• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.75-82
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• 2010

Indoor cultivation plots for watermelon plant mostly have salt-accumulation problem because of continuous cropping especially with the heavy applications of chemical fertilizers. Thus, this study was conducted to investigate selected soil properties and watermelon growth condition as affected by the application of different farming practices in the salt-affected soils of greenhouse plots used for continuous watermelon production. Five different practice conditions in the experimental plots were applied, 1) a conventional farming practice (CFP), 2) a nitrogen-phosphorus-potassium (NPK) fertilizer management practice (FMP), and 3) the FMP with different amounts (5, 10, and 15 ton $ha^{-1}$)of fresh rice straw treatments (FMP-RS), for three years of study. As comparing with CFP plots, soil organic matter content gradually increased during the experimental years, whereas it decreased in the FMP only plot. Soil pH was not changed in the CFP and FMP plot, but it declined in the FMP-RS plots; however, it increased again from the third year in the FMP-RS plots with applying 10 and 15 ton $ha^{-1}$ of RS treatments. The concentrations of exchangeable cations, $Ca^{2+}$ and $Mg^{2+}$, except $K^+$, and water-soluble anions, ${NO_3}^-$, $Cl^-$, ${SO_4}^{2-}$ and ${PO_4}^{3-}$, markedly decreased in FMP and FMP-RS plots. In particular, the application of rice straw tended to significantly decrease the ion concentrations, especially most anions, in the first year, but there was no more decrease in the second and third study years. With relation to the ion concentrations, the changes of electrical conductivity (EC) after applying the management practices showed very similar to those of the ion concentrations. In addition, incidence of withered watermelon plant after applying the management practices dramatically declined from approximately 20% in the CFP plot to 3.5% in the FMP-RS plots. Water melon fruit weight was also improved by the management practices, especially FMP-RS. Therefore, the fertilizer and/or fresh rice straw application management practices are beneficial to improve salt-affected soils and watermelon plant growth condition.

• Applied Biological Chemistry
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• v.17 no.3
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• pp.149-176
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• 1974

Eight substituted diphenyl ether herbicides and some of their photoproducts were studied in terms of solution phase photolysis under simulated environmental conditions by using a Rayonet photochemical reactor. The test compounds absorbed sufficient light energy at the wavelength of 300 nm to undergo various photoreactions. All the photoproducts were confirmed by means of tlc, glc, ir, ms, and/or nmr spectrometry. The results obtained are summarized as follows: Solution phase photolysis of C-6989: An exceedingly large amount of p-nitrophenol formed strongly indicates the readiness of the ether linkage cleavage of this compound as the main reaction in all solvents used. Photoreduction of nitro to amino group(s) and photooxidation of trifluoromethyl to carboxyl group were recognized as minor reactions. Aqueous photolysis of p-nitrophenol: Quinone(0.28%), hydroquinone (0.66%), and p-aminophenol (0.42%) were confirmed as photoproducts, in addition to a relatively small amount of an unknown compound. The mechanisms of formation of these products were proposed to be the nitro-nitrite rearrangement via $n{\rightarrow}{\pi}^*$ excitation and the photoreduction through hydrogen abstractions by radicals, respectively. Solution phase photolysis of Nitrofen: Photochemical reduction leading to the p-amino derivative was the main reaction in n-hexane. In aqueous solution, the photoreduction of nitro to amino group and hydroxylation predominated over the ether linkage cleavage. Nucleophilic displacement of the nitro group by hydroxide ion and replacement of chlorine substituents by hydroxyl group or, to a lesser extent, hydrogen were also observed as minor reactoins. Solution phase photolysis of MO-338: Photoreduction of the nitro to amino group was marked in the n-hexane solution photolysis. In the aqueous solution, photoreduction of the nitro substituent and hydroxylation were the main reactions with replacement of chlorine substituents by the hydroxyl group and hydrogen, and cleavage of the ether linkage as minor reactions. Photolyses of MC-4379, MC-3761, MC-5127, MC-6063, and MC-7181 in n-hexane and cyclohexane: Photoreduction of the nitro group leading to the corresponding amino derivative and replacement of one of the halogen substituents by hydrogen from the solvent used were the key reactions in each compound. Aqueous photolysis of MC-4379: Cleavage of the ether linkage, replacement of the carboxymethyl by hydroxyl group, hydroxylation, and replacement of the nitro by hydroxy group were prominent with photoreduction and dechlorination as minor reactions. Aqueous photolysis of MC-3761: Cleavage of the ether linkage, replacement of the carboxymethyl by hydroxyl group, and photoreduction followed by hydroxylation were the main reactions. Aqueous photolysis of MC-5127: Replacement of carboxyethyl by hydrogen was predominant with ether linkage cleavage, photoreduction, and dechlorination as minor reactions. It was obvious that the decarboxyethylation proceeded more readily than decarboxymethylation occurring in the other compounds. Aqueous photolysis of MC-6063: Cleavage of the ether linkage and photodechlorination were the main reactions. Aqueous photolysis of MC-7181: Replacement of the carboxymethyl group by hydrogen and monodechlorination were the remarkable reactions. Cleavage of the ether linkage and hydroxylation were thought to be the minor reactions. Aqueous photolysis of 3-carboxymethyl-4-nitrophenol: The photo-induced Fries rearrangement common to aromatic esters did not appear to occur in the carboxymethyl group of this type of compound. Conversion of nitro to nitroso group was the main reaction.

