• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.4
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• pp.322-331
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• 2016

Oil budget calculator identifies the removal pathways of spilled oil by both natural and response methods, and estimates the remaining oil required response activities. A oil budget calculator was newly developed as a response tool for Deepwater Horizon oil spill incident in Gulf of Mexico in 2010 to inform clean up decisions for Incident Comment System, which was also successfully utilized to media and general public promotion of oil spill response activities. This study analyzed the theoretical background of the oil budget calculator and explored its future application to Korea. The oil budge calculation of four catastrophic marine pollution incidents indicates that 3~8% of spilled oil was removed mechanically by skimmers, 1~5% by in-situ burning, 4.8~16% by chemical dispersion due to dispersant operation, and 37~56% by weathering processes such as evaporation, dissolution, and natural dispersion. The results show that in-situ burning and chemical dispersion effectively remove spilled oil more than the mechanical removal by skimming, and natural weathering processes are also very effective to remove spilled oil. To apply the oil budget calculator in Korea, its parameters need to be optimized in response to the seasonal characteristics of marine environment, the characteristics of spilled oil and response technologies. A new algorithm also needs to be developed to estimate the oil budget due to shoreline cleanup activities. An oil budget calculator optimized in Korea can play a critical role in informing decisions for oil spill response activities and communicating spill prevention and response activities with the media and general public.

• Journal of Radiation Protection and Research
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• v.25 no.2
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• pp.75-80
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• 2000

The predicted results of INDAC code were compared with measured $^3H$ concentrations in air and pine-needle around the Wolsung site. The optimal sets of input data to INDAC were in addition selected by comparing the measured values with the predicted values of INDAC based on various conditions such as the release modes of effluents into the environment, the classification of wind classes, and the consideration of terrain. The predicted $^3H$ concentrations in air and pine-needle were shown to have good agreement with measured values, although there are some limitations such as uncertainties in measured values, complex topology around the site, and the land-sea breeze effects. The assumption on the $^3H$ behavior in vegetables or plants that the ratio of $^3H$ concentration in plant water to $^3H$ concentration in atmospheric water is 1/2 was shown to be conservative in terms of the audit calculation performed by the regulator. It was also found that data sets based on mixed mode and no terrain data were not appropriate for the audit calculation ensuring the compliance with regulations. Thus, if the mixed mode is considered as the release mode of effluents into the environment, meteorological data measured at 58 m height and terrain data should be used to evaluate the atmospheric dispersion factor.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.657-672
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• 2008

The purposes of this study are to investigate the hydrogeochemical characteristics of groundwaters around Keumsan municipal landfill, and to evaluate the contaminant dispersion from the landfill and its environmental impact. To achieve these goals, groundwater quality logging, hydrochemical analysis, multivariate statistical analysis, and contaminant transport modeling were performed. The water quality logging indicated a leaking from the landfill at the depth of 4-12m around a leachate sump. Electrical conductivity data indicated that groundwaters within 70-100m from landfill were affected by the landfill leakage. Principal components 1 and 2 obtained from principal components analysis (PCA) reflect the influence of leachate and the characteristics of aquifer media, respectively. The results of principal component analysis also indicated the natural attenuation processes such as cation exchange, sorption, and microbial biodegradation. The modeling results showed that groundwater flow westward along a valley from the landfill and contaminants transport accordingly.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.4
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• pp.295-303
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• 2012

Based on the data observed and analyzed on a groundwater flow system in the KURT (KAERI Underground Research Tunnel) site, the transport of radionuclides, which were assumed to be released at the supposed position, was calculated on the time-domain. A groundwater pathway from the release position to the surface was identified by simulating the groundwater flow model with the hydrogeological characteristics measured from the field tests in the KURT site. The elapsed time when the radionuclides moved through the pathway is evaluated using TDRW (Time Domain Random Walk) method for simulating the transport on the time-domain. Some retention mechanisms, such as radioactive decay, equilibrium sorption, and matrix diffusion, as well as the advection-dispersion were selected as the factors to influence on the elapsed time. From the simulation results, the effects of the sorption and matrix diffusion, determined by the properties of the radionuclides and underground media, on the transport of the radionuclides were analyzed and a decay chain of the radionuclides was also examined. The radionuclide ratio of the mass discharge into the surface environment to the mass released from the supposed repository did not exceed $10^{-3}$, and it decreased when the matrix diffusion were considered. The method used in this study could be used in preparing the data on radionuclide transport for a safety assessment of a geological disposal facility because the method could evaluate the travel time of the radionuclides considering the transport retention mechanism.

• Nuclear Engineering and Technology
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• v.22 no.1
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• pp.20-28
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• 1990

In this study the migration experiment using packed column with crushed tuff was conducted as a basic research to develop migration model of radionuclides through geologic media. The main emphasis was put on evaluating the validity of migration models. For this, two models were introduced: one is the model which is based on the assumption of instantaneous equilibrium reaction and the other the model based on kinetic process such as intraparticle diffusion. The coefficient of hydrodynamic dispersion in packed column was determined using iodine as nonsorbing tracer. The hydrodynamic dispersion coefficient, D$_{L}$ was shown to be 0.11$\times$10$^{-2}$ $\textrm{cm}^2$/min under the condition of the column porosity of 0.483 and the average water velocity of 0.915$\times$10$^{-2}$ cm/min. The distribution coefficient, Kd of Cs-137 on crushed tuff was 11.3 cc/g at the concentration of 2$\times$10$^{-6}$ M and the temperature of 2$0^{\circ}C$. The breakthrough curve of Cs-137 through packed column was shown to have an asymmetric curve in which long trailing tail appears at the end part of the curve. The results obtained from the comparison of introduced models with experimental data indicated that the mass transfer model with intraparticle diffusion as rate-controlling step simulated the behaviors of Cs-137 migration more adequately, when compared with the bulk reaction model in which the assumption of instantaneous equilibrium reaction was maded. Consequently, the intraparticle diffusion was found to be an important factor in the migration of Cs-137 through packed column.n.

