• Journal of the Korean earth science society
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• v.37 no.1
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• pp.11-20
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• 2016

Diatoms were studied from the trench sediments around Bangudae petroglyphs in order to better understand the depositional environment before and after the construction of Sayeon dam in Ulsan. There were no diatoms produced from the sediments before the dam construction while the diatoms were produced from the sediments (depth of trench 228 cm) after the construction of the dam. Seventy-five species of diatoms of 27 genera were identified in the trench sediments. The number of diatom valves per gram of dry sediment ranged from $0.2-5.8{\times}10^5g^{-1}$. Four diatom assemblage zones were identified according to the frequency of critical taxa as follows: assemblage zone I, from 228 to 150 cm; assemblage zone II, from 150 to 122 cm; assemblage zone III, from 122 to 62 cm; and assemblage zone IV, from 62 to 0 cm. In addition, based on the environmental indicator species, an analysis was carried out to measure eutrophication, acidity and $Cl^-$ value. Results of the eutrophication and $Cl^-$ values were as follows. Based on the lower 74 cm horizons, the degree of eutrophication middle-high to $Cl^-$ values were lower, upper horizons appeared to eutrophication in the low, and $Cl^-$ values were high. Acidification from low horizons of 122 cm showed a neutral-alkaline degree whereas it exhibited acid in the upper part. In particular, regarding nutrients (TP and TN), the index taxa showed a higher TP value at 175 cm while higher TN value at 62 cm.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.137-144
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• 2000

The observations on the seasonal fluctuation and distributional characteristic of organic matters on surface sediments and its origin were carried out at the 25 stations in Keogeum-sudo, southern coast of Korean Peninsula from February to October in 1993. I made an analysis on the environmental factors for surface sediments such as temperature, ignition loss, chemical oxygen demand, pheopigment, total sulphide, water content, mud content in grain size, COD/IL ratio and COD/sulphide ratio. The results are as follows ; 1) The range of temperature on the surface sediments was between 6.2${\circ}C$ and 24.6${\circ}C$. The highest mean temperatuer of mud was 24.0${\circ}C$ in summer, the lowest 6.6${\circ}C$ in winter. 2) Ignition loss(IL) fluctuated between 1.2% in winter and 16.8% in spring, that is to say, the seasons of increasing in temperature were very high ignition loss. 3) Chemical oxygen demand(COD) showed the highest mean value of 20.52 mg/g dry in summer within the range of 15/46~32.78 mg/g dry, while showed the lowest of 5.79 mg/g dry in winter within the range of 7.4~17.39 mg/g dry. 4) Pheopigment concentrations showed the highest mean value of 4.85 $\mu\textrm{g}$/g dry in autumn within the range of 0.84~9.21 $\mu\textrm{g}$/g dry, while it did the lowest mean value of 1.97 $\mu\textrm{g}$/g dry in summer within the range of 0.23~4.83 $\mu\textrm{g}$/g dry. 5) Total sulphide (H2S) fluctuated between no detect(ND) in spring, and 2.43 mg/g dry in sutumn. The highest mean value was 0.68 mg/g dry in sutumn, the lowest was 0.16 mg/g dry in spring. 6) Water content(WC) and mud content in grain size showed the mean value of 43.2% within the range of 26.5~59.7% and 91.0% within the range of 57.8~99.2%, respectively. 7) By the analytical results on the source of organic matter, it had been dumped from the seaweed farms in Keogeum-sudo coastal waters.

• The Korean Journal of Petroleum Geology
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• v.7 no.1_2 s.8
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• pp.1-6
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• 1999

Natural gas hydrate, a solid compound of natural gas (mainly methane) and water in the low temperature and high pressure, is widely distributed in permafrost region and deep sea sediments. Gas hydrate stability field (GHSF), which corresponds to the conditions of a stable existence of solid gas hydrate without dissociation, depends on temperature, pressure, and composition of gas and interstitial water. Gas hydrate-saturated sediment are easily recognized by the bottom simulating reflector (BSR), a strong-amplitude sea bottom-mimic reflector in seismic profiles. It is known that BSR is associated with the basal boundary of the GHSF, The purpose of this study is to define the GHSF and its occurrence in the southwestern part of Ulleung Basin, East Sea. The hydrothermal gradient is measured using the expandable bathythermograph (XBT) and the geothermal gradient data are utilized from previous drilling results for the adjacent area. By the laboratory work using methane and NaCl $3.0 wt{\%}$ solution, it is shown that the equilibrium pressures of the gas hydrate reach to 2,920.2 kPa at 274.15 K and to 18,090 kPa at 289.95 K for the study area. Consequently, it is interpreted that the lower boundary of the GHSF is about 210 m beneath 400-m-deep sea bottom and about 480 m beneath 1,100-m-deep sea bottom. The resultant boundary is well matched with the depth of the BSR obtained from the seismic data analysis for the study area.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.344-355
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• 2003

