• Applied Biological Chemistry
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• v.39 no.3
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• pp.200-205
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• 1996

This experiment was conducted to characterize and quantify the free sugars (glucose, fructose, sucrose, maltose) contained in many different portions of watermelon (Citrus vulgaris L.) and muskmelon (Cucumis melo var. reticulatus Naud.) fruits by High Performance Liquid Chromatography (HPLC). Free sugars were mainly fructose, glucose, sucrose, and their contents were variable among portions. Total free sugar contents were higher in the stylar end and side than in the stem end of both watermelon and muskmelon. Total free sugar contents increased from the periphery toward the central core in watermelon and except central core content seeds in muskmelon Ratio of nonreducing to reducing sugars [(fructose + glucose)/sucrose] was gradually decreased from the periphery toward the middle area in watermelon, though the central core showed higher value than the middle area. For the edible portion of muskmelon, the ratio was decreased toward middle area, and no significant difference was observed between the central core and the middle area. However, reducing sugars and nonreducing sugar were all increased from the periphery toward the central core in watermelon. In contrast with watermelon, reducing sugars were decreased in muskmelon.

• Journal of Environmental Impact Assessment
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• v.31 no.5
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• pp.296-309
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• 2022

This study investigated the mobility of inorganic elements (As, Cd, Pb, and Zn) that existed as acid extractable and reducible forms in flooded soils with a pot experiment involving rice cultivation. In general, it is known that soil inorganic elements that existed as an acid extractable form which includes exchangeable, carbonates, non-specifically sorbed, and specifically sorbed have mobility. However, the result of the experiment revealed that each inorganic elements of rice roots grown from flooded soils had different characteristics. The concentrations of Arsenic existed as both forms and the concentrations of cadmium and lead existed as a reducible form in the soils showed a high causal relationship with the concentrations of those elements in the roots of rice plants. The concentrations of zinc, an essential plant element, didn't show a causal relationship. Therefore it is necessary to consider the soil's environmental characteristics such as drained/flooded condition, oxidation/reduction condition, etc. for the mobility assessment of inorganic elements. The concentrations of the reducible form of arsenic, cadmium, and lead in flooded environment such as a paddy field should be also considered because the mobility of these elements combined with Fe/Mn increases in the reduction condition.

• Journal of the Mineralogical Society of Korea
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• v.26 no.4
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• pp.219-228
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• 2013

To understand characteristics of biogeochemical corrosion for the metal canisters that usually contain the radioactive wastes for a long-term period below the ground, some metal materials consisting of cast iron and copper were reacted for 3 months with D. desulfuricans, a sulfate-reducing bacterium, under a reducing condition. During the experiment, concentrations of dissolved metal ions were periodically measured, and then metal specimen and surface secondary products were examined using the electron microscopy to know the chemical and mineralogical changes of the original metal samples. The metal corrosion was not noticeable at the absence of D. desulfuricans, but it was relatively greater at the presence of the bacterium. In our experiment, darkish metal sulfides such as mackinawite and copper sulfide were the final products of biogeochemical metal corrosion, and they were easily scaled off the original specimen and suspended as colloids. For the copper specimen, in particular, there appeared an accelerated corrosion of copper in the presence of dissolved iron and bacteria in solution, probably due to a weakening of copper-copper binding caused by a growth of other phase, iron sulfide, on the copper surface.

• Korean Journal of Microbiology
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• v.38 no.2
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• pp.133-138
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• 2002

Microbial Fe (III) reduction is important for the biogeochemical cycle in the sediment of freshwater system. Also, the Fe (III) reducing mechanism make a model of oxidizing organic compounds and reducing toxic heavy metals, such as chrome or uranium. Thirty-seven strains which have Fe (III) reducing activity were isolated from sediments in lake Soyang and Chunho reservoir. The initial concentration of Fe (II) was the highest in sediments of lake Soyang. However, the highest Fe (III) reducing activity was shown in Chunho reservoir. All isolates were tested for Fe (III) reducing activity. Strains C2 and C3, which were isolated from sediments of Chunho reservoir, showed the highest activity. These strains were tested to see if they utilize various electron donors such as glucose, yeast extract, acetate, ethanol and toluene. Significantly, glucose and yeast extract were used as electron donors. Also these strains were conformed to use humid acid and nitrate as electron accepters. The 16S rRNA sequences of strains C2 and C3 were closely related to Aeromonas hydrophila with 95% similarity.

