• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.1
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• pp.1-17
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• 2019

In this study, the surveys were carried out from October (2016) to October (2017) along the tidal flat of Geunso Bay, Taean Peninsula of the western edge of Korea. The sampling trips were carried out for a total of 16 times, once or twice a month. In order to investigate the monthly variation of the microphytobenthos (MPB) biomass, community composition and photo-physiology were analyzed by HPLC (High performance liquid chromatography). The total chlorophyll a (TChl a) concentrations used as an indicator of biomass of MPB in the upper 1 cm sediment layer ranged from 40.4 to $218.9mg\;m^{-2}$ throughout the sampling period. TChl a concentrations showed the maximum level on $24^{th}$ of February and remained high throughout March after which it started to declined. The biomass of MPB showed high values in winter and low values in summer. The monthly variations of Phaeophorbide a concentrations suggested that the low grazing intensity of the predator in the winter may have partly attributed to the MPB winter blooming. As a result of monthly variations of the MPB community composition using the major marker pigments, the concentrations of fucoxanthin, the marker pigment of benthic diatoms, were the highest throughout the year. The concentrations of most of the marker pigments except for chlorophyll b (chlorophytes) and peridinin (dinoflagellates) increased in winter. However, the concentrations of fucoxanthin increased the highest, and the relative ratios of the major marker pigments to TChl a except fucoxanthin decreased during the same period. The vertical distribution of Chl a and oxygen concentrations in the sediments using a fluorometer and an oxygen micro-optode Chl a concentrations decreased with oxygen concentrations with increasing depth of the sediment layers. Moreover, this tendency became more apparent in winter. The Chl a was uniformly vertical down to 12 mm from May to July, but the oxygen concentration distribution in May decreased sharply below 1 mm. The increase in phaeophorbide a concentration observed at this time is likely to be caused by increased oxygen consumption of zoobenthic grazing activities. This could be presumed that MPB cells are transported downward by bioturbation of zoobenthos. The relative ratios (DT/(DD+DT)) obtained with diadinoxanthin (DD) and diatoxanthin (DT), which are often used as indicators of photo-adaptation of MPB, decreased from October to March and increased in May. This indicated that there were monthly differences in activity of Xanthophyll cycle as well.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.76-90
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• 2000

The estimation of material cycle of pollutants is necessary for the environment management in coastal zone. Model for material budgets are useful tools to understand the phenomena of natural system and to provide an insight into the complex processes including physical, chemical and biological processes occuring in natural system. Budgets of fresh water, salt and nutrients were estimated in order to clarify the characteristics of seasonal material cycle in Keum river estuary. Inflow volumes of freshwater into system was approximately 1.014×10/sup 8/～12.565×10/sup 8/m³/month and discharge in Keum river has occupied 99.7% of total freshwater. Seasonal variations of freshwater volume in the system were found to be very high in the range of about 4 ～ 14 times due to rainfall in summer season. Existing water mass of freshwater in system calculated by salt budget was approximately 0.339×10/sup 8/～0.652×10/sup 8/m³. Mean residence time of freshwater was calculated to be about 1.6～10.0day, and exchange time was calculated to be about 2.2～11.9day. Mean residence time was short as 1.6day in summer due to precipitation, and long as 10.1day in winter due to a drought. Inflow masses of DIP and DIN were approximately 5.57～32.68ton/month and 234.93～2,373.39ton/month, respectively. Seasonal inflow mass of DIP was larger than the outflow mass except for summer season. Thus, we postulate that accumulation of DIP in the system will happen. Residence times of DIP and DIN were calculated to be 1.1～6.4day and 1.8～10.9day, respectively. The ratio of water residence time versus DIP, DIN residence time was calculated to be 0.39～2.31 times and 0.83～1.13 times, respectively.

• The Korean Journal of Pharmacology
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• v.20 no.2
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• pp.23-34
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• 1984

To investigate diurnal variations of opiate receptor binding and its modification by experimental condition or treatment of various centrally-acting drugs, the amount of maximum $^3H-morphine$ binding in rat midbrain homogenates was measured at 4 hour intervals for 24 hours. Animals were conditioned under the controlled L : D, 12 : 12 cycle or D: D, 12 : 12 cycle, for 3 weeks and treated with 0.5 ml of physiological saline or drugs for 2 weeks. A highly significant diurnal rhythm with peak at 22 hour of early dark phase with an amplitude$(0.68{\pm}0.06\;pmole/mg\;protein)$ of +51.1% and nadir $(0.33{\pm}0.03\;mole/mg\;prtein)$ at 18 hour of late light phase with an amplitude of -26.6% was found in control group. 24 tour mean of $^3H-morphine$ binding was $0.45{\pm}0.03\;pmole/mg$ protein respectively. Constant dark adaptation or treatment of reserpine, pargyline, imipramine, amphetamine and chlorpromazine modified the diurnal rhythm in the time of peak and nadir binding shape, phase, amplitude of the diurnal curve and 24 hour mean of $^3H-morphine$ binding. However, Kd values were not changed in all experimental groups : Statistical analysis at times of least and great binding indicates that the differences in $^3H-morphine$ binding were due to changes not in the affinity, but in the number of binding sites. The results are interpreted with regard to the diurnal rhythm of opiate receptor finding. The modes of action of psychoactive drugs are closely related to postulated changes of receptor sensitivity in neuropharmacological aspects.

