• Journal of the Korean Society for Marine Environment & Energy
• /
• v.10 no.3
• /
• pp.127-137
• /
• 2007

To confirm whether or not the Electrochemical Disinfection System (EDS) meet with the D-2 regulation established by IMO (International Maritime Organization), the biological treatment efficacy of the EDS was assessed using three groups of natural marine plankton (bacteria, $10-50\;{\mu}m$ and $>50\;{\mu}m$ sized organisms). Influent water was passed through the EDS under the flow velocity ($23.8\;m^3/hr$) and test design was consisted of control (no treatment) and experimental (10 ppm and 30 ppm) condition for total residual chlorine (TRC). And the biological condition of the influent water followed the standards established by the guidelines for the approval of ballast water management systems. The disinfection efficacy of the $10-50\;{\mu}m$ sized organisms (phytoplankton) was assessed by three kinds of measurements using photomicroscope, epifluorescence microscope and fluorometer (fumer Designs 10-AU). After being passed through the EDS, all motile phytoplankton lost their motility under photomicroscope, the colour of chlorophyll fluorescence fumed from red into green under epifluorescence, and the high chlorophyll fluorescence (Expt. 1: 6.95, Expt. 2: 7.11) detected by fluorometer decreased into value not detected. These results indicated phytoplankton community was totally killed after electrochemical disinfection treatment. Survivorship of the larger organisms than $50\;{\mu}m$ was determined based on the appendage's movement under a stereomicroscope. Natural assemblage collected from ambient seawater was killed shortly after being passed through the EDS, whereas some Artemia remained alive. However, no live Artemia was found after 24 hour further exposure to each TRC concentration (10 and 30 ppm) under darkness. After electrochemical treatment, the target bacteria such as aerobes, coliform and Escherichia coli were completely killed on the basis of CFU (colony forming unit) on Petrifilm plate ($3\;M^{TM}$) after 48 hr incubation. Moreover, no regrowth was found in the three groups of plankton during five days under additional exposure to the treated water. These results indicated that the disinfection efficiency of the EDS on the three groups of plankton satisfy D-2 regulation.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.40 no.3
• /
• pp.1-11
• /
• 2012

This study focused on establishing a natural rainwater circulation system using rainwater meant for relatively large urban development projects such as a new town development. In particular, when the location selection techniques for individual elements of a natural rainwater circulation system are developed for the integrated rainwater management, changes in hydrological environment will be minimized and the natural water circulation would be restored to realize the low impact development (LID). In that case, not only the excess will be reduced but water space and green areas in a city would also increase to improve the urban sustainability. First of all, there were five elements selected for the location selection of a rainwater circulation system intended for the integrated rainwater management: rainwater collection, infiltration, filtration, retention and movement spaces. After generating these items, the location selection items and criteria were defined for each of the five elements. For a technique to apply the generated evaluation items and criteria, a grid cell analysis was conducted based m the suitability index theory, and thematic maps were overlapped through suitability assessment of each element and graded based on the suitability index. The priority areas were identified for each element. The developed technique was applied to a site where Gim-cheon Innovation City development is planned to review its feasibility and limitations. The combined score of the overlapped map for each element was separated into five levels: very low, low, moderate, high and very high. Finally, it was concluded that creating a rainwater circulation system conceptual map m the current land use plan based on the outcome of the application would be useful in building a water circulation system at the de1ailed space planning stage after environmental and ecological planning. Furthermore, we use the results of this study as a means for environment-friendly urban planning for sustainable urban development.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.22 no.4
• /
• pp.327-339
• /
• 2020

Transpiration is the movement of water into the atmosphere through leaf stomata of plant, and it accounts for more than half of evapotranspiration from the land surface. The measurements of transpiration could be conducted in various ways including eddy covariance and water balance method etc. However, the transpiration measurements of individual trees are necessary to quantify and compare the water use of each species and individual component within stands. For the measurement of the transpiration by individual tree, the thermometric methods such as heat dissipation and heat pulse methods are widely used. However, it is difficult and labor consuming to maintain the transpiration measurements of individual trees in a wide range area and especially for long-term experiment. Therefore, the sharing of sapflow data through database should be useful to promote the studies on transpiration and water balance for large spatial scale. In this paper, we present sap flow database, which have Granier type sap flux data from 18 Korean pine (Pinus koraiensis) since 2011 and 16 (Quercus aliena) since 2013 in Mt.Taehwa Seoul National University forest and 18 needle fir (Abies holophylla), seven (Quercus serrata), three (Carpinus laxiflora and C. cordata each since 2013 in Gwangneung. In addition, the database includes the sapling transpiration of nine species (Prunus sargentii, Larix kaempferii, Quercus accutisima, Pinus densiflora, Fraxinus rhynchophylla, Chamecypans obtuse, P. koraiensis, Betulla platyphylla, A. holophylla, Pinus thunbergii), which were measured using heat pulse method since 2018. We believe this is the first database to share the sapflux data in Rep. of Korea, and we wish our database to be used by other researchers and contribute a variety of researches in this field.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.1 no.1
• /
• pp.53-68
• /
• 1981

