• Korean Journal of Soil Science and Fertilizer
• /
• v.39 no.6
• /
• pp.403-408
• /
• 2006

Fluvio-marine paddy soils in Korea consist of high silt content and have the hardpan located below 20~30 cm from surface soil. This properties cause poor rice rhizosphere conditions such as low permeability and porosity, high bulk density and hardness. The aims of this study was to investigate the effect of popped rice hulls compost(PRHC) on soil fertility changes in the Fluvio-marine plain paddy soils. Total nitrogen content and nitrogen mineralization rate of PRHC were 1.17 and 33.5, respectively, and its C/N ratio was 35.4. Application of PRHC increased the content of organic matter and exchangeable potassium and improved the bulk density and porosity. The content of $NH_4-N$ in soil was high in the PRHC plot until maximum tillering stage. An uptake amount of fertilized nitrogen was greater in standard fertilization plot at early growth stage, however, it was greater more in PRHC plots at the ripening period than in standard fertilization plot. Among the PRHC treated plots, uptake amount was the greatest in 50% PRHC plot during the all growth period. Nitrogen efficiencies were higher in PRHC plot during the all growth period. Rice yields in all PRHC plots were lower than in standard fertilization, however, the yield of 40% PRHC plot was similar with that of standard.

• Economic and Environmental Geology
• /
• v.48 no.3
• /
• pp.187-197
• /
• 2015

Oriental mineral medicines are single or mixture of more than one mineral species or rock/fossil which are used to treat disease. Mineral medicines remove harmful or useless substances to decrease toxicity and secondary effects, and cause the manufacture of medical compounds with increased efficacy. The extraction test is an accepted in vitro system to predict the bioaccessibility of major and minor elements from mineral medicine. It incorporates gastrointerstinal tract parameters representative of a human body that including stomach and small intestinal pH which are the same as digestion condition. The bioaccessibility of a mineral medicine is the fraction that is soluble in the gastrointestinal environment and is available for absorption. Reaction path modeling in the human body can predict digestion with gastric fluid as well as absorption in the small intestine, existence in body fluids and reaction progress of the exhaust process according to pH conditions in body. Also reaction path modeling can predict bioavailability, which is equal to existence rate in the body and the form and amount of a medicine in the body after intake. The study results from predicating the existence form mineral medicines in the body, and proving the effective ingredient using bioaccessibitily and human risk assessment, suggest these that should be necessary data for new medicine development.

• Journal of Food Hygiene and Safety
• /
• v.38 no.3
• /
• pp.89-98
• /
• 2023

Currently, no guidelines exist regarding the maximum residues of pesticides in edible oil which is a processed food commonly consumed in Korea. This lack of guidelines hinders the evaluation of the safety of edible oil in terms of pesticide contamination. In this study, an analysis method based on heat distillation and GC-MS/MS was established by optimizing the extraction and purification procedure for 68 pesticides. Important variables in the thermal distillation procedure included heating temperature and time, and we found the nitrogen flow rate as a mobile phase and the type of dissolving solvent were not considerably affected. The determination coefficient (R²) of the residual pesticide was 0.99 or higher, and the quantitative limit (LOQ) was 0.01-0.02 mg/L. The average recovery rate (n=5) was 66.1-120.0% and the relative standard deviation was lower than ±10% when 68 pesticides were spiked at concentrations of 0.01-0.02, 0.1, and 0.5 mg/L. In addition, the within-laboratory precision was less than ±11%, meeting the Korea Food and Drug Safety Evaluation Institute's Guidelines on Standard Procedures for Preparing Food Testing Methods (2016). Therefore, the test method developed in this study can be used as a test method for managing the safety of the residual pesticide concentration in edible oil.

• Journal of the Korean Society of Food Culture
• /
• v.13 no.4
• /
• pp.261-266
• /
• 1998

In an attempt to evaluate the effects of alkali agents on properties of Ramyon, cooking quality, textural and sensory properties were examined. The shear extrusion force of Ramyon made from sample A(potassium carbonate 64%, sodium carbonate 14%, sodium pyrophosphate 2% and sodium metaphosphate 20%), sample B(potassium carbonate 31%, sodium carbonate 39% , sodium pyrophosphate 1%, sodium metaphosphate 15%, sodium polyphosphate 8%, sodium phosphate monobasic 4% and sodium phosphate dibasic 2%), sample C(potassium carbonate 60%, sodium carbonate 33% and sodium pyrophosphate 7%), and sample D(potassium carbonate 44%, sodium carbonate 27%, sodium metaphosphate 27% and sodium polyphosphate 2%) were 12.80(kgf), 10.35(kgf), 9.05(kgf) and 8.45(kgf), respectively, but that of control I was 5.24(kgf). The hardness of Ramyon manufactured with sample A, B, C and D were 18.57(kgf), 16.48(kgf), 14.26(kgf) and 12.34(kgf), respectively, but that of control I was 11.23(kgf). At cooking quality examination of Ramyon made from several alkali agents, weight of cooked Ramyon was increased but volume was appeared in vice versa. Extraction amounts of Ramyon manufactured with several alkali agents during cooking were from 35% to 38%, but that of control I was 70%. These changes will provided many advantages in the preparation of Ramyon. The $I_2$ reaction value(${\alpha}-degree$ of noodle) of Ramyon manufactured with several alkali agents and control were shown to almost same values, from 2.10 to 2.20. Sensory properties of cooked Ramyon which was manufactured with several alkali agents showed quite acceptable.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.13 no.2
• /
• pp.121-128
• /
• 2008

