can also be applied to the northern basin, the ratio D/G in the northern basin becomes 0.51 again.View full abstractDownload PDF (340K) -
Yasuhiko TEZUKA1985 Volume 46 Issue 2 Pages 145-148
Published: April 30, 1985
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSTo obtain clues for the elucidation of the mechanism of nitrate accumulation in the hypolimnion of the north basin of Lake Biwa during summer stratification, the numbers of nitrifying bacteria and concentrations of nitrate plus nitrite and ammonium in the water body and bottom sediments were determined during the stagnation period of 1982.
The numbers of nitrifying bacteria were small (below one cell per ml) in the water body, but fairly large (9 × 101- 4 × 103 cells per ml) in the surface sediments. Concentrations of nitrate plus nitrite were about two times higher in the surface sediments than those in the deepest layer of the water body. In addition, ammonium was not detected in the water body, but rather in high concentrations (8-26 mg N per l) in the surface sediments.
The above results suggest that the nitrate accumulation in the hypolimnion of Lake Biwa during summer stratification is mainly due to the active nitrification in the bottom sediments and subsequent liberation of nitrate to the hypolimnion.View full abstractDownload PDF (592K)
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