• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.8-17
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• 2006

Laboratory scale experiments were performed to investigate the removal efficiency of the in-situ chemical oxidation method and the air-sparging method for diesel contaminated soil and groundwater. Two kinds of diesel contaminated soils (TPH concentration : 2,401 mg/kg and 9,551 mg/kg) and groundwater sampled at Busan railroad station were used for the experiments. For batch experiments of chemical oxidation by using 50% hydrogen peroxide solution, TPH concentration of soil decreased to 18% and 15% of initial TPH concentration. For continuous column experiments, more than 70% of initial TPH in soil was removed by using soil flushing with 20% hydrogen peroxide solution, suggesting that most of diesel in soil reacted with hydrogen peroxide and degraded into $CO_2$ or $H_2O$ gases. Batch experiment for the air-sparging method with artificially contaminated groundwater (TPH concentration : 810 mg/L) was performed to evaluate the removal efficiency of the air-sparging method and TPH concentration of groundwater decreased to lower than 5 mg/L (waste water discharge tolerance limit) within 72 hours of air-sparging. For box experiment with diesel contaminated real soil and groundwater, the removal efficiency of air-sparging was very low because of the residual diesel phase existed in soil medium, suggesting that the air-sparging method should be applied to remediate groundwater after the free phase of diesel in soil medium was removed. For the last time, the in-situ box experiment for a unit process mixed the chemical oxidation process with the air-sparging process was performed to remove diesel from soil and groundwater at a time. Soil flushing with 20% hydrogen peroxide solution was applied to diesel contaminated soils in box, and subsequently contaminated groundwater was purified by the air-sparging method. With 23 L of 20% hydrogen peroxide solution and 2,160 L of air-sparging, TPH concentration of soil decreased from 9,551 mg/kg to 390 mg/kg and TPH concentration of groundwater reduced to lower than 5 mg/L. Results suggested that the combination process of the in-situ hydrogen peroxide flushing and the air-sparging has a great possibility to simultaneously remediate fuel contaminated soil and groundwater.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.spc
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• pp.30-36
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• 2022

A sensor is needed to continuously and automatically measure the change in HNS concentration in industrial facilities that directly discharge to the sea after water treatment. The basic function of the sensor is to be able to detect ppb levels even at room temperature. Therefore, a method for increasing the sensitivity of the existing sensor is proposed. First, a method for increasing the conductivity of a film using a conductive carbon-based additive in a nanoparticle thin film and a method for increasing ion adsorption on the surface using a catalyst metal were studied.. To improve conductivity, carbon black was selected as an additive in the film using ITO nanoparticles, and the performance change of the sensor according to the content of the additive was observed. As a result, the change in resistance and response time due to the increase in conductivity at a CB content of 5 wt% could be observed, and notably, the lower limit of detection was lowered to about 250 ppb in an experiment with organic solvents. In addition, to increase the degree of ion adsorption in the liquid, an experiment was conducted using a sample in which a surface catalyst layer was formed by sputtering Au. Notably, the response of the sensor increased by more than 20% and the average lower limit of detection was lowered to 61 ppm. This result confirmed that the chemical resistance sensor using metal oxide nanoparticles could detect HNS of several tens of ppb even at room temperature.

• Journal of Chest Surgery
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• v.34 no.8
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• pp.583-590
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• 2001

