• Composites Research
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• v.31 no.5
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• pp.282-287
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• 2018

In this paper, we explore interfacial properties of the mineralized CNTs when they are employed as reinforcing fillers in a polymer nanocomposite using molecular dynamics (MD) simulations. Recently, several studies on mineralizing carbon nanotubes (CNTs) with an aid of nitrogen doping to CNTs have been reported. However, there is a lack of studies on the reinforcing effects of the mineralized CNTs when it is employed as a filler of nanocomposites. Silica ($SiO_2$) is used as a mineral material and poly (methyl metacrylate) (PMMA) is used as a polymer matrix. Pull-out simulations are conducted to obtain the interfacial energy and the interfacial shear stress. It was found that the silica mineralized CNTs have higher interfacial interaction with the polymer matrix. In the future, by examining various thermomechanical properties of the mineralized-CNT-filler/polymer nanocomposites, we will search for potential applications of the novel reinforcing filler.

• Journal of Environmental Science International
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• v.27 no.3
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• pp.179-193
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• 2018

Nitrogen budgets in Sihwa-ho in 2010 were estimated using a mass balance approach. Major nitrogen fluxes sources can be divided into three sections: cities, agricultural area, and forest. Surplus nitrogen 2,030~2,214 ton/yr (2,123 ton/yr in average) was discharged to Sihwa Lake. 20% of the surplus nitrogen is removed from the wetland and 60% is removed tidal flats. Therefore net nitrogen discharge from Sihwa basin is estimated to be 650~708 ton/yr (679 ton/yr in average). Wet and dry nitrogen deposition and load from non-point sources ware estimated to be 97 ton/yr and 69 ton/yr, deposition is using CAMx model. So estimated total nitrogen discharge into Sihwa-ho was 817~875 ton/yr (846 ton/yr in average). The atmospheric load explains 11.1~11.9% (11.5% in average) of the total nitrogen load Sihwa-ho.

• Journal of Environmental Health Sciences
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• v.27 no.2
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• pp.145-152
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• 2001

The purpose of this study was to determine nitrogen dioxide(NO$_2$) decay rate by reaction between NO$_2$ and interior materials in Korean residence. The results of this research could be helpful to choose the interior construction materials and to study on reduction of indoor air pollutants. The results of this research are as follows; For 30 residences in Seoul and Incheon from October 2000 to march 2001, the mean of infiltration rate was 0.70$\pm$0.44 ACH, and single-detached houses (7 houses) and apartments (19 houses) were 0.97$\pm$0.55 ACH and 0.61$\pm$0.34 ACH, respectively. The $CO_2$ decay followed approximately first-order process ($R^2$=0.97$\pm$0.02). There existed a statistic significance in filtration rate between houses built in 1980’s and built in 1990’s by t-test (p<0.02). Mean of NO$_2$ decay rates in 26 residence3s except 4 residences was 0.94$\pm$0.49hr$^{-1}$ , and also 0.86$\pm$0.49hr$^{-1}$ , 0.97$\pm$0.50hr$^{-1}$ in single-detached houses and apartments, respectively. Mean NO$_2$ decay rates in houses built in 1980’s were 0.78$\pm$0.37hr$^{-1}$ , 1.33$\pm$1.03hr$^{-1}$ , respectively. Nothing were showed statistical significance among indoor temperature, indoor humidity, and NO$_2$ decay rate. However, NO$_2$ decay rates had a tendency to increase by increase of temperature and humidity. Average volume/surface of participated houses was 0.55$\pm$0.07m and mean NO$_2$ deposition velocity was calculated as 1.46$\pm$0.59msec$^{-1}$ .

• Composites Research
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• v.36 no.4
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• pp.275-280
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• 2023

Because polymer-based composites are lightweight and have excellent properties, their demand is growing rapidly as a way to fulfill properties that are difficult to achieve with a single material. As a result, there has been a lot of research on polymer nanocomposites, which are made by dispersing particles with a size of 1-100 nm in a polymer matrix. In addition, many nanocomposites using thermoplastic resins as matrix materials are being studied. In this study, poly(ethylene terephthalate) (PET)-based nanocomposites containing organic nanoclays modified with cetyltrimethylammonium bromide (CTAB) as interlayer materials were prepared. Among various nanoclays, vermiculite (VMT) has been studied to increase the mechanical and thermal properties of polymeric materials due to its low cost, abundant reserves and unique properties. However, the strong interlayer bonding of VMT has limited its utilization due to its poor exfoliation and dispersion performance within polymer matrices. In this study, the mechanical properties of the VMT content were confirmed by tensile tests, the dispersion of VMT particles in the PET matrix was evaluated by TEM cross-sectional images, and the nitrogen gas barrier properties were evaluated.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.223-233
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• 2010