Most clays under sustained load exhibit time-dependent deformation because of creep movement of soil particles and many investigators have attempted to relate their findings to the creep behavior of natural ground and to the long-term stability of slopes. Since the creep behavior of clays may assume a variety of forms depending on such factors as soil plasticity, activity and water content, it is difficult and complicated to analyse the creep behavior of clays. Rheological models composed of linear springs in combination with linear or nonlinear dashpots and sliders, are generally used for the mathematical description of the time-dependent behavior of soils. Most rheological models, however, have been proposed to simulate the behavior of secondary compression for saturated clays and few definitive data exist that can evaluate the behavior of non-saturated clays under the action of sustained stress. The clays change gradually from a solid state through plastic state to a liquid state with increasing water content, therefore, the rheological models also change. On the other hand, creep is time-dependent, and also the effect of thixotropy is time-function. Consequently, there may be certain correlations between creep behavior and the effects of thixotropy in compacted clays. In addition, the states of clay depend on water content and hence the height of the specimen under drained conditions. Futhermore, based on present and past studies, because immediate elastic deformation occurs instantly after the pressure increment without time-delayed behavior, the factor representing immediate elastic deformations in the rheological model is necessary. The investigation described in this paper, based on rheological model, is designed to identify the immediate elastic deformations and the effects of thixotropy and height of clay specimens with varing water content and stress level on creep deformations. For these purposes, the uniaxial drain-type creep tests were performed. Test results and data for three compacted clays have shown that a linear top spring is needed to account for immediate elastic deformations in the rheological model, and at lower water content below the visco-plastic limit, the effects of thixotropy and height of clay specimens can be represented by the proposed rheological model not considering the effects. Therefore, the rheological model does not necessitate the other factors representing these effects. On the other hand, at water content higher than the visco-plastic limit, although the state behavior of clays is visco-plastic or viscous flow at the beginning of the test, the state behavior, in the case of the lower height sample, does not represent the same behavior during the process of the test, because of rapid drainage. In these cases, the rheological model does not coincide with the model in the case of the higher specimens.

• Korean Journal of Environment and Ecology
• /
• v.34 no.4
• /
• pp.274-281
• /
• 2020

This study aimed to investigate the autumn spawning by bitterling (A. rhombeus) inside mussel (Unio douglasiae) and the adaptation characteristics at the Bongseocheon Stream of Mankyeonggang River. The survey was carried out between August 2015 and July 2016. The spawning season was from September to November, and 17-75 (36.2 ± 16.44) eggs were found from mature females. During the survey period, 476 mussels were collected, 129 (27.1%) of spawned A. rhombeus. Mussels that spawned eggs, embryos, and larva of A. rhombeus (46.3 ± 4.55 mm, n = 129) were larger than than those that did not spawn (42.6 ± 8.51 mm, n = 347). The appearance frequency of A. rhombeus larva before and after the formation of lens was 99.8% (n = 597) vs. 0.2% (n = 1) from October 2015 to March 2016, 25.6% (n = 23) vs. 74.4% (n = 67) in April 2016, 0% (n = 0) vs. 100% (n = 40) on May 2016. The number of eggs, embryos, and larvae of A. rhombeus inside the mussels were 1-18 (5.6 ± 3.81). The number and appearance frequency of A. rhombeus eggs, embryos, and larvae inside the mussel according to mussel gill demibranchs position were 1 (0.01 ± 0.09, n = 1) and 0.78% in the left outer demibranch, 1-18 (2.33 ± 3.31, n = 63) and 48.84% in the left inner demibranch, 1-15 (2.97 ± 3.79, n = 76) and 58.91% in the right inner demibransh, and 1-12 (0.33 ± 1.71, n = 7) and 5.43% in the right outer demibransh. The highest frequency of the developmental position of eggs, embryos, and larvae occurred 71.8% (n = 445) in lower part 3 (L3) before formation lens and 94.4% (n = 102) in L3 after formation lens, indicating that L3 was dominating position for eggs, embryos, and larvae. More eggs, embryos, and larvae of A. rhombeus were found more often in the inner demibranshs than outer demibranchs. Since A. rhombeus is a species that spawn in the autumn and thus avoids the competition with interspecific and glochidia. However, they have to spend the winter in low water temperature. Consequently, we assume that A. rhombeus have evolved toward embryonic diapause under the low water temperature before the formation of lens and spawning inside the supracranchial cavity to save the transit energy from the water space to the suprabranchial cavity after the achieving movement ability with the formation of lens.

