All issues
Volume 53, Issue 3
Displaying 1-7 of 7 articles from this issue
- |<
- <
- 1
- >
- >|
-
Kunimitsu INOUCHI, Tadao KAKINUMA1992 Volume 53 Issue 3 Pages 187-196
Published: July 24, 1992
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThis paper deals with the phenomenon of seawater intrusion into a confined aquifer with a semi-permeable layer, using a hydrodynamic dispersion model. The numerical solutions by the finite-element method are obtained for various values of hydraulic conductivity in the semi-permeable layer and groundwater level at the inlet of the aquifer. Two values of the dispersion coefficient in the semi-permeable layer are adopted: one is the same value as that in the permeable layer (uniform dispersion coefficient); the other is one hundredth of that in the permeable layer (small dispersion coefficient).
The main results are as follows: For relatively high hydraulic gradients, the semi-permeable layer restrains saltwater intrusion into the lower permeable layer. In the semi-permealble layer, saltwater intrudes further inland in the case of the uniform dispersion coefficient, and retreats in the case of the small dispersion coefficient, in comparison with an aquifer without a semi-permeable layer and the upper or lower permeable layers. For relatively low hydraulic gradients, the semi-permeable layer restricts saltwater intrusion into the upper permeable layer, and expands saltwater intrusion into the lower permeable layer in the case of the small dispersion coefficient, though it hardly affects the concentration distribution in the case of the uniform dispersion coefficient. Each circulating current is found near the outlets of the upper and lower permeable layers. It should be noted that groundwater flows upward near the outlet of the semi-permeable layer, and its speed increases with an increase in the hydraulic gradient in the permeable layer.View full abstractDownload PDF (587K) -
Siba Prasad ADHIKARY, Jayanti Kumari SAHU1992 Volume 53 Issue 3 Pages 197-205
Published: July 24, 1992
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSStudies on monthly variation of physico-chemical features and phytoplankton population of Chilka lake during January to December 1989 has been made and compared the differences among four different sectors of the lake. In addition, certain hydrographical parameters of the lake and distribution of algal forms in its different sectors was also studied during March 1988 to June 1990. Seasonal fluctuation of physico-chemical features depends on the discharge of fresh water by catchment rivers and inflow of salt water from sea.
Phytoplankton population was rich in the southern sector and poor in the northern sector. The composition of phytoplankton in different sectors in the same month were heterogeneous. The major groups of phytoplanktons were diatoms and blue-green algae. The diatoms were abundant in southern sector, where autochthonous species were dominated showing small two peaks in July and October 1989, and outer channel sector, where allochthonous species were dominated throughout the year. The blue-green algae were abundant in the central sector and northern sector. Of the dominant seaweeds, Chaetomorpha linum was widely distributed in the lake followed by Enteromorpha intestinalis, E. compressa, Ulva lactuca and Cladophora glomerata. The agarophyte, Gracilaria verrucosa, which was occurring widely in the lake five decades ago, is now restricted to a specific area in the central sector.View full abstractDownload PDF (523K) -
Yasuhiro SATOH, Vera ALEXANDER, Eiji TAKAHASHI1992 Volume 53 Issue 3 Pages 207-216
Published: July 24, 1992
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSThis paper presents the first attempt at determining dissolved organic carbon (DOC) in lake waters covering the vast Alaskan area from the northernmost arctic coast through the subarctic to the maritime region.
Based on the water chemistry, Alaskan lakes examined are classified into four groups. 1) Brackish water lakes: Distributed near the seacoast. The DOC level was low to moderate (1.7-5.9 mgC⋅l-1). Water had measurable salinity. 2) Colored water lakes: Dominant in the arctic and interior Alaska. The concentration of DOC was as high as 7-46 mgC⋅l-1. TN and TP were eutrophic to hypertrophic levels, while Chl. a was oligotrophic to eutrophic levels, which indicates the predominant contribution of biologically unavailable forms of N and P, including organic ones, to the TN and TP pools. The uniqueness of Alaskan colored waters, including arctic bog waters on the tundra, lies in their nearly neutral pH in comparison with a low pH of around 4 for colored bog waters elsewhere in the world. 3) Clear water lakes: Distributed mainly in interior Alaska and southward. The DOC level was 1.1-19.5 mgC⋅l-1. 4) Glacier meltwater lakes: Distributed mainly in the maritime as well as the transitional region between maritime and continental climates. A large amount of glacial silt makes the lake water turbid and characteristically gray in color. The DOC concentration (1.1-1.5 mgC⋅l-1) was lower than that in any other group.View full abstractDownload PDF (611K) -
M.A. KHAN, D.P. ZUTSHI1992 Volume 53 Issue 3 Pages 217-221
Published: July 24, 1992
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe paper evaluates the energy flux of primary producer stock in three lakes in Kashmir, India. The major components were macrophytes, accounting for about 86% contribution, followed by phytoplankton. The morpho-edaphic characteristics of ecosystems favour high growth of macrophytes.View full abstractDownload PDF (245K) -
Masako TABATA, Hiroaki NAGAOKA, Shizuo SUZUKI1992 Volume 53 Issue 3 Pages 223-230
Published: July 24, 1992
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSThe distribution of phosphatase-producing bacteria in Lake Shinseiko and their physiological properties were studied. The activities of alkaline phosphatase were 20-80 nmol⋅1-1⋅min-1 for unfiltrated lake water and 10-25 nmol⋅1-1min-1 for the filtrates. The number of phosphatase-producing bacteria was calculated to be 100-10000 cfu⋅ml-1. The bacteria were mostly found in the epilimnion during the stratification period and uniformly distributed vertically in the water column during the circulation period.
Most of the phosphatase-producing bacteria utilized glucose-6-phosphate, β-glycerophosphate and ADP as a sole P source, but scarcely utilized ATP, DNA, lecithin and phytic acid. Among these phosphatase-producing bacteria, one strain which produced extracellular alkaline phosphatase, was identified as Acinetobacter sp. and used for further growth and phosphatase experiments. The production of the enzyme increased abruptly after disappearance of phosphate in the culture medium.View full abstractDownload PDF (440K) -
Eville GORHAM1992 Volume 53 Issue 3 Pages 231-248
Published: July 24, 1992
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSAir pollution owing to fossil-fuel combustion has a long.history, but only since the 1950's has the long-range transport of gases, acids, and metals through the atmosphere to distant and hitherto uncontaminated lakes and streams been a matter of concern to scientists and citizens. Since the 1940's, radioactive fallout and a variety of new organic micropollutants have also spread to remote surface waters through the atmosphere. Only in the case of acid deposition has such long-range transport of air pollutants (LRTAP) been implicated unambiguously in damage to aquatic ecosystems and to the organisms that inhabit them. Nevertheless, contamination by radioactive fallout, and by trace organics and metals, may well be close to or above thresholds for such damage. There is, therefore, a need to determine such thresholds by a program of broad-scale surveys of aquatic ecosystems, local studies of population dynamics, paleoecological investigations, long-term monitoring, and long-term experiments upon whole lakes and streams, including a recovery phase.View full abstractDownload PDF (1232K) -
1992 Volume 53 Issue 3 Pages 249-251
Published: July 24, 1992
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (371K)
- |<
- <
- 1
- >
- >|