Spatio-temporal variations of long-term water qualities (COD, SS, $Chl-{\alpha}$, N-related nutrients (TN, TDN, $NO_3^-$, $NH_4^+$), P-related nutrients (TP, TDP, $PO_4^{3-}$)) at two stations (St. SD, St. GG) in the Geumgang Reservoir were investigated from August 2001 to July 2008. Statistical methods such as t-test, factor analysis, and multi-regression analysis were applied to the water quality data in the reservoir as well as mass balances on TP. From the temporal comparisons of the water qualities between 2002 and 2007, average concentrations of $NH_4^+$, $PO_4^{3-}$, and TDP gradually decreased down by 60%, 24%, 52% in 2007. However, those of TP and $Chl-{\alpha}$ increased to 99% and 423% during the period. From the spatial comparisons between the two stations, St. GG showed higher concentrations for all of the N- and P-related nutrients than in St. SD, while opposite result for the $Chl-{\alpha}$. The factor analysis showed that "the seasonal variations of N- and P-related nutrients" were the two dominant factors occupying 49% of total variances of water qualities. Based on this result, multi-regression analysis executed for the two most influential parameters (TP and $Chl-{\alpha}$) focusing on the seasonal variations of these parameters: SS and $Chl-{\alpha}$ has contributed decisively to the concentrations of TP during the wet and dry season, respectively. On the other hand, COD and TP has been important for the $Chl-{\alpha}$ during the wet and dry season, respectively. From the established mass balances of TP loadings in the Geumgang Reservoir, Other Sources (60%) occupied the greatest contribution and Fluvial Input (38%) and Sediment (1%) during the wet season. However, both Fluvial Water (48%) and Other Sources (47%) supplied comparable amount of inputs and Sediment (5%) showed significantly increased input during the dry seasons. Recently especially during the dry winter seasons, migrating bird's excretion was estimated to contribute up to 8% of total TP input and 21% of Other Sources.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.655-668
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• 1994

Conventional deodorization filters using soil and compost reach the capacity limitation of deodorization in short period, because its removal mechanism primarily depends on adsorption. Therefore, in this study the experiment was performed on the removal of ammonia which is a strong inorganic malodor, frequently emitted from night soil treatment plants and sewage treatment plants, by seeding activated sludges on the bio-peat containing higher organic contents, water conservation capacity, permeability and lower pressure drop. As a result, in raw peat filter natural ammonia outlet was observed in consequence of pH increase resulted from ammonia ionizing in liquid phase. Ammonia removal mechanism primarily depended on the adsorption onto the anion colloidal substances in peat. In peat bio-filter, theoretical ammonium salts ratio was higher than that of raw peat, resulted from slight pH increase by microorganism activity, however, the experimetal value of ammonia-nitrogen accumulated in bio-peat was lower than that of raw peat because of nitrification by nitrifying bacteria. In the initial reaction period, adsorption was predominant in the ammonia removal mechanism, but nitrification was conspicuous after the middle period. Mass balance of nitrogen was established using experimental data of input $NH_3$ loading, output $NH_3$ loading, $NH_4{^+}$-N, $NO_x$-N, and Org-N. The critical time of unsteady state, which is the maximum activating point of microorganism in bio-filter, was determined using experimental data, and the ammonia adsorption curve was computed using regression analysis. On the basis of the results obtained by above analysis, the delay days for the saturation of adsoption capacity in peat bio-filter was calculated.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1777-1787
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• 2000

The purpose of this study was to select an effective and economical alkali source for sulfur-utilizing autotrophic denitrification. Tests on acid neutralization and denitrification at various alkali/sulfur mixing ratios were performed for charcoal, briquette ashes, sea shell, and limestone. The results of the experiments showed that sea shell was the most effective alkali source because it could provide more surface area than limestone, and the optimal alkali/sulfur mixing ratio was 1/1(V/V). In a sulfur/sea shell packed bed reactor, the denitrification efficiency was above 90% up to a loading rate of 116 g $NO_3{^-}-N/m^3-day$. but the denitrification efficiency deteriorated to 48% at the loading rate of 145 g $NO_3{^-}-N/m^3-day$. The average $SO_4{^{2-}}$ generation per g of $NO_3{^-}-N$ removed was 7.02 g, which is lower than the theoretical value of 7.54 g. Denitrification and sulfate generation appeared to be a first-order and a zero-order reaction with a reaction rate constant of 0.146 /hr and -53.1 mg/L-hr, respectively. According to nitrogen mass balance, 71~109%, with an average of 90%, of the removed nitrogen was recovered as $N_2$ gas.