• Geophysics and Geophysical Exploration
• /
• v.7 no.3
• /
• pp.164-173
• /
• 2004

To delineate geothermal water movement at the Pohang geothermal development site, Self-Potential (SP) survey and monitoring were carried out during pumping tests. Before drilling, background SP data have been gathered to figure out overall potential distribution of the site. The pumping test was performed in two separate periods: 24 hours in December 2003 and 72 hours in March 2004. SP monitoring started several days before the pumping tests with a 128-channel automatic recording system. The background SP survey showed a clear positive anomaly at the northern part of the boreholes, which may be interpreted as an up-flow Bone of the deep geothermal water due to electrokinetic potential generated by hydrothermal circulation. The first and second SP monitoring during the pumping tests performed to figure out the fluid flow in the geothermal reservoir but it was not easy to see clear variations of SP due to pumping and pumping stop. Since the area is covered by some 360 m-thick tertiary sediments with very low electrical resistivity (less than 10 ohm-m), the electrokinetic potential due to deep groundwater flow resulted in being seriously attenuated on the surface. However, when we compared the variation of SP with that of groundwater level and temperature of pumping water, we could identify some areas responsible to the pumping. Dominant SP changes are observed in the south-west part of the boreholes during both the preliminary and long-term pumping periods, where 3-D magnetotelluric survey showed low-resistivity anomaly at the depth of $600m\~1,000m$. Overall analysis suggests that there exist hydraulic connection through the southwestern part to the pumping well.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.7 no.2
• /
• pp.60-67
• /
• 2002

To determine whether nitrogen (N) uptake by phytoplankton below the euphotic zone in the Yellow Sea is considerable, we measured the uptake rates of nitrate and ammonium using $^{15}N$-labeled stable isotope $K^{15}NO_{3}$ and $^{15}NH_{4}Cl$, in May and November 1997 at total 10 stations. Depth-integrated uptake rates of nitrate and ammonium over the euphotic zone during this study ranged from 1.8 to 15.3 mg N $m^{-2}$ $d^{-1}$ and from 5.0 to 132.2 mg N $m^{-2}$ $d^{-1}$, respectively, and ammonium uptake predominated at 9 of 10 stations (1.9-19.4 fold). Depth-integrated uptake rates of nitrate and ammonium over the whole water column ranged from 2.9 to 22.0 mg N $m^{-2}$ $d^{-1}$ and from 15.7 to 175.5 mg N $m^{-2}$ $d^{-1}$, respectively. The significant proportion of whole water column N uptake was attributed to uptake by phytoplankton below the euphotic zone, ranging from 13.0 to 86.2% for nitrate and from 13.8 to 67.8% for ammonium, indicating that phytoplankton N uptake below the euphotic zone is at times considerable in the study area. The results suggest that when phytoplankton below the euphotic zone in the Yellow Sea are again entrained into the euphotic zone by a certain physical forcing such as turbulent mixing and the vertical movement of thermocline, these episodic events may significantly affect the material fluxes within the euphotic zone. Furthermore, the results suggest that a portion of regenerated production estimated from $^{15}N$-ammonium uptake should be included in new production estimates, which otherwise could be underestimated in the Yellow Sea.

• Applied Biological Chemistry
• /
• v.47 no.3
• /
• pp.344-350
• /
• 2004

This study was conducted to develop and assess the applicability of mixed-bed ion exchange resin capsules for water quality monitoring in small agricultural watershed. Recoveries of resin capsules for inorganic N and P ranged from 96 to 102%. The net activation energies and pseudo-thermodynamic parameters, such as ${\Delta}G^{o\ddag},\;{\Delta}H^{o\ddag},\;and\;{\Delta}S^{o\ddag}$ for ion adsorption by resin capsules, exhibited relatively low values, indicating the process might be governed by chemical reactions such as diffusion. However, those values increased with temperature coinciding with the theory. The reaction reached pseudo-equilibrium within 24 hours for $NH_4-N\;and\;NO_3-N$, and only 8 hours for $PO_4-P$, respectively. The selectivity of resin capsules were in the order of $NO_3\;^-\;>\;NH_4\;^+\;>\;PO_4\;^{3-}$, coinciding with that of encapsulated Amberlite IRN-150 resin. At the initial state of equilibrium, the resin adsorption quantity was linearly proportional to the mass of ions in the streams, but the rate of movement leveled off, following Langmuir-type sorption isotherm. The overall results demonstrated that the resin capsule system was suitable for water quality monitoring in small agricultural watershed, judging from the reaction mechanism(s) of the resin capsule and the significance of model in field calibration.