• Journal of Aquaculture
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• v.7 no.4
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• pp.239-249
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• 1994

This study was conducted to elucidate mixing characteristics of the media to dertermine hydraulic model parameters of the three phase fluidized bed for the water quality management of aquaculture. The volume and H/D ratio of the reactor were 1.76 Liter and 10.9, respectively. The experimental results showed that variance $(\sigma^2)$ and dispersion number $(D/{\mu}L)$ were above 0.47 and $0.35\~\infty$, respectively. Therefore, the condition of the reactor was almost ideal complete mixing. The dependence of the overall oxygen-transfer coefficient $(K_{La})$ on each experimental variables through a multple linear regression was given by the following equation ; $$K_{La}\;=\;44.9(D_i/D_c)^{-0.4611}\;A_f^{0.8622}\;C_m^{-0.0746}\;d_p^{-0.4302}$$

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.96-101
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• 2010

A pulse radar system has been developed recently to detect dormant underground tunnels that are deeply located at depths of hundreds of metres. To check the ability of the radar system to detect an obliquely oriented tunnel, five different borehole pairs in the tunnel test site were chosen so that the horizontal lines-of-sight cut the tunnel axis obliquely, in $15^{\circ}$ steps. The pulse radar signatures were measured over a depth range of 20 m around the centre of the air-filled tunnel. Three canonical parameters, consisting of the arrival time, attenuation, and dispersion time were extracted from the first and second peaks of the measured radar signatures. Using those parameters, the radar system can detect obliquely oriented tunnels at various angles up to 45 from the transmitter-receiver line of sight.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.1-7
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• 2003

A modified model was developed for solute transport in porous media that can consider the movement of an LNAPL above the water table. From the results of sensitivity analyses with and without considering LNAPL movement, there are some differences according to the hydraulic gradient, the quantity of oil leakage and dispersivity. The mean deviation between the model in this study and a conventional model without LNAPL movement increases as the hydraulic gradient decreases and the quantity of oil leakage increases. Variation of dispersivity has no influence on the magnitude of the mean deviation. However, the spatial distribution of the deviation between the two models is wider as dispersivity increases. Furthermore, groundwater is at high risk of contamination in the vertical direction in the case that transverse dispersion value is large. A conventional model underestimates the concentration of solute in an aquifer where the movement of an LNAPL cannot be negligible: Based on the study results, it is important to understand how fast the LNAPL moves on the water table for realistic prediction of solute transport in an aquifer with the movable LNAPL on the water table.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.419-429
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• 2014

Recent studies have been reported the presence of Endocrine Disrupting Compounds, Pharmaceuticals and Personal Care Products (EDC/PPCPs) in surface and wastewater, which could potentially affect to the complicate behavior in coupled presence of nano-colloid particles and surfactants (adsorption, dispersion, and partitioning). In this study, the adsorption of EDC/PPCPs by Single Walled Carbon Nanotubes (SWNTs) as a representative of nano-particles in cationic surfactant solutions were investigated. Hydrophobic interactions (${\pi}-{\pi}$ Electron Donor-Acceptor) have been reported as a potential adsorption mechanisms for EDC/PPCPs onto SWNTs. Generally, the adsorptive capacity of the relatively hydrophobic EDC/PPCPs onto SWNTs decreased in the presence of cationic surfactant (Cetyltrimethyl Ammonium Bromide, CTAB). This study revealed that the competitive adsorption occurred between CTAB cations and EDC/PPCPs by occupying the available SWNT surface (CTAB adsorption onto SWNTs shows five-regime and maximum adsorption capacity of 370.4 mg/g by applying the BET isotherm). The adsorption capacity of $17{\alpha}$-ethinyl estradiol (EE2) on SWNT showed the decrease of 48% in the presence of CTAB. However, the adsorbed naproxen (NAP) surely increased by forming hemimicelles and resulted in a favorable media formation for NAP partition to increase SWNTs adsorption capacity. The adsorbed NAP increased from 24 to 82.9 mg/g after the interaction of CTAB with NAP. The competitive adsorption for EDC/PPCPs onto SWNTs is likely to be a key factor in the presence of cationic surfactant, however, NAP adsorption showed a slight competition through $CH_3-CH_3$ interaction by forming hemimicelles on SWNT surface.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.269-273
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• 2013

Underwater acoustic channels are generally recognized as one of the most difficult communication media because of the multipath propagation, dispersion, and so on. MIMO (Multiple-input multiple-output) techniques have been actively pursued in underwater acoustic communications recently to increase the data rate over the bandwidth-limited channels. The transmit diversity techniques can be applied in this case, and one of them is Alamouti's scheme. In this paper the performances of the transmit diversity technique are evaluated via experiment. Two transmitters and two receivers were used in experiment, and the experiment was performed in indoor water tank. The error rate 5~8% was confirmed in experimental results, and these are the improved values than the error rate 14.8% for SISO(Single-input single-output) channel under same data rate condition.