• Journal of the Korean Electrochemical Society
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• v.23 no.2
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• pp.25-38
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• 2020

Photoelectrochemical water splitting has been considered as the most promising technology for generating hydrogen energy. Transition metal dichalcogenide (TMD) compounds have currently attracted tremendous attention due to their outstanding ability towards the catalytic water-splitting hydrogen evolution reaction (HER). Herein, we report the synthesis method of various transition metal dichalcogenide including MoS₂, MoSe₂, WS₂, and WSe₂ nanosheets as excellent catalysts for solar-driven photoelectrochemical (PEC) hydrogen evolution. Photocathodes were fabricated by growing the nanosheets directly onto Si nanowire (NW) arrays, with a thickness of 20 nm. The metal ion layers were formed by soaking the metal chloride ethanol solution and subsequent sulfurization or selenization produced the transition metal chalcogenide. They all exhibit excellent PEC performance in 0.5 M H₂SO₄; the photocurrent reaches to 20 mA cm^-2 (at 0 V vs. RHE) and the onset potential is 0.2 V under AM1.5 condition. The quantum efficiency of hydrogen generation is avg. 90%. The stability of MoS₂ and MoSe₂ is 90% for 3h, which is higher than that (80%) of WS₂ and WSe₂. Detailed structure analysis using X-ray photoelectron spectroscopy for before/after HER reveals that the Si-WS₂ and Si-WSe₂ experience more oxidation of Si NWs than Si-MoS₂ and Si-MoSe₂. This can be explained by the less protection of Si NW surface by their flake shape morphology. The high catalytic activity of TMDs should be the main cause of this enhanced PEC performance, promising efficient water-splitting Si-based PEC cells.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.2
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• pp.95-106
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• 1998

To reduce the environmental contamination and to utilize fly ash massively produced from the coal power plant every year, we synthesized the artificial zeolite using fly ash treated with alkaline, and then analyzed the mineralogical and morphological properties by X-ray, IR, and SEM. The amount of $NH_4{^+}$, $K^+$, and $H_2PO_4{^-}$ adsorbed by the fly ash and the artificial zeolite were determined with reaction time, amount of adsorbate used, ion concentrations. The results obtained from the pot experiments packed with the top soil, amended with granulated artificial zeolite which was made by treatment of 4% polyvinylalcohol, showed that CEC of the artificial zeolite was $257.7cmol^+kg^{-1}$, that was almost 36 times greater than that of fly ash. The ratio of $SiO_2/Al_2O_3$ decreased but the amount of Na increased. The physico-chemical properties analyzed by X-ray, IT, and SEM represented that the artificial zeolite synthesized had a similar morphological structure to that of the natural zeolite. The structures of the artificial zeolite had a significantly enlarged surface having a lot of pores, while the fly ash looked like spherical smooth shape with having not pores on the surface. Thus, the artificial zeolite was successfully synthesized. The results of adsorption isotherms of fly ash and artificial zeolite showed that the amount of $NH_4{^+}$, $K^+$, and $H_2PO_4{^-}$ adsorbed increased as the equilibrium concentration increased, while $NH_4{^+}$ was strongly adsorbed on the surface of fly ash and artificial zeolite than that of $K^+$. The most distinctive growth of Chinese cabbage was found from the top soil(NPK + soils + 20% of granulated artificial zeolite + 5% of compost). Therefore, we concluded that one of the most effective methods to effectively recycle a fly ash was to make the artificial zeolite as we did in this experiment.

