• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.947-956
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• 2009

Residual petroleum hydrocarbons after an oil spill may accumulate in the marine benthic ecosystem due to their high hydrophobicity. A lot of monitoring data are required for the estimation of ecosystem exposure to residual petrochemicals in an ecological risk assessment in the affected region. To save time and cost, the environmental exposure to them in the affected ecosystem can also be assessed using a simple food-web bioaccumulation model. In this study, we evaluated residual concentrations of four selected polycyclic aromatic hydrocarbons (phenanthrene, anthracene, pyrene, and benzo[a]pyrene) in a hypothetic benthic ecosystem composed of six species under two exposure scenarios. Body-residue concentration ranged 5~250 mg/kg body depending on trophic positions in an extreme scenario in which the aqueous concentrations of PAHs were assumed to be one-tenth of their aqueous solubility. In addition, bioconcentration factors (BCFs) and bioaccumulation factors (BAFs) were evaluated for model species. The logarithm of bioconcentration factor (log BCF) linearly increased with increasing the logarithm of 1-octanol-water partition coefficient (log $K_{OW}$) until log $K_{OW}$ of 7.0, followed by a gradual decrease with further increase in log $K_{OW}$ without metabolic degradation. Biomagnification became significant when log $K_{OW}$ of a pollutant exceeded 5.0 in the model ecosystem, indicating that investigation of food-web structure should be critical to predict biomagnifications in the affected ecosystem because log $K_{OW}$ values of many petrochemicals are higher than 5.0. Although further research is required for better site-specific evaluation of exposure, the model simulation can be used to estimate the level of the ecosystem exposure to residual oil contaminants at the screening level.

• Journal of the Korean earth science society
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• v.28 no.1
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• pp.64-74
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• 2007

The marine seismic prospecting using a research vessel in the shallow sea near the coastal area has certain limits according to the water depth and survey environment. Also, for the electrical resistivity survey at seashore area, one may need a specially designed high-voltage source to penetrate the very conductive surface layer. Therefore, we have conducted a feasibility study on the application of magnetotelluric method (MT), a passive geophysical method, on investigating of shallow marine environment geology. Our study involves both theoretical modeling and field survey at the tidal flat area which represent the very shallow marine environment. We have applied the audio-frequency magnetotelluric (AMT) method to the intertidal deposits of Gunhung Bay, west coast of Korea, and analysed the field data both qualitatively and quantitatively to investigate the morphology and sedimentary stratigraphy of the tidal flat. The inversion of AMT data well reveals the upper sedimentary layer of Holocene intertidal sediments having a range of 13-20 m thickness and the erosional patterns at the unconformable contact boundary. However, the AMT inversion results tend to overestimate the depth of basement (30-50 m) when compared with the seismic section (27-33 m). Since MT responses are not significantly sensitive to the resistivity of middle layer or the depth of basement, the AMT inversion result for basement may have to be adjusted using the comparison with other geophysical information like seismic section or logging data if possible. But, the AMT method can be an effective alternative choice for investigating the seashore area to get important basic informations such as the depositional environment of the tidal flat, sea-water intrusion and the basement structure near the sea shore.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.187-194
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• 2011

In compliance with an international law about the ocean dumping of the sludge, the proper sewage treatment process which occurs from the wastewater treatment process has been becoming problem. Generally the sewage and the sludge are controlled from anaerobic condition when the sewage is treated and land filled, where the methane$(CH_{4})$ and the nitrous oxide $(N_{2}O)$ from this process are discharged. Because these gases have been known as one of the responsible gases for global warming, the wastewater treatment process is become known as emission sources of green house gases(GHG). This study is to suggest a new approach of estimate and environmental assessment of greenhouse gas emissions and sludge emissions from wastewater treatment processes. It was carried out by calculating the total amounts of GHG emitted from biological wastewater treatment process and the amount of the sludgegenerated from the processes. Four major biological wastewater treatment processes which are Anaerobic/Anoxic/Oxidation$(A_{2}O)$, Bardenpho, Virginia Initiative Plant(VIP), University of Cape Town(UCT)are used and GPS-X software is used to model four processes. Based on the modeling result of four processes, the amounts of GHG emissions and the sludge produced from each process are calculated by Intergovernmental Panel on Climate Change(IPCC) 2006 guideline report. GHG emissions for water as well as sludge treatment processes are calculated for environmental assessment has been done on the scenario of various sludge treatments, such as composting, incineration and reclamation and each scenario is compared by using a unified index of the economic and environmental assessment. It was found that Bardenpho process among these processes shows a best process that can emit minimum amount of GHG with lowest impact on environment and composting emits the minimum amount of GHG for sludge treatment.

