• Title/Summary/Keyword: sediment balance

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The Environmental Impacts of Seasonal Variation on Characteristics of Geochemical Parameters in Lake Shihwa, Korea (시화호의 계절변화에 따른 지화학적 환경요인 특성 연구)

  • Kim Tae-Ha;Park Yong-Chul;Lee Hyo-Jin;Kim Dong-Hwa;Park Jun-Kun;Kim Sung-Jun;Lee Mi-Yeon
    • Journal of Environmental Science International
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    • v.13 no.12
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    • pp.1089-1102
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    • 2004
  • Seasonal variation of biogeochemical characteristics was determined in Lake Shihwa from October 2002 to August 2003. When the lake was artificially constructed for the freshwater reservoir in 1988, the development of the strong haline density stratification resulted in two-layered system in water column and hypoxic/anoxic environment prevailed in the bottom layer due to oxidation of accumulated organic matters in the lake. Recently, seawater flux to the lake through the sluice has been increased to improve water quality in the lake since 2000, but seasonal stratification and hypoxic bottom layer of the lake still developed in the summer due to the nature of artificially enclosed lake system. As the lake is still receiving tremendous amount of organic matters and other pollutants from neighboring streams during the rainy summer season, limited seawater flux sluicing into the lake may not be enough for the physical and biogeochemical mass balance especially in the summer. The excess of accumulated organic matters in the bottom layer apparently exhausted dissolved oxygen and affected biogeochemical distributions and processes of organic and inorganic compounds in the stratified two-layered environment in the summer. During the summer, ammonia and dissolved organic carbon remarkably increased in the bottom layer due to the hypoxic/anoxic condition in the bottom layer. Phosphate also increased as the result of benthic flux from the bottom sediment. Meanwhile, dissolved organic carbon showed the highest value at the upstream area and decreased along the salinity gradient in the lake. In addition to the sources from the upstream, autochthonous origin of particulate organic carbon from algal bloom in the lake might be more important for sustaining aggravated water quality and development of deteriorated bottom environment in the summer. The removal of trace metals could be attributed to scavenging by strong insoluble metal-sulfide compounds in the hypoxic/anoxic bottom layer in the summer.

Chemical Mass Balance of Materials in the Keum River Estuary: 1. Seasonal Distribution of Nutrients (금강하구의 물질수지: 1. 영양염의 계절적 분포)

  • Yang, Jae-Sam;Jeong, Ju-Young;Heo, Jin-Young;Lee, Sang-Ho;Choi, Jin-Yong
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.4 no.1
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    • pp.71-79
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    • 1999
  • As part of an on-going project investigating flux of materials in the Keum River Estuary, we have monitored seasonal variations of nutrients, suspended particulate matter (SPM), chlorophyll, and salinity since 1997. Meteorological data and freshwater discharge from the Keum River Dike were also used, Our goal was to answers for (1) what is the main factor for the seasonal fluctuation of nutrients in the Keum River Estuary? and (2) are there any differences in nutrient distributions before and after the Keum River Dike construction? Nitrate concentrations in the Keum River water were kept constant through the year. Whereas other nutrients varied with evident seasonality: high phosphate and ammonium concentrations during the dry season and enhanced silicate contents during the rainy season. SPM was found similar trend with silicate. During the rainy season, the freshwater discharged from the Keum River Dike seemed to dilute the phosphate and ammonium, but to elevate SPM concentration in the Keum Estuary. In addition, the corresponding variations of SPM contents in the estuarine water affected the seasonal fluctuations of nutrients in the Estuary. The most important source of the nutrients in the estuarine water is the fluvial water. Therefore, the distribution patterns of nutrients in the Estuary are conservative against salinity. Nitrate, nitrite and silicate are conservative through the year. The distribution of phosphate and ammonium on the other hand, display two distinct seasonal patterns: conservative behavior during the dry season and some additive processes during the rainy days. Mass destruction of freshwater phytoplankton in the riverine water is believed to be a major additive source of phosphate in the upper Estuary. Desorption processes of phosphate and ammonium from SPM and organic matter probably contribute extra source of addition. Benthic flux of phosphate and ammonium from the sediment into overlying estuarine water can not be excluded as another source. After the Keum River Dike construction, the concentrations of SPM decreased markedly and their role in controlling of nutrient concentrations in the Estuary has probably diminished. We found low salinity (5~15 psu) within 1 km away from the Dike during the dry season. Therefore we conclude that the only limited area of inner estuary function as a real estuary and the rest part rather be like a bay during the dry season. However, during the rainy season, the entire estuary as the mixing place of freshwater and seawater. Compared to the environmental conditions of the Estuary before the Dike construction, tidal current velocity and turbidity are decreased, but nutrient concentrations and chance of massive algal bloom such as red tide outbreak markedly increased.

