• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.1-13
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• 2019

The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) resulted in the deposition of large quantities of radionuclides over parts of eastern Japan. Radioactive contaminants have been observed over a large area including forests, cities, rivers and lakes. Due to the strong adsorption of radioactive cesium by soil particles, radioactive cesium migrates with the eroded soil, follows the surface flow paths, and is delivered downstream of population-rich regions and eventually to coastal areas. In this study, we developed a model to simulate the transport of contaminated sediment in a watershed hydrological system and this model was compared with observation data from eroded soil observation instruments located at the Korea Atomic Energy Research Institute. Two methods were applied to analyze the soil particle size distribution of the collected soil samples, including standardized sieve analysis and image analysis methods. Numerical models were developed to simulate the movement of soil along with actual rainfall considering initial saturation, rainfall infiltration, multilayer and rain splash. In the 2019 study, a numerical model will be used to add rainfall shield effect by trees, evaporation effect and shield effects of surface water. An eroded soil observation instrument has been installed near the Wolsong nuclear power plant since 2018 and observation data are being continuously collected. Based on these observations data, we will develop the numerical model to analyze long-term behavior of radionuclides on land as they move from land to rivers, lakes and coastal areas.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.350-357
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• 2000

This paper evaluated the influence of point source and flow events on inorganic nitrogen fractions at 17 sites of Taechung Reservoir during 1993${\sim}$1994. Total nitrogen (TN) averaged 1.53 mg/L during the study and ranged between 0.70 and 2.56 mg/L. Dissolved inorganic nitrogen(DIN) accounted for >90% of TN regardless of season and location, indicating a nitrogen-rich system showing eutrophic${\sim}$hypereutrophic conditions. Some 67${\sim}$94% of DIN was NO$_{3}$-N, whereas mean level of NH$_{4}$-N was less than 5% of DIN. During monsoon 1993, dilution of NO$_{3}$-N was evident in the headwaters as a result of mixing of lake water with rain water, while NH$_{4}$-N increased>100% compared to the premonsoon. Values of NH$_{4}$-N had a positive correlation with rainfall (r=0.85; p<0.001) and negative correlations with theoretical water residence time(r=-0.90; p<0.001) and conductivity(r=-0.78, p<0.001), respectively. These outcomes suggest that NH$_{4}$-N came from external input from the watershed during the monsoon. In both years, mean TN was greater in the mid-lake sites than any other sites. A great amount of TN in the mid-lake was most pronounced in monsoon 1994 because of an accumulated influence of the point sources during low inflow. Overall data suggest that concentrations of TN in this system did not show large differences along the longitudinal gradients and its distributions is likely determined by point-sources rather than inflow regime.

• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1859-1867
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• 2021

This study investigated seasonal characteristics of the particulate matter (PM) in the atmosphere and rainwater quality in Busan, South Korea, and evaluated the seasonal effect of PM₁₀ concentration in the atmosphere on the rainwater quality using multivariate statistical analysis. The concentration of PM in the atmosphere and meteorological observations(daily precipitation amount and rainfall intensity) are obtained from automatic weather systems (AWS) by the Korea Meteorological Administration (KMA) from March 2020 to August 2020. Rainwater samples (n = 216, 13 rain events) were continuously collected from the beginning of the precipitation using the rainwater collecting device at Pukyong National University. The samples were analyzed for pH, EC (electrical conductivity), water-soluble cations(Na⁺, Mg²⁺, K⁺, Ca²⁺, and NH₄⁺), and anions(Cl^-, NO₃^-, and SO₄^2-). The concentration of PM₁₀ in the atmosphere was steadily measured before and after the precipitation with a custom-built PM sensor node. The measured data were analyzed using principal component analysis (PCA) and Pearson correlation analysis to identify relationships between the concentration of PM₁₀ in the atmosphere and rainwater quality. In spring, the daily average concentration of PM₁₀ (34.11 ㎍/m³) and PM_2.5 (19.23 ㎍/m³) in the atmosphere were relatively high, while the value of daily precipitation amount and rainfall intensity were relatively low. In addition, the concentration of PM₁₀ in the atmosphere showed a significant positive correlation with the concentration of water-soluble ions (r = 0.99) and EC (r = 0.95) and a negative correlation with the pH (r = -0.84) of rainwater samples. In summer, the daily average concentration of PM₁₀ (27.79 ㎍/m³) and PM_2.5 (17.41 ㎍/m³) in the atmosphere were relatively low, and the maximum rainfall intensity was 81.6 mm/h, recording a large amount of rain for a long time. The results indicated that there was no statistically significant correlation between the concentration of PM₁₀ in the atmosphere and rainwater quality in summer.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1285-1294
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• 2021