• Journal of Korean Society of Forest Science
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• v.89 no.1
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• pp.77-84
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• 2000

In order to understand the chemical binding forms of Cd in terms of its binding strength in wood, the radial distribution of it through dendroanalysis and its different chemical fractions in trunk wood of mature red pine(Pinus densiflora L.) trees grown in a relatively unpolluted area, in Kangwon-Province, were examined. Total Cd concentration in stem wood was determined by dry digestion and $H_2O$ and 0.01 M solutions of citric acid, malic acid, $CaCl_2$, $MgCl_2$, $Na_2EDTA$ were used as extracting solutions for Cd. Extracting efficiencies of applied solutions were expressed as % of Cd concentration extracted by $Na_2EDTA$ which extracted all Cd instead of Cd total concentration. Total concentration of Cd decreased from the innermost rings near pith towards the the outermost rings near cambium. Especially through the transition zone this tendency was observed clearly. $H_2O$ was the least effective extractant of Cd, then extracting efficiency increased in the order $MgCl_2$ < $CaCl_2$ $Na_2EDTA$ (extracted all Cd). According to the radial position, extracting efficiency of Cd was ranging from 7 to 30% by $H_2O$ and even from 60 to 95% by citric acid. The Cd extracting efficiencies of $H_2O$ and organic acids increased continuously from the stem center to outermost annual rings, whereas salts showed somewhat different tendency, suddenly decreasing near the outermost ring. The results are discussed with regard to the different chemical binding forms of Cd and the mobility of Cd in wood and comparable with ones in previous studies on Pinus sylvestris and Quercus patraea. According to the results, usefulness of radial distribution pattern of Cd in pine tree trunks for retrosective biomonitoring is questioned.

• Journal of the Mineralogical Society of Korea
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• v.30 no.2
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• pp.45-57
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• 2017

Two single crystals of fully dehydrated $Cd^{2+}$-exchanged zeolites Y were prepared by the exchange of ${\mid}Na_{75}{\mid}[Si_{117}Al_{75}O_{384}]-FAU$ ($Na_{75}-Y$, Si/Al = 1.56) with aqueous $0.05M\;Cd(NO_3)_2$ (pH = 3.65) at 294 K, followed by vacuum dehydration at 723 K (crystal 1) and a second crystal, similarly prepared, was exposed to zeolitically dried benzene for 72 hours at 294 K and evacuated (crystal 2). Their structures were determined crystallographically using synchrotron X-rays and were refined to the final error indices using $F_o$>$4{\sigma}(F_o)$ of $R_1/wR_2=0.040/0.121$ and 0.052/0.168, respectively. In crystal $1({\mid}Cd_{36}H_3{\mid}[Si_{117}Al_{75}O_{384}]-FAU)$, $Cd^{2+}$ ions primarily occupy sites I and II, with additional $Cd^{2+}$ ions at sites I', II', and a second site II. In crystal $2({\mid}Cd_{35}(C_6H_6)_{24}H_5{\mid}[Si_{117}Al_{75}O_{384}]-FAU)$, $Cd^{2+}$ ions occupy five crystallographic sites. The 24 benzene molecules are found at two distinct positions within the supercages. The 17 benzene molecules are found on the 3-fold axes in the supercages where each interacts facially with one of site IIa $Cd^{2+}$ ions. The remaining 7 benzene molecules lie on the planes of the 12-rings where each is stabilized by multiple weak electrostatic and van der Waals interactions with framework oxygens.

