• Title/Summary/Keyword: 생지화학 반응

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Sorption Characteristics of Uranium on Goethite and Montmorillonite under Biogeochemical Reducing Conditions (생지화학적 환원조건에서 우라늄의 침철석 및 몬모릴로나이트에 대한 수착 특성)

  • Lee, Seung Yeop;Cho, Hye-Ryun;Baik, Min Hoon;Jung, Euo Chang;Jeong, Jongtae
    • Journal of the Mineralogical Society of Korea
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    • v.25 no.4
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    • pp.263-270
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    • 2012
  • Two kinds of uranium species, oxidized uranium(VI) and reduced uranium(IV), were prepared to be interacted with goethite and montmorillonite to identify sorption characteristic of uranium species, which are very sensitive to the redox-reaction. The reduced uranium was prepared by diluting a substantial uranium(IV) that was concomitantly produced during a sulfate reduction via a sulfate-reducing bacterium. The sorption amount of uranium(IV) by the minerals was relatively lower than that of uranium(VI) because the aqueous uranium(IV) had fine colloidal forms to cause its weak adsorption onto the mineral surfaces. We found that the uranium(IV) phase has a nano-colloid character by the transmission electron microscope, suggesting that the uranium species possibly migrating with the flow of groundwater in underground environments can be the colloidal uranium(IV) as well as the ionic uranium(VI).

Sulfate Reduction in the Marine Environments: Its Controlling Factors and Relative Significance in Mineralization of Organic Matter (해양환경의 황산염 환원율 조절요인 및 유기물 분해에 있어 황산염 환원의 중요성)

  • 현정호;이홍금;권개경
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.8 no.2
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    • pp.210-224
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    • 2003
  • Sulfate reduction is a microbiological process which occurs ubiquitously in anaerobic marine environment. Sulfate reducing bacteria play a significant role in anaerobic decomposition of organic matter and regeneration of inorganic nutrients which supports the primary production in the water column (i.e., benthic-pelagic coupling) and, in special case, could be responsible for the harmful algal bloom in the coastal marine environment. Summary of the sulfate reduction rates reported in various marine sedimentary environments revealed that supply of organic substrates and presence of various electron acceptors (i.e., $O_2$, NO$_{3}$$^{[-10]}$ , Fe(III) and Mn(IV), etc.) for other aerobic and anaerobic respiration directly affect the sulfate reduction rate and relative significance of sulfate reduction in organic matter mineralization. Significance of temperature, macrophytes and bioturbation is discussed as factors controlling supply of organic substrates and distribution of electron acceptors. Finally, we suggest studies on the anaerobic microbiological processes associated with biogeochemical element cycles in the coastal environments of Korea where massive operation of organic enriched fish cage farm, frequent occurrence of toxic algal bloom and hypoxia and conservation of tidal flat are of major environmental issues.

Effects of streambed geomorphology on nitrous oxide flux are influenced by carbon availability (하상 미지형에 따른 N2O 발생량 변화 효과에 대한 탄소 가용성의 영향)