• Journal of the Korean Wood Science and Technology
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• v.17 no.1
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• pp.3-11
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• 1989

This study was carried out to investigate the physical and mechanical properties. durability of adhesive bond and paint film for the basic data which were required to determine the suitability as a raw material for furniture the laminated veneer lumber (LVL) with pitch pine (Pinus rigida Mill). The results obtained were as follows; 1) The proper pressing time for making the LVL was over 45 second per milimeter of LVL thickness. 2) The bending strength of the LVL was lower than that of the solid wood but the compressive strength of the LVL was similar to that of the solid wood. The strength increased with the decrease of veneer thickness. 3) The impact bending absorbed energy of the LVL was 0 to 0.3 kg.m/$cm^2$ in the direction of parallel to the grain. The energy of the LVL was lower than that of the solid wood (0.68 kg.m/$cm^2$). 4) In warm water soaking and cold-dry tests, delamination of adhered layers surface crack, swelling, and color change were not found when the hot pressing time was over 45 second per milimeter of LVL thickness. As a result of soak under vacuum test shrinkage in the direction of parallel to the grain was about -1.0 percent and. was about 3.0 percent in the direction of the perpendicular to the grain. 6) The film cacks on the LVL's surface after the wet and cold-dry test were not found at all. 7) In the use of the LVL for interior decoration it was considered that the surface of the LVL be overlaid crossly with fancy veneers of birch and paulownia, etc. This cross overlayirg methods have resulted in few cracks on the fancy veneer.

• Journal of the Korean earth science society
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• v.26 no.3
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• pp.240-252
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• 2005

The relationships between wave and wind around the Korean Peninsula have been analyzed with the data from the buoys moored at five stations (Dugjug-do, Chilbal-do, Geomoon -do, Geoje-do, Donghae) by Korea Meteorological Administration. Generally, the relationship between wave and wind is the highest at the stations in the West Sea and the lowest at the stations in the South Sea, and the middle at the station in the East Sea. The characteristics shown at each station are as follows. Highest wave is developed at Chilbal-do with strong northwesterly wind in winter because the sea is opened in the wind direction and wave is amplified by shoaling effect. At Chilbal-do, wave directions coincide with wind directions relatively well. On the other hand, waves are not fully developed at Dugjug-do in winter due to limited fetch since the sea is blocked by Hwanghae-do in the northwest direction. The limitation in fetch is more serious at the stations in the South Sea. In the South Sea, the direction of dominant northerly wind is blocked by land so that wave heights are small even with very strong northerly wind. In the South Sea, whatever wind direction is, waves dominantly come in the direction from the East China Sea, which are from the south at Geomoon-do and the southwest at Geoje-do. At these directions, waves are coming even with weak wind. At the station in the East Sea, waves are highly developed due to vast area, but not so high as in Chilbal-do because wind and wave directions do not coincide in many cases. As shown, wind direction is important in the wave development as well as wind speed. The reason is that the fetch is determined by wind direction. In the case of long-lasted wind with fixed direction at Chilbal-do and Dugjug-do, wave directions are well coincident with wind directions and wave heights increase with response time, which is the duration between the highest wind and wave. However, in the case of disagreement between wind and wave directions at the station in the East Sea, wave heights do not increase as highly as at Chilbal-do and Dugjug-do in spite of strong wind and longer response time. The results show us that waves are highly developed with strong wind, long fetch, and long duration, and also show that wave development ratios are different at different stations due to environmental factors such as the direction towards sea or land, bottom topography, and the scales of adjacent seas.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.706-712
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• 1999