Water quality model applicable paddy field was developed using field experiment during 1999 ${\sim}$ 2002. This model involves inputs from fertilization and sediment release as dirac delta function and continuous source function, respectively, and can simulate various processes such as ponded depth, surface drainage, total nitrogen concentration and total phosphorus concentration in a daily basis. The model was calibrated using data collected from field experiments which was irrigated with ground water and validated from field experiments which was irrigated with surface water. The nutrient concentration of surface water depended on the fertilization and dirac delta function can efficiently explain the valiance of nutrient concentration of surface water by fertilizer. As a result of calibration and validation, this model demonstrates good agreement. The model fit efficiencies ($R^2$) of ponded depth, surface concentration of TN and TP were 0.93,0.98 and 0.95, respectively for calibration, and those of TN and TP were 0.99 and 0.70, respectively for validation. We can apply lake and reservoir model to analysis paddy field considered with shallow ponded system, but it will need so many parameters and have much uncertainty. Fortunately, paddy field have a series of cultural practices yearly basis, such as irrigation-fertilization-forced drain-harvest with a similar time , so simple model may explain the mechanism for paddy field. Water quality model for paddy field developed in this study is simply, needs little parameters, but appeared high applicability to evaluate paddy filed drainage. We recommend this model to estimate nutrient loading from paddy field and establish best management practice.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.735-749
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• 2018

In this study, one studied the principal factors and water-quality components that determine the concentration of chemical oxygen demand (COD) in seawater in estuaries, such as the Han, Geum, Youngsan, Seomjin, and Nakdong rivers in Korea. The principal factors determining the concentration of COD in seawater indicated by the principal component analysis were salinity, exogenous origin and autochthonous resources based on chlorophyll-a. Moreover, organic matter in the submarine sediment layer also had a secondary effect. Regression slope assessed the contribution of water-quality components to determine the concentration of COD in the estuary. One found that the effect of salinity on the overall survey was significant. Moreover, the effect of chlorophyll-a was also appeared in April and August. In each estuary, the most significant contribution factor was chlorophyll-a in the Nakdong River and salinity in the Han and Yongsan rivers. The contribution of salinity and chlorophyll-a were found to be the largest in the Geum River. The salinity and chlorophyll-a in the Seomjin River showed a low contribution.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.726-734
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• 2018

The total number of Sea Area Utilization Consultation in the environment management sea areas reviewed from 2015 to 2017 were 60. The number of development projects in the environment conservation sea areas decreased steadily, but special management sea areas increased. Development types in environment management sea areas showed that artificial structure installation was the highest ratio, followed by fishery port development and construction of habor and coastal maintenance and sea water intake and draining. By comparing the trend of water quality changes using marine environment information system (MEIS) data in the environment management areas from 2006 to 2017, COD showed no significant changes but the environment conservation sea areas increased slightly, and the concentration of TN and TP decreased. Gwangyang and Masan bays in the special management sea areas and Gamak bay in the environment conservation sea areas displayed oxygen deficient mass in the summer. As the use of development projects of the environment management sea areas are performed continuously, an analysis of the status of sufficient water quality changes is necessary for environmental impact assessment (Sea Area Utilization Consultation) in the marine environment and should be evaluated mainly for management of contamination by diagnosing thoroughly water quality effects and the pollution of sediment. Especially, the water quality goal for the purpose of designation in each of the environment management sea areas is set clearly, connection with pollution source control and the total pollution load management system (TPLMS) should be proposed and measured to reduce the amount of contaminated water.

• Korean Journal of Environment and Ecology
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• v.29 no.5
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• pp.743-752
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• 2015

We studied the spatio-temporal microalgal (phytoplankton and benthic diatoms) and environmental changes of the Hajeonri intertidal zone from February to November 2014. Seawater and phytoplankton analysis were conducted all through the months. The species, composition and abundance of phytoplankton and environmental factors were measured. As a result, diatom was dominant among a total of 113 species identified. On a seasonal basis (Feb. May, Aug., Nov.), we carried out studies on benthic diatoms on the surface of the sediments and their habitats at nine stations on the transect line at Hajeonri at low tide. The grain of the surface sediments was mainly composed of sandy silt and sandy mud. Organic pollution level was low. Benthic microalgal biomass (chlorophyll ${\alpha}$) was high in the spring and summer. A total of 163 benthic diatom species were identified. Navicula sp.1 and Paralia sulcata were dominant over the study period. Five diatom species were observed both in water column and on surface sediment at the same time.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.157-171
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• 2001