The aim of this study was to compare one-year graft patency after coronary artery bypass grafting without cardiopulmonary bypass(OPCAB) with that of conventional CABG and that of on-pump beating CABG, and to demonstrate any differences in patency of various conduits among the three groups. Material and Method: We analyzed the results of OPCAB cases(group I; n=122) compared with those of conventional CABG cases(group II; n=65) and those of on-pump beating CABG cases(group III; n=19). In group I, coronary angiography(CAG) was performed immediately postoperatively and 1 year after surgery. In group II and III, CAG was performed 1 year after surgery. Graft patency was graded as grade A(excellent), grade B(fair), or grade O(occluded). Result: The average number of distal anastomoses in groups I, II, and II were 3.1$\pm$1.1, 3.7$\pm$0.9, and 3.6$\pm$0.9, respectively. In group I, postoperative CAG was performed in 92%(112/122) of patients before discharge. The patency rate(grade A+B) was 96.4$(162/168) for arterial grafts, and 85.6%(160/187) for saphenous vein grafts(SVG). One-year follow-up CAG was performed in 74%(90/122) of patients. The patency rate was 97.8%(132/135) for arterial grafts, and 67.9%(106/156) for SVG. In group II, one-year follow-up CAG was performed in 65%(42/65) of patients. The patency rate(grade A+B) was 93.5%(43/46) for arterial grafts, and 86.8%(33/38) for SVG. Conclusion: Our results demonstrated that the patency rate of SVG after OPCAB was significantly lower than that of arterial grafts in the early postoperative CAG(p<0.001), and was also significantly lower than those of SVG of group II(p<0.001) and group III(p<0.01) in the postoperative one-year CAG, although there was no significant difference is one-year patency of arterial grafts among the three groups. Our data suggest that a specific perioperative anticoagulant therapy may be advisable in patients undergoing OPCAB with SVG.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.9 no.2
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• pp.227-236
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• 1998

Objectives：Conduct disorder is one of the most frequent diagnosis in outpatient and inpatient mental health facilities for children and adolescents. This study investigated the clinical characteristics of children and adolescents with conduct disorder. Methods：The study employed a retrospective review of 45 inpatients diagnosed with conduct disorder by DSM-IV criteria at SNUH Child Psychiatric Unit from 1993, March to 1998, September. Results：The results were as follows：1) The sex ratio was 2：1, male dominant. Mean age on admission was $12.8{\pm}2.4$ years old(male：$12.2{\pm}2.3$, female：$14.1{\pm}2.1$). The mean age of male subjects was significantly lower than that of female subjects(p<.05). 2) We classified all subjects according to child- or adolescent-onset type by DSM-Ⅳ. Childhoodonset type was 42.2%, and adolescent-onset, 57.8%. The onset of male subjects were significantly earlier than that of female subjects(p<.05). 3) The most common complaint was 'serious violation of rules'(77.8%) by DSM-Ⅳ dimensions, while the most common single symtom was 'run away from home overnight at least twice while living in parental or parental surrogate home'(48.9%). 4) The comorbid psychopathology of the subjects were frequently described as follows, in order of frequency：substance use(42.2%), ADHD(35.6%), depression(20.0%), tic disorder(11.1%), bipolar disorder(4.4%). 5) On MMPI, both Pd and Ma subscales got the highest scores. The mean of total IQ by KEDIWISC was $100.0{\pm}15.1$. Female subjects' IQ was higher than that of male subjects. 6) Regarding the number of visits to the OPD after discharge, many subjects(33.3%) had visited OPD fewer than four times. Conclusions：In this study, the male to female ratio of adolescent type showed a decreasing trend. An interesting finding was the fact that socio-economic circumstances, as well as the level of education among patients, were higher than those of previous studies. The subjects' problem were also principally self contered and posed no threat to others.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.1
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• pp.24-35
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• 2016

To assess the relationship between environmental factors and seasonal phytoplankton community structure, we investigated abiotic and biotic factors in Ulsan Bay, Korea. We divided the bay into two areas based on geographical characteristics and compared the difference in each factor between inner and outer bay with t-test statistics. As a result, temperature in the outer bay was higher than that of the inner bay during winter (t = -5.833, p < 0.01) and autumn (p > 0.05). However, opposite trend was observed during spring (t = 4.247, p < 0.01) and summer (t = 2.876, p < 0.05). Salinity was significantly lower in the inner bay than in the outer bay in winter, spring, and summer (p < 0.01). However, the salinity was not significantly different between the inner and the outer bay in the autumn (p > 0.05). In particular, high nutrient concentration was observed in most stations during winter season due to vertical well mixing. The nutrient concentration was significantly higher in surface layers of inner bay after rainfall, particularly in the summer. The relative contribution (approximately 70%) of < $20{\mu}m$ (nano and pico) size phytoplankton was increased in all seasons with continuously low nutrients from the offshore water due to their adaption to low nutrient without other large competitors. Interestingly, high population of Eutreptiella gymnastica was kept in the inner bay during the spring and summer associated with high DIN (nitrate+nitrite, ammonium) after river discharge following rainfall, suggesting that DIN supply might have triggered the increase of Eutreptiella gymnastica population. In addition, high density of freshwater species Oscillatoria sp. and Microcystis sp. were found in several stations of the inner bay that were provided with large amounts of freshwater from the Tae-wha River. Diatom and cryptophyta species were found to be dominant species in the autumn and winter. Of these, centric diatom Chaetoceros genus was occupied in the outer bay in the autumn. Cryptophyta species known as opportunistic micro-algae were found to have high biomass without competitors in the inner bay. Our results demonstrated that Ulsan Bay was strongly affected by freshwater from Tae-wha River during the rainy season and by the surface warm water current from the offshore of the bay during dry season. These two external factors might play important roles in regulating the seasonal phytoplankton community structures.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.3
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• pp.317-324
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• 2007