• Resources Recycling
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• v.30 no.5
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• pp.25-31
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• 2021

Smelting reduction of spent lithium-ion batteries results in the production of metallic alloys in which reduced cobalt, nickel and copper coexist. In this study, we investigated the leaching of the metallic alloys containing the above three metals together with iron, manganese, and silicon. The mixture of hydrochloric acid and hydrogen peroxide as an oxidizing agent was employed, and the effect of the concentration thereof, the reaction time and temperature, and pulp density was investigated to accomplish the complete leaching of cobalt, nickel, and copper. The effect of the hydrogen peroxide concentration and pulp density on the leaching was prominent, compared to that of reaction time and temperature, especially in the range of 20 to 80℃. The complete leaching of the metals present in metallic alloys, except silicon, was accomplished using 2 M HCl and 5% H₂O₂ with a pulp density of 30 g/L for 150 min at 60℃.

• Economic and Environmental Geology
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• v.36 no.1
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• pp.39-48
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• 2003

The removal of chromate from aqueous solution using finely ground pyrite and biotite was investigated by batch experiments and the kinetics and the mechanism of chromate reduction were discussed. The chromate reduction by pyrite was about hundred times faster than that by biotite and was also faster at pH 3 than at pH 4. When pyrite was used, more than 90% of initial chromate was reduced within four hours at pH 4 and within 40 min. at pH 3. However, more than 400 hours was taken for the reduction of 90% of initial chromate by biotite. The results indicate that the rate of chromate reduction was strongly depending on the amount of Fe(II) in the minerals and on the dissolution rate of Fe(II) from the minerals. The reduction of chromate at pH 4 resulted in the precipitation of (Cr, Fe)(OH))$_3$$_{ (s)}$, which is believed to have limited the concentrations of dissolved Cr(III) and Fe(III) to less than expected values. When biotite was used, amounts of decreased Fe(II) and reduced Cr(Ⅵ) did not show stoichiometric relationship, which implying there was not only chromate reduction by ferrous ions in the acidic solution but also heterogeneous reduction of ferric ions by the structural ferrous iron in biotite. However, the results from a series of the experiments using Pyrite showed that concentrations of the decreased Fe(II) and the reduced Cr(Ⅵ) were close to the stoichiometric ratio of 3:1. It was because the oxidation of pyrite rapidly created ferrous ions even in oxygenated solutions and the chromate reduction by the ferrous ions was significantly faster than ferrous ion oxygenation.

• Economic and Environmental Geology
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• v.39 no.2 s.177
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• pp.151-162
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• 2006

Characteristics and changes of groundwater qualify were investigated in a riverbank filtration area at Daesan-myeon, Changwon City, Korea. The total dissolved solids (TDS) in groundwater samples collected in October were much less than that in March, indicating the mixing with recharged water from precipitation, as well as the changes of dissolved oxygen profiles at monitoring wells from March to October. Redox processes at depths appeared to trigger Fe and Mn contamination of groundwater in riverbank deposits. Amorphous oxyhydroxides md carbonate minerals such as $MnCO_3$ were probably the reactive phases for dissolved Fe and Mn, respectively. Groundwater contamination by nitrate-nitrogen $(NO_3-N)$ was controlled by the redox processes and subsequent denitrification at the sampled depths. Distribution of $NO_3-N$ concentrations at monitoring wells suggested that the nitrate contaminants were originated from agricultural facilities on the riverbank deposits. Some of monitoring wells, DS-2, D-2, DS-3, SJ-1, and SJ-3, were only partially penetrated into the sand/gravel aquifer, and subsequently, could not fully function to detect the water quality changes for the pumping wells. Proper measures, with regulating agricultural activities in the riverbank deposits, should be carried out to prevent groundwater contamination of the riverbank filtration area.

