• Journal of radiological science and technology
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• v.21 no.2
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• pp.36-42
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• 1998

Treatment of a large diseased area with electron often requires the use of two or more adjoining fields. In such cases, not only electron beam divergence and lateral scattering but also fields overlapping and separation may lead to significant dose inhomogeneities(${\pm}20%$) at the region of junction of fields. In this study, we made Acrylic Electron Wedges to improve dose inhomogeneities(${\pm}5%$) in these junction areas and to apply it to clinical practices. All measurements were made using 6, 9, 12, 16, 20 MeV Electron beams from a linear accelerator for a $10{\times}10\;cm$ field at 100cm of SSD. Adding a 1 mm sheet of acryl gradually from 1 mm to 15 mm acquires central axis depth dose beam profile and isodose curves in water phantom. As a result, for all energies, the practical range was reduced by approximately the same distance according to the acryl insert, e.g. a 1 mm thick acryl insert reduces the practical range by approximately 1 mm. For every mm thickness of acryl inserted, the beam energy was reduced to approximately 0.2 MeV. These effects were almost Independent of beam energy and field size. The use of Acrylic Electron Wedges produced a small increase(less than 3%) in the surface dose and a small increase(less than 1%) in X-ray contamination. For acryl inserts, thickness of 3 mm or greater, the penumbra width increased nearly linear for all energies and isodose curves near the beam edge were nearly parallel with the incident beam direction at the point of penumbra width($35\;mm{\sim}40\;mm$). We decide heel thickness and angle of the wedge at this point. These data provide the information necessary to design Acrylic Electron Wedge which can be used to improve dose uniformity at electron field junctions and it will be effectively applied to clinical practices.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.4
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• pp.369-377
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• 1998

To examine various aspects of Hg exchange processes, we measured Hg$^{\circ}$concentration gradients over soil surfaces in a residential area of Seoul during Sept. 1997. From these measurements, we found that Hg$^{\circ}$concentrations in lower(20 cm) and upper(200 cm) levels varied in the range of 3.15~14.38 (5.30$\pm$1.88: N=236) and 2.07~15.10ng/m$^3$(4.06$\pm$1.69: N=236), respectively. When our data were divided into emission and dry deposition, emission of Hg$^{\circ}$was overwhelmingly dominant (up to 98% in frequency) over dry deposition. The concentration gradients for emission and deposition events were 1.29$\pm$0.86(N=231) and -1.0$\pm$1.27ng/m$^3$(N=5), respectively. The observation of excessively high concentrations in both levels and development of strong gradients suggest that our study site be greatly affected by certain pollution sources of mercury. In face, those data were quite comparable to that had previously been observed from highly contaminated soil environs of Tennessee, USA. To provide some insights into the processes governing the Hg$^{\circ}$exchange processes, we have conducted correlation analyses between Hg$^{\circ}$data and other concurrently determined meteorological plus chemical data. In general, Hg$^{\circ}$concentrations of both levels exhibited similarly the existence of strong correlations with parameters like windspeed, temperature, and relative humidity. Although its concentration gradient data showed similarly strong correlations with meteorological parameters, they showed somewhat unique patterns in that their correlations with Hg$^{\circ}$concentration were noticeably stronger for the lower level than the upper level. To provide rough estimates of Hg$^{\circ}$fluxes in this study, we computed its flux using our gradient data and the predicted K values from previous studies. According to this approach, Hg$^{\circ}$emissions were generally in the range of 103$\pm$80(N=231), while its depositions, being scarcely found, were on the similar magnitude of -92$\pm$128ng/m$^2$/hr(N=5). The findings of excessive emission of Hg$^{\circ}$in residential area of Korea suggests that contamination of mercury be a significant process and hence be dealt more seriously.