Fluorescence measurements of dissolved organic matter(DOM) have the superior advantages over other analysis tools for applying to water quality management. A preliminary study was conducted to test the feasibility of applying synchronous fluorescence measurements for tracing and monitoring pollution sources in a small stream located in an upstream area of the Sooyoung watershed in Busan. The water quality of the small stream is affected by leachate from sawdust pile and discharge of untreated sewage. The sampling sites included an upstream site, two pipes discharging untreated sewage, leachate from sawdust, and a downstream site. Of the five field samples, the leachate was distinguished from the other samples by a high peak at a lower wavelength range and a blunt peak at 350nm, suggesting that synchronous fluorescence can be used as a discrimination tool for monitoring the pollution. The efficacy of various indices derived from the spectral features to discriminate the pollution source was tested for well-defined mixture of the sawdust leachate and the upstream stream by comparing (1)the difference between measured values and those predicted based on mass balance and the characteristics of the two samples and (2)the linear correlations between index values and mass ratios of the sample mixtures. Of various discrimination indices selected, fluorescence intensities at 276 nm$({\Delta}\lambda=30nm)$and 347 nm$({\Delta}\lambda=60nm)$ were suggested as promising potential discrimination indices for the sawdust pollution source. Despite the limited number of samples and the study area, this study illustrates the evaluation process that should be followed to develop rapid, low-cost discrimination indices to monitor pollution sources based on end member mixing analyses.

• Journal of Korean Society of Forest Science
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• v.53 no.1
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• pp.44-55
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• 1981

Neutral sulfite precooked fir chips were refined in the Asplund Laboratory Defibrator at various temperature ($20^{\circ}C$, $120^{\circ}C$ and $180^{\circ}C$). The effects of refining temperatures on the physical property and morphological structure of the resulting pulps were discussed. Yields of precooked chips (84%, 92% and 100%) and refining temperature affected remarkably the yield of refined pulp, its beatability, sheet strength and morhphological characteristics. Pulp yield and beatability decreased with increasing refining temperature. Fiber surface of unbeaten pulp from precooked chips of 84% yield was to some extent covered by the secondary wall, while that of the pulp form precooked yield of 92% by the compound middle lamella. In the case of uncooked chips, fibers were damaged heavily, and the exposed fiber surface resulted from the equal amount of the secondary wall and the compound middle lamella. In the case of pulps prepared from precooked chips of higher yields (92% and 100%), sheet strength increased linearly as sheet density increased. But at the same sheet density, pulp from lower precooked yield (84%) had better sheet strength after open discharge refining as compared to pressurized refining, because pulp from the former had much amounts of fines fraction of higher water retention value than the latters. And there was observed a little difference in fiber length distribution but nearly similar in its morphology with increasing refining temperature.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.92-100
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• 2016

