• Journal of Environmental Science International
• /
• v.8 no.5
• /
• pp.593-600
• /
• 1999

In order to determine the changes of sediment facies and metal levels in surface sediments after the construction of Shiwha Lake, surface sediments were sampled at 8 sites located on the main channel monthly from June, 1995 to August, 1996 and analysed for 12 metals (Al, Fe, Mn, V, Cr, Co, Ni, Cu, Zn, Cd, As and Pb) by ICP/AES and ICP/MS. Two groups of sampling sites(the inner lake with 3 sites and the outer lake with 5 sites) are subdivided by the surface morphology ; the inner lake is a shallow channel area with a gentle slope, while the outer lake is relatively deep and wide channel with a steep slope which has many small distributaries. After the construction of dam, fine terrestrial materials were deposited near the outer lake, which resulted in the change of major sediment facies from sandy silt to mud. With the deposition of fine sediments in the outer lake, anoxic water column induced the formation of sulfide compounds with Cu, Cd, Zn and part of Pb. Metal (Cr, Ni, Cu, Zn and Cd) contents in sediments increased up to twice within 2 years after the construction of dam. This is due to the direct input of industrial and municipal wastes into the lake and the accumulation of metals within the lake. In addition, frequent resuspension of contaminated sediments in a shallow part of the lake may make metal-enriched materials transport near the outer lake with fine terrestrial materials. As the enrichment of Cu, Zn, Cd and part of Pb in the Shiwha Lake may be related to the formation of unstable sulfide compounds by sulfate reduction in anoxic water or sediment column, the effect of mixing with open coastal seawater is discussed.

• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.505-512
• /
• 1998

In this study, two-layer thermal barrier coatings composed of plasma sprayed 0.3mm $ZrO_2(8wt% Y_2o_3)$ ceramic coating layer and O.lmm $NiCrAlCoY_20_3$ bond coating layer on AISI 316 were investigated microstructure of the coating, oxidation of the metallic bond coating and adhesive strength to evaluate the durability of coating layer after cyclic and isothermal test at 90$0^{\circ}C$. And quantitative phase analysis of $ZrO_2(8wt% Y_2o_3)$ ceramic coating was performed as a function of thermal exposure time using XRD technique. The results showed that the amount of m - 2rO, phase in the coating was slightly increased with increasing thermal exposure time at 90$0^{\circ}C$. The c/a ratio of t' - $ZrO_2$ in the as-sprayed coating was 1.0099 and slightly increased to 1.0115 after 100 hours heat treatment. It was believed that $Y_2O_3$ in high yttria tetragonaJ(t') was transformed to low yttria tetragonaJ(t) by $Y_2O_3$ diffusion with increasing thermal exposure time. The adhesive strength was gradually decreased as thermal exposure time increased. After the isothermal test, the failure predominantly occured in ceramic coating layer. On the other hand. the specimens after cyclic thermal test were mostly failed at bond coating/ceramic coating interface. The failure was oeeured by decreasing the bond strength between bond coating and oxide scale which were formed by oxidation of the metallic elements within bond coating and by thermal stress due to thermal expansion mismatches between the oxide scale and ceramic coating.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2004.11a
• /
• pp.66-74
• /
• 2004

The sliding wear behavior of $ZrO_2-22wt\%MgO\;(MZ)\;and\;ZrO_2-8wt\%Y_2O_3\;(YZ)$ deposited on a casting aluminum alloy with bond layer (NiCrCoAlY) by plasma spray against an SiC ball was investigated under dry test conditions at room temperature. At all load conditions, the wear mechanisms of the MZ and the YZ coatings were almost the same. The wear mechanisms involved the forming of a smooth film by material transferred on the sliding surface and pullout. The wear rate of the MZ coating was less than that of the YZ coating. With an increase normal load the wear rate of the studied coatings increased. The SEM was used to examine the sliding surfaces and elucidate likely wear mechanisms. The EDX analysis of the worn surface indicated that material transfer was occurred from the SiC ball to the disk. It was suggested that the material transfer played an important role in the wear performance.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.24 no.4
• /
• pp.478-483
• /
• 2014

Objectives: The main objective of this study is to assess the levels of hazardous substances in floor dust in primary schools located in the city of Busan in Korea. Materials and Methods: An on-site investigation of three primary schools was performed between April and May 2013. The hazardous substances measured in this study were 14 heavy metals (Cu, Fe, Pb, Mn, Ni, Zn, Cr, Cd, As, Al, Sn, Co, Mo and Si) and the biological agents were bacteria, fungi and endotoxin). Results: Among the heavy metals, Cd, Co, Pb and Cr were not detected in the floor dust from the three primary schools. The mean levels of other heavy metals were as follows: $20({\pm}10)ng/cm^2$ for As, $30({\pm}20)ng/cm^2$ for Al, $5({\pm}4)ng/cm^2$ for Sn, $20({\pm}20)ng/cm^2$ for Mo, $1,340({\pm}620)ng/cm^2$ for Si, $110({\pm}100)ng/cm^2$ for Cu, $240({\pm}50)ng/cm^2$ for Fe, $30({\pm}30)ng/cm^2$ for Mn, $10({\pm}10)ng/cm^2$ for Ni, and $50({\pm}30)ng/cm^2$ for Zn. It was found that mean concentrations of bacteria, fungi and endotoxin in the floor dust of primary schools were $4.7{\time}10^7({\pm}2.2{\time}10^7)cfu/cm^2$, $6.3{\time}10^6({\pm}6.4{\time}10^6)cfu/cm^2$, and $8,140({\pm}5,801)EU/cm^2$, respectively. The predominant species identified in the floor dust of the primary schools were Pseudomonas spp. for bacteria and Penicillium spp.,Cladosporidium spp.,and Aspergillus spp. for fungi, which would be somewhat similar to the microbial distribution pattern of other general environments. Conclusions: Based on the results obtained from this study, the levels of heavy metals, microbes and endotoxin distributed in the floor dust of primary school were higher than those reported for other general facilities. Thus, preventive measures should be prepared for the health care of children.