PSD (particle size distribution) for 2,000 mg/$\ell$ natural loess in seawater showed normal distribution cure at 0 minute settling time, accompanying with very large particle distribution range with its mean particle diameter of 31.6 $\mu$m and coencient of variance of $72.6\%$, With elapsed time it showed that the PSD was rapidly changed from normal distribution cure to abnormal distribution curve, steepened the right-hand side of it and its coefficient of variance was getting increased because of rapid settling of large size particles, Cumulative weight distribution showed that 2,000 mg/$\ell$ natural loess in seawater was almost $100\%$ constituted of particles bigger than 20 $\mu$m in diameter. Ratio of $V_s/(D_{bm})^{1/2}$ for loess particles in seawater was increased with increase of particle size in geometrical progression. Almost all loess particles in seawater had Stokes settling velocity not less than 2,255 times of Brownian diffusion coefficient, There was almost to EDL (about 0.4 nm) around natural loess particles in seawater, Thus, there was always LVDW attractive force between loess particles approaching each other in seawater, and almost no EDL repulsive force. Loess particles were not always in the condition of easy floe formation. Concentration of natural loess in seawater increasing from 400 mg/$\ell$ to 10,000 mg/$\ell$, characteristics of the settling was changed from Type I settling (discrete settling) to Type II settling (flocculation settling). PVD (particle volume distribution) showed that natural loess particles in seawater were largely constituted of two types of particles, such as rapidly settling particles and suspended and dispersed particles for a long time. Amount of the latter was much less than that of the former.

• Journal of The Korean Society of Grassland and Forage Science
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• v.27 no.4
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• pp.297-312
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• 2007

This study is conducted to evaluate economical value of Jeju grassland and validity of its preservation, and draw up several measures to support. To measure its economical value, this study examined its environmental value and social and cultural value. For environmental value, this study used replacement method while it applied CVM method, a widely used method, to assess social and cultural value and two-level two-best choice selection method, which ask questions by assuming virtual circumstances to avoid reflecting some biased opinions. Jeju grassland has multiple functions-environmental functions such as preventing soil corrosion and flood, handling animal excrement, and purifying air, and social and cultural functions such as promoting physical and mental health and providing recreation places. From the results of the feasibility study, Jeju grassland's annual multiple functions are assessed to have a total $397,115{\sim}418,995$ million won worth. In addition, it is found that Jeju visitors recognize Jeju grassland for its functions to contribute to public interests. That is, they think it can provide attractive views and educational and recreational places and promote emotional development. Especially, many people presented their ideas that it be continuously preserved since it is worthwhile for us and our next generations. To preserve grassland's cultural resource, which create a huge economic value like this, the Government has to support a certain amount of financial aid for turning to a better grassland environment and its maintenance to realize environment-friendly livestock farming on Jeju Island and promote its tourism industry and consequently, add more value to Jeju.

• Land and Housing Review
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• v.9 no.3
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• pp.1-8
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• 2018

In Europe and the United States, the use of limit states design has almost been established for pile foundation design. According to the global trend, the Ministry of Land, Transport and Maritime Affairs has established the basic design criteria of the bridge under the limit state design method. However, it is difficult to reflect on the design right now because of lack of research on resistance coefficient of the pile method and ground condition. In this study, to obtain the resistance coefficient of PHC bored pile which is widely used in Korea, the bearing capacity calculated by the LH design standard and the bridge design standard method, the static load test(21 times) and the dynamic load test(EOID 21 times, Restrike 21) The reliability analysis was performed on the results. The analysis of the resistance coefficient of PHC bored pile by loading test was analyzed by adding more than two times data. As a result, the resistance coefficient obtained from the static load test(ultimate bearing capacity) was 0.64 ~ 0.83 according to the design formula and the target reliability index, and the resistance coefficient obtained from the dynamic load test(ultimate bearing capacity) was 0.42~0.55. Respectively. The resistance coefficient obtained from the modified bearing capacity of dynamic load test(EOID's ultimate end bearing capacity + restrike's ultimate skin bearing capacity) was 0.55~0.71, which was reduced to about 14% when compared with the resistance coefficient obtained by the static load test(ultimate bearing capacity). As a result of the addition of the data, the resistivity coefficient was not changed significantly, even if the data were increased more than 2 times by the same value or 0.04 as the previous resistance coefficient. In conclusion, the overall resistance coefficient calculated by the static load test and dynamic load tests in this study is larger than the resistance coefficient of 0.3 suggested by the bridge design standard(2015).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.3
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• pp.215-221
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• 1976