• Analytical Science and Technology
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• v.26 no.1
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• pp.86-90
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• 2013

$^{222}Rn$ concentrations in the groundwater samples without standard material due to the short half-life (3.82 day) were measured through the establishment of the counting efficiency of LSC (Liquid Scintillation Counter) using a standard source of $^{226}Ra$. This study for Quality Assurance/Quality Control (QA/QC) of $^{222}Rn$ analysis was performed to analyze blank samples, duplicate samples, samples of groundwater sampling before and after. In-situ blank samples collected were in the range of 0.44~6.28 pCi/L and laboratory samples were in the range of 1.66~4.95 pCi/L. Their correlation coefficient was 0.9691 and the source contamination from sampling, migration and keeping of samples were not identified. The correlation coefficient between original and duplicate samples from 65 areas was 0.9987. Because radon is an inert gas, in case of groundwater sampling, it is considered to affect the radon concentration. We analyzed samples separately by groundwater sampling before and after using distilled water, but there is no significant difference for $^{222}Rn$ concentrations in distilled waters of two types.

• Economic and Environmental Geology
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• v.24 no.2
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• pp.97-105
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• 1991

Oxygen and sulfur isotope composition of pyrophyllite and pyrite from six pyrophyllite deposits in the Yangsan-Milyang areas (the Cheonbulsan, Dumyong, Dongrae, Youkwang, Sungjin and Milyang mines), and five deposits in the Whasoon-Dado-Haenam areas (the Byuksong, Songseok, Dado, Bugock and Nowha mines) were measured. Pyrophyllite ores both from the Yangsan-Milyang areas and the Dado-Haenam areas are composed mainly of high alumina minerals such as pyrophyllite, sericite and kaolinite. Most of altered rocks show diagnostic chacteristics of bleaching effect. Major minerals of the Songseok ore deposit in the Whasoon area are pyrophyllite, and diaspore with minor amounts of kaolinite and quartz. The Byuksong ores from the Whasoon area were composed mainly of andalusite, kaolinite, pyrophyllite and mica with small amounts of chloritoid, quartz and carbonaceous matter. The Byuksong and Songseok ores show metamorphic textures such as porphyroblastic, and pressure solution textures, and have low whiteness values, The ${\delta}^{18}O$ values of pyrophyllite from the Cheonbulsan and Dumyong mines in the Yangsan area, and the Dado and Nowha mines in the Dado-Haenam areas were in the range of 0.23~5.36%,. The relatively low 8 180 values provide conclusive evidence for hydrothermal activity in these deposits. The ${\delta}^{18}O$ values of pvrophvllite from the Songseok mine in the Whasoon area were measured as 6.70-8.13%, and these higher ${\delta}^{18}O$ values suggest that the Songseok ore deposit have been probably subjected to metamorphism. ${\delta}^{34}$S(pyrito) values from the Cheonbulsan, Dumyong, Youkwang, Dongrae, Sungjin and Milyang deposits in the Yangsan-Milyang areas, and the Dado pyrophyllite deposits in the Dado area range from -5.8 to 2.7%, which means that the pyrite sulfur could be of igneous origin. ${\delta}^{34}$S(pyrito) from the Nohwa mine in the Haenam area is, however, measured as -12.4%" implying the contamination of sulfur derived from the sedimentary country rocks. All of the studied high alumina deposits in the Yangsan-Milyang areas and the Dado-Haenam areas were hydrothermal in origin, whereas the Byuksong and Songseok ore deposits in the Whasoon area were probably of metamorphic origin.

• Korean Journal of Environmental Agriculture
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• v.12 no.3
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• pp.239-246
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• 1993