• Journal of the Mineralogical Society of Korea
• /
• v.17 no.3
• /
• pp.189-199
• /
• 2004

Cretaceous sedimentary rocks bearing dinosaur tracks in the Goseong interchange area were studied for their conservation and public display in the aspect of applied mineralogy. Black clay layers alternate with silt layers in the sedimentary rocks. The verical and horizontal fissures are commonly filled with calcite veinlets, supergenetic iron and manganese oxides. The rocks are composed of quartz, albite, K-feldspar, calcite, chlorite, illite, muscovite, and biotite, with minor apatite and rutile. Silt layers are relatively rich in calcite and albite, whereas clay layers are abundant in quartz, illite, and chlorite. Al, Fe, Mg, K, Ti, and P are enriched in the clay layers, while Ca, Na, and Mn in silt. Most of trace elements including V, Cr, Co, Ni, Cs, Zr, REE, Th, and U are enriched in clay layers. Inorganic carbon are present in silt layers as calcite, while organic carbon in black clay layers. The black clay layers were partly altered to yellow clay layers along the fissures, simultaneously with the decrease of organic carbon. Selective exfoliation of clay-rich black and yellow clay layers, calcite matrix of silt layers and calcite infillings of fissures are estimated as the major weakness potentially promoting chemical and physical degradation of the track-bearing rock specimens.

• Spatial Information Research
• /
• v.14 no.1 s.36
• /
• pp.129-150
• /
• 2006

Mineral potential mapping is an important procedure in mineral resource assessment. The purpose of this study is to analyze mineral potential using weight of evidence model and a Geographic Information System (GIS) environment to identify areas that have not been subjected to the same degree of exploration. For this, a variety of spatial geological data were compiled, evaluated and integrated to produce a map of potential mineral in the Gangreung area, Korea. for this, a spatial database considering mineral deposit, topographic, geologic, geophysical and geochemical data was constructed for the study area using a GIS. The used mineral deposits were non-metallic(Kaolin, Porcelainstone, Silicastone, Mica, Nephrite, Limestone and Pyrophyllite) deposits of sedimentary type. The factors relating to mineral deposits were the geological data such as lithology and fault structure, geochemical data, including the abundance of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sr, V, Zn, $Cl^-,\;F^-,\;{PO_4}^{3-},\;{NO_2}^-,\;{NO_3}^-,\;SO_{42-}$, Eh, PH and conductivity and geophysical data, including the Bouguer and magnetic anomalies. These factors were used with weight of evidence model to analyze mineral potential. Probability models using the weight of evidence were applied to extract the relationship between mineral deposits and related factors, and the ratio were calculated. Then the potential indices were calculated by summation of the likelihood ratio and mineral potential maps were constructed from Geographic Information System (GIS). The mineral potential maps were then verified by comparison with the known mineral deposit areas. The result showed the 85.66% in prediction accuracy.