This study investigated the effects of Pb/Tl ratio, Pb concentration and concomitant matrix elements on the measurement of Pb isotope ratios using multi-collector ICP/MS (AXIOM MC model). Accuracy and reproducibility of Pb isotope ratios in NBS 981 solution were estimated for 42 data measured from March to August 2001. Pb isotopes measured in rocks, bronzes and sediments were compared to data measured by TIMS. Reproducibilities for $^{206}Pb/^{204}Pb,\; ^{207}Pb/^{204}Pb,\;and\;^{208}Pb/^{204}Pb$ ratio were about 500 ppm (2sd) and for $^{207}Pb/^{206}Pb$\;and\;^{208}Pb/^{206}Pb$ were 100~200 ppm for 200 ng of Pb in NBS 981 solution. The optimum conditions for the analysis of Pb isotope ratios with AXIOM MC for best accuracy and reproducibility were defined as follows; 1) Pb/Tl ratio is about 10 2) Pb concentration is about 100 ng/ml 3) correction for mass discrimination is performed by exponential law using 2.3887 of $^{205}Tl/^{203}Tl$ and Pb mass fractionation factor empirically obtained from $ln(^{208}Pb/^{206}Pb)-ln(^{205}Tl/^{203}Tl)$ relationship. The sample data measured with MC/ICP/MS for acid-digested and chemically separated rock samples, and acid-digested bronze samples and sediment samples coincide with those of TIMS within analytical errors. Therefore, MC/ICP/MS is a rapid analytical technique for Pb isotope ratios with the similar precision compared with TIMS.

• Economic and Environmental Geology
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• v.9 no.1
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• pp.1-11
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• 1976

It is believed that geological survey, drilling and geophysical survey which was carried out on Tertiary deposits in Pohang is a valuable but through the studying of many Tertiary sediments in Japan discovered many questions on analysis of final report prepared by National geological survey. The main reason is: 1. The seismic sound velocity which have regulated in the final report prepared by geological survey for Tertiary deposits in Pohang was 1,500-2,000m/sec in spite of oil bearing sediments of same age in Japan are 2,000-3,800m/sec. These may means the requirement of reconsideration of seismic velocity for Tertiary deposits in Pohang and required to have a dipper drilling. 2. Stratigraphically, geophysically, and paleontologically, the Tertiary deposits in Pahang land area is similar with that of Nishiyama-Hunakawa formations of Akita oil field in Japan. Nishiyama-Hunakawa formation is the main oil bearing formation in Japan. 3. Those valcanic rock including andestitic rock and liparitic rock which have extensively distributed over either at land area or at sea bottom, assumed by geological survey as the base of Tertiary sediments. But in case of Japan many oil bearing deposits are in over laid by these kind of volcanic rock. Therefore a possible of same condition with Japan is presumable on Tertiary sediments in Pohang. 4. It is believed that the Tertiary sediments of land area in Pohang is the extension of offshore basin but is wandering that the final report submitted by geologic survey have not remain any word on report of ECAFE discribed so much problematics as followed: A. Although it was assumed that no great thickness exceeding 1,000 meters, or major structures would be encountered in the Tertiary offshore sequence, it was hoped that shallow hydrocarbon deposits might be found, because these sediment are lithologically similar to those of the same age in the producing area of the northwest Honshu region of Japan where hydrocarbon are extracted from depths of only 500 to 600 meters. B. Four possible hydrocarbon trap conditions are represented in the survey area: anticlinal folds, faults, pinch outs, along the igneous basement and lateral facies changes. C. Most of the prime possible reservoir area are beyond the 50 meter water depth mark, except for the structures in Yonil Bay. D. Despite the shallowness of the offshore basin, sufficient trap condition exist in the area to warrant further exploration for hydrocarbon. 5. All of the problems mentioned above have gave us a strong reasons to have us hesitating to make a final conclusion on Tertiary problems in Pohang, before to have a drill to a depth to 3,000 meters or more whatever it is the Tertiary or a Mesozoics below 1,000 meters.

• Ecology and Resilient Infrastructure
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• v.4 no.4
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• pp.207-215
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• 2017

Hydraulic issues such as flow resistance, side wall correction, sediment, erosion and deposition, and channel design have close relation with distribution of bed shear stresses but the measurement of the distribution of bed shear stresses is not easy. In this study the Preston tube which makes possible relatively simple measurement of bed shear stresses is used to analyze the characteristics of bed shear distribution in compound open channels with different depth ratio. The Preston tubes are made and calibrated to develop the calibration formula and then they are applied to measure bed shear stress distribution in 5 cases depth ratio condition of compound channels. The results are compared with former experiment data, and characteristics of bed shear stress distributions are studied with different channel scales and Reynolds numbers. Although bed shear distributions with depth ratio show overall agreement with former studies, some differences are verified in bed shear variation, formation of inflection point in main channel, and distribution near floodplain junction which are due to high Reynolds number. Through the study applicability of the Preston tubes are also verified and characteristics of bed shear distribution in compound channels are suggested with Reynolds number and depth ratio.