In this study, noise arresting effect of the noise control room from the transmission of surrounding noise was tested when the packing noise control rooms were set up in the test room in which the prerecorded noise from an engine room was reradiated at the same level as the original pressure. The inner space of control room A is $3.389m^3(1.19\times1.19\times2.14m)$ having walls furnished with plywood board 9mm in thickness and noise control room door$(60\times45cm) $ and illumination lamp are placed. In case of the control room B, noise absorption board(10mm fiber board which holds the corntype concavity with diameter of 5mm, depth 5mm, space 15mm) is adhered to the internal ceiling and styrol foam boards(20mm) to the walls. The other struction is same as the control room A. Type C is the same as B except wool board(Glass Fiber, 33mm) on the walls. Type D is same as type A except that the thickness of wall is 12mm and wood pyramid type cone$(5\times5\times13cm)$ is adhered to the ceiling ana walls(Fig. 1). When the recorded noise and vibrated noise were controlled in various levels. The noise pressure which passed through the control rooms was measured by sound level meter(Bruel & Kjar 2205, measuring range 37-140dB). In order to calculate the absorption rate in the control rooms the noise pressure was measured at different distances when the recorded noise pressure was radiated. The followings are the results obtained from the experiment. 1. When the noise pressure of the test room was 60dB, transmission rate of type A was $69.7\%$ and increased $3.3\%$ per 10dB. At the same condition, the rate was $53.9\%$ and increased $4.5\%$ per 10dB in type D. Type D was the most effective in noise arresting of the four and the effect was D,C,B and A in order(Fig.2). 2. When the oscillator sound and vessels noise were radiated in 1,000Hz, at one meter distance to the type A and D, the oscillator sound pressure were 77dB and 73dB, while the vessels noise pressure were 73.3dB and 66.2dB respectivley(Fig.3). 3. Refering to the influence of the frequency to the lower oscillator sound(1,000Hz) pressure, both type C and D were almost same at 140cm but type C was 0.3dB lower than type D at 20cm distance(Fig.4).

• Economic and Environmental Geology
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• v.52 no.3
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• pp.223-230
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• 2019

The calcination of oyster shells have been studied as the possible substitute for the limestone used as an absorbent of $SO_2$ gas. However, since pure shells can not be used in calcination process, some impurities are contained and the changes in the characteristics of the calcination products are expected. In this study, the surface characteristics of the calcination products are investigated by mineralogical analysis according to the contents of NaCl, which can be derived from sea water, and sediments on the surface of the shell as impurities. The marine sediments on the shells were mainly composed of quartz, albite, calcite, small amounts of amphibole and clay minerals such as ilite, chlorite and smectite. After calcination of oyster shells mixed with 0.2-4.0 wt% sediments at $900^{\circ}C$ for 2 hours, regardless of the dehydration, dehydroxylation, and phase change of these minerals at the lower temperature than this experiment, no noticeable changes were observed on the specific surface area of the calcined product. However, when mixed with 0.1 to 2.0 wt% NaCl, the specific surface area generally increases as compared with the shell sample before calcination. The specific surface area increases with increasing amount of salt, and then decreases again. This is closely related to the changes of surface morphology. As the amount of NaCl increases, the morphology of the surface is similar to that of gel. It changes into a slightly angular, smaller particle and again looks like gel with increasing amount of NaCl. Our results show that NaCl affects morphological changes probably caused by melting of some oyster shells, but may have different effects on the specific surface area of calcination product depending on the NaCl contents.