• Journal of Soil and Groundwater Environment
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• v.6 no.3
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• pp.3-12
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• 2001

This study conducted to Investigate the movement of fertilized nutrients in a volcanic ash soil in Jeju using by the pressure-vacuum soil water sampler. The percolated water to measure the ion concentration of leachates was taken from a lysimeter at depths of 20, 40, 60, 80, 100 and 120 cm in the soil in where a corn and potato were cultivated as a preceding and succeeding crop, respectively. Fertilizers of N-$P_2$O$_{5}$-$K_2$O were applied at the rate of 36-30-30 kg $10a^{-1}$ for the corn and 28-22-24 kg $10a^{-1}$ for the potato prior to planting of both crops. The highest concentrations of Cl , $NO_3$-N, $Ca^{+2}$ and $K^+$ in percolates were showed at 20cm and 40cm in soil depth at one month after fertilizing, and then gradually moved and reduced into below soil depths. At 5.5 months after fertilization, the concentrations in all soil depths were similar with the value of before fertilization. At depth of 120cm, the concentration of NO$_3$-N and the other cations in leachate was highest 1 to 1.5 months after fertilization. pH in percolated water was negatively correlated with NO$_3$-N concentration while the concentration of $NO_3$-N showed positive correlation between Cl, $Ca^{+2}$ and $Mg^{+2}$ concentrations. This result indicated that those cations can be leached out by accompanied with $NO_3$-N.

• Journal of Wetlands Research
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• v.17 no.2
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• pp.203-208
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• 2015

To identify the effect of fallen cherry blossom on the artificial pond ecosystem, microcosm experiment was conducted into the aquatic decomposition of Prunus species petals. Petals were put in $1mm^2$ mesh nylon litter bags. For treatment group, one flower litter bag was placed into each pot microcosm ($27{\times}20{\times}8cm^3$) filled with influent water from the artificial pond, whereas control group microcosm contained pond water only. Decomposition time were set differently (4, 8, 12, 16 days) among treatment groups. At the end of experiment, most petals were decomposed and only 32.3% of initial dry weight remained with the decay rate (k) of $7.06{\times}10^{-2}day^{-1}$. $NO_3-N$ concentration of microcosm water decreased sharply from 1.90 mg/L at first to 0.02 mg/L, whereas $NH_4-N$ concentration increased from 0.03 mg/L to 2.85 mg/L continually. $PO_4-P$ concentration was 0.03 mg/L at first and increased to 2.39 mg/L by decomposition. Therefore, available phosphorus seems to have leached with higher rate than nitrogen from the petals litter. Increase about 0.02 mg/L in $PO_4-P$ concentration could be estimated in artificial pond from the calculation on the total quantity of fallen blossoms. This result suggests that available phosphorus from the decomposed Prunus petals could cause eutrophication in the artificial pond.

• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Resources Recycling
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• v.29 no.1
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• pp.81-88
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• 2020

Recovery of gallium and indium from waste light emitting diodes has been emphasized gradually owing to high content of gallium and indium. This study was established the recovery of gallium (Ga³⁺) and indium (In³⁺) from waste gallium nitride was contained in waste light-emitting diodes. The procedure was divided into the following steps; characteristic analysis, alkaline roasting, and leaching. In characteristic analysis part, the results were used as a theoretical basis for the acid leaching part, and the chemical composition of waste light emitting diodes is 70.32% Ga, 5.31% Si, 2.27% Al and 2.07% In. Secondly, with reduction of non-metallic components by alkaline roasting, gallium nitride was reacted into sodium gallium oxide, in this section, the optimal condition of alkaline roasting is that the furnace was soaked at 900℃ for 3 hours with mixing Na₂CO₃. Next, leaching of waste light emitting diodes was extremely important in the process of recovery of gallium and indium. The result of leaching efficiency was investigated on the optimal condition accounting for the acid agent, concentration of acid, the ratio of liquid and solid, and reaction time. The optimal condition of leaching procedures was carried out for 2.0M of HCl liquid-solid mass ratio of 30 ml/g in 32minutes at 25℃ and about 96.88% Ga and 96.61% In were leached.