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The physical geography in general:yesterday and tomorrow (자연지리학 일반: 회고와 전망)

  • Son, Ill
    • Journal of the Korean Geographical Society
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    • v.31 no.2
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    • pp.138-159
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    • 1996
  • There has been a tendency for Geomorphology and Climatology to be dominant in Physical Geography for 50 years in Korea. Physical Geography is concerned with the study of the totality of natural environment through the integrated approaches. But, an overall direction or a certain paradigm could not be found, because major sub-divisions of Physical Geography have been studied individually and the subjects and the approaches in studying Physical Geography are enormously diverse. A consensus of opinion could not also exist in deciding what kind of the sub-divisions should be included in the physical geography in general and how those should be summarized. Furthermore it would be considered imprudent to survey the studies of Physical Geography besides those of Geomorphology and Climatology due to the small number of researchers. Assuming that the rest of Physical Geographical studies with the exception of Geomorphological and Climatological studies are the Physical Geography in general, the studies of Physical Geogrpahy in general are summarized and several aspects are drown out as follows. First the descliption of all possible factors of natural environments was the pattern of early studies of Physical Geography and the tendency is maintained in the various kinds of research and project reports. Recently Physical Geographers have published several introductory textbooks or research monographs. In those books, however, the integrated approaches to Physical Geography were not suggested and the relationship between man and nature are dealt with in the elementary level. Second, the authentic soil studies of Physical Geographers are insignificant, because the studies of soil in Physical Geography have been mostly considered as the subsidiary means of Geomorphology Summarizing the studies of Soil Gegraphy by physical geographers and other Pedologists, the subjects are classified as soil-forming processes, soil erosions, soil in the tidal flat and reclaimed land, and soil pollution. Physical Geographers have focused upon the soil-forming processes in order to elucidate the geomorphic processes and the past climatic environment. The results of other subjects are trifling. Thirdy Byogeygrayhers and the results of studies are extremely of small number and the studies of Biogeography in Korea lines in the starting point. But, Biogeography could be a more unifying theme for the Physical-human Geography interface, and it would be expected to play an active part in the field of environmental conservation and resource management. Forth, the studies of Hydrogeography (Geographical Hydrology) in Korea have run through the studies of water balance and the morphometric studies such as the drainage network analysis and the relations of various kinds of morphometric elements in river. Recently, the hydrological model have introduced and developed to predict the flow of sediment, discharge, and ground water. The growth of groundwater studies is worthy of close attention. Finally, the studies on environmental problems was no mole than the general description about environmental destruction, resource development, environmental conservation, etc. until 1970s. The ecological perspectives on the relationship between man and nature were suggested in some studies of natural hazard. The new environmentalism having been introduced since 1980s. Human geographers have lead the studies of Environmental Perception. Environmental Ethics, Environmental Sociology, environmental policy. The Physical geographers have stay out of phase with the climate of the time and concentrate upon the publication of introductory textbooks. Recently, several studies on the human interference and modification of natural environments have been made an attempt in the fields of Geomorphology and climatology. Summarizing the studies of Physical Geography for 50 years in Korea, the integrated approaches inherent in Physical Geography disappeared little by little and the majol sub-divisions of Physical Ceography have develop in connection with the nearby earth sciences such as Geology, Meteorology, Pedology, Biology, Hydrology, etc been rediscovered by non-geographers under the guise of environmental science. It is expected that Physical Geography would revive as the dominant subject to cope with environmental problems, rearming with the innate integrated approaches.

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