• Journal of Animal Environmental Science
• /
• v.16 no.2
• /
• pp.143-152
• /
• 2010

Conditions for artificial culture of Lemna Paucicostata and its nutritional values were examined in this study. Lemna P. was cultured using artificial wastewater and a bioreactor (total volume $2,630\;cm^3$, working volume $2,240\;cm^3$) was operated at conditions of 6,250 lux and $28^{\circ}C$. Water flow affected the growth of Lemna P.: growth rate was very high (more than $1.1\;d^{-1}$) at a condition of no-water movement, but it was very low (less than $0.15\;d^{-1}$) when water moved slowly. The growth of Lemna P. was higher in $16h\;d^{-1}$ light cycle than in Sand $24h\;d^{-1}$, and it was also severely affected by the initial $NH_4$-N levels of wastewater. The growth rate of Lemna P. was high in lower $NH_4$-N level, indicating that the growth rate is in inverse proportion to $NH_4$-N concentration in wastewater. However, the contents of crude protein (CP) of Lemna P. were proportional to the initial $NH_4$-N concentration. The CP contents of Lemna P. cultured at 2, 10, 50 and 100 $NH_4$-N mg $L^{-1}$ was 18, 24, 37, 43%, respectively, showing the Lemna P. cultured at 50 and $100\;mg\;L^{-1}$ had similar protein contents to linseed (CP 35%), cottonseed (CP 38%) and soybean (CP 45%). Fat, protein, fiber, NDF and ADF contents of Lemna P. harvested at conditions of $16h\;d^{-1}$ light cycle and less than $2\;mg\;L^{-1}$ of $NH_4$-N level was 2.8, 18, 27, 20, 41 and 65.7%, respectively. Since the growth rate of Lemna P. was very high (more than $1.1\;d^{-1}$) at those conditions, it was convinced that mass production of valuable protein and fiber sources are feasible. In particular, since the Lemna P. has unsaturated fatty acids found mainly in animal fat as well as beneficial fatty acids to health such as C18:ln9c, C18:2n6c, C20:5n3 and C22:2, the Lemna P. biomass would be a highly valuable alternative feed source to grains.

• Journal of Wetlands Research
• /
• v.23 no.4
• /
• pp.317-326
• /
• 2021

The present study was carried out with a view to understand the distribution and ecology of Clihton retropictus (Martens, 1879), a class II endangered wildlife designated and protected by the Ministry of Environment, Republic of Korea, and to suggest the effective conservation and management measures for this species and its habit. First, the distribution of Clihton retropictus was investigated nationwide, and environmental factors such as salinity and substratum were analyzed in consideration of the ecological characteristics of this species. In addition, the individual size, density, and movement of Clihton retropictus per each district surveyed were analyzed. Due to its nature of inhabiting in the brackish water zone, the analysis showed that the salinity of this species was 0.7 ~ 16.6‰ at low tide and 1.0 ~ 17.3% at high tide. It was learned from the analysis of substratum that its composition in each river under investigation was slightly different, but most of substratum had a higher composition ratio than gravel (pebble, 16 ~ 64 mm). On the other hand, the size of each individual was checked by measuring the length of its diameter, and there was almost no change in the individual when the inhabited range of Clihton retropictus was short. However, there was tendency that the longer the habitat range, the bigger the individual size. From surveying the population density by season, it was made clear that, during the summer (July to August) and fall (September to October), the density was relatively higher while the number of individuals decreased significantly during winter (November to December) when the water temperature was lowered. In an effort to effectively establish conservation and management measures, the moving distance was measured, and it became known that, during the surveys in summer and fall when the individuals were active, the individuals moved in more distances than during the winter survey. The results of this study are expected to be utilized as basic data for establishing effective management plans such as creation of habitats for Clihton retropictus, its migration projects and selection of migration destinations which get unavoidable due to development projects.