As an aquatic ecotoxicity test method, a bioassay using the inhibition of sporualtion of the green macroalga, Ulva pertusa, has been developed. Optimal test conditions determined for photon irradiance, pH, salinity and temperature were $100\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, $7{\sim}9$, $25{\sim}35\;psu$ and $15{\sim}20^{\circ}C$, respectively. The validity of the test endpoint was evaluated by assessing the toxicity of four metals (Cd, Cu, Pb, Zn) and elutriates of sewage or waste sludge collected from 9 different locations. When the metals were assayed, the $EC_{50}$ values indicated the following toxicity rankings: Cu ($0.062\;mg{\cdot}L^{-1}$) > Cd ($0.208\;mg{\cdot}L^{-1}$) > Pb ($0.718\;mg{\cdot}L^{-1}$) > Zn ($0.776\;mg{\cdot}L^{-1}$). When compared with other commonly used bioassays of metal pollution listed on US ECOTOX database, the sporualtion test proved to be the most sensitive. Ulva sporulation was significantly inhibited in all elutriates with the greatest and least effects observed in elutriates of sludge from industrial waste ($EC_{50}=6.78%$) and filtration bed ($EC_{50}=15.0%$), respectively. The results of the Spearman rank correlation analysis for $EC_{50}$ data versus the concentrations of toxicants in the sludge presented a significant correlation between toxicity and four heavy metals(Cd, Cu, Pb, Zn). The method described here is sensitive to toxicants, simple to use, easy to interpret and economical. It is also easy to procure samples and maintain cultures. The present method would therefore probably make a useful assessment of aquatic toxicity of a wide range of toxicants. In addition, the genus Ulva has a wide geographical distribution and species have similar reproductive processes, so the test method would have a potential application worldwide.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.9
• /
• pp.37-45
• /
• 2016

This study analyzes the environmental and durability problems of traditional (LW) grouting method. And the proposed method was compared to the others effects by analyzing the in-situ applicability and effect of performance of the method using the silica sol. This study analyzed the eco-friendly, effects of high strength silica sol through laboratory tests. The effects of the construction process were identified through the field tests. The compressive strength was increased by 1.3 times compared to the LW method and the shrinkage is 3~8 times less than that of LW method with water glass. No toxicity, which could affect soil contamination. In particular, it was confirmed that the Toxicity fish also survived with little pH change in the concentration tank. Also it confirmed the construction effects through field test. Field tests are a standard penetration test, permeability test, LLT, BST. Permeability was reduced to $1{\times}10^{-5{\sim}-6}cm/sec$.

• The Korean Journal of Pesticide Science
• /
• v.19 no.4
• /
• pp.370-393
• /
• 2015

This study was conducted to compare STQ method, multi-residue method in Korean food code and QuEChERS method for validated selected and accuracy, reproducibility and efficiency. A total of 45 selected and targeted pesticides were the analyzed by GC and 5 of them were crops (apple, potato, green pepper, rice, soy bean). $R^2$ values were calculated in the standard calibration curve was over 0.990. Recovery tests were performed by three replications in two levels and the relative standard deviation of the repeated experiments was less than 30%. The average percentage of recoveries in the multi-residue method in Korean food code was 89.13%, QuEChERS method was 92.45% and STQ method was 85.28%. In addition, matrix effects in multi-residue method in Korean food code was 24.61%, QuEChERS method was 23.98% and STQ method showed 11.24%. The STQ method is easy and showed high clean-up effect in extracting the sample solution than the QuEChERS method and clean-up with C18, PLS, PSA cartridge columns. A large volume of the sample was injected in order to compensable for the problem, that occurred due to high detection limit in the analyser. When the STQ method was applied using a large volume injector, the standard calibration curve showed a higher linearity $R^2=0.990$, and method detection limit was 0.01 mg/kg. It showed an average recovery of 91.84% and the relative standard deviations of three replications repeated in two level process was less than 30% and had an average matrix effect of 17.90%.

