• Korean Journal of Environmental Biology
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• v.34 no.1
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• pp.18-29
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• 2016

The effects of water temperature, salinity, water column nutrient contents, and phytoplankton primary productivity on pigment composition and concentration, as well as primary productivity of Pyropia yezoensis Ueda purple lavers were studied at the primary cultivation areas in the Manho (Jindo-Haenam) region on the southwestern coast of Korea in March 2014. The water temperature was $9.1{\sim}9.6^{\circ}C$, salinity was 32.5~33.1, and transparency was 0.7~1.5 m. The shallow euphotic depth resulted from the high turbidity. Water column dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and silicate concentrations were $3.59{\sim}5.73{\mu}M$, $0.16{\sim}0.41{\mu}M$, and $12.41{\sim}13.94{\mu}M$, respectively. Chlorophyll a (Chl a) concentration was $0.51{\sim}1.25{\mu}g\;L^{-1}$. Nanoplankton ($0.7{\sim}20{\mu}m$ size class) accounted for 58% of the total Chl a concentration. Fucoxanthin was the dominant photosynthetic pigment at all sites. Microplankton ($20{\sim}200{\mu}m$ size class) accounted for 64% of the total fucoxanthin concentration. The primary productivity of phytoplankton was $57.72{\pm}4.67(51.05{\sim}66.71)mg\;C\;m^{-2}d^{-1}$. The nanoplankton ($0.7{\sim}20{\mu}m$ size class) accounted for 77% of the total phytoplankton primary productivity. The calculated phytoplankton primary productivity was $11,337kg\;C\;d^{-1}$. The primary productivity of Pyropia blades was $1,926{\pm}192(1,102{\sim}2,597)mg\;C\:m^{-2}d^{-1}$, i.e., calculated as $39,295kg\;C\;d^{-1}$. The total primary productivity of phytoplankton and Pyropia blades was $50,632kg\;C\;d^{-1}$. The primary productivity of Pyropia blades was 3.5 times greater than that of phytoplankton in the Manho region on the southwestern coast of Korea.

• Particle and aerosol research
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• v.9 no.1
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• pp.7-21
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• 2013

Twelve-hour size-resolved atmospheric aerosols were measured to determine size distributions of water-soluble organic carbon(WSOC) during daytime and nighttime, and to investigate sources and formation pathways of WSOC in individual particle size classes. Mass, WSOC, ${NO_3}^-$, $K^+$, and $Cl^-$ at day and night showed mostly bimodal size distributions, peaking at the size range of $0.32-0.55{\mu}m$(condensation mode) and $3.1-6.2{\mu}m$(coarse mode), respectively, with a predominant condensation mode and a minor coarse mode. While ${NH_4}^+$ and ${SO_4}^{2-}$ showed unimodal size distributions which peaked between 0.32 and $0.55{\mu}m$. WSOC was enriched into nuclei mode particles(< $0.1{\mu}m$) based on the WSOC-to-mass and WSOC-to-water soluble species ratios. The sources and formation mechanisms of WSOC were inferred in reference to the size distribution characteristics of inorganic species(${SO_4}^{2-}$, ${NO_3}^-$, $K^+$, $Ca^{2+}$, $Na^+$, and $Cl^-$) and carbon monoxide. Nuclei mode WSOC was likely associated with primary combustion sources during daytime and nighttime. Among significant sources contributing to the condensation mode WSOC were homogeneous gas-phase oxidation of VOCs, primary combustion emissions, and fresh(or slightly aged) biomass burning aerosols. The droplet mode WSOC could be attributed to aqueous oxidation of VOCs in clouds, cloud-processed biomass burning aerosols, and small contributions from primary combustion sources. From the correlations between WSOC and soil-related particles, and between WSOC and sea-salt particles, it is suggested that the coarse mode WSOC during daytime is likely to condense on the soil-related particles($K^+$ and $Ca^{2+}$), while the WSOC in the coarse fraction during nighttime is likely associated with the sea-salt particles($Na^+$).

• Journal of Korean Society on Water Environment
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• v.21 no.2
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• pp.147-152
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• 2005

Fermentation efficiencies of organic wastes from the variety of sources were evaluated based on the production of total volatile acids(TVA) in batch reactor. Mixing and pH were not significant factors in producing TVA from the organic wastes. After a 10-day fermentation, final TVA concentrations in piggery, cattle, poultry, and primary settled sludge of domestic wastewater were 8,900, 2,900, 7,370 and 1,630 mg/L, respectively. The pH of organic wastes was decreased from neutral to 5.7. The ratio of TVA to $NH_4{^+}-N$ produced from the animal waste ranged from 11.5 to 30.1, whereas, that in the primary settled sludge of domestic wastewater, was 5.4. Possibility of fermented organic wastes as the electron donors for denitrification in the activated sludge was investigated. In both acclimated and nonacclimated activated sludge, higher denitrification rates were obtained with fermented piggery sludge added than with either methanol or acetate added. The fermented organic acids derived from the primary settled sludge gave the higher denitrification rate ($4.2mg\;NO_3-N/g\;vss{\cdot}hr$) in the acclimated activated sludge. Denitrification rate was $1.5mg\;NO_3-N/g\;vss{\cdot}hr$ in the nonacclimated sludge with the fermented acids from the primary settled sludge of domestic wastewater added.