In recent years, as rainfall is concentrated and rainfall intensity increases worldwide due to climate change, the scale of flood damage is increasing. Rainfall of a previously unobserved magnitude falls, and the rainy season lasts for a long time on record. In particular, these damages are concentrated in ASEAN countries, and at least 20 million people among ASEAN countries are affected by frequent flooding due to recent sea level rise, typhoons and torrential rain. Korea supports the domestic flood warning system to ASEAN countries through various ODA projects, but the communication network is unstable, so there is a limit to the central control method alone. Therefore, in this study, an artificial intelligence-based flood prediction model was developed to develop an observation station that can observe water level and rainfall, and even predict and warn floods at once at one observation station. Training, validation and testing were carried out for 0.5, 1, 2, 3, and 6 hours of lead time using the rainfall and water level observation data in 10-minute units from 2009 to 2020 at Junjukbi-bridge station of Seolma stream. LSTM was applied to artificial intelligence algorithm. As a result of the study, it showed excellent results in model fit and error for all lead time. In the case of a short arrival time due to a small watershed and a large watershed slope such as Seolma stream, a lead time of 1 hour will show very good prediction results. In addition, it is expected that a longer lead time is possible depending on the size and slope of the watershed.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.793-804
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• 2000

Even thought the distribution of the rainfall in the watershed is spatially and temporally vareid, the simulation of the runoff from the watershed is frequently conducted with the constant rainfall distribution assumption. However, the runoff simulated with this assumption indicates over the certain accuracy limitation and the difference by this assumption is bigger in the case of the moving storm which can be frequently indicated with the typhoon, cyclone and hurricane and so on. In this paper, the runoff characteristics of the moving storm are investigated using GIS technique and the isohyetal map observed from 16:00 to 23:00 on August 2, 1999 to the Chun Yang rain gage. The runoff simulated by the moving storms moving to the eight different directions is compared with the others and indicates the big difference with the maximum runoff in the SE direction in the Bokha experimental watershed. Also, the runoff by the moving storm having different moving velocities is compared with the others and indicates the big difference with the bigger discharge in the slowly moving storm. Through the simulation using GIS technique in the watershed, the advantages of the easy preparation of the data and the short computational time can be obtained.

• Journal of Korea Water Resources Association
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• v.52 no.10
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• pp.753-761
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• 2019

Localized heavy storm is one of the major causes of flood damage in urban regions. According to the recent disaster statistics in South Korea, the frequency of urban flood is increasing more frequently, and the scale is also increasing. However, localized heavy storm is difficult to predict, making it difficult for local government officials to deal with floods. This study aims to construct a Flood risk matrix (FRM) using ensemble weather prediction data and to assess its applicability as a means of reducing damage by securing time for such urban flood response. The FRM is a two-dimensional matrix of potential impacts (X-axis) representing flood risk and likelihood (Y-axis) representing the occurrence probability of dangerous weather events. To this end, a regional FRM was constructed using historical flood damage records and probability precipitation data for basic municipality in Busan and Daegu. Applicability of the regional FRMs was assessed by applying the LENS data of the Korea Meteorological Administration on past heavy rain events. As a result, it was analyzed that the flood risk could be predicted up to 3 days ago, and it would be helpful to reduce the damage by securing the flood response time in practice.

• Journal of environmental and Sanitary engineering
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• v.8 no.2
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• pp.25-48
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• 1993

International concern over the environmental pollution is ever increasing, and diversified countermeasures must be devised in Korea also. Global trend, damages, problems and countermeasures with respect to issues mentioned in the Rio Declaration, such as prevention of ozone layer destruction, reduction of migratory atmospheric pollution between neighboring countries, and prevention of global greenhouse effect, were discussed in this report. Conclusion of the report is summarized as follows : A. Measurement, Planning and Monitoring (1) Development and implementation of a global network for measurement and monitoring from the global aspects such factors as related to acid rain(Pioneer substances, pH, sulfate, nitrate), effect of global temperature(Air temperature, $CO_2$, $CH_4$, CFC, $N_2O$) and destruction of ozone layer($CFC_S$). (2) Establishment of network system via satellite monitoring movement of regional air mass, damage on the ozone layer and ground temperature distribution. B. Elucidation of Present State (1) Improvement and development of devices for carbon circulation capable of accurately forecasting input and output of carbon. (2) Developmental research on chemical reactions of greenhouse gas in the air. (3) Improvement and development of global circulation model(GCM) C. Impact Assessment Impact assessment on ecosystem, human body, agriculture, floodgate, land use, coastal ecology, industries, etc. D. Preventive Measures and Technology Development (1) Development and consumption of new energy (2) Development of new technology for removal of pioneer substances (3) Development of substitute matter for $CFC_S$ (4) Improvement of agriculture and forestry means to prevent the destruction of ozone layer and the greenhouse effect of the globe (5) Improvement of housing to prevent the destruction of ozone layer and the greenhouse effect of the globe (6) Development of new technology for probing underground water (7) Preservation of forest (8) Biomass 5. Policy Development (1) Development of strategy model (2) Development of long term forecast model (3) Development of penalty charge effect and expense evaluation methods (4) Feasibility study on regulations By establishing the above mentioned measures for environmentally sound and sustainable development to establish the right to live for humankind and to preserve the one and only earth.

