• Title, Summary, Keyword: diatom

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Engineering Characteristics of Diatom Modified Soil Mixture (Diatom 혼합토의 공학적 특성)

  • Kim, Kyu-Sun
    • Journal of the Korean Geotechnical Society
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    • v.28 no.5
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    • pp.77-84
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    • 2012
  • The engineering characteristics of natural sediments containing diatom microfossils have been investigated for their abnormal deformation and strength behavior for a few decades. The presence of disk or hollow shape diatoms causes low compressibility, high hydraulic conductivity, and high shear strength of sediments. Some of these unusual differences show the characteristic of diatom owing to the interlocking of large interparticle porosity and angular particles. This phenomenon implies the possible use of diatom as modification materials to change the engineering performance of soil mixtures. This paper describes the engineering characteristics of diatom-kaolin mixture to investigate the engineering properties of diatom modified soils using conventional geotechnical tests and elastic and electromagnetic wave propagation tests. Experimental test results show the performance improvement by increasing diatom contents and the performance degradation by the breakage of interlocking between diatom particles under high effective stress.

Origins and Paleoceanographic Significance of Layered Diatom Ooze from Bransfield Strait in the Northern Antarctic Peninsula around 2.5 kyrs BP

  • Yoon, Ho-Il;Kim, Yea-Dong;Park, Byong-Kwon;Kang, Cheon-Yun;Bae, Sung-Ho;Yoo, Kyu-Chul
    • Ocean and Polar Research
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    • v.24 no.3
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    • pp.301-311
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    • 2002
  • We used diatom and porewater data of two piston cores from the central subbasin and one from the western subbasin in the Bransfield Strait in the northern Antarctic Peninsula to elucidate the depositional mechanism of the layered diatom ooze. The layered diatom ooze is characterized by an abundance of organic carbon, biogenic silica, sulfde sulfur, and lower porewater sulfate concentration. This lack of pore-water sulfate concentration in the diatom ooze interval may reflect development of reducing micro-environment in which bacterially mediated sulfate reduction occurred. The negative relationship between the total organic carbon and sulfate contents, however, indicates that sulfate reduction was partly taking place but does not control organic carbon preservation in this unit. Rather, well-preserved Chaetoceros resting spores in the layered diatom ooze indicate a rapid sedimentation of the diatom as a result of repetitive iceedge blooms on the Bransfield shelf during the cold period (around 2500 yrs BP) when the permanent seaice existed on the shelf, During this period, it is expected that the downslope-flowing cold and dense water was also formed on the Bransfield shelf as a result of sea ice formation, playing an important role for the formation of layered diatom ooze in the Bransfield subbasins.

Change of Hydraulic Properties of Sand due to Fine Diatom Particle Migration (미세 Diatom 입자 이동에 의한 모래지반의 투수 특성 변화)

  • Pyo, Won-Mi;Lee, Jong-Sub;Lee, Joo Yong;Hong, Won-Taek
    • Journal of the Korean Geotechnical Society
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    • v.34 no.2
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    • pp.19-32
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    • 2018
  • During the process of gas hydrate extraction in the deep seabed, fine diatom particle migration occurs, which causes the seabed slope failure and the productivity deterioration of the gas hydrate. Therefore, a study related with the changes of the ground characteristics due to the fine particle migration is required. The objective of this study is to investigate the change of hydraulic properties of sand due to the migration of fine diatom particle in sandy soils. In order to simulate the sediments of the Ulleung basin gas hydrate in the East Sea, fifteen sand-diatom mixtures that have different diatom volume fractions (DVF) are prepared. During the falling head permeability tests, the coefficients of permeability are measured according to the DVF. In addition, for the simulation of the fine diatom particle migration, constant head permeability tests are conducted by applying the hydraulic pressures of 3 kPa, 6kPa, and 9 kPa on a specimen composed of two layers: a specimen with 50% DVF in upper layer and a specimen with 0% DVF in lower layer. Furthermore, the coefficient of permeability and the electrical resistivity of the migration zone are measured during the constant head permeability test. The falling head permeability tests show that the coefficient of permeability decreases as the DVF of the specimen increases. In addition, the gradient of the coefficient of permeability curve decreases in the DVF range of 10%~50% compared with that of 0%~10%, and increases above 50% in DVF. The result of constant head permeability tests shows that the coefficient of permeability decreases and electrical resistivity increases in the migration zone due to the fine diatom particle migration. This study demonstrates that fine diatom particle migration reduces the permeability of the soils and the behavior of the migration zone due to the fine diatom particle migration may be estimated based on the reversal relationship between the coefficient of permeability and the electrical resistivity.