• Journal of Korean Society of Forest Science
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• v.90 no.1
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• pp.133-138
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• 2001

Increased base cation loss and Al mobilization, a consequence of soil acid neutralization responses, are common in air polluted areas showing forest decline. The prediction models of acid neutralization responses were developed by using indicators of soil acidification level(pH, and base saturation) in order to assess the forest soil sensitivity to acidification. The soil acidification level was greatest in Namsan followed by Kanghwa, Ulsan, and Hongcheon, being contrary to regional total $ANC_H$ pattern through soil columns leached with additional acid ($16.7mmol_c\;H^+/kg$), Both base exchange and Al dissolution were main acid neutralization processes in all study regions. There were low base exchange and high Al dissolution in the regions of the low total $ANC_H$. The $ANC_M$ by sulfate adsorption was greatest in Hongcheon compared with other regions even though the AN rate was very low as 6.4%. Coefficients of adjusted determination of simple and multiple regression models between soil acidification level indicators and the acid neutralization responses were more than 0.52(p<0.04) and 0.89(p<0.01), respectively. The result suggests that soil pH and base saturation are available indicators for predicting the acid neutralization responses. These prediction models could be used as an useful method to measure forest soil sensitivity to acidification.

• Elastomers and Composites
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• v.38 no.3
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• pp.243-250
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• 2003

Polyurethane waterproof (PW) coatings are increasingly demanded in Korea for repairing cracks on old building roofs and construction of many sporting facilities. Calcium carbonate, a common filler, is incorporated in PW compositions. In this study, PW coatings were prepared by substituting a part of calcium carbonate with fly ash. The maximum amounts of calcium carbonate which can be substituted by fly ash obtained in the cyclone and bag filter dust collectors were 20 and 10%, respectively. It was found that the curing rate of PWs ran be controlled by varying the amount of Pb-octoate catalyst. The elongations at break as well as tensile strength and tear strength of PW coatings containing fly ash could also be adjusted such that their values were comparable to those of a standard PW coating by varying relative amounts of some components. However, the amount of cadmium, mercury, and lead leached from PW coatings containing fly ash obtained from the bag filter collector exceeded the respective allowed upper limits, mainly due to the initial high contents of them in the fly ash. On the other hand, PW coatings containing fly ash obtained from the cyclone collector exhibited better mechanical properties and did not release any significant amounts of the heavy metals. Thus, it was concluded that PW coatings containing fly ash can be utilized for practical applications as long as an appropriate fly ash is used.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.641-647
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• 2015

Monitoring of soil fertility by long-term application of fertilizers is necessary to improve the fertility of soil and the productivity of crop. The objective of this study was conducted to investigate the changes of exchangeable Mg by continuous application of fertilizers from 1969 to 2014. The treatments were no fertilization (No fert.) and fertilization (NPK, NPK+C, NPK+S, and NPK+CS). The concentration of exchangeable Mg in No fert., NPK+C, and NPK+S treatments tended to increase from 1965 to 1975, but decrease gradually from 1976 to 1987, and increase again after 1988. Based on these, the changes of exchangeable Mg were divided into period I ('69 ~'75), period II ('76~'87), and period III ('88~'14). Especially, exchangeable Mg decreased in the period II. This was presumed that a significant amount of Mg from topsoil were leached into subsoil by break of plow pan and some of subsoil was incorporated into topsoil according to change of plowing depth by replacement of tillage machinery. It could be possible that exchangeable Mg in NPK, NPK+S, and NPK+CS was accumulated in the depth of 15~20 cm. For the period III, exchangeable Mg in No fert., NPK, NPK+C, NPK+S, and NPK+CS treatments increased at rates of 0.013, 0.018, 0.015, 0.023, and $0.024cmolckg^{-1}{\cdot}yr^{-1}$ respectively. Exchangeable Mg level in NPK+S was lower than the other treatments in the period I and period II, but higher than in the period III. This result was attributed to replacement of silicate fertilizer type from wollastonite (Mg 0.3%) to silicate fertilizer (Mg 3%). Also, exchangeable Mg level of No fert. treatment increased, which showed that Mg concentration of irrigated water had the greatest impact on Mg accumulation of soil. Recently, Mg level of irrigated water tended to increase, indicating that Mg concentration of water will affect greatly the concentration of exchangeable Mg of soil in the future. Like these, the changes of exchangeable Mg were greatly influenced by agricultural environment such as plowing depth, plow pan, content of fertilizer, and quality of irrigated water. Considering these agricultural environment, the proper management of soil is needed for the improvement of soil fertility and crop productivity.

