• Economic and Environmental Geology
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• v.39 no.2 s.177
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• pp.181-190
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• 2006

Garnet has been suggested as one of the most promising material for the immobilization of radionuclide in high level waste. But data on its chemical durability are sufficiently available. Accordingly, Gd and Ce garnets were synthesized as imitators for $Pu^{3+}\;and\;Pu^{4+}$ were synthesized, and their leaching rates, the parameters of the chemical durability were measured by changing the conditions. In distilled water, the ranges of leaching rates of Gd and Ce were $1.2{\times}10^{-4}{\sim}4.6{\times}10^{-6}g/m^2/day\;and\;7.5{\times}10^{-5}{\sim}1.8{\times}10^{-7}g/m^2/day$, respectively. A comparison with previous data suggests that the chemical durabilities of garnets synthesized from this study are superior to those of other waste forms. Additional leaching experiments were performed with 0.01M-HCl and 0.01M-NaOH solutions to see Gd and Ce leaching at acidic and alkalinity conditions. In 0.01 H-HCl solution, the ranges of leaching rates of Gd and Ce were $2.5{\times}10^{-1}{\sim}6.9{\times}10^{-3}g/m^2/day\;and\;3.7{\times}10^{-1}{\sim}3.1{\times}10^{-3}g/m^2/day$, respectively, while were $3.1{\times}10^{-4}{\sim}1.3{\times}10^{-6}g/m^2/day\;and\;1.8{\times}10^{-3}{\sim}0g/m^2/day$, respectively in 0.01M-NaOH solution. It is believed that leaching data can be used in understanding chemical durabilities of waste from garnets in acidic and alkaline conditions.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.123-136
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• 2010

In order to remediate heavy metal contaminated Nong island, Maehyang-ri shooting range soils through the batch reactor scale washing were evaluated. The experiment texture soil of N3 in the Nong island at north side incline was (g)mS containing 12.9% gravel, 47.0% sand, 35.1% silt and 5.0% clay. And the N3 soil area was contaminated with Cd($22.5\pm1.9$ ppm), Cu($35.5\pm4.0$ ppm), Pb($1,279.0\pm5.1$ ppm) and Zn($403.4\pm9.8$ ppm). The EDTA(ethylene diamine tetra acetic acid, $C_{10}H_{16}N_2O_8$) in the N3 soil was observed as most effective extractants among the 5 extractants(citric acid, EDTA, phosphoric acid, potassium phosphate and oxalic acid) tested. And chemical partitioning of heavy metals after washing N3 soil with EDTA was evaluated. Removal efficiency of residual fractions was higher than that of non-residual fractions. To choose EDTA extractant which is the most effective in soil washing technology using batch reactor process cleaning Pb and Zn contaminated sits; Pb and Zn removal rates were investigated 92.4%, 94.0% removal(1,000 mM, soil:solution=5, $20^{\circ}C$, 24 hour shaking, pH=2, 200 RPM), respectively. The results of the batch test showed that the removal efficiency curve was logarithmic in soil was removal. Thus, EDTA washing process can be applied to remediate the Pb and Zn contaminated soil used in this study.

• Economic and Environmental Geology
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• v.49 no.5
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• pp.371-380
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• 2016