• Korean Journal of Environmental Agriculture
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• v.31 no.2
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• pp.157-163
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• 2012

BACKGROUND: For the safety of imported agricultural products, the study was conducted to develop the analytical method of unregistered pesticides in domestic. The analytical method of 6 pesticides, chlorthal-dimethyl, clomeprop, diflufenican, hexachlorobenzene, picolinafen, and propyzamide, for a fast multi-residue analysis were established for two different type crops, orange and brown rice by GC-ECD and confirmed by mass spectrometry. METHODS AND RESULTS: The analytical method was evaluated to limit of quantification, linearity and recoveries. The crop samples were extracted with acetonitrile and performed cleanup by liquid-liquid partition and Florisil SPE to remove co-extracted matrix. The extracted samples were analyzed by GC-ECD with good sensitivity and selectivity of the method. The limits of quantification (LOQ) range of the method with S/N ratio of 10 was 0.02~0.05 mg/kg for orange and brown rice. The linearity for targeted pesticides were $R^2$ >0.999 at the levels ranged from 0.05 to 10.0 mg/kg. The average recoveries ranged from 74.4% to 110.3% with the percentage of coefficient variation in the range 0.2~8.8% at two different spiking levels (0.02 mg/kg and 0.2 mg/kg, 0.05 mg/kg and 0.5 mg/kg) in brown rice. And the average recoveries ranged from 77.8% to 118.4% with the percentage of coefficient variation in the range 0.2~6.6% at two different spiking levels (0.02 mg/kg and 0.2 mg/kg, 0.05 mg/kg and 0.5 mg/kg) in orange. Final determination was by gas chromatography/mass spectrometry/selected ion monitoring (GC/MS/SIM) to identify the targeted pesticides. CONCLUSION: As a result, this developed analytical method can be used as an official method for imported agricultural products.

• Journal of the Korean Chemical Society
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• v.17 no.5
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• pp.346-352
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• 1973

The quantitative separations of a mixture containing equal amounts of each cation such as Mn(Ⅱ), Cr(Ⅲ), V(Ⅴ), Cu(Ⅱ), Ni(Ⅱ), Co(Ⅱ), and Fe(Ⅲ) are carried out by the elution through $35cm{\times}3.14cm^2$ column of cation exchange resin, $Dowex 50w{\times}12$. The eluents are a mixture of 0.6 M sodium chloride and 0.1 M sodium tartrate (pH = 2.00 and 4.50) for Fe(Ⅲ), V(Ⅴ), Cu(Ⅱ), Ni(Ⅱ) and Co(Ⅱ), and a mixture of 3 M sodium chloride and 0.1 M sodium tartrate (pH = 4.50) or a mixture of 0.7 M sodium chloride and 0.5 M sodium oxalate (pH = 4.50 and 5.00) for Mn(Ⅱ) and Cr(Ⅲ). The subsidiary cations in a standard iron mixture such as V(Ⅴ), Cu(Ⅱ), Ni(Ⅱ), Mn(Ⅱ) and Cr(Ⅲ) are separated together from the large amount of Fe(Ⅲ) through $15cm{\times}3.14cm^2$ column of the resin, $Dowex 1{\times}8$, by elution with the eluent of 4.0 M hydrochloric acid. A small amount of Fe(Ⅲ), however, is eluted together with Cu(Ⅱ). V(Ⅴ), Ni(Ⅱ), Mn(Ⅱ) and Cr(Ⅲ) eluted together are separated quantitatively through $10cm{\times}3.14cm^2$ column of the resin,$Dowex 50w{\times}12$. Cu (Ⅱ) and a small amount of Fe(Ⅲ) are separated quantitatively through $10cm{\times}3.14cm^2$ column of the resin, $Dowex 50w{\times}12$, by the elution with a mixture of 0.6 M sodium chloride and 0.1 M sodium tartrate (pH = 2.00 and 4.50) as an eluent. By the conditions obtained in the separations of the standard iron mixture, Fe(Ⅲ) and all of the subsidiary cations in steel are quantitatively separated.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.125-133
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• 1995