• Korean Journal of Food Science and Technology
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• v.50 no.6
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• pp.697-700
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• 2018

This study investigated changes in amygdalin of maesil liqueurs during leaching and ripening, and their qualities during ripening. Maesil was leached at $24^{\circ}C$ for 3 months in a commercial soju (30% alcohol). During leaching, amygdalin contents dramatically increased by 1 month, remained at a plateau by 2 months, and then decreased at 3 months. Once completion of leaching, maesil liqueurs were ripened for 3 months together with maesil (ML1) and maesil flesh itself (ML2), and without maesil (ML3). During ripening, amygdalin contents significantly decreased for all treatments, and the reduction in amygdalin rapidly proceeded in the order: ML2>ML1>ML3. Alcohol contents decreased for ML1 and ML2, while remained constant for ML3. Their pH and titratable acidity observed only subtle changes, and their color became increasingly darker. Overall results suggested that the long-term ripening of maesil liqueurs containing maesil or maesil flesh (without seeds) may resolve the concern on their amygdalin toxicity.

• Resources Recycling
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• v.30 no.5
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• pp.57-66
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• 2021

In this study, we attempted to separate and recover Cu from low-grade copper ore by a hydrometallurgical process. The leaching sample obtained after crushing and sieving by 0.355 mm of low-grade copper ore contained 1.5% Cu, 4.7% Fe, 1.0% Mn, and 0.3% Zn. The Cu in the oxide ore was very well leached into sulfuric acid and 97% Cu leaching efficiency was achieved at 80℃ and 3 M sulfuric acid (H₂SO₄). From the leaching solution, Cu was separated by solvent extraction from Fe, Mn, and Zn using LIX984N. The separation tendency between Cu and other metals was confirmed through the distribution ratio and separation factor. By plotting the McCabe-Thiele Diagram, the optimum condition for recovering Cu is 5 vol.% LIX984N, 2-stage counter-current solvent extraction, and an O/A ratio of 0.5. Using this method, 99% of the Cu was extracted and a CuSO₄ solution was finally obtained that contained 1.6 g/L Cu after the stripping process using 2 M H₂SO₄.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.259-269
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• 2021

The effects of the physicochemical properties of soil such as soil pH, cation exchange capacity, and organic matter content on single extraction of Cd, Cr, Cu, Ni, Pb, and Zn using CaCl2, HOAc, HNO3, and DTPA were statistically investigated for 69 agricultural soils in Korea. Correlation analysis and multiple regression analysis were applied for soil samples which were grouped on the basis of average values of the physicochemical properties of the soil. Diluted HNO3 extracted higher concentrations of Cr, Cu, Ni, and Pb when compared with the other extractants, however, similar amounts of Cd and Zn were extracted by HOAc with HNO3. The results of correlation analysis indicated that DTPA extraction showed a high correlation with other single and pseudo-total extraction methods, and the physicochemical properties of soil influenced the concentrations of heavy metals leached by the single extraction methods. In the case of Zn, high correlations between pseudo-total and the studied single extraction methods were observed. As a result of regression analysis, it was found that the physicochemical properties of the soil could explain up to 74% of variances of the single extraction results. These results indicate that the physicochemical properties of the soil can have a direct influence on the concentrations of heavy metals extracted by the single extraction methods.