• Economic and Environmental Geology
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• v.51 no.5
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• pp.429-438
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• 2018

Since concrete is a hardened aggregates of various materials, it needs to be crushed for chemical analyses. However, the effect of sample crushing on the analytical results has not been precisely assessed till today. In this study, we prepared concrete test pieces using Portand cements and fly ashes as binding materials, and ponded ashes and sands as aggregates and analyzed the heavy metals of the test pieces using Standards for Fair Testing of Soil Contamination (SFTSC) and Wastes (SFTW). For this, each test piece was partially crushed at first and sieved for separation of grains of <0.15 mm, 0.15-0.5 mm, and 0.5-5 mm from the same crushed samples (Crushing Method I). Results of those samples using SFTSC showed a clear trend that analyzed heavy metal concentrations are higher in the finer fractions. Particularly, fractions with <0.15 mm indicated much higher concentrations than the theoretical ones, which were calculated based on the concentrations of individual materials and their mixing fractions. In contrast, the analytical results were generally comparable with the theoretical ones when the test pieces were totally pulverized such that all the crushed grains were <0.15 mm in size (Crushing Method II). These results are associated with the fact that cement materials and fly ashes, which are high in heavy metals relative to other materials, are enriched in the fine fractions. The analytical results using the SFTW derived very low concentrations in most of parameters and did not indicate the dependence of concentrations on the crushing methods due to using distilled water as leaching agent.

• Journal of Life Science
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• v.21 no.5
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• pp.746-752
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• 2011

The contents of bioactive materials (e.g. polyphenolics compounds, flavonoids, minerals, and fatty acids) and antioxidative activities (DPPH (${\alpha}$,${\alpha}$'-diphenyl-${\beta}$-picrylhydrazyl) free radical scavenging activity, peroxidation of linoleic acid and rat hepatocyte microsome, and Fe/Cu reducing power) were tested by in vitro experimental models using water, ethanol and methanol extracts of leaves (TOL) and fruits (TOF) from Thuja orientalis. Methanol extract from TOL showed the highest extraction yield (12.90%) as well as contents of polyphenolic compounds (16.02%) and flavonoids (0.25%). Major minerals were Ca, K, and Mg. Major fatty acids were palmitic and lauric acids in TOL and palmitic and decanoic acids in TOF. In oxidation of in vitro models using DPPH free radical scavenging activity, Fe/Cu reducing power, $Fe^{2+}$/ascorbate-induced linolenic acid peroxidation by ferric thiocyanate and thiobarbituric acid (TBA) methods, and autooxidation of rat hepatic microsomes membrane, anti-oxidative activities were stronger in all extracts of TOL than in those of TOF in a dose-dependent manner. From these results, methanol extract of TOL was shown to have the most potent anti-oxidative properties and the highes content of antioxidative compounds such as polyphenolic compounds and flavonoids.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.769-774
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• 2005

Fluosilicic acid(H2SiF6) is recovered as an aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded H3PO4 or HF. Generally, fluosilicates are the salts produced by the reaction of H2SiF6 and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. This study was performed to know mechanical properties and watertightness using fluosilicates based composite made from fluosilicates and other compounds. Mix proportions for experiments were modulated at 0.45 of water to cement ratio and $0.0-2.0\%$ of adding ratio of fluosilicates based composite. Evaluation for mechanical properties of concrete was conducted to know fresh state of concrete, hardening state of concrete, and watertightness. Evaluation for watertightness of concrete was carried out permeability, absorption test and porosity analysis. In addition. Scanning Electron Microscopy(SEM) and Energy Dispersive X-Ray(EDX) used for investigating micro-structure and atomic component distributed in hardened concrete. It is ascertained that characteristics of mechanical properties and watertightness was more improved than non-added because of packing role of fluosilicates based composite and pozzolanic reaction of soluble $SiO_2$. Also, concrete added fluosilicates based composite had a tendency to delay setting time and only $0.5\%$ addition of fluosilicates based composite delayed 150 minutes compared with non-added.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.61-70
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• 2012

Recently, the government has been working feverously to save energy and reduce greenhouse gas emission by enacting Basic Act on Low Carbon Green Growth at the national level. Improving the insulation performance of building exterior and insulator can reduce the energy in the building sector. This study is about developing light-weight foamed concrete insulation panel that can be applied to buildings to save energy and to find the optimal condition for the development of insulation materials that can save energy by enhancing its physical, kinetic and thermal characteristics. Various experimental factors and conditions were considered in the study such as foam agent types (AES=Alcohol Ethoxy Sulfate, AOS=Alpha-Olefin Sulfonate, VS=Vegetable Soap, FP=Fe-Protein), foam agent dilution concentration (1, 3, 5%), and foam percentage (30, 50, 70%). Experiment results indicated that the surface tension of aqueous solution including foam agent, was lower when AOS was used over other foam agents. FP produced relatively stable foams in 3% or more, which produced unstable foams containing high water content and low surface tension when diluted at low concentration. Depending on foam agent types, compressive strength and thermal conductivity were similar at low density range but showed some differences at high concentration range. In addition, when concentrations of foam agent and foaming ratio increased, pore size increased and open pores are formed. In all types of foam agent, thermal conductivity were excellent, satisfying KS standards. The most outstanding performance for insulation panel was obtained when FP 3% was used.