The crystal structure of dehydrated, partially Co(II)-exchanged zeolite X, stoichiometry Co2+Na+-X (Co41+Na10Si100Al92O384) per unit cell, has been determined from three-dimensional X-ray diffraction data gathered by counter methods. The structure was solved and refined in the cubic space group Fd3:α=24.544(1)Å at 21(1)℃. The crystal was prepared by ion exchange in a flowing stream using a solution 0.025 M each in Co(NO3)2 and Co(O2CCH3)2. The crystal was then dehydrated at 380℃ and 2×10-6 Torr for two days. The structure was refined to the final error indices, R1=0.059 and R2=0.046 with 211 reflections for which I > 3σ(I). Co2+ ions and Na+ ions are located at the four different crystallographic sites. Co2+ ions are located at two different sites of high occupancies. Sixteen Co2+ ions are located at the center of the double six-ring (site I; Co-O = 2.21(1)Å, O-Co-O = 90.0(4)°) and twenty-five Co2+ ions are located at site II in the supercage. Twenty-five Co2+ ions are recessed 0.09Å into the supercage from its three oxygen plane (Co-O = 2.05(1)Å, O-Co-O = 119.8(7)°). Na+ ions are located at two different sites of occupandies. Seven Na+ ions are located at site II in the supercage (Na-O = 2.29(1)Å, O-Na-O = 102(1)°). Three Na+ ions are statistically distribyted over site III, a 48-fold equipoint in the supercages on twofold axes (Na-O = 2.59(10)Å, O-Na-O = 69.0(3)°). Seven Na+ ions are recessed 1.02Å into the supercage from the three oxygen plane. It appears that Co2+ ions prefer sites I and II in order, and that Na+ ions occupy the remaining sites, II and III.

• Applied Biological Chemistry
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• v.15 no.2
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• pp.93-109
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• 1972

Three lots of Chung-Kook-Jang were prepared by the use of 2 strains of Bacillus subtilis and Bacillus natto. For four samples taken from each lot in 12 hrs interval changes of nitrogenous compounds, insoluble protein, water soluble protein, peptides, free amino acids, amino and ammonia nitrogens during Chung-Kook-Jang fermentation, were studied together with the changes of moisture, pH, proteolytic enzyme activity. In addition the average peptide length of the peptides of a Bacillus subtilis lot was determined by the method of molecular sieving using ion exchange resin. The results were as follows: 1. The contents of moisture and total-nitrogen changed little in all samples throughout the fermentation as it would be expected. 2. In all three experimental lots the pH became higher gradually from the initial value of 6.65 to the final $7.5{\sim}7.85$ during the fermentation. Proteolytic enzyme activities, in accordance with this pH change, steadily increased up to $48{\sim}60$ hrs. of fermentation and then slightly decreased, probably affected by the high pH. The most strong proteolytic activity was observed in the experimental Chung-Kook-Jang fermentation lot using the Bacillus subtilis K-27 isolated by the author. 3. The contents of insoluble protein nitrogen in soybeans increased markedly (5%) by the cooking, after steeping 12 hrs in water. During the Chung-Kook-Jang fermentation, however, it decreased from 1/2 to 1/10 of that of the cooked soybeans. 4. The contents of water soluble protein nitrogen (5%) whereas, greatly decreased to the value of 1.0% by the cooking; but little changed further during the fermentation, 5. The total contents (0.25%) of peptides, amino, and ammonia-nitrogens, PAA-N., increased almost double by the cooking and steadily became higher as the fermentation proceeded, reaching finally up to$4{\sim}7%$ in 72 hrs fermentation. 6. The amounts of free amino acids of soybean generally decreased during the processing of cooking, even some of them like glutamic acid were destroyed completely, However in the subsequent Chung-Kook-Jang fermentation for 72 hrs., they showed from several to a few hundreds folds increases depending upon the kinds of amino acids. Valine which was contained in HCl-hydrolyzed steeped or cooked soybeans in amounts $220{\sim}267mg%$ was not detected at all as the free amino acid in all fermented samples. 7. Average peptide length (APL) of all fractions, eluted and fractionated by using the Dowex-50 ion exchange resin column, and fraction collector showed the highest value for the cooked soybean and then decreased as the fermentation proceeded. The APL value of effluent showed the highest in 12 hrs fermented sample, The value decreased thereafter by fermentation.