  • Ko, Jongmin;Kim, Youngsun;Ji, Un;Kang, Hojeong
    • Journal of Korea Water Resources Association
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    • v.52 no.11
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    • pp.917-929
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    • 2019
  • Denitrification in streams is of great importance because it is essential for amelioration of water quality and accurate estimation of $N_2O$ budgets. Denitrification is a major biological source or sink of $N_2O$, an important greenhouse gas, which is a multi-step respiratory process that converts nitrate ($NO_3{^-}$) to gaseous forms of nitrogen ($N_2$ or $N_2O$). In aquatic ecosystems, the complex interactions of water flooding condition, substrate supply, hydrodynamic and biogeochemical properties modulate the extent of multi-step reactions required for $N_2O$ flux. Although water flow in streambed and residence time affect reaction output, effects of a complex interaction of hydrodynamic, geomorphology and biogeochemical controls on the magnitude of denitrification in streams are still illusive. In this work, we built a two-dimensional water flow channel and measured $N_2O$ flux from channel sediment with different bed geomorphology by using static closed chambers. Two independent experiments were conducted with identical flume and geomorphology but sediment with differences in dissolved organic carbon (DOC). The experiment flume was a circulation channel through which the effluent flows back, and the size of it was $37m{\times}1.2m{\times}1m$. Five days before the experiment began, urea fertilizer (46% N) was added to sediment with the rate of $0.5kg\;N/m^2$. A sand dune (1 m length and 0.15 m height) was made at the middle of channel to simulate variations in microtopography. In high- DOC experiment, $N_2O$ flux increases in the direction of flow, while the highest flux ($14.6{\pm}8.40{\mu}g\;N_2O-N/m^2\;hr$) was measured in the slope on the back side of the sand dune. followed by decreases afterward. In contrast, low DOC sediment did not show the geomorphological variations. We found that even though topographic variation influenced $N_2O$ flux and chemical properties, this effect is highly constrained by carbon availability.

Effect of Rehmanniae Radix and Pear Phenolic Compound on the STZ-Treated Mice for Induction of Diabetes (생지황(Rehmanniae Radix)과 배의 Phenolic Compound가 Streptozotocin으로 유발된 고혈당 생쥐에 미치는 영향)

  • 김정상;나창수
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.33 no.1
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    • pp.66-71
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    • 2004
  • This study has been carried out to investigate effect of Rehmanniae Radix (RR) and pear phenolic compound (PC) on the hyperglycemic mice induced with streptozotocin (STZ). For this purpose, male mice were fed with a 0.2 mL RR extract (S group) and the pear PC (90 mg/kg/day) dissolved in a 0.2 mL RR extract (SPC group) while the control group received the same commercial diet for 6 weeks. The blood glucose contents were examined from tail vein blood once a week for 6 weeks. Samples of pancreas removed after the experimental period were processed for the immunohistochemical identification of $\beta$-cells. The levels of serum glucose were decreased significalntly (p<0.05) in the S and SPC groups compared with the control group. The BUN and creatinine levels were significantly (p<0.05) decreased in SPC group compared with the control group. Intraperitoneal glucose tolerance tests peformed at 24 hours before that period revealed that glucose tolerances in S and SPC group were ameliorated. Immunohistochemical analyses of the pancreases revealed that a lot of insulin- positive $\beta$-cells were contained in a Langerhas's islets of S and SPC groups compared with the control group, and the number of Langerhas's islets were significalntly increased in S (p<0.01) and SPC (p<0.05) groups. These results suggest that RR extract and pear PC could recover the damages induced by STZ in the hyperglycemic mice.

Importance of Polar Phytoplankton for the Global Environmental Change (전 지구 환경변화에 대한 극지 식물플랑크톤의 중요성)

  • 강성호;강재신;이상훈;김동선;김동엽
    • Korean Journal of Environmental Biology
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    • v.18 no.1
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    • pp.1-20
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    • 2000
  • There are increasing evidences of climate change in the Antarctic and Arctic Oceans, especially elevated temperature due to the continuous burning of the fossil fuels and ultraviolet B(UV-B) flux within the ozone hole. Light-dependent, temperature-sensitive, and fast-growing organisms respond to these physical and biogeochemical changes. Polar marine phytoplankton, which are pioneer endemic species and important carbon contributors in the polar waters, are therefore highly suitable biological indicators of such changes. By virtue of light requirement, the primary producers are exposed to extreme seasonal fluctuations in temperature, photosynthetically active radiation, and UV radiation. Local environmental warming and increased UV-B radiation during ozone depletion may have profound effects on the primary producers that are primary carbon producers in the polar water. Small changes in climate temperature and solar radiation may have profound effects on the activity threshold of the polar phytoplanktion. To demonstrate biological response to the environmental changes, standardized representative natural and biological parameters are needed so that replicate samples (including controls) can be taken over extended periods of time. In this paper, we review general characteristics of polar phytoplankton, their environment, environmental changes in the polar waters, the effects on the environmental changes to the polar phytoplankton, and the importance of the polar phytoplankton to understand the global environmental changes. [Biological indicators, Global environmental change, Polar phytoplankton, UV].