• Economic and Environmental Geology
• /
• v.30 no.3
• /
• pp.209-222
• /
• 1997

The Hoenam area, up the Taecheong lake, composed mainly of low grade coal-bearing metapelites within the Ogcheon Supergroup. These coal formations are developed discontinuously several hundred meters and swelling from 10 to 300 cm along the host metapelites. Although the formations have been mined for coal, but already mined out, and the formations were higher content (mean value of 42 samples) of environmental toxic elements as As (13 ppm). Ba (1.81 wt. %), Cd (2 ppm), Cr (188 ppm), Cu (87 ppm), Mo (214 ppm), Pb (25 ppm), Sb (3 ppm), Se (12 ppm), U (55 ppm), V (2124 ppm) and Zn (234 ppm) than the host metapelites and the NASC. The Al, Ti, Mg, K and Na contents in stream sediments derived from the Hando and Bugook mine area were highly concentrations than the samples from the Samseongjeil mine area. The mean value (wt. %) of Fe (10.07), Mn (0.15), Ca (0.84), P (0.18) and Ba (0.77) influenced by the Samseongjeil mine were higher than the other mine drainage sediments. The mean content (ppm) of environmental toxic elements in drainage sediments from the Samseongjeil mine were taken As (2083), Cu (447), Mo (202), Ni (720), Pb (42), U (250), V (1070) and Zn (2632), which are extremely high concentrations against NASC and EPA. Characteristics of elemental behavior and dispersion of the all toxic elements are the same as increased with increasing U, V, and Cu. Rare earth elements in the sediments are enriched with LREE (La, Ce and Nd) from the drainage on strong concentration of toxic elements. The pH of stream water is neutral, but pH of the sediments ranged from 4.92 to 6.93 (mean 6.22), those are slightly acid in the Hando mine area. Major elements in the host rocks at the Hoenam area are mostly depleted especially Ca, excepting Ti and Ba, normalized with NASC. The sediments were highly enriched of Ti, Fe, Mg, Mn and Ba, but depleted of Al, K, Ca, Na and P on the basis of host rocks and NASC. Minor and environmental toxic elements in the host rocks were strongly enriched all elements (As, Cd, Mo, Se, D, V and Zn), excepting Co, Ni and Sr. Enrichment index (mean value) about toxic elements (As, Cr, Cu, Fe, Ni, Pb and Zn) of the sediments in this area have taken 41.35 (Hando mine drainage; 2.73, Samseongjeil mine drainage; 113.14 and Bugook mine drainage; 8.19), those are seriously contaminated by environmental toxic elements.

• Resources Recycling
• /
• v.27 no.4
• /
• pp.16-22
• /
• 2018

Inconel713C which of a commercial Ni super alloy have the compositions of 70 wt.% Ni, 12 wt.% Cr, 6 wt.% Al and 4 wt.% Mo. In this study, solvent extraction has been performed to separate Mo from the synthetic leaching solution, formation of Inconel713C alloy similarly and is found the optimum conditions of recovery of Mo from the leaching solution. The effects of some variables, such as the nature and concentration of the extractants, $H_2SO_4$ concentrations, and the presence of impurities were investigated. The extraction percentage of Mo by Cyanex272 is 96% in the condition of pH 1 and 4% of concentration of Cyanex272 but Alamine336 is 99% in the condition of the range of pH 1 to 4 and 1 wt.% of concentration of Alamine336. In the case of Alamine336, the extraction percentage of Mo is increased by increasing of the concentration of Alamine336. The optimum condition of this experiment is pH 1 in aqueous phase, 1% concentration of Alamine336 and activation ratio of $H_2SO_4$ 1:0.5.

• Korean Chemical Engineering Research
• /
• v.49 no.6
• /
• pp.720-725
• /
• 2011

Gold catalysts supported on metal-oxides were prepared by co-precipitation using the various metal nitrates and chloroauric acid as precursors, and effect of water addition on the catalytic activity in CO oxidation was investigated. Among the various supported gold catalysts, Au/$Co_{3}O_{4}$ and Au/ZnO catalysts showed the excellent activity for CO oxidation. Water in the reactant gas had a negative effect on the oxidation activity over Au/$Co_{3}O_{4}$ catalysts and a positive effect on that over Au/ZnO, which means the activity depends strongly on the nature of support. It was also confirmed that no significant change in the particle size of gold was observed after reaction both in dry and wet conditions. This fact suggested that the deactivated catalyst due to a carbonate species could be regenerated by water addition in the reactant gas.

• Economic and Environmental Geology
• /
• v.44 no.5
• /
• pp.373-386
• /
• 2011

Geochemical study was performed on black slates and interbedded U-bearing coaly slates in Deokpyeongri area, the representative uranium mineralized district of the Ogcheon Metamorphic Belt, to discuss the genetic environments of the uranium deposit. REE concentration (254 ppm) of the black slates is higher than that (169 ppm) of the coaly slates and NASC-normalized REE patterns of the coaly slates show remarkable positive Eu anomaly. l11e redox-sensitive trace elements such as V, Cr, Co, Ni, Mo and U in the coaly slates are highly enriched compared to the black slates, especially for V of 24 times, Mo of 62 times, and U of 60 times. In additions, Pd and Pt are also enriched in the coaly slates. Positive Eu anomaly and the noticeable enrichment of the elements listed above compared to those of NASC indicate that those elements were not derived from common seawater but deposited under high temperature and reducing environment of submarine hydrothermal activities. Wide compositional ranges of major elements ($SiO_2/Al_2O_3$: 3.98~11.88, $Al_2O_3/Na_2O$: 25.6~139.06, $K_2O/Na_2O$: 6.80~46.85) also suggest that the source rocks of the sediments are mixtures of sedimentary rocks and igneous rocks. Higher sulfur contents in the coaly slates, 2.6 wt.%, than those in the black slates, 0.6 wt.% also indicates that the former was influenced by hydrothermal activities containing much sulfur. These geochemical characteristics are similar to the genetic environments of South China type PGE deposits (Mo-Ni-Zn-PGE) which is geotectonically correlated with the Ogcheon Metamorphic Belt and is known as sedimentary-exhalative deposits. In conclusions, the uranium and other metallic elements mineralization seems to have occurred in the sedimentary basin that was affected by submarine hydrothermal activities and rich in organic materials under oxygen-poor environments as well.