• Journal of the Mineralogical Society of Korea
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• v.15 no.4
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• pp.329-344
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• 2002

Mineralogical and chemical characterization of some domestic bentonites, such as quantitative XRD analysis, chemical leaching experiments, pH and CEC determinations, were done without any separation procedures to understand their relationships among mineral composition, characteristics, and cation exchange properties. XRD quantification results based on Rietveld method reveal that the bentonites contain totally more than 25 wt% of impurities, such as zeolites, opal-CT, and feldspars, in addition to montmorillonite ranging 30～75 wt%. Cation exchange properties of the zeolitic bentonites are deeply affected by the content of zeolites identified as clinoptilolite-heulandite series. Clinoptilolite is common in the silicic bentonites with lighter color. and occurs closely in association with opal-CT. Ca is mostly the dominant exchangeable cation, but some zeolitic bentonites have K as a major exchangeable cation, The values of cation exchange capacity (CEC) determined by Methylene Blue method are comparatively low and have roughly a linear relationship with the montmorillonite content of the bentonite, though the correlated data tend to be rather dispersed. Compared to this, the CEC determined by Ammonium Acetate method, i.e.‘Total CEC’, has much higher values (50～115 meq/100 g). The differences between those CEC values are much greater in zeolitic bentonites, which obviously indicates the CEC increase affected by zeolite. Other impurities such as opal-CT and feldspars seem to affect insignificantly on the CEC of bentonites. When dispersed in distilled water, the pH of bentonites roughly tends to increase up to 9.3 with increasing the alkali abundance, especially Na, in exchangeable cation composition. However, some bentonites exhibit lower pH (5～6) so as to regard as ‘acid clay’. This may be due to the presence of $H^{＋}$ in part as an exchangeable cation in the layer site of montmorillonite. All the works of this study ultimately suggest that an assesment of domestic bentonites in grade and quality should be accomplished through the quantitative XRD analysis and the ‘Total CEC’measurement.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.435-450
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• 2005

The purpose of the study is to analyze the hydrogeochemical characteristics by multivariate statistical method, to interpret the hydrogeochemical processes for the new variables calculated from principal components analysis (PCA), and to infer the groundwater flow and circulation mechanism by applying the geostatistical methods for each element and principal component. Chloride and nitrate are the most influencing components for groundwater quality, and the contents of $NO_3$ increased by the input of agricultural activities show the largest variation. The results of PCA, a multivariate statistical method, show that the first three principal components explain $73.9\%$ of the total variance. PC1 indicates the increase of dissolved ions, PC2 is related with the dissolution of carbonate minerals and nitrate contamination, and PC3 shows the effect of cation exchange process and silicate mineral dissolution. From the results of experimental semivariogram, the components of groundwater are divided into two groups: one group includes electrical conductivity (EC), Cl, Na, and $NO_3$, and the other includes $HCO_3,\;SiO_2,$ Ca, and Sr. The results for spatial distribution of groundwater components showed that EC, Cl, and Na increased with approaching the coastal line and nitrate has close relationship with the presence of agricultural land. These components are also correlated with the topographic features reflecting the groundwater recharge effect. The kriging analysis by using principal components shows that PC 1 has the different spatial distribution of Cl, Na, and EC, possibly due to the influence of pH, Ca, Sr, and $HCO_3$ for PC1. It was considered that the linear anomaly zone of PC2 in western area was caused by the dissolution of carbonate mineral. Consequently, the application of multivariate and geostatistical methods for groundwater in the study area is very useful for determining the quantitative analysis of water quality data and the characteristics of spatial distribution.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.169-187
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• 2023

Aggregates from 84 cities and counties in Korea were tested for quality to allow analysis of the physical characteristics of aggregates from river, land, and forest environments. River and land aggregates were analyzed for 18 test items, and forest aggregates for 12 test items. They were classified according to watershed and geology, respectively. The observed physical characteristics of the river aggregates by basin were as follows: aggregates from the Geum River basin passed through 2.5, 1.2, 0.6, 0.3, 0.15, and 0.08 mm sieves; clay lumps constituted the Nakdong River basin material; aggregates from the Seomjin River basin passed through 10, 5, and 2.5 mm sieves; those from the Youngsang River basin passed through 1.2, 0.6, 0.3, 0.15, and 0.08 mm sieves; and aggregates from the Han River basin passed through 10, 5, 2.5, 1.2, 0.6, 0.3, and 0.08 mm sieves, Stability; Standard errors were analyzed for the average amount passing through 10, 0.6, and 0.08 mm silver sieves, and performance rate showed different distribution patterns from other physical characteristics. Analysis of variance found that 16 of the 18 items, excluding the absorption rate and the performance rate, had statistically significant differences in their averages by region. Considering land aggregates by basin, those from the Nakdong River basin excluding the Geum River basin had clay lumps, those from the Seomjin River basin had 10 and 5 mm sieve passage, aggregates from the Youngsang River basin had 0.08 mm sieve passage, and those from the Han River basin had 10, 0.6, and 0.08 mm sieve passage. The standard error of the mean of the quantity showed a different distribution pattern from the other physical characteristics. Analysis of variance found a statistically significant difference in the average of all 18 items by region. Analyzing forest aggregates by geology showed distributions of porosity patterns different from those of other physical characteristics in metamorphic rocks (but not igneous rocks), and distributions of wear rate and porosity were different from those of sedimentary rocks. There were statistically significant differences in the average volume mass, water absorption rate, wear rate, and Sc/Rc items by lipid.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.289-302
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• 2023