• Journal of Environmental Science International
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• v.23 no.5
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• pp.743-753
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• 2014

The number concentrations and the water soluble ionic concentrations of $PM_{2.5}$ have measured at Gosan site in Jeju, Korea, from March 2010 to December 2010, to clarify their characteristics. $PM_{2.5}$ number concentrations vary from 22.57 to $975.65particles/cm^3$ with an average value of $240.41particles/cm^3$, which have been recorded evidently high in spring season as compared with those in other season. And the concentrations in small size ranges are greatly higher than those in large size ranges, so the number concentration in the size range $0.25{\sim}0.45{\mu}m$ has more than 94% of the total number concentration of $PM_{2.5}$. The major ionic components in $PM_{2.5}$ are $SO{_4}^{2-}$, $NH_4{^+}$ and $NO_3{^-}$, which are mainly originated from anthropogenic sources, on the other hand, the concentrations of $Cl^-$, $K^+$, $Ca^{2+}$ and $Mg^{2+}$ are recorded relatively lower levels. The concentrations of the major ionic components are very high in spring season, but the concentration levels of the other components are recorded significantly high in winter season. On the other hand, in summer season, the lowest concentration levels are observed for overall components as well as the sum of them. The concentration ratios of nss-$SO{_4}^{2-}/SO{_4}^{2-}$ and nss-$Ca^{2+}/Ca^{2+}$ are 98.1% and 88.9%. And the concentration ratio of $SO{_4}^{2-}/NO_3{^-}$(3.64) is greatly higher than the value in urban area due to no large $NO_x$ emission sources in the measurement. In addition, the correlation and the factor analysis for the number and the ionic concentrations of $PM_{2.5}$ are performed to identify their sources. From the Pearson correlation analysis and the factor analysis, it can be suggested that the smaller parts(< $0.5{\mu}m$) of $PM_{2.5}$ is contributed by anthropogenic sources, but the sources of the remaining larger parts of $PM_{2.5}$ are not able to be specified sources in this study.

• Resources Recycling
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• v.21 no.4
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• pp.44-52
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• 2012

The purpose of this study is to confirm the possibility of obtaining high grade coal from fixed carbon 20.68% coal. Also, the mineralogical, physical/chemical and liberation characteristics was found with the aim of decrease in ash amount, during the pre-processing of clean coal technology. In this study, batch flotation and microbubble column flotation that was appropriate for the processing of fine particles was used with the variation in kinds and quantity of frother, collector and depressant. Also grinding time, air flow rate and feeding rates were examined. As a result of batch flotation, using pulp density 20%, collector DMU-101+dodecyl amine(100 mL/ton), frother pine oil (200 mL/ton), depressant sodium silicate(1 kg/ton), obtained the result of ash rejection 81.55% and combustible recovery 70.23%. In result of microbubble column flotation, the result was ash rejection 83.85% and combustible recovery 70.42% under the condition of pulp density 5%, grinding time 5 min. collector DMU-101+DDA(100 mL/ton), frother AF65(5.4 L/ton), depressant SMP(3.5 kg/ton), wash water(360 mL/min.) and air flow rate(1,197 mL/min.).

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.1
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• pp.1-6
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• 2004

Agricultural recycling of livestock wastes by composting has lots of beneficial effects on crop production and soil fertility. Most of composts are made from pig manure and water content controller such as saw dust, bark, rice hulls etc. by aerobic processing. But the insufficient supply of saw dust, bark etc. cause the indiscreet use of industrial waste having heavy metals and toxic synthetic chemicals. This research investigated the present quality status of organic by-product fertilizers, and suggested the way of quality interpretation under the statistical approaches based on median, mean and weighted average value. Since the data of one hundred of samples for heavy metal contents (Cd, Pb, Cu, and Cr) and OM/N showed extremely left-skewed distribution, the median was more useful than the mean in representing the characteristics of distribiition for each items. The weighted average value will be a useful index for the quality based on the total amount of producing.