• Journal of the Korean earth science society
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• v.22 no.5
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• pp.415-422
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• 2001

Studies of atmospheric general circulation in the troposphere and stratosphere are very important to understand the influence of human activities on the global climate and its change. Recently, the existence of an annual cycle in the circulation has been reported by a number of studies. In this study, the residual mean meridional circulation is calculated by the TEM momentum and continuity equations for the period from December 1985 to November 1995 (10 years), and the long-term variations of the circulation and mass fluxes across the 100hPa surface are examined. The multiple regression statistical model is used to obtain quantitatively the long-term variations. This study is focused especially on mean meridional circulation in the troposphere and stratosphere associated with ENSO (El Ni${\tilde{n}}$o-Southern Oscillation) which is known as a cause of the unusual weather, global climate, and its change. The results show that the global scale troposphere-stratosphere mean meridional circulation is intensified during El Ni${\tilde{n}}$o event and QBO (quasi-biennal oscillation) easterly phase and weakened during La Ni${\tilde{n}}$o event and QBO westerly phase. The signal of Mount Pinatubo volcanic eruption in June 1991 is obtained. Due to the volcanic eruption the global scale troposphere-stratosphere mean meridional circulation is abruptly intensified.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.202-208
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• 2009

In order to understand the circulation of nutrient between muddy tidal flat and the surrounding coastal area, tidal time-scale variations in nutrient concentrations were seasonally investigated at the entrance of Hampyeong Bay. The results show that the temperature was higher in ebb tide and lower in flood tide during the summer, but it was lower in ebb tide and higher in flood tide during the autumn/winter. The salinity was higher in flood tide and lower in ebb tide during the summer/winter because of the inflow of external sea water resulting from the increase in the tide level. By contrast, the salinity was lower in flood tide and higher in ebb tide during the autumn. Salinity difference was lower than 0.3 psu between flood tide and ebb tide during survey period. Meanwhile, all nutrient concentrations observed in Hampyeong Bay was lower in flood tide and higher in ebb tide during the summer, and by contrast, it was higher in flood tide and lower in ebb tide during the winter. Characteristically, no clear variation of concentrations was found depending on the tide level during the autumn. This tidal variations imply that the muddy tidal flat of Hampyeong Bay supplies nutrients to the seawater in summer and removes nutrient from the seawater in winter. During tidal cycle, seasonal variation of nutrient concentration in seawater is considered as the result of complex interactions between the mud flat and external sea water.

• Ocean and Polar Research
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• v.30 no.3
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• pp.225-238
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• 2008

In order to investigate the effects of intertidal sediments on the nutrient cycle in coastal environments, the benthic fluxes of ammonium, nitrate, nitrite, phosphate, and silicate at two stations on the intertidal flat of Keunso Bay were determined during each season. The efflux of ammonium was observed at S1 and resulted from the diffusion of remineralized ammonium and acceleration caused by the bioirrigation of macrofauna. The influx of ammonium at S2 was probably due to nitrification in the water column. The influx of nitrate was observed at both stations during all seasons, indicating that the nitrate in the pore water was removed by denitrification. Vigorous bioirrigation led to the efflux of dissolved inorganic nitrogen (DIN) at S1, whereas the influx of DIN at S2 was predominantly caused by denitrification. Contrary to the diffusive and bio-irrigated release of remineralized phosphate from the sediment at S1, the influx of phosphate was observed at S2, which may be attributable to adsorption onto iron oxides in the aerobic sediment layer. Silicate, which is produced by the dissolution of siliceous material, was mostly released from the sediment by molecular diffusion and bioirrigation. However, the influx of silicate was observed at S2 during spring and winter, which was ascribed to adsorption by particulate matter or assimilation by benthic microphytes. The annual fluxes of DIN were 328 mmol $m^{-2}yr^{-1}$ at S1 and -435 mmol $m^{-2}yr^{-1}$ at S2. The annual fluxes of phosphate were negative at both sites (-2.8 mmol $m^{-2}yr^{-1}$ at S1 and -28.9 mmol $m^{-2}yr^{-1}$ at S2), whereas the annual fluxes of silicate were positive at both sites (843 mmol $m^{-2}yr^{-1}$ at S1 and 243 mmol $m^{-2}yr^{-1}$ at S2).