This study aims to identify the mineraloical and petrographical characteristics of caprock from drilling cores of Pohang basin as a potential $CO_2$ storage site. Experiments and modeling were conducted in order to investigate the geochemical and mineralogical caprock effects of carbon dioxide. A series of autoclave experiments were conducted to simulate the interaction in the $scCO_2$-caprock-brine using a high pressure and temperature cell at $50^{\circ}C$ and 100 bar. Geochemical and mineralogical alterations after 15 days of $scCO_2$-caprock-brine sample reactions were quantitatively examined by XRD, XRF, ICP-OES investigation. Results of mineralogical studies, together with petrographic data of caprock and data on the physicochemical parameters of brine were used for geochemical modeling. Modelling was carried out using the The Geochemist's Workbench 11.0.4 geochemical simulator. Results from XRD analysis for caprock sample showed that major compositional minerals are quartz, plagioclase, and K-feldspar, and muscovite, pyrite, siderite, calcite, kaolinite and montnorillonite were included on a small scale. Results from ICP-OES analysis for brine showed that concentration of $Ca^{2+}$, $Na^+$, $K^+$ and $Mg^{2+}$ increased due to dissolution of plagioclase, K-feldspar and muscovite. Results of modeling for the period of 100 years showed that the recrystallization of kaolinite, dawsonite and beidellite, at the expense of plagioclase and K-feldspar is characteristic. Volumes of newly precipitation minerals and minerals passing into brine were balanced, so the porosity remained nearly unchanged. Experimental and modeling results indicate the interaction between caprock and $scCO_2$ during geologic carbon sequestration can exert significant impacts in brine pH and solubility/stability of minerals.

• Economic and Environmental Geology
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• v.43 no.1
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• pp.13-20
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• 2010

Acid mine drainage (AMD) from abandoned mine sites typically has low pH and contains high level of various heavy metals, aggravating ground- and surface water qualities and neighboring environments. This study investigated removal of heavy metals in a biological treatment system, mainly focusing on the removal by adsorption on a substrate material. Bench-scale batch experiments were performed with a mushroom compost to evaluate the adsorption characteristics of heavy metals leached out from a mine tailing sample and the role of SRB in the overall removal process. In addition, adsorption experiments were perform using an artificial AMD sample containing $Cd^{2+}$, $Cu^{2+}$, $Pb^{2+}$ and $Zn^{2+}$ to assess adsorption capacity of the mushroom compost. The results indicated Mn leached out from mine tailing was not subject to microbial stabilization or adsorption onto mushroom compost while microbially mediated stabilization played an important role in the removal of Zn. Fe leaching significantly increased in the presence of microbes as compared to autoclaved samples, and this was attributed to dissolution of Fe minerals in the mine tailing in a response to the depletion of $Fe^{3+}$ by iron reduction bacteria. Measurement of oxidation reduction potential (ORP) and pH indicated the reactive mixture maintained reducing condition and moderate pH during the reaction. The results of the adsorption experiments involving artificial AMD sample indicated adsorption removal efficiency was greater than 90% at pH 6 condition, but it decreased at pH 3 condition.

• Economic and Environmental Geology
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• v.50 no.1
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• pp.35-44
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• 2017

The Hadong-Sancheong Proterozoic anorthosite complex occurs in the southwestern region of the Ryongnam massif. The geology of the area mainly consists of metamorphic rocks of the Jirisan metamorphic complex as basement rocks, charnockite, and the Hadong-Sancheong anorthosite, which are intruded by the Mesozoic igneous rocks. Hadong-Sancheong anorthosite complex is divided into the Sancheong anorthosite and the Hadong anorthosite which occur at north-southern and south area of the Jurassic syenite, respectively. The Hadong Fe-Ti-bearing dike-like ore bodies developed intermittently in the Hadong anorthosite with north-south direction and extend about 14 km. The Hadong Fe-Ti-bearing ore bodies consist mainly of magnetite and ilmenite with rutile, titanite, and minor amounts of sulfides(pyrrhotite, pyrite, chalcopyrite and sphalerite). The Hadong Fe-Ti-bearing ore bodies show a paragenetic sequence of magnetite-ilmenite ${\rightarrow}$ magnetite-ilmenite-pyrrhotite ${\rightarrow}$ ilmenite-pyrrhotite-rutile-titanite(and/or pyrite) ${\rightarrow}$ sulfides. Equilibrium thermodynamic interpretation of the mineral paragenesis and assemblages indicate that early Fe-Ti-bearing ore mineralization in the ore bodies occurs at about $700^{\circ}C$ which corresponds to oxygen fugacity of about $10^{-11.8}{\sim}10^{-17.2}$ atm with the decrease tendency of sulfur fugacity to about $10^0$ atm as equilibrium of $Fe_3O_4-FeS$. The change of ore mineral assemblages from Fe-Ti-bearing minerals to sulfides in late ore mineralization of the ore bodies indicates that oxygen fugacity would have slightly decreased to ${\geq}10^{-20.2}$ atm and increased sulfur fugacity to ${\geq}10^0$ atm.