• Korean Journal of Environmental Agriculture
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• v.28 no.1
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• pp.32-37
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• 2009

This study was conducted to assess the impact of agricultural land use on the water quality in mountain village farmlands. Two soil types, paddy and upland soil were analysed for their chemical properties. Although, pH and organic matter contents were not significantly different to each other, concentrations of available P and exchangeable K and Ca were much higher in upland soil compared with those in paddy soil. The results of water quality analysis indicated that, in Goseong-cheon watershed, the nutrients contents were much higher in downstream area than in upstream area. Particularly, the elevation of $COD_{Mn}$ and T-P were significant during rainy season. When paddy fields coexist with upland fields, SS, T-N, and T-P concentrations in paddy fields were lower than those of upland fields. This may indicate that paddy fields possess an water-purifying ability by absorbing nutrients. This effect may reduce excessive nutrients discharged into the neighboring streams which may cause eutrophication problem. The difference between inflow and outflow of nitrogen and phosphorus during the cultivation period were measured as -98.9 kg $ha^{-1}$ and -29.7 kg $ha^{-1}$, which means that nutrient outflow was higher than inflow. This may suggest that much nutrient was discharged during the crop harvest period.

• Korean Journal of Environmental Agriculture
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• v.23 no.1
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• pp.7-14
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• 2004

This study was conducted to investigate the effect on agricultural environment and crop productivity by different amount of applied fertilizer in consideration of irrigation water quality. N, P and K contents of irrigation water used in this experiment were 6.16, 0.26 and 9.37 mg/L, respectively. N, P and K Concentrations of runoff water were lower than those of inflow water during rice cultivation. N, P and K Concentrations of ponded and percolated water were changed according to the amount and time of applied fertilization. During rice cultivation in paddy soil, nitrogen balance was closed to 0 in SFT 50% (50% level of soil testing fertilization), 0.14 kg/ha, but it was 95.3 kg/ha in CF (conventional fertilization) treatment In SW 50% and STF (soil testing fertilization) treatment yield of perfect rice was not greatly different as compared with CF treatment due to the superiority of ripening rate, 1,000 grains weight and milling characteristics. Mechanical paratability of rice was excellent in NF (non fertilization) treatment, STF 50% treatment showed higher in nutrient availability and fertilizers use efficiency than other treatments.

• Korean Journal of Environmental Agriculture
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• v.33 no.1
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• pp.44-51
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• 2014

BACKGROUND: Water quality of rural areas are susceptible to agricultural nutrient input and supply such as chemical fertilizer and livestock manure. This study was conducted to evaluate the usefulness of nutrient (N and P) indices in understanding spatial variations of water quality across Chonnam province which is a typical agricultural region in Korea. METHODS AND RESULTS: The nutrient indices including chemical fertilizer supply, livestock manure production, and nutrient balance were correlated with water quality data (T-N, T-P, BOD, and COD) for the twenty-two districts of the province. Concentration of T-N were positively correlated with chemical fertilizer supply, livestock manure N production, and nutrient balance (P<0.05 or P<0.01). Meanwhile, T-P concentration was not correlated with these nutrient indices; however, there was a tendency that T-P concentration increases with livestock manure P production (P=0.06) and with nutrient balance (P=0.09). These results suggest that T-N concentration is susceptible to both chemical fertilizer and livestock manure; whereas T-P is likely to be affected by livestock manure rather than chemical fertilizer. The concentrations of BOD and COD were also positively (P<0.05 or P<0.01) correlated with livestock manure production. CONCLUSION: This study shows the usefulness of nutrient indices in understanding spatial variations of water quality and suggests that livestock manure rather than chemical fertilizer can be a more critical water pollution source and thus highlights the need for more attention to livestock manure treatments for rural water quality management.