The study area was Gangnim-myeon, Hoengseong-gun, Gangwon-do, composed of the Chiaksan gneiss complex, and it was revealed that the concentrations of uranium (U) and thorium (Th) within the groundwater of the study area exceeded their water quality standards. Hence, artificial weathering experiments were conducted to elucidate mineralogically the mechanisms of their leaching using drilling cores obtained from the corresponding groundwater aquifers. First of all, the mineralogical compositions of core samples were observed, and the results indicated that the content of clinochlore, a member of the chlorite group of minerals that can form through low- and intermediate-temperature metamorphisms, was relatively higher. In addition, the Th concentration was measured ten times higher than that of U. The results of artificial weathering experiments suggested that the Th concentrations gradually increased through the dissolution of radioactive-element-bearing minerals up to the first day, and then they tended to decrease. It could be attributed to the fact that Th was leached with the dissolution of thorite, which might be a secondary mineral, and then dissolved Th was re-precipitated as the various forms of salt, such as sulfate. Even though the U content was lower than that of Th in the core samples, the U concentration was one hundred times higher than that of Th after the weathering experiments. It is likely caused by the gradual dissolution and desorption of U included in intensively weathered thorite or adsorbed as a form of UO₂²⁺ on the mineral surface. In addition, the leaching tendency of U and Th was positively correlated with the bicarbonate concentration. However, the concentrations between U and Th in groundwater exhibited a relatively lower correlation, which might result from the fact that they occurred from different sources, as aforementioned. Among various kinetic models, the parabolic diffusion and pseudo-second-order kinetic models were confirmed to best fit the dissolution kinetics of both elements. The period that would be taken for the U concentration to exceed its drinking-water standard was inferred using the regressed parameters of the best-fitted models, and the duration of 29.4 years was predicted in the neutral-pH aquifers with relatively higher concentrations of HCO₃, indicating that U could be relatively quickly leached out into groundwater.

• Korean Journal of Food Science and Technology
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• v.43 no.5
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• pp.588-596
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• 2011

Wild grape extract (WGE) was added into hwajeon at different concentrations (0, 5, 15, 30, 50% of water). The resulting hwajeon were analyzed for their physicochemical and sensory properties. With increasing concentrations of WGE, the pH of dough and hwajeon decreased, and their degrees brix and color intensity increased, presumably due to the presence of tartaric acid, sugar, and anthocyanin in the WGE. The WGE-enriched hwajeon showed higher hardness, gumminess, and chewiness than control hwajeon, which might have been because the sugar and tartaric acid in the WGE partially inhibited starch gelatinization during heat processing. Nevertheless, all the sensory properties and preference were higher in WGE-enriched hwajeon than controls, which could be partially attributed to the fact of that the WGE-enriched hwajeon retained relatively higher moisture. It is suggested that WGE-enriched hwajeon with high preference could be prepared without loss of hwajeon quality.

• Korean Journal of Food Science and Technology
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• v.49 no.6
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• pp.575-583
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• 2017

Germination is a well-known economical technique that has been utilized to enhance the nutritional value of brown rice. Owing to its higher nutritive quality, germinated brown rice has received significant attention in the past decade. In this study, the physicochemical and cooking properties of specialty brown rice (SBR) were analyzed before and after germination. Germination enhanced cooking properties such as water absorption, expanded volume, and increased solid solubility of cooked SBR. The SBR texture measured using tensipresser, was significantly improved by germination. The hardness of cooked SBR was decreased by germination, but stickiness was increased. Pasting analysis of the SBR flours revealed a decrease in all viscosity values (peak viscosity, breakdown, setback, and final viscosity) after germination. However, the gelatinization temperature remains unchanged upon germination. Additionally, amylose content and amylopectin chain length distribution of SBR starch were slightly changed by germination. These results indicate that germination leads to a substantial improvement in the cooking properties and texture of SBR.

