• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.3
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• pp.259-263
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• 1983

This experiment was carried out to investigate the effect of pH at coagulation on fatty acid and sterol composition of green LPC. Green juice of Italian ryegrass, red clover, oats and alfalfa was adjusted at pH 4, 6, 8 and heated at $85^{\circ}C$ for ten minutes. Green LPC was taken from the above green juice. The results obtained were as follows. 1. Green LPC of Italian ryegrass, oats and alfalfa contained much on the order of linoleic acid, palmitic acid and linolenic acid. Methyl ester of these three fatty acid accounted for 70.4% to 86.2% of total fatty acid methyl ester. Green LPC of red clover contained much palmitic acid, linoleic acid, and linolenic acid. These three fatty acid methyl ester accounted for 82.5% to 86.2% of total fatty acid methyl ester. 2. Linolenic acid was highest in the green LPC of red clover, oats and alfalfa which was adjusted at pH 8 and heated and coagulated, and next at pH 6, and pH 4, respectively. Linolenic acid was highest in the green LPC of Italian ryegrass which was adjusted at pH 6, next pH 8, and pH 4. 3. Green LPC of red clover and alfalfa contained cholesterol. The all green LPC contained campesterol, stigmasterol and sitosterol. 4. Sterol was highest in the green LPC of Italian ryegrass, red clover and oats which was adjusted at pH 8 and next at pH 4, and pH 6, respectively. Sterol was highest in the green LPC of alfalfa which was adjusted at pH 8, and next at pH 6, and pH 4, respectively.

• The Korean Journal of Ecology
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• v.21 no.1
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• pp.65-72
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• 1998

Various effects of simulated acid rain by $HNO_3$ and $H_2SO_4$ with pH 3.2, 4.2 and 5.6 were investigated in Melilotus suaveolens Ledeb, a biennial legume dominating the disturbed and poor soil vegetations. The nitric acid treatment of pH 3.2 resulted in 121% increase of the plant height compared to that of pH 5.6 during early growth, although 17% decrease was detected with the sulfuric acids. During 14 days of treatment, leaf biomass and chlorophyll content increased 168% and 133% with pH 3.2 nitric acid rain but decreased 20% and 38%, respectively, with sulfuric acid rain. Nitrogen content in various organs was also determined after 42 days of nitric acid treatment. It increased 480% and 387% by pH 3.2 and 4.2 in leaves, 212% and 214% in stems and 247% and 249% in roots. However, the same treatment with the sulfuric acid showed a considerable reduction in this content, indicating that the nitric acid was a nitrogen source. Nodule formation assayed revealed 15% decrease with pH 3.2 in contrast to 157% increase in pH 4.2, further suggesting an enhancement effect by the additional nitrogen source. Contrary to this, the nodule formation was reduced up to 43-71% by sulfuric acid rains. Specific nitrogen fixation activities of nodules estimated at pH 3.2, 4.2 and 5.6 nitric acid rain were 36.7, 42.8 and 47.3 ${\mu}mol\;C_2H_4{\cdot}g^{-1}\;fw\;nodule{\cdot}h^{-1}$, while those of sulfuric acid rain exhibited 1 nmol $C_2H_4{\cdot}plant^{-1}{\cdot}h^{-1}$ with pH 3.2, 177 with pH 4.2 and 179 with pH 5.6, yet it increased 2, 115 and 286 respectively corresponding to the three sulfuric acid concentrations. Further implications of the simulated acied rain were also discussed in the study.

• Journal of the Korean Ceramic Society
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• v.39 no.7
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• pp.699-703
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• 2002

In order to see the effect of pH on the formation of ettringite, pH was controlled with addition of boric acid, hydrochloric acid, nitric acid and potassium hydroxide during the formation of ettringite. The behavior of ettringite formation was discussed with XRD, SEM analysis. The result was that ettringite was unstablely formed with stabilization of aluminate gel and gypsum at below PH 10.