Effects of Predator Addition to the Algicidal Bacterium in Controlling Diatom Sephanodiscus hantzschii Dominating the Eutrophic Pal′tang Reservoir, Korea (살조세균과 초식성 섭식자의 혼합배양에 의한 녹조제어효과)

  • Kim Baik-Ho;Ka Soon-Kyu;Han Myung-Soo
    • Journal of environmental and Sanitary engineering
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    • v.19 no.2
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    • pp.23-29
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    • 2004
  • An algicidal effect of endemic algicidal bacterium (Pseudomonas putida) and rotifer zooplankton (Brachionus calyciflorus) on diatom Stephanodiscus hantzschii were examined in the filtered water, and were compared with those of bacterium plus ciliate. Bacteria removed as 80% of the diatom within 3.5 days, while ciliate and zooplankton suppressed 57% and 40% of diatom during the same period, respectively. Mixed treatment of bacteria plus ciliate removed as 54% of diatoms, while that of bacteria plus zooplankton decreased as 85%. Although single bacteria and mixed treatment of bacteria plus zooplankton quickly decreased the diatom in the initial of experiment, bacteria plus ciliate perfectly removed the diatom in culture flask within 5.5 days of the study. On the other hand, other single and mixed treatments did not clear the diatom during the same period, and over 10% of them still remain in culture flask. Predator biomass in the presence of algicidal bacteria showed the growth patterns; zooplankton gradually decreased, and ciliate sustained over 0.5 cells/ml. These results indicated that the addition of ciliate to the algicidal bacterium in controlling the diatom Stephanodiscus hantzschii is more effective than that of zooplankton. Therefore, this synergistic interaction relationship between the bacterium and ciliate play an important role in the bio-manipulation using bio-agents to control the diatomal bloom in freshwater lakes and streams.

Quantitative Reconstruction of Sea Level Change Using Diatom-Based Transfer Function at Sinduk-ri, Gochang-Gun Since the Middle Holocene (규조기반 전이함수를 활용한 Holocene 중기 이후 고창군 신덕리 일대의 정량적 해수면 변동)

  • Kim, Jeong-Yun;Yoon, Soon-Ock;Yang, Dong Yoon;Hwang, Sangill
    • Journal of The Geomorphological Association of Korea
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    • v.24 no.3
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    • pp.13-25
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    • 2017
  • This study is quantitative reconstruction of palaeo sea level records around Sinduk-ri, Gochang-Gun. 7 cores were collected from GC14 to GC18 in order to examine the entire sedimentary facies and reconstruct the sea level records. The cores were analysed by AMS, sedimentary facies, diatom and WA-pls. As a result of the diatom analysis, diatom zone were classified as No diatom zone, B1 zone, M zone and B2 zone. The result of WA-pls was that the sea level was about 1.5m lower than the present level around 6,000 BP and about 1m lower during last 5,000 BP. Thereafter, sea level rose to the present during the Mc sub-diatom zone period. Moreover, during the Md sub-diatom zone period, sea level was about 0.5m higher than the present.

Water Quality Assessment using Trophic Status Index and Attached Diatom Index in 10 Reservoirs including Ye-dang Reservoir of Chungcheongnam-do (충남 예당저수지를 포함한 10개 저수지의 영양단계 및 부착규조지수를 이용한 수질평가)

  • Song, Mi-Ae;Kim, Ji-Won;Kim, Hun-Nyun;Kong, Dong-Soo;Lee, Ok-Min
    • Korean Journal of Ecology and Environment
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    • v.44 no.2
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    • pp.155-171
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    • 2011
  • The research assessed water quality using physico-chemical factors, trophic status index and attached diatom index in 10 reservoirs located in Chungcheongnam-do from October 2007 to June 2008. The physico-chemical water quality assessments revealed that Dangjin-gun (St. 1~5), which displayed a high chemical oxygen demand (V and VI) and chlorophyll-${\alpha}$ (Eutrophic-Hypereutrophic), was more polluted than Yesan and Cheongyang-gun. The sample were also hypereutrophic [trophic status index (TSI) 74.6] and ${\beta}$-mesosaprobic [diatom assemblage index to the organic water pollution (DAIpo) 44.47]. Yesan and Cheongyang-gun. Which were mid-level in their pollution status, were eutrophic (TSI 56.9) and ${\alpha}$-oligosaprobic (DAIpo 60.11). TSI correlated strongly with the attached diatom index (of DAIpo 0.60~0.62, and trophic diatom index of 0.72~0.74). Hence, the attached diatom index can be used with the trophic status assessment of lakes using TSI, and lake trophic status index (LTSI).