• Economic and Environmental Geology
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• v.29 no.2
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• pp.215-225
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• 1996

All the radionuclides in high-level nuclear waste will decay to harmless levels eventually but for some radionuclides decay is so slow that their radiation remains dangerous for times on the order of tens or hundreds of thousands of years. At the present time, the most favorite disposal plan for high-level radioactive waste is a mined geological disposal in which canister enclosing stable solid form of radioactive waste is placed in mined cavities locating hundred meters below the surface. The chief hazard in such disposal is dissolution of radionuclides from the waste in the groundwater that will eventually carry the dissolved radionuclides to surface environments. The hazard from possible escape of the radionuclides through groundwater can be delayed by engineered and geologic barriers. The engineered barriers can become useless by unexpected geologic catastrophe such as volcanism, earthquake, and tectonic movement and by fraudulent work such as careless construction, improperly welded canisters within the first few decades or centuries. As a result, dangerously radioactive waste which is still intensively radioactive is directly exposed to attack by moving groundwater. All the more, it is almost impossible to control repositories for times more than 10,000 years. Therefore, naturally controlled geologic, barriers whose properties will not be changed within 10,000 years are important to guarantee the safety of repositories of high-level radioactive waste. In Sweden and France, the suitability of granite for the mined geological disposal of high-level waste has been studied intensively. According to the research in Sweden and France, granites has the following physio-chemical characteristics which can delay the transportation of radionuclide by groundwater. First, the permeabilities of granites decreases as the depth increases and is $10^{-8}{\sim}10^{-12}m/s$ at depth below 300 m. Second, groundwater at depth below 300 m has pH=7-9 and reducing condition (Eh=-0.1~0.4). This geochemical condition is desirable to prevent both canister and solid waste from corrosion. Third most radionuclides are not transported by low solubilities and some radionuclide with high solubility such as Cs and Sr are retarded by absorption of geologic media through which ground water flows. Therefore, if high-level waste is disposed at depth below 300 m in the granite body which has a low permeability and is geologically stable more than 10,000 years, the safety of repositories from the hazard due to radionuclide escape can guaranteed for more than 10,000 years.

• Journal of Microbiology and Biotechnology
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• v.30 no.6
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• pp.937-945
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• 2020

N-acyl-homoserine lactone (AHL)-mediated quorum sensing (QS) plays a major role in development of biofilms, which contribute to rise in infections and biofouling in water-related industries. Interference in QS, called quorum quenching (QQ), has recieved a lot of attention in recent years. Rhodococcus spp. are known to have prominent quorum quenching activity and in previous reports it was suggested that this genus possesses multiple QQ enzymes, but only one gene, qsdA, which encodes an AHL-lactonase belonging to phosphotriesterase family, has been identified. Therefore, we conducted a whole genome sequencing and analysis of Rhodococcus sp. BH4 isolated from a wastewater treatment plant. The sequencing revealed another gene encoding a QQ enzyme (named jydB) that exhibited a high AHL degrading activity. This QQ enzyme had a 46% amino acid sequence similarity with the AHL-lactonase (AidH) of Ochrobactrum sp. T63. HPLC analysis and AHL restoration experiments by acidification revealed that the jydB gene encodes an AHL-lactonase which shares the known characteristics of the α/β hydrolase family. Purified recombinant JydB demonstrated a high hydrolytic activity against various AHLs. Kinetic analysis of JydB revealed a high catalytic efficiency (k_cat/K_M) against C4-HSL and 3-oxo-C6 HSL, ranging from 1.88 x 10⁶ to 1.45 x 10⁶ M^-1 s^-1, with distinctly low K_M values (0.16-0.24 mM). This study affirms that the AHL degrading activity and biofilm inhibition ability of Rhodococcus sp. BH4 may be due to the presence of multiple quorum quenching enzymes, including two types of AHL-lactonases, in addition to AHL-acylase and oxidoreductase, for which the genes have yet to be described.

• Korean Journal of Environmental Biology
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• v.36 no.1
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• pp.62-72
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• 2018

In order to provide important information for the efficient management of the identified farm ecosystem in Jinju Bay, we investigated the spatial and temporal distribution of the phytoplankton community using a UPLC pigment analysis and a CHEMTAX program from the timeframe of February 2013 to January 2014. In addition, we measured the available physical and chemical parameters controlling the distribution of the phytoplankton communities. As a result of this comprehensive pigment analysis, it was noted that the Diatoms were the predominant species with an average of 77.1% as noted located in Jinju Bay. It was discovered that during the summer season, the phytoplankton community composition was changed by a reduction of diatoms and noted increases of the Cryptophytes, Prasinophytes, and Dinoflagellates. Especially, it was noted that the Cryptophytes and Prasinophytes were shown with an average of 18.8% and 17.8% in June, respectively. However, it was revealed that the Cryptophytes and Prasinophytes were not shown by a microscopic observation. The phytoplankton community composition was correlated with the temperature and salinity variations as noticed in the Jinju Bay. Therefore, the water temperature and freshwater inputs in the Jinju Bay were important environmental factors for controlling the phytoplankton community composition and the varying Cryptophytes and the noted amounts of Prasinophytes as well.