• Korean Journal of Organic Agriculture
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• v.20 no.1
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• pp.37-48
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• 2012

This study was conducted to evaluate the effects of ground cover treatments on the nutrient contribution in a 'Niitaka' pear ($Pyrus$ $pyriforia$) orchard. Treatments included; 1) sod culture, 2) winter cover crop [ryegrass+hairy vetch], and 3) winter [ryegrass+hairy vetch]+summer [greensolgo (sudan grass ($Sorghum$ $bicolor$ L.))+ nemajanghwang (crotalaria ($Crotalaria$ $juncea$ L.)] cover crops. Ryegrass and hairyvetch were seeded with 6.4 kg/10a and 3.0 kg/10a, respectively, on October 17 of 2008, and greensolgo and nemajanghwang were seeded with 2.0 kg/10a and 3.0 kg/10a, respectively, on June 4 of 2009 at a diligent farmer in Boseong in Chonnam. Winter+summer cover crops provided greater amounts of dry weight, followed by winter cover crop and sod culture. The difference of amounts of dry weight from the ground covers affected to the levels of total N, P, and K contents, which were greater nutrient levels than those of recommended nutrient requirement for satisfying 10- to 12-year-old pear tree growth. Greater amounts of dry weight from the ground covers increased organic matter and concentrations of K and Mg in soil. Foliar nutrient concentrations, as an indicator of nutrient status of a tree, were not affected by application of ground cover treatments.

• Journal of Life Science
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• v.27 no.10
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• pp.1121-1129
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• 2017

The authors evaluated the scavenging activities of ABTS+ radical, hydroxy radical (OH), nitric oxide (NO), and ferric ion reducing antioxidant power (FRAP) from ethanol extracts of four edible alga, Enteromorpha linza, Porphyra tenera, Sargassum fusiforme, and Undaria pinnatifida. ABTS+ scavenging activity was analyzed according to the method of Brand-Williams et al. ABTS+ scavenging activity of S. fusiforme was evaluated to 61.8% at 8.0 mg/ml. ABTS+ scavenging activity of P. tenera was evaluated to 35.7% at 8.0 mg/ml. P. tenera and U. pinnatifida showed similar inhibitions of ABTS+ scavenging activity. According to the results of the OH assay in seaweed, inhibitory activities were in the order of S. fusiforme > P. tenera > U. pinnatifida > E. linza. The results showed scavenging activity for NO in the following order of potency: S. fusiforme > P. tenera > U. pinnatifida > E. linza with concentration values of 8.0 mg/ml. The NO scavenging activities of dough, which was instant noodles mixed with S. fusiforme and 3.5% salt, were 27.2% at 8.0 mg/ml. After boiling for 5 minutes, FRAP scavenging activity of instant noodles mixed with extracts of U. pinnatifida was evaluated to 31.5% at 8.0 mg/ml. S. fusiforme showed the highest inhibition activity of ABTS+, OH, NO, and FRAP among the four algae. Thus, these findings provide evidence that P. tenera, U. Pinnatifida, S. fusiforme, and E. linza extracts could become sources of natural antioxidants.

• 한국해양학회지
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• v.25 no.1
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• pp.8-20
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• 1990

A series of pore water data were obtained during the different time over one year period between October 1987 and October 1988, from a site on a muddy intertidal flat, located in the Kyeong-gi Bay, west coast of Korea, The results have revealed that the tidal flat is an environment of active nutrient the subface supplied by the overlying seawater is almost completely removed from the pore water at depth of about 10 cm below the sediment surface. The nutrients such as ammonium and phosphate are produced through this process and subsequently accumulated in the pore water forming steep gradients near the sediment surface. Below the main sulfate redirection zone, a secondary peak of dissolved sulfate was often observed. Greal seasonal variation of the pore water nutrient profiles was observed, which was particularly clear in their maximum concentration as well as in their concentration gradient. The rate constants of sulfate reduction and nutrient regeneration, estimated by using a diagenetic model (Berner, 1980), differ by an order of magnitude between the summer and winter seasons. The difference in sediment temperature may account for most of the calculated variation. The C:N:P ratio, calculated from the pore water nutrient gradients also exhibits a slight seasonal difference. The organic matter being decomposed by sulfate reduction appears to be depleted in depleted in nitrogen, compared to the average marine organic matter.