In order to clarify the possible contamination of rice straw used as a crude feed for livestock, Korean native cattle and cow, by pesticides, the samples collected from 21 sites in Korea were analyzed by a multiresidue method for 10 pesticides with GLC to obtain the following results. 1. Detection limits were 0.001ppm in butachlor, 0.002ppm in chlorpyrifos, 0.003ppm in BPMC, pirimiphos-methyl and diazinon, 0.004ppm in fenitrothion, 0.005ppm in phenthoate, 0.009ppm in IBP, 0.015ppm in carbofuran, and 0.03ppm in carbaryl. 2. In recovery tests, 73-101% of the pesticides applied were recovered, the recovery being low in carbofuran and chlorpyrifos. 3. Butachlor, 2-chloroacetanilide herbicide, and BPMC, carbaryl, and carbofuran, carbamate insecticides, were not detected in any sample. 4. In organophosphorus insecticides, the amounts of fenitrothion in sample No. 1, 2, 4, 5, 7, 12, 20 and 21 were in the range of 0.01-0.05ppm, those of phenthoate detected in sample No. 10 and 12 were 0.4 and 0.17ppm, respectively, and those of IBP in all samples, with the exception of sample No. 7, 12, 16, 17, 20, and 21, were in the range of 0.01-0.20ppm. The residues of chlorpyrifos, diazinon, and pirimiphos-methyl were not detected.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.409-419
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• 2023

Acid mine drainage(AMD) treatment is classified as both passive and active treatment. During the treatment, about 5,000 tons of neutralization sludge is generated as a by-product per year in Korea. This study was conducted to evaluate the characteristics of sludge generated from physico·chemical treatment processes as an active treatment from 5 different sources (D, H, S, T, Y) and the possibility of the sludges being recycled. The sludges have a pH range of 5.86 ~ pH 7.89, and a water content range of 51% ~ 82%. Most of particle sizes were less than 25 ㎛. In analysis of inorganic elements, the concentration of Al, Fe, and Mn were between 1,189 mg/kg ~ 129,344 mg/kg, 106,132 mg/kg ~ 338,011 mg/kg, and 3,472 mg/kg ~ 11,743 mg/kg, respectively. The concentration of As and Zn in sludge-T, Cd in sludge-D, Ni in sludge-H, Zn in sludge-S, and Cd in sludge-Y exceeded the soil contamination standards of Korea. The results from 2 separate kinds of leaching test, the Korea Standard Leaching Test(KSLT) and Toxicity Characteristic Leaching Procedure(TCLP), showed that all the sludges met the Korea groundwater standards. From the XRD and SEM-EDS analysis, the peaks of calcite and quartz were found in the sludges. The sludge also had a high proportion of Fe and O, and the majority of the composition was amorphous iron hydroxide.

• Korean Journal of Environmental Agriculture
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• v.35 no.2
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• pp.87-96
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• 2016

BACKGROUND: The objective of this study is to evaluate the soil quality to cultivate crops in urban garden.METHODS AND RESULTS: During the period of six month from March to August 2015, measured eight heavy metals, seven Organic items and Fluorine on seventeen urban sites and thirty-one suburban sites in Gwangju city.METHODS AND RESULTS: The average concentration and range of heavy metal in soil are 0.15 mg/kg(ND-0.6) for Cd, 14.9 mg/kg(1.5-33.3) for Cu, 4.4 mg/kg(0.4-71.8) for As, 0.05 mg/kg(ND-1.366) for Hg, 24.7 mg/kg(13.1-62.7) for Pb, 102.5 mg/kg(49.1-276.4) for Zn and 9.2 mg/kg(ND-90.1) for Ni but Cr⁶⁺ is not detected. The average value and range of soil fertility items are 253.5mg/kg(76.6-1766.0) for fluorine, 6.4(4.8-7.7) for pH, 20.3 g/kg(5.0-44.0) for orangic matters, 562.7 mg/kg (28.0-1672.0) for available phosphate, 0.6 cmol⁺/kg (0.1-2.3) for K, 9.7 cmol⁺/kg (2.7-22.0) for Ca, 3.0 cmol⁺/kg (0.9-7.4) for Mg, 1.0 ds/m(0.2-2.9) for conductivity. The concentration of Hg in Suburban area is 0.005 mg/kg lower than 0.134 mg/kg in urban area. Also, the concentration of As, Cd, Ni and Zn is lower than urban area as 32%, 37%, 51%, 71% respectively.CONCLUSION: According to SPI index of soil contamination, 39 sites are first degree and 8 sites are second degree and 1 site(41th) is fourth degree. Pb and Cd are not detected and As is detected tiny amounts in plants grown polluted soil, so heavy metals have not moved to plants.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.4
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• pp.223-232
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• 1998