• Economic and Environmental Geology
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• v.32 no.1
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• pp.73-82
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• 1999

The objectives of this study are to investigate soil contamination in the vicinity of abandoned Au-Ag mine and to apply a remediation technique of liming to tailings. In the study area of the Imcheon Au-Ag mine, soils were sampled in and around the mine the analyzed by Atomic Absorption Spectrometry extracted by both 0.1N HCl and aqua regia. Elevated levels of Cd, Cu, Pb and Zn concentrations extracted by 0.1N HCl were found in soils taken from tailings site. These high contents directly influenced metal concentrations in soils taken in the vicinity of the site. This is mainly due to clastic movement by wind and effluent of mine waste water. In addition, relatively enriched concentrations of the metals were found in soils extrated by aqua regia due to strong decomposition of the samples compared with 0.1N HCl extration. According to the statistical approach, metal concentrations in soils by 0.1N HCl had a positive correlation with those by aqua regia extraction. Mine waste waters and stream waters were also sampled around the mine in spring and summer and analyzed by AAS for Cd, Cu, Pb and Zn, and by Ion Chromatography for anions. Like soils developed over tailings, significant levels of metals and sulphates were found in the mine waste waters ranging of 0.2~0.3, 0.5~2.0, 0.2~2.8, 30~50 and 1,240~4,700 mg/l of Cd, Cu, Pb, Zn and $SO_4^{2-}$, respectively. These elevated levels influenced in the stream waters in the vicinity of the tailings site. In seasonal variation of metal and anion contents, relatively high levels were found in waters sampled on summer due to leaching the metals and anions from tailings by rain. This study also examined the possibility of lime treatment for remediation of acid mine tailings and assumed to be 46 tones of pulverized lime for neutralization of the tailings.

• Journal of Ocean Engineering and Technology
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• v.23 no.4
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• pp.64-68
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• 2009

It has been observed that coated steel structures deteriorate more rapidly than the designed lifetime due to acid rain caused by air pollution, etc. Therefore, improving the corrosion resistance of anti-corrosive paint is very important in terms of safety and the economic point of view. In this study, the corrosion resistance of five kinds of anti-corrosive paints, including the Acryl, Fluorine, and Epoxy resin series, were investigated with electrochemical methods, such as corrosion potential measurements, polarization curves, diffusion limiting current density, etc. As a result, the corrosion resistance of the F101 specimen with the fluorine resin series was found to be superior to the other specimens, while E100 with the epoxy resin series also showed a somewhat good corrosion resistance. Furthermore, it was observed that the amount of water and oxygen entering the inner side of a painted film increased with an increase in immersion time, irrespective of the kind of resin series. However, the oxygen diffusion limiting current density of a specimen with good corrosion resistance was relatively decreased compared to other specimens, because of the difficulty of oxygen diffusion penetrating to the inner side of the film. Consequently it is suggested that we can qualitatively evaluate the corrosion resistance of an anti-corrosive paint by measuring the diffusion limiting current density as an electrochemical method.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1168-1179
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• 2006

The validity of an unsteady two-dimensional(2-D) numerical hydrodynamic and pollutant dispersion model(2DNHPDM) was evaluated using the data obtained from I-sa streams in Sooncheon, Chonnam, during rain-fall run-off. Field observations was conducted for 35 hours during the 10 hours rainfall event on 7th May 2005. The water level, 2-D velocity, flow field, and COD at seven points selected along the river were measured at intervals of one hour. The model was applied to describe two-dimensional movement of dissolved pollutants in meandering non-uniform river. Major physical processes affecting the lateral and horizontal mixing of the river flow were simulated. The model was proved effective in describing the hydrodynamics and dispersion of the river pollutants from its major tributaries as well as non-point sources.