• Research in Plant Disease
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• v.16 no.1
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• pp.81-85
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• 2010

Arabidopsis seedlings subjected to low pH stress in the range of pH 5.6-4.0 did not show significant retardations in root and shoot growths. Treatment of pH 3.5-2.5 resulted in significant reductions in root and shoot length, especially in roots. Chlorophyll contents in seedlings increased during acid treatment of pH 5.6-4.0, but decreased by stronger acid treatment of pH 4.0 and lower pHs. Total carotenoid contents showed similar trend to chlorophyll contents by increasing during pH 5.6-3.5 treatments and decreasing by pH 3.0-2.5. Anthocyanin contents increased under acid stress of pH 5.6-3.0 and showed great reduction at pH 2.5. The ratios of carotenoids/chlorophylls and anthocyanins/chlorophylls increased by acid stress treatments. That indicates plants try to adjust physiologically to acid stress and protect chlorophylls by increasing carotenoid and anthocyanin contents. However, different responses of chlorophylls and anthocyanins to acid stress indicate both pigments play different roles in protecting plant from acid stress.

• Journal of Environmental Science International
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• v.32 no.3
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• pp.191-195
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• 2023

This study aimed to investigate the effect of amino acid additives to weaned piglet diets on the pH and volatile fatty acids of pig slurries. A total of 135 weaned 22 -day-old piglets (Yorkshire x Landrace x Duroc) were used in this 56-d study. The three dietary treatments were as follows: (1) Control as a basal diet, (2) 1% amino acid additive and (3) 2% amino acid additive. Both pH and acetic acid values at 71 and 78 days were significantly different in all treatment groups (p<0.05). In addition, significant differences in propionic acid values were observed among treatment groups at 64 and 78 days (p<0.05). However, pH, acetic acid, and propionic acid values did not differ between 1% and 2% amino acid treatment groups. In conclusion, adding 1% and 2% amino acid to weaned piglet diets reduced the pH, acetic acid and propionic acid contents of pig slurries by acting as a probiotic. This may help formulate increase management strategies for improving the pig housing environment.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.7
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• pp.1307-1318
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• 2000

The purpose of this study is to investigate the degradation characteristics of oxalic acid and citric acid by $UV/H_2O_2$ oxidation. For this purpose, the effects of pH, $H_2O_2$ dosage and the concentration of each compounds on the degradation of oxalic acid and citric acid by $UV/H_2O_2$ were investigated. Oxalic acid was effectively degraded at the wavelength of 254 nm, while the degradation efficiency of citric acid was very low at the same wavelength. It was also found that both organic substances were not degraded by the injection of $H_2O_2$ only. The optimum pH of degradation of oxalic acid and citric acid was 4 and 4 to 6, respectively. In the case of $UV/H_2O_2$ oxidation, the degradation efficiency was increased by increasing $H_2O_2$ dosage. The degradation efficiency decreased when the dose of $H_2O_2$ exceeds 200 mg/L. From these results, it can be concluded that the optimum reaction conditions for the degradation of oxalic acid and citric acid by $UV/H_2O_2$ oxidation were pH 4 and 200mg/L of $H_2O_2$.

• Preventive Nutrition and Food Science
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• v.5 no.3
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• pp.131-135
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• 2000

The inhibitory effect of various organic acids on the growth and survival of Escherichia coli O157:H7 in tryptic soy broth with 0.6% yeast extract at 37$^{\circ}C$ or 4$^{\circ}C$ was determined. Minimal inhibitory pHs of acetic acid, citric acid, fumaric acid, hydrochloric acid and lactic acid were 5.0, 4.0, 4.5, 4.0 and 4.5, respectively. Acetic acid (0.012 m) showed the strongest antimicrobial activity, based on the pH values or equivalent molar concentrations, followed by lactic acid (0.0006 M), fumaric acid (0.004M) and citirc acid (0.004 M), respectively, E. coli O157:H7 with an initial inoculum of {TEX}$10^{7}${/TEX} CFU/ml and {TEX}$10^{5}{/TEX} CFU/ml in tryptic soy broth supplemented with 0.6% yeast extract, acidified to target pH with citric, fumaric and lactic acids at 37$^{\circ}C$, was completely inactivated after 7 d and 5 d incubation, respectively, except for the acetic acid (9 d). The bactericidal effect decreased at the same pH when the incubation temperature a was reduced from 37$^{\circ}C$ to 4$^{\circ}C$. The pH values of 0.2% acetic (pH 5.1), 0.6% citric (pH 4.2) and 0.4% lactic acid (pH 4.3) in TSBYE were almost correspondent to the minimal inhibitory pH values on E. coli O157:H7 of acetic (pH 4.0), citric (pH 4.0) and lactic acids (pH 4.5).