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Importance of Extracellular Enzyme Activities in Northern Peatland Biogeochemistry-Possible Coupling with Trace Gas Emission and DOC Dynamics (북구 이탄습지의 생지화학적 반응에 있어서 체외효소의 중요성-미량기체 발생량 및 용존유기탄소 동태와의 연관성에 대하여)

  • Freeman, Chris;Park, Seok-Soon;Kang, Ho-Jeong
    • Korean Journal of Ecology and Environment
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    • v.39 no.4 s.118
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    • pp.435-444
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    • 2006
  • A suite of extracellular enzyme activities involved in organic carbon decomposition were determined in three northern peatlands (a bog, a fen, and a swamp) over a 12 month period along with trace gas ($CO_2$ and $N_2O$) flux and DOC dynamics in the wetlands. The activities varied $0.008-0.066\;{\mu}mole\;g^{-1}\;min^{-1}$, $0.003-0.021\;{\mu}mole\;g^{-1}\;min^{-1}$, $0.003-0.016\;{\mu}mole\;g^{-1}\;min^{-1}$, $0.004-0.047\;{\mu}mole\;g^{-1}\;min^{-1}$, for ${\beta}-glucosidase$, cellobiohydrolase, ${\beta}-xylosidase$, and N-acetylglucosaminidase, respectively. In general, the activities were highest in the forested swamp followed by the fen and the bog. When the data from three wetlands are combined, the enzyme activities exhibited significant positive correlations with trace gas emission and available carbon. Further, the average activity of 4 enzymes explained about 20-40% of the variations of trace gas emssion and available carbon. The results indicate that enzymes related to the mineralization of organic carbon may play an important role in trace gas flux and DOC dynamics in northern peatlands.

Phosphorus Phases in the Surface Sediment of the South Sea (남해 표층 퇴적물에서의 인의 존재상)

  • SON Jaekyung;LEE Tongsup;YANG Han Soeb
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.32 no.5
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    • pp.680-687
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    • 1999
  • To understand the role of shelf sediment in phosphorus biogeochemical cycle, we carried out sequential sediment extraction (SEDEX) of P and porewater analysis on 14 core samples collected in the South Sea of Korea, SEDEX classified P-pools into 5 phases and results are grouped into two categories: reactive P (loosely sorbed-P and Fe bound-P) and refractory P (detrital inorganic-p, authigenic mineral-P and organic-P). Total P concentrations are decreased with sediment depth in all samples as a result of dissolution to porewater. Reactive P comprises about $20\~50\%$ of total P, and iron bound-P is the major form consisting $70\~80\%$ of reactive P-pool. Iron bound-P decreases sharply with depth. Depth profiles of dissolved P concentration in porewater show mirror image of iron bound-P, revealing the role of FeOOH as a regulator of reactive P supply to overlying water column. Authigenic mineral-P consists less than $5\%$ of total P, thus removal of reactive P by converting into refractory P seems inefficient in shelf sediment. This implies that continental shelf sediment sequesters P temporarily rather than permanently. Results show local variation. Nakdong estuary receiving large amount of terrigenous input shows the highest concentration of total P and reactive P. Here iron oxyhydroxides at the surface sediment control the water column flux of P from sediment. Although total P content at the surface is comparable (500$\~$600 ${\mu}g{\cdot}g^{-1}$) between the South Sea and East China Sea, the former contains more iron bound-P and less derital inorganic-P than the latter. Reasons for the difference seem due in part to particle texture, and to biological productivity which depends roughly on the distance from land.

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