Low-temperature conversion of nitrogen oxides using plasma-assisted hydrocarbon selective catalytic reduction of (HC-SCR) was investigated. Plasma was created in the catalyst-packed bed so that it could directly interact with the catalyst. The effect of the reaction temperature, the shape of catalyst, the concentration of n-heptane as a reducing agent, the oxygen content, the water vapor content and the energy density on $NO_x$ removal was examined. $NO_x$ conversion efficiencies achieved with the plasma-catalytic hybrid process at a temperature of $250^{\circ}C$ and an specific energy input (SIE) of $42J\;L^{-1}$ were 83% and 69% for one-dimensional Ag catalyst ($Ag\;(nanowire)/{\gamma}-Al_2O_3$) and spherical Ag catalyst ($Ag\;(sphere)/{\gamma}-Al_2O_3$), respectively, whereas that obtained with the catalyst-alone was considerably lower (about 30%) even with $Ag\;(nanowire)/{\gamma}-Al_2O_3$ under the same condition. The enhanced catalytic activity towards $NO_x$ conversion in the presence of plasma can be explained by the formation of more reactive $NO_2$ species and partially oxidized hydrocarbon intermediates from the oxidation of NO and n-heptane under plasma discharge. Increasing the SIE tended to improve $NO_x$ conversion efficiency, and so did the increase in the n-heptane concentration; however, a further increase in the n-heptane concentration beyond $C_1/NO_x$ ratio of 5 did not improve the $NO_x$ conversion efficiency any more. The increase in the humidity affected negatively the $NO_x$ conversion efficiency, resulting in lowering the $NO_x$ conversion efficiency at the higher water vapor content, because water molecules competed with $NO_x$ species for the same active site. The $NO_x$ conversion efficiency increased with increasing the oxygen content from 3 to 15%, in particular at low SIE values, because the formation of $NO_2$ and partially oxidized hydrocarbon intermediates was facilitated.

• Economic and Environmental Geology
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• v.36 no.2
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• pp.89-101
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• 2003

River deposits and farmland soils were analyzed to investigate the pollution level of heavy metals in the vicinity of the Goro abandoned Zn-mine. Surface (0-40 cm) and subsurface (40-100 cm) soils were collected around a main river located at the lower part of the Goro mine, and analyzed by ICP-MS for Cd, Cu, Pb, Zn and Cr after 0. 1N HCI extraction and by AAS for As after IN HCI extraction. Concentrations of cadmium and lead at the surface river deposits close to the mine were over the Soil Pollution Warning Limit (SPWL), and 43% of sample sites (6 of 14 samples) were over SPWL for As suggesting that river deposits were broadly contaminated by arsenic. Results from farmland soil analysis showed that surface soils were contaminated by heavy metals, while only arsenic was over SPWL at 50% of sampling sites. Main pollution mechanism around the Goro mine was the discharge of mine tailing and waste rocks from the storage site to the river and to adjacent farmland during flood season. Pollution Grades for sample locations were prescribed by the Law of Soil Environmental Preservation, suggesting that the pollution level of heavy metals around the Goro mine was serious, and the remediation operation fur arsenic and the isolation of mine tailing and waste rocks from river and farmland should be activated to protect further contamination. The area needed to clean up was estimated from pollution distribution data and the remediation methods such as a soil washing method and a soil improvement method were considered as the further remediation operation for arsenic contaminated soils and river deposits around the Goro abandoned mine.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.212-221
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• 2011

Wastewater treatment plants (WWTPs) are required to meet the reinforced discharge standards which are differentiated as 0.2, 0.3 and 0.5 mg-TP/L for the district I, II and III, respectively. Although most of WWTPs are operating advanced biological phosphorus removal system, the supplementary phosphorus treatment facility using chemical addition should be required almost at all WWTPs. Therefore, water quality data from several exemplary full-scale plants operating phosphorus treatment process were analyzed to evaluate the reliability of removal performance. Additionally, a series of jar tests were conducted to find optimal coagulants dose for phosphorus removal by chemical precipitation and to describe characteristics of the reaction and sludge production. Chemical costs and the increasing sludge volume in physicochemical phosphorus removal process were estimated based on the results of jar tests. The minimum coagulant (aluminium sulfate and poly aluminium chloride) doses to keep TP concentration below 0.5 and 0.2 mg/L were around 25 and 30 mg/L (as $Al_2O_3$), respectively, in the mixed liquor of activated sludge. In the tertiary treatment facility, relatively lower coagulant doses of 1/12~1/3 the minimum doses for activated sludge were required to achieve the same TP concentrations of 0.2~0.5 mg/L. Increase in suspended solids concentration due to chemical precipitates in mixed liquor was estimated at 10~11%, compared to the concentration without chemical addition. When coagulant was added into mixed liquor, chemical (aluminium sulfate) cost was estimated to be 4~10 times higher than in secondary effluent coagulation/separation process. Sludge production to be wasted was also 4~10 times higher than secondary effluent coagulation/separation process.