• Economic and Environmental Geology
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• v.36 no.4
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• pp.285-293
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• 2003

Tailings of Dukum mine in the vadose and saturated zone were investigated to reveal the mobility of metal elements and the condition of mineralogical solubility according to redox environments throughout the geochemical analysis, thermodynamic modelling, and mineralogical study for solid-samples and water samples(vadose zone; distilled water: tailings=5 : 1 reacted, saturated zone; pore-water extracted). In the vadose zone, sulfide oxidation has generated low-pH(2.72∼6.91) condition and high concentration levels of S $O_4$$^{2-}$(561∼1430mg/L) and other metals(Zn : 0.12∼l57 mg/L, Pb : 0.06∼0.83 mg/L, Cd : 0.06∼l.35 mg/L). Jarosite$(KFe_3(SO_4)_2(OH)_6)$ and gypsum$(CaSO_4{\cdot}2H_2O$) were identified on XRD patterns and thermodynamics modelling. In the saturated zone, concentration of metal ions decreased because pH values were neutral(7.25∼8.10). But Fe and Mn susceptible to redox potential increased by low-pe values(7.40∼3.40) as the depth increased. Rhodochrosite$(MnCO_3)$ identified by XRD and thermodynamics modelling suggested that $Mn^{4+}$ or $Mn^{3+}$ was reduced to $Mn^{2+}$. Along pH conditions, concentrations of dissolved metal ions has been most abundant in vadose zone throughout borehole samples. It was observed that pH had more effect on metal solubilities than redox potential. How-ever, the release of co-precipitated heavy metals following the dissolution of Fe-Mn oxyhydroxides could be the mechanism by which reduced condition affected heavy metal solubility considering the decrease of pe as depth increased in tile saturated zone.

• Journal of Animal Science and Technology
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• v.45 no.5
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• pp.825-834
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• 2003

Chicken thigh from a retail market were used as experimental samples. Some chicken samples of raw state were packaged with PVDC at an aerobic and vacuum condition. The other samples were cooked until core temperature arrived at 70$^{\circ}C$ and then packaged immediately in the same way of raw samples. After samples were irradiated by electron beam at 6 kGy, they were stored in a refrigerator. Identification and quantity of cholesterol oxides were made at 0 and 7 days of storage, respectively. During the early stage of storage, 7$\beta$-hydroxycholesterol, $\alpha$,$\beta$-epoxide, cholestanetriol and 7-ketocholesterol were produced from the raw meat samples, and the production of these chemicals were significantly higher(P〈0.05) from the samples with aerobic packaging than those with vacuum packaging. With storage time, 7$\alpha$-hydroxycholesterol, 6-ketocholesterol and some other chemicals, which were not found during the early stage of storage, were found. Also, the formation of these chemicals were significantly increased(P〈0.05) with storage time. Cholesterol and lipid oxidation products of cooked meat after irradiation and irradiated meat after cooking were significantly increased(P〈0.05) with storage time for all treatments, and vacuum packaging results in showed significantly lower value(P〈0.05) than aerobic packaging. Summarizing the aforementioned results, it was found that the formation of cholesterol and lipid oxides and lipid oxidation was more easily affected by packaging condition than irradiation.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.2
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• pp.172-180
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• 2007