• Korean Journal of Soil Science and Fertilizer
• /
• v.41 no.2
• /
• pp.103-111
• /
• 2008

This study was carried out to investigate the optimal application rate and time of mixed expeller cake (MEC) for the replacement of chemical fertilizer. Dongjin-1, as cultivated rice was used at Fluvio-marine deposit in Honam plain paddy field. Soil chemical properties were improved by the application of MEC. Contents of total nitrogen and organic matter were higher in 70%, 100% plots of basal dressing than standard fertilizer application (SFA) plot. Cation exchangeable capacity was highly increased in 70% plot of basal dressing. Also, the content of organic matter in soil was increased with MEC application. Cation exchangeable capacity, total nitrogen and available phosphate were decreased according to late application time. The content of inorganic nitrogen in soil showed high tendency at more application rate of MEC, and nitrogen mineralization at harvest season have finished in 50%, 70% plots of basal dressing. The content of inorganic nitrogen in soil was increased according to late application time, however it was decreased in the late period of growth. Leaf color value became darker with increased application rate of MEC. Leaf color was dark green in MEC application plots at panicle formation stage, on the other hand, it was light green in 50%, 70% plots of basal dressing at heading stage. SPAD reading value of leaf-color was high during the whole growth stage in MEC application plots. More application rate of MEC showed higher tendency of fertilizer nitrogen absorption. Nitrogen use efficiency was the highest in 70% plot of basal dressing. Absorbed amount of fertilized nitrogen was increased in 10~15days before transplanting and nitrogen use efficiency was high according to the late application time. The ratio of perfect kernel and the content of protein on hulled rice showed high tendency at the less application rate of MEC. The ratio of head rice on milled rice showed high tendency at the less application rate of MEC. Rice yield increased 4% in 100% and 70% plots of basal dressing compare with SFA ($5.18Mg\;ha^{-1}$) plot respectively. Ear and culm length of rice were long according to the late application time, while the numbers of spikelet and ear were increased and the percentage of ripened grain was decreased. Rice yield was increased 2~5% in all MEC application plots compared to SFA plot and especially, increased 10~15days before transplanting in application plots. The optimal application rate and time of MEC on normal paddy field in plain were concluded that 70% basal dressing and 10~15days before transplanting

• Korean Journal of Food Science and Technology
• /
• v.31 no.4
• /
• pp.931-937
• /
• 1999

Styrene dimers and trimers from polystyrene cup noodle containers were analyzed by GC and GC/MS extracted with various simulants. For the quantitation of styrene dimers and trimers, 1,3-diphenylpropane (DP) and benzyln-butyl phthalate (BBP) were chosen as the standards. The results showed that the average of the styrene dimers in the containers was 603 ppm, and that of trimers was 5731 ppm. Four styrene dimers, including 1,2-diphenyl-cyclobutane, were identified as well as seven trimers such as 2,4,6-triphenyl-l-hexene. The migration of the styrene dimers and trimers, from the cup noodle containers of polystyrene into foods, was conducted using simulants including boiling water as well as soybean oil and n-heptane. In addition to, the analysis of each migrated styrene was also performed filled with boiling water into noodle and soup after certain time (5, 10, 20, 30 min). The results showed that the migration of styrene dimers and trimers from cup noodle containers was not detected in the case of using boiled water or soybean oil as a simulant, while styrene dimers and trimers were detected 1.18 ppm and 14.21 ppm, respectively, when heptane was adopted as a simulant. In the case of filling with boiled water into noodle and soup, both styrenes were not detected at 5 min and 10 min, however, some samples standing for 20 min released styrene dimers and trimers as much as 0.009 ppm, and 0.019 ppm for 30 min.

• Korean Journal of Soil Science and Fertilizer
• /
• v.41 no.2
• /
• pp.75-82
• /
• 2008

In order to establish environmentally friendly phosphorus(P) and potassium(K) fertilizer application rates for rice cultivation in Korea, a field experiment was conducted in two different characterized paddy soils, higher and lower P and K content in soil from 2005 to 2006 in Suwon, Korea. Chuchong which is typical rice variety in Korea, was selected for experiment. Rice yields in base P-K fertilizer level ($30-30kg\;ha^{-1}$) and no P-K fertilizer level were 97~98% and 93~97% of standard P-K fertilizer level ($45-57kg\;ha^{-1}$), respectively. At the lower content of P and K in immatured paddy soil, the yield of no P plot was decreased by 7% compared to that of standard P-K plot. Significant difference in rice yield and yield characteristics was found neither in standard P-K fertilization plot nor in base P-K fertilization plot. There was no significant difference in P and K uptake at the harvest stage between standard P-K fertilizer plot and base P-K fertilizer plot. Phosphorus and K uptake was slightly decreased in no fertilizer plots compared to standard fertilizer plot. Phosphorus and K use efficiency of rice plant in base fertilizer plot was higher than that in standard fertilizer plot. Available phosphorus and exchangeable potassium content in soil at the harvest stage were increased in both standard and base fertilizer plot. But no significant difference of P and K content in ? was found between standard fertilizer plot and base fertilizer plot. Rice quality characteristics such as proportion of brewers rice, damaged kernel, broken rice, and content of amylose and protein were lowered in the base fertilizer plot than the standard fertilized plot, while the proportion of perfect kernel increased in the base fertilizer plot From the results, we generally recommend the base P-K fertilization ($30-30kg\;ha^{-1}$) instead of standard P-K fertilization ($45-57kg\;ha^{-1}$) for rice cultivation in Korea.