Dynamics of Epilithic Diatom Communities and Biological Water Quality Assessment in Geum River and Downstream Yongdam (금강과 용담댐 하류하천 부착규조 군집 동태 및 생물학적 수질 평가)

  • Park, Yeon-Jeong;Kim, Han-Soon;Ban, Yang-Jin;Lee, Hee-Suk
    • Journal of The Korea Society For Environmental Analysis
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    • v.20 no.3
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    • pp.138-144
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    • 2017
  • This study was conducted to investigate the water quality of the Geum River and downstream Yongdam using Diatom Assemblage Index to organic water pollution (DAIpo) and Trophic Diatom Index (TDI). Water quality parameters, such as Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Total Phosphorus (TP), were analyzed. A total of 99 diatom taxa belonging 27 genera and 75 diatom taxa belonging 25 genera were identified in the epilithic diatom communities of Geum River and downstream Yongdam, respectively. In Geum River, the dominant species were indifferent and saprophilous taxa, such as Achnanthes minutissima, Fragilaria crotonensis, Nitzschia inconspicua, Nitzschia palea, and Cyclotella atomus. However, the dominant species were in indifferent and saproxenous taxa, such as Achnanthes minutissima, Cocconeis placentula var. lineata, and Reimeria sinuata in downstream Yongdam. The mean biological indices (DAIpo and TDI) indicated poor water quality in Geum River but good water quality in downstream Yongdam.

Seasonal Variation of Diatom at Lowland Swamps in Haman County, Korea (함안 자연늪 산 균조류의 계절적 소장)

  • 정영호
    • Journal of Plant Biology
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    • v.30 no.2
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    • pp.117-133
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    • 1987
  • The diatoms were investigated at three lowland swamps in Haman county form July, 1983 to July, 1984 on monthly interval. Seasonal changes of standing crops, the variation of dominant species and species composition were studied. The maximum of standing crops showed bimodal pattern at Chilnalpol and Yujnnup. Dominant species were Navicula crytocephala, Cocconeis placentula, Achnanthes minutissima, Achnanthes lanceolata, Synedra ulna, Eunotia lunaris. Dominant species changed seasonally. Total 166species of diatom were identified. Three lowland swamps supported a rich diatom flora composed of many species typically associated with benthic diatom.

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Study of the Correlation Between Diatom and Environmental Variables for Palao-Sealevel Reconstruction in the Korea Peninsula: Case Study of the Eastern Tidal Flat of Gomso Bay (한반도 고해수면 변동 복원을 위한 규조-환경변수 상관관계 연구: 곰소만 동부 조간대 지역을 대상으로)

  • Kim, Jeong-Yun;Yoon, Soon-Ock;Yang, Dong Yoon;Hwang, Sang ill
    • Journal of The Geomorphological Association of Korea
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    • v.24 no.2
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    • pp.79-90
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    • 2017
  • This study investigated the correlation between the diatom community and the environmental variables on the tidal flat surface of the eastern part of Gomso Bay in the West coast of Korea in order to utilize the quantitative sea level record as a basic data. 24 sediment samples at 10cm intervals downstream of the Galgok Stream were used for diatom analysis, grain size analysis and CCA. As a result of diatom analysis, marine diatoms dominated at lower altitudes and the ratio of diatoms to fresh water diatoms and brackish diatoms increased toward upland. As a result of CCA, the contribution of environmental variables was analyzed as 25.3% at altitude, 21.6% at sand, 13.3% at skewness, etc. This means that altitude above sea level has the greatest influence on the diatom composition in the tidal flat surface. It suggests that the contribution of environmental variables at altitude above sea level can be used as a basic data for the quantitative records for reconstruction of paleo-sea level.

Recovery of Diatom Skeleton from Low Grade Diatomaceous Earth by Shape Separation Method Using Fluid Field

  • Lee, Minyong;Yoon, Ki-Byung;Shigehisa Endoh
    • Proceedings of the IEEK Conference
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    • pp.349-352
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    • 2001
  • Shape separation method - a separation process which utilizes the fact that particles of different shape behave differently in force fields- is regarded as an useful measure for recycling, mineral processing, upgrading powdered material and so on. In this study, a trial was given to shape separation method using fluid field to recover pure diatom skeleton - which is thought to have many uses in itself and potential for various applications -from low grade diatomaceous earth of southeastern part of the Korean Peninsula. The striking difference of shape between diatom skeleton and other minerals like clay and quartz made it natural to choose shape separation method. Considering the size of particles to be separated, among many possible methods of shape separation, hydrodynamic field using hydrocyclone was adopted. And it resulted in recovery of pure diatom skeleton with high purity

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