The Okmyong Waste Landfill which is one of major industrial waste landfills in Korea has been used for 10 years since January, 1988. The groundwater in range of 2∼3 km from the landfill is a little acidic and has high concentrations of EC, NO$_3$, and SO$_4$ because of acidic rain in Pohang. The groundwater pattern in Piper's trilinear diagram belongs to Ca-SO$_4$and Na-SO$_4$types, but Ca-SO$_4$type is more predominant. The groundwater of five monitoring wells at the landfill area is a litle alkaline and has high concentrations of TS, COD, Na, Cl, SO$_4$, Alkalinity and F because of the effect of the leachates. They also have high heavy metals of Mn, Zn, Pb, Cr and Ni but toxic organic compounds are not detected. Their groundwater pattern is Na-SO$_4$type and distinguished from the groundwater pattern Na-Cl types of the Nanjido and the Seokdae Municipal Waste Landfills. The range of groundwater contamination which is validated up to now is about 120m west from the entrance of the Okmyong Waste Landfill. To prevent the dispersion of the leachates to the outside, cutoff walls should be constructed at the boundary of the landfill. Several pumping wells should also be developed at the landfill so that the contaminated groundwater can be pumped and treated at a leachate-treatment plant in the landfill.

• Analytical Science and Technology
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• v.22 no.3
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• pp.201-209
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• 2009

Four heavy metals (Pb, Cd, As, and Hg) in 38 species (total 325 samples) of oriental animality medicines were monitored by inductively coupled plasma-mass spectrometry (ICP-MS) and automatic mercury analyzer (AMA). The detected concentration range of Pb, Cd, As was presented as $0.02{\mu}gkg^{-1}$ $(D.L){\sim}11.29mgkg^{-1}$, $0.01{\mu}gkg^{-1}$ $(D.L){\sim}2.50 mgkg^{-1}$, $0.12{\mu}gkg^{-1}$ $(D.L){\sim}5.27mgkg^{-1}$, respectively. In case of Hg, it the concentration range was $0.01{\sim}77.11mgkg^{-1}$ except one sample which exceeded detection limit. In all samples of Amydae Carapax and Gallnut, it was not detected over the maximum residue limits of metals. Pb is in charge of the greatest portion of contamination in 22 species of animality medicines, and in case of Hg, 54.46% of total samples were over the maximum residue limits. Therefore, environmental levels of Pb and Hg are needed to continue the researches and the studies for tracking pollution source are required.

• Journal of Soil and Groundwater Environment
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• v.10 no.1
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• pp.6-12
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• 2005

Contamination of soils and groundwater by leakage of petroleum compounds from underground storage tanks (USTs) has become great environmental issues. Conventional methods such as soil vapor extraction (SVE) used for the remediation of unsaturated soils contaminated with volatile organic compounds might not be applied for the removal of semi-volatile organic compounds such as diesel fuels and PCBs, which have low volatility and high hydrophobicity. The objective of this study is to develop a hot air injection method to remove semi-volatile compounds. Additionally, operation parameters such as temperature, air flow rate, and water content are evaluated. Experimental results show that diesel ranged organics (DROs) are removed in the order of volatility of organic compounds. As expected, removal efficiency of organics is highly dependent on the temperature. It is considered that more than $90\%$ of organic contaminants whose carbon numbers range between 17 and 22 can be removed efficiently by the hot air injection-extraction method (modified SVE) over the $100^{\circ}C$. It is also found that increased air flow rate resulted in high removal rate of contaminants. However, air flow rate over 40 cc/min is not effective for the operation aspects, due to mass transfer limitation on the volatilization rate of the contaminants. The effect of the water content on the decane removal is minimal, but some components show large dependence on the removal efficiency with increasing water content.