• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.9
• /
• pp.918-924
• /
• 2008

This research investigates the influences of the presence of aquatic macrophytes on the changes of biogeochemistry in the sediments through the comparative analysis of porewater and sediments. From the in situ measurements, elevated SO$_4{^{2-}}$ concentrations were observed in the rhizosphere during the growing season, which was resulted from the oxidation of reduced sulfide in the sediments by the oxygen release from the plant roots. There was sufficient AVS in the sediments to induce observed SO$_4{^{2-}}$ concentrations. The amount of oxygen in the oxidation of AVS to produce observed SO$_4{^{2-}}$ concentrations is 0.85 g/m$^2$ day which is relevant to the results of other researches. The AVS concentrations in the vegetated sediments increased with the depth whereas there is higher mass of AVS in the surface of the non-vegetated sediments. This shows that evapotranspiration induces the transportation of SO$_4{^{2-}}$ in the surface water into the anaerobic sediments. In addition, the elevated organic content caused by the presence of plants increased $\beta$-glucosidase activities which play an important role in the carbon cycle of the sediments.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.17 no.2
• /
• pp.120-129
• /
• 2012

We investigated seasonal variation of sediment-water oxygen and inorganic nitrogen fluxes, and denitrification at tidal flat sediments located in the Nakdong River Estuary from July 2005 to September 2006. Net oxygen fluxes, measured with sediment incubations at in situ temperature, varied from -37.0 to $0.5mmol\;O_2\;m^{-2}\;d^{-1}$. Oxygen fluxes into the sediments from the overlying water increased due to the increased water temperature. Denitrification rate ($4{\sim}2732{\mu}mol\;N\;m^{-2}\;d^{-1}$) in this study was higher compared to the other Korean coast measured with the same method. Denitrification showed the same seasonal variation as oxygen fluxes. Denitrification rate based on $^{15}N$-nitrate showed a strong correlation with nitrate flux into the sediments from the overlying water. Denitrification via "water column supplied nitrate ($D_w$)", calculated from Isotope pairing technique, also correlated well with nitrate flux into the sediments. Nitrate from water column seems to account for seasonal variation of denitrification in Nakdong River Estuary. To understand general patterns and trends of biogeochemical processes of sediments in the Nakdong River Estuary, we categorized biogeochemical fluxes measured in this study according to direction and sizes of fluxes. Type 1(high oxygen and inorganic nitrogen fluxes into the sediments and high denitrification) occurred in summer, whereas Type 2(low oxygen and inorganic nitrogen fluxes into the sediments and low denitrification) occurred in rest of the season. Intertidal flat sediments seem to react sensitively to influence of freshwater from the Nakdong River.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.18 no.1
• /
• pp.1-13
• /
• 2012

We measured various geochemical parameters, including the grain size, loss on ignition(LOI), total organic carbon(TOC), total nitrogen(TN), total sulfur(TS) and metallic elements, in surface sediment collected from 19 stations in Gamak Bay in April 2010 in order to understand the sedimentary types, the origin of organic matters, and the distribution patterns of alkali(Li, Na, K, Rb) and alkaline earth(Be, Mg, Ca, Sr, Ba) elements. The surface sediments were mainly composed of mud. The concentrations of Chlorophyll-a, TOC, TN, TS and LOI in sediment were the highest at the cultivation areas of fish and shellfish in the northern and southern parts of the bay. The redox potential(or oxidation-reduction potential) showed the positive value in the middle part of the bay, indicating that the surface sediment is under oxidized condition. The organic materials in sediment at almost all of stations were characterized by the autochthonous origin. Based on the overall distributions of metallic elements, it appears that the concentrations of alkali and alkaline earth elements except Ba in sediment are mainly influenced by the dilution effect of quartz. The concentrations of Sr and Ba are also dependent on the secondary factors such as the effect of calcium carbonate and the redox potential.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.22 no.1
• /
• pp.1-17
• /
• 2017

This study was conducted to investigate the nutrient distribution and controlling factors in small stream estuaries. The seasonal variations of nutrient concentration (nitrate, ammonium and phosphate) were observed from 2010 to 2012 in the three streams located in Dang-hang (closed estuary: Go-seong, open estuary: Gu-man and Ma-am). The nutrient concentrations in Go-seong were significantly higher than other estuaries, because Go-seong is relatively large and has large nutrient load from the watershed. The dyke located at the estuary, also, caused the high nutrient concentration by reducing the dilution and increasing residence time. In all three streams, nitrate concentration was high at upstream and decreased toward the downstream, because high load of nutrient input were located at upstream. Dilution and biogeochemical removal toward the downstream also caused the trends. Especially, denitrification, a typical nitrogen removing process showed clear tendency of gradual decreasing from upstream to downstream. However, Ammonium and phosphate concentrations were high at upstream and decreased toward the downstream only when the nutrient loads from the rivers were high. Nutrient concentrations were low in summer and high in winter. Freshwater discharge in summer caused a decrease of the residence time and increase of the transport of nutrients to downstream and reduced the nutrient concentrations in the estuary. Nutrient removal by the biological production during high temperature periods also affected the low nutrient concentrations. Small stream estuaries showed distinct nutrient dynamics. It is necessary to understand these characteristics in order to properly manage the small stream estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.4
• /
• pp.349-358
• /
• 2007