• Economic and Environmental Geology
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• v.36 no.1
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• pp.27-38
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• 2003

Arsenic contamination around Au-Ag mining areas occurs mainly from the oxidation of arsenopyrite which is frequently contained in mine tailings. In weathered tailings, oxidation of sulfide minerals typically results in the formation of abundant ferric (oxy)hydroxides or (oxy)hydroxysulfates near the tailings surface, and arsenic may be associated with these secondary precipitates. In this study, solid phases of arsenic in weathered tailings of some Au-Ag mines were investigated through the SEM/EDS and sequential extraction analyses. The stability of As solid phases and the leaching potential were assessed with the variation of pH and Eh conditions. Oxidation of sulfides in the tailings samples was indicated by depletion of S molar concentrations compared to As and heavy metals. Under XRD examinations, jarosite as an Fe-oxyhydroxysulfate was found in the tailings of Deokeum, Dongil and Dadeok, and scorodite as an As-bearing crystalline mineral was identified from Dadeok which has the highest concentration of As (4.36 wt.%). Beudantite-like phases and some Pb-arsenates were also found under SEM/EDS analysis, and most of As phases were associated with Fe-(oxy)hydroxides and (oxy)hydroxysulfates despite a few arsenopyrite from Samgwang and Gubong. Sequential extraction analysis also showed that As was present predominantly as coprecipitated with Fe hydroxides from Dongil, Dadeok and Myungbong (72∼99%), and as sulfides (58%) and Fe hydroxide-associated forms (40%) from Samgwang and Gubong. In the tailings leaching experiment, As was released with high amounts by the dissolution of As-bearing Fe(oxy)hydroxysulfates in the lowest pH (2.7) conditions of Deokeum, and by desorption under alkaline conditions of Samgwang and Gubong. Higher leaching rates of arsenite(+3) were found under acidic conditions, which pose a higher risk to water quality. Changes in pH and Eh conditions coupled with microbial processes could influence the stabilities of the As solid phases, and thus, time amendments or landfilling of weathered tailings may result in enhanced As mobilization.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.3
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• pp.348-356
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• 2008

For the effective use of rainbow trout, the seasoned and dried rainbow trout slice (SR) was prepared and its characterization was compared with the commercial skipjack tuna (CSS) and pork products (CSP) by determining chemical components and sensory evaluation. The moisture content of SR, 20.5%, was lower, and the lipid content of SR, 7.5%, was higher than those of commercial products, CSS and CSP. The protein content of SR (41.4%) was higher than that of CSS (28.6%), but lower than that of CSP (50.1%). The water activity of SR was 0.654, which was lower than those of CSS and CSP, 0.724 and 0.771, respectively. According to the results, the color of SR was lower in lightness and redness and higher in browning index and ${\Delta}$E value than that of commercial products. The texture of SR was harder than that of CSS, but softer than that of CSP. According to the result of taste value, the taste of SR was stronger than that of CSP, while weaker than that of CSS. The mineral (Ca, P, and Fe), total amino acid contents, and the n-3/n-6 of SR showed significant levels in nutrition and health functional senses.

• Korean journal of food and cookery science
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• v.26 no.5
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• pp.636-648
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• 2010

Two types of wild grape extracts(WGE) prepared by different methods were added into butter-top bread at different concentrations(0, 5, 10, 15, 20% of water). Then, the resulting breads were analyzed for their physicochemical and sensory properties in order to identify whether or not the WGE-enriched breads were comparable to control bread in terms of qualities and preferences. Wild grape sugar mixture(WGS), which was prepared by osmotic dehydration of wild grape fruits with the same amounts of sugar, presented significantly lower moisture content and titratable acidity as well as higher pH and sugar content compared to wild grape juice(WGJ), which was produced by boiling the fruits in a vacuum jar and squeezing. The pH of the doughs and breads containing WGE tended to decrease with increasing amounts of WGE, and this phenomenon was more appreciable in those containing WGJ than WGS. This was presumably due to the higher contents of tartaric acid in WGJ. For both types of extracts, hardness, gumminess, and chewiness of the doughs decreased with the addition of WGE, nevertheless, which properties were not remained in the resulting breads. This could be partially attributed to the relatively high degree of baking loss and lower pH of the WGE-enriched breads than those of control bread. Contrary to the mechanical analyses, the sensory properties of the breads were dependent on the WGE type. That is, WGJ-enriched bread showed lower consistency and moistness than control bread, which consequently led to relatively lower overall acceptability. However, WGS addition did not adversely affect the sensory properties of the bread. In particular, addition of 5% WGS somewhat improved the physical and sensory qualities of the bread. Thus, WGE-enriched bread could be produced without loss of bread quality when prepared with 5% WGS.