Among the nuclear medicine imaging methods available today, $H_2^{15}O-PET$ is most widely used by cognitive neuroscientists to examine regional brain function via the measurement of regional cerebral blood flow (rCBF). The short half-life of the radioactively labeled probe, $^{15}O$, often allows repeated measures from the same subjects in many different task conditions. $H_2^{15}O-$ PET, however, has technical limitations relative to other methods of functional neuroimaging, e.g., fMRI, including relatively poor time and spatial resolutions, and, frequently, insufficient statistical power for analysis of individual subjects. However, recent technical developments, such as the 3-D acquisition method provide relatively good image quality with a smaller radioactive dosage, which in turn results in more PET scans from each individual, thus providing sufficient statistical power for the analysis of individual subject's data. Furthermore, the noise free scanner environment $H_2^{15}O$ PET, along with discrete acquisition of data for each task condition, are important advantages of PET over other functional imaging methods regarding studying state-dependent changes in brain activity. This review presents both the limitations and advantages of $^{15}O-PET$, and outlines the design of efficient PET protocols, using examples of recent PET studies both in the normal healthy population, and in the clinical population.

• Economic and Environmental Geology
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• v.37 no.3
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• pp.303-309
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• 2004

Pyrochlores were known as promising materials for the immobilization of radioactive actinide. Accordingly, we synthesized pyrochlores with Gd$_2$Ti$_2$$O_7$ and Gd$_2$Zr$_2$$O_7$compositions by sintering method, and studied its properties and phase relations in Gd-Ti-O and Gd-Zr-O system. The mixed powders were pressed into pellets under 200-400 kgf/cm$^2$ at room temperature. and then sintered at 1000-1$600^{\circ}C$ for 0.5-40 hours. The synthesized samples were analyzed and were identified with XRD and SEM/EDS analyses. The optimal synthetic conditions of pyrochlores with Gd$_2$Ti$_2$$O_7$composition were at 140$0^{\circ}C$/0.5hrs, 130$0^{\circ}C$/3hrs and 120$0^{\circ}C$/20hrs. Its chemical composition was $Gd_{2.0-2.1}$$Ti_{1.9-2.0}$$O_7$ and similar to the stoichiometric composition without any relationship in temperature and atmosphere. The optimal synthetic conditions of pyrochlores with $Gd_{2}$$Zr_{2}$$O_7$composition were at 155$0^{\circ}C$/40hrs and 1$600^{\circ}C$/30hrs. The compositions of pyrochlore synthesized from these optimal conditions were irregular with $Gd_{1.5-2.4}$$Zr_{1.7-2.4}$$O_7$. Such heterogeneity indicates that the reaction rate of pyrochlore with Gd$_2$Zr$_2$$O_7$composition is very low, and then its equilibrium state could not be attained even for 40 hours which was the longest sintering time in this research.

• Economic and Environmental Geology
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• v.44 no.6
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• pp.485-492
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• 2011

Sorption of cyanide on granular activated carbon and attenuation of the cyanide by UV-light over a wide range of conditions such as pH and concentration were investigated through batch experiments. Cyanide uptake by activated carbon is much effective at $[CN]_{ini}$ < 2 mg/L. The sorption of cyanide on activated carbon at pH 7.0 is greater than that of pH 9.0. It is found that the ratio of CN uptake to CN in solution increases at pH 9.0 whereas at pH 7.0 the ratio decreases, suggesting that reactivity of activated carbon increases as a function of pH. The sorption of cyanide rapidly increases during the first 30 min, followed by sharp desorption until 3hr, and then the sorption increases and reaches the maximum sorption during the duration of experiments, implying that the sorption mode could be changed through conformational change during the initial stage of the cyanide uptake by activated carbon. Total amount of cyanide desorbed from the activated carbon during the period of desorption experiments is less than 1.5% of total sorbed cyanide, indicative of strong and stable sorption of cyanide on the activated carbon. The sorption with mixture of activated carbon and Ham-Baek sludge shows less effective on the removal of the cyanide. It is noted that UV-light is much effective on the removal of cyanide but also the attenuation is achieved until $[CN]_{tot}$ is up to 10 mg/L. Our findings demonstrate that both activated carbon and UV-light are very effective on the attenuation of cyanide over a wide range of environmental conditions.