In order to understand biogeochemical cycles of organic carbon in the permeable intertidal sandy sediments of the Nakdong estuary, we estimated the organic carbon production and consumption rates both in situ and in the laboratory. The Chl-a content of the sediment and the nutrient concentrations in below surface pore water in the sandy sediment were lower than in the muddy sediment. The sediment oxygen consumption rates were relatively high, especially when compared with rates reported from other coastal muddy sediments with higher organic carbon contents. This implied that both the organic carbon degradation and material transport in the sandy sediment were enhanced by advection-related process. The simple mass balance estimation of organic carbon fluxes showed that the major sources of carbon in the sediment would originate from benthic microalgae and detrital organic carbon derived from salt marsh. The daily natural biocatalzed filtration, extrapolated from filtration rates and the total area of the Nakdong estuary, was one order higher than the maximum capability of sewage plants in Busan metropolitan city. This implies that the sandy sediment contributes greatly to biogeochemical purification in the area, and is important for the re-distribution of materials in the coastal environment.

• 한국생물공학회:학술대회논문집
• /
• 2004.07a
• /
• pp.35-45
• /
• 2004

This paper reviewed effects of global climatic changes on wetland biogeochemistry, Wetlands play key roles in global as well as local material cycle, which includes carbon sequestration, $CH_4$ emission and DOC leaching, Increased air temperature, elevated $CO_2$ levels and changed precipitation patterns are believed to affect those processes substantially by modifying oxygen supply, carbon sources, and decomposition rates. For example, elevated $CO_2$ may increase $CH_4$ emission as well as DOC leaching from wetlands. In addition, interactions of multiple effects warrant further investigation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.11 no.2
• /
• pp.95-102
• /
• 2013

There was a study for biological characteristics, except for physico-chemical and mineralogical properties, on the natural bentonite that is considered as a buffer material for the high-level radioactive waste disposal site. A bentonite slurry that was prepared from a local 'Gyeongju bentonite' in Korea was incubated in a serum bottle with nutrient media over 1 week and its stepwise change was observed with time. From the activated bentonite in the nutrient media, we can find a certain change of both solid and liquid phases. Some dark and fine sulfides began to be generated from dissolved sulfate solution, and 4 species of sulfate-reducing bacteria (SRB) were identified as living cells in samples that were periodically taken and incubated. These results show that sulfate-reducing (or metal-reducing) bacteria are adhering and existing in the powder of bentonite, suggesting that there may be a potential occurrence of longterm biogeochemical effects in and around the bentonite buffer in underground anoxic environmental conditions.

• Analytical Science and Technology
• /
• v.6 no.4
• /
• pp.401-404
• /
• 1993

Rehmanniae Radix Preparata is manufactured with Rehmanniae Radix accoding to KP V. For quality control of Rehmanniae Radix Preparata, its standard component is required. The methanol extracts of Rehmanniae Radix crudus, Rehmanniae Radix, Rehmanniae Radix preparata were divided into the three groups of ether, butanol and aqueous fraction by liquid-liquid separation. In the comparative TLC of ether fraction, the characteristic component of Rehmanniae Radix preparata was found. The ether fraction was evaporated and separated on the silica gel column with chloroform-methanol and further separated on the preparative silica gel TLC with chloroform-methanol-water. The component was illucidated as 5-(hydroxymethyl)-2-furancarboxaldehyde(5-HMF). 5-HMF was not found in Rehmanniae Radix crudus and found in Rehmanniae radix in much less Quantities than Rehmanniae Radix Preparata.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.4
• /
• pp.581-585
• /
• 2003

Utilities of kiwi fruit powder prepared from post-mature kiwi fruit in bakery products such as bread and cookie were investigated. The characteristics of bread and cookie with different amounts of kiwi fruit powder were examined through physical measurement (color specific volume, crumb firmness, spread ratio, and extensibility) and seneory evaluation. In baking performance of frozen dough with kiwi fruit powder, $L^{*}$, $a^{*}$, and $b^{*}$ values of crust and specific volume gradually decreased as the concentration of kiwi fruit powder increased. Crumb firmness had significant difference compared to bread without kiwi fruit powder, and sensory characteristics of breads with kiwi fruit powder were more poor than bread without kiwi fruit powder. In a cookie with kiwi fruit powder although specific volume was not significantly different, the spread ratio of cookie and cookie toughness significantly decreased; furthermore, cookie extensibility significantly increased as an amount of kiwi fruit powder increased. Hardness and moistureness of cookies in sensory evaluation had a similar tendency as toughness and extensibility of cookies. Therefore, post-mature kiwi fruit could be utilized to improve the cookie qualities.ies.s.

• Economic and Environmental Geology
• /
• v.45 no.2
• /
• pp.189-194
• /
• 2012

The consequences of microbe-mineral interaction often resulted in the chemical, structural modification, or both in the biologically induced mineral. It is inevitable to utilize the high powered resolution of electron microscopy to investigate the mechanism of biogenic mineral transformation at nano-scale. The applications of transmission electron microscopy (TEM) capable of electron energy loss spectroscopy (EELS) to the study of microbe-mineral interaction were demonstrated for two examples: 1) biogenic illite formation associated with structural Fe(III) reduction in nontronite by Fereducing bacteria; 2) siderite phase formation induced by microbial Fe(III) reduction in magnetite. In particular, quantification of the changes in Fe-oxidation state at nanoscale is essential to understand the dynamic modification of minerals resulted from microbial Fe reduction. The procedure of EELS acquisition and advantages of EELS techniques were discussed.