• Journal of Environmental Health Sciences
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• v.29 no.2
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• pp.1-6
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• 2003

This paper reports on a pilot scale comparison of PACS coagulation with and without pH preadjustment. The pH of the water was adjusted with carbon dioxide and sulfuric acid. Process performance was assessed on the basis of total organic carbon(TOC), UV absorbance, turbidity and disinfection by-product(DBP) precursors. Coagulation pH appeared to be a determining factor for maximum NOM removal. The optimum coagulation pH in order to decrease TOC and turbidity were pH 7. Preadjustment of pH 7 increased TOC removal to as much as 43, 47 percent with sulfuric acid and carbon dioxide. Moreover, coagulation at pH 7 caused a reduction in UV$_{254}$, THMFP and HAAFP compared to the baseline coagulation. For preadjustment of pH 7 with carbon dioxide, the percentage of TOC, UV$_{254}$, THMFP and HAAFP shows the reduction rate of 3.8, 0.5, 4.8, 9.4％ comparing to the coagulation rendition using sulfuric acid. Acid addition to depress pH during coagulation decrease Langelier Saturation Index(LSI), potentially causing increase corrosion in water distribution systems. LSI for carbon dioxide and sulfuric acid at pH 6 was -2.3, -3.3. Therefore, carbon dioxide was more effective at controlling corrosion than sulfuric acid.

• The Korean Journal of Ecology
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• v.21 no.2
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• pp.117-124
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• 1998

To clarify the effects of acid precipitates on histological damage, water status, and growth of Pinus densiflora green house experiment applyin simulated acid rain was carried out. Contact angle of water droplet on needles of P. densiflora seedlings treated with simulated acid rain of different pHs simulated acid rain was, the more rapid transpiration was. Leaf water potential after water withdrawal was also reduced rapidly in proportion to acidity of simulated acid rain. Height growth of P. densiflora seedlings treated with simulated acid rain of pH 2 decreased, while growth of seedlings treated with that of pH 3 and 4 increased comparing with that treated with normal rain of pH 5.6. pH of cultivated soil in pH 2 plot was acidified with the amount of simulated acid rain applied but that in pH 3 and 4 plots did not show any directional change. From those results, it could be interpreted that decrease of height growth in pH 2 plot was originated from multiple effects of water deficit from rapid transpiration and soil acidification. On the other hand, increased of height growth in pH 3 and 4 plots would be originated from the supply of N and S included in simulated acid rain.

• Korean Journal of Environmental Biology
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• v.18 no.3
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• pp.315-322
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• 2000

Effects of the simulated acid rain on the growth response and the structural features were studied with the 3 month old seedlings of G. biloba and P. thunbergii treated with acid rain of pH 5.6, 4.0, 3.2, and 2.4. The diameter and area of tracheid cells in the transectioned stem of G. biloba decreased with acidity of simulated acid rain. The wall thickness of tracheid cells was the thinest at pH 2.4, but there was no different at other levels of pH. Increasing of the acidity, the height of tracheid cells were reduced steadily. The diameter and area of tracheid cells of the transectioned root reduced with decreasing pH of acid rain, but those at pH 3.2 were larger than those at control. The wall thickness and height of tracheid cells of root were gradually decreased with acidity of acid rain. The size variation of the fusiform cambial initials in the stem of G. biloba sections tangentially showed a shortening tendency with treatment of acid rain. The length of ray initials was the shortest at pH 2.4 and reduced with decreasing pH of acid rain. The diameter, area, wall thickness, and height of the tracheid cells in P. thunbergii stem and root decreased with decreasing pH of acid rain. The areas of the pith, cortex, and xylem in P. thunbergii treated with acid rain decreased, but the cortex and pith areas increased significantly after exposure to acid rain of pH 3.2 compared with control.