• Journal of The Korean Astronomical Society
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• v.54 no.2
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• pp.61-70
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• 2021

We investigate 20 post-coronal mass ejection (CME) blobs formed in the post-CME current sheet (CS) that were observed by K-Cor on 2017 September 10. By visual inspection of the trajectories and projected speed variations of each blob, we find that all blobs except one show irregular "zigzag" trajectories resembling transverse oscillatory motions along the CS, and have at least one oscillatory pattern in their instantaneous radial speeds. Their oscillation periods are ranging from 30 to 91 s and their speed amplitudes from 128 to 902 km s-1. Among 19 blobs, 10 blobs have experienced at least two cycles of radial speed oscillations with different speed amplitudes and periods, while 9 blobs undergo one oscillation cycle. To examine whether or not the apparent speed oscillations can be explained by vortex shedding, we estimate the quantitative parameter of vortex shedding, the Strouhal number, by using the observed lateral widths, linear speeds, and oscillation periods of the blobs. We then compare our estimates with theoretical and experimental results from MHD simulations and fluid dynamic experiments. We find that the observed Strouhal numbers range from 0.2 to 2.1, consistent with those (0.15-3.0) from fluid dynamic experiments of bluff spheres, while they are higher than those (0.15-0.25) from MHD simulations of cylindrical shapes. We thus find that blobs formed in a post-CME CS undergo kinematic oscillations caused by fluid dynamic vortex shedding. The vortex shedding is driven by the interaction of the outward-moving blob having a bluff spherical shape with the background plasma in the post-CME CS.

• Journal of Forest and Environmental Science
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• v.29 no.4
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• pp.314-323
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• 2013

To examine surface erosion and sediment export patterns on a hillslope, which was devastated by a shallow landslide and which was slowly revegetating by natural plant species, we surveyed variations in surface erosion depth on the upper-, middle- and lower-section of the hillslope, and subsequent sediment yield from the whole hillslope. The result showed that, with the passing of year, surface erosion on the devastated hillslope was regulated by higher rainfall intensity due to the supply-limitation of exportable sediment, and its variation range decreased. In addition, surface erosion on the upper-section with steep slope was regulated by higher rainfall intensity, which might result in raindrop erosion, compared to it on the lower-section with relatively gentle slope. Besides, the sediment yield from the devastated hillslope had nonlinear relationship with surface erosion depth on the hillslope because sediments on the hillslope are exported downwards while repeating their cycle of transport and redistribution. Our findings suggest the establishment of management strategy to prevent sediment-related disasters occurred during torrential rainfall events, which was based on the continuous field investigation on the hillslope devastated by landslides.

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.530-540
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• 2008

The temporal and spatial variations of size-structured phytoplankton dynamics in Youngsan Lake were investigated to explore potential mechanims controlling the dynamics in the Youngsan Lake. Field data were collected monthly from February to October, 2003 at 6 stations along the axis of Youngsan Lake. In this study, phytoplankton (chlorophyll $\alpha$) were categorized into three size classes: micro-size ($>20{\mu}m$), nano-size ($2{\sim}20{\mu}m$) and pico-size ($<20{\mu}m$). Water temperature, light attenuation coefficients, PAR (photosynthetically active radiation) and suspended solids were measured to analyze relationship between physical-chemical properties and size structure of phytoplankton. Phytoplankton blooms developed during March, July and October in the upper region of the main stem whereas small-scaled spring bloom was observed in the lower region. The scales of phytoplankton blooms were higher in the upper regions than the lower region and blooms were predominated by micro-size class in upper region but predominated by nano-size class in lower region. Growth of size-structured phytoplankton appeared to be controlled by rather light availability than temperature-dependant metabolisms in the system. Phytoplankton growth may be also supported by ambient nutrients available in the water column from analyses of chlorophyll $\alpha$ vs. nutrient concentrations including nitrite+nitrate and orthophosphate. Growth of nano-sized phytoplankton alone appeared to be supported by orthophosphate as well as nitrite+nitrate indicating that response of phytoplankton to nutrient inputs may be size-dependent.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.791-799
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• 2005

The phased isolation intra-clarifier ditch system used in this study is a simplified novel process enhancing simultaneous removal of biological nitrogen and phosphorus in municipal wastewater in terms of elimination of additional pre-anaerobic reactor, external clarifier, recycle of sludge, and nitrified effluent recirculation by employing intrachannel clarifier. Laboratory-scale phased isolation ditch system was used to assess the treatability on municipal wastewater. When the system was operated at the HRTs of 6~12hours, SRTs of 9~31days, and cycle times of 2~8hours, the system showed removals of BOD, TN, and TP as high as 88~97%, 70~84%, and 65~90%, respectively. The rainfall in Korea is generally concentrated in summer because of site-specific characteristics. Especially, the wet season has set in on June to August. In combined sewers, seasonal variations are primarily a function of the amount of stormwater that enters the system. In order to investigate the effect of hydraulic shock loading on system performance, the laboratory-scale system was operated at an HRT of 6hours (two times of influent flowrate) during two cycles (8hours). The system performance slightly decreased by increasing of influent flowrate and decreasing of system HRT. Nitrification efficiency and TN removal were slightly decreased by increasing of influent flowrate (decreasing of system HRT), whereas, the denitrification was not affected by hydraulic shock loading. However, the higher system performance could be achieved again after four cycles. Thus, the phased isolation technology for enhanced biological nutrient removal in medium- and small-scale wastewater treatment plants suffering fluctuation of influent quality and flowrate.