• Journal of Korean Society on Water Environment
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• v.23 no.1
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• pp.19-26
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• 2007

The lab-scale BNR processes fed with Municipal Wastewater Before or After Primary Clarifier (MWBPC or MWAPC) were operated to observe the behavior of particle organic matter in terms of nitrification and denitrification efficiency. As a result of the fractionation of the COD from MWBPC or MWAPC using an aerobic respirometric serum bottle reactor, the total mass of biodegradable organic matter from MWBPC is about 52% greater than the mass from MWAPC. Batch reactors were operated to observe the effect of the Particulate Organic Matter (POM) on substrate utilization for denitrification. Although the consumption of POM for denitrification was observed, the increment of the Specific Denitrification Rate (SDNR) was not great. In terms of the effect of POM on nitrification at different HRTs, activate sludge reactors were operated to determine the optimal HRT when MWBPC and MWAPC were fed relatively. All reactors showed a great organic matter removal efficiency. Reactors fed with MWAPC had obtained the nitrification efficiency above 90% when the HRT of 4 hr, at least, was maintained, while reactors fed with MWBPC had same efficiency when the HRT longer than 5 hr was kept. Three parallel $A^2/O$ systems fed with MWBPC or MWAPC relatively were operated to investigate the effects of POM on BNR processes with varying the HRT of an anoxic reactor. For all systems, the efficiency of organic matter removal and denitrification, respectively, was great and about the same. In case of denitrification efficiency, system with MWAPC had 1.5% lower than system with MWBPC at the same HRT of anoxic reactor of 2 hr, and the increasing the HRT of the anoxic reactor by 1 hr in systems fed with MWBPC resulted in a 3.5% increment. The denitrification rate was similar while the consumption of organic matter in systems fed with MWBPC was higher than system fed with MWBPC. It suggests that POM in MWBPC was not be used significantly as a substrate for denitrification in system with the HRT of 3 hr of an anoxic reactor.

• Corrosion Science and Technology
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• v.11 no.4
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• pp.141-150
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• 2012

Stress corrosion cracks in Alloy 600 compact tension specimens tested at $325^{\circ}C$ in a simulated primary water environment of pressurized water reactor were analyzed by analytical transmission electron microscopy and secondary ion mass spectroscopy (SIMS). From a fine-probe chemical analysis, oxygen was found on the grain boundary just ahead of the crack tip, and chromium oxides were precipitated on the crack tip and the grain boundary attacked by the oxygen diffusion, leaving a Cr/Fe depletion (or Ni enrichment) zone. The oxide layer inside the crack was revealed to consist of a double (inner and outer) layer. Chromium oxides existed in the inner layer, with NiO and (Ni,Cr) spinels in the outer layer. From the nano-SIMS analysis, oxygen was detected at the locations of intergranular chromium carbides ahead of the crack tip, which means that oxygen diffused into the grain boundary and oxidized the surfaces of the chromium carbides. The intergranular chromium carbide blunted the crack tip, thereby suppressing the crack propagation.

• Ocean and Polar Research
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• v.25 no.4
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• pp.459-468
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• 2003

Annual variation of water qualities in the Shihwa Lake were observed 18 times from June 1996 to October 2001. We studied at the station of the upper streams and near the water gate of lake. After the flow of the outer seawater through the water gate, the surface salinity in Shihwa Lake increased to the range of 25-30 psu in both stations after October 1998. Due to the declination of the salinity differences between the surface and the bottom water, the pycnocline in which had existed until 1997 has weakened, and made the water column mix vertically. This led to the improvement of anoxic/hypoxic environment at bottom waters after April 1998. However, despite the continuous flow of the outer seawater, the concentrations of chlorophyll-a at surface layer were varied from $2{\mu}g/l\;to\;60{\mu}g/l$, and these values indicated the eutrophication. The following organic matter load was greatly influencing the surface layer's COD concentration. During the rainy season, the salinity at the surface layer to the below 15 psu resulting in stratification between the surface and bottom layer. Organic matters that were provided from the surface layer to the bottom layer due to active primary production in the year exhausted dissolved oxygen at the bottom layer, and the bulks of organic matters at bottom gave rise to hypoxic or anoxic environment. It was observed that the enrichment of ammonia and phosphate were main factors to worsen the water quality of the Shihwa Lake. The results of examining the annual variations in Shiwha Lake through principal component analysis shown that water characteristics in the rainy season were similar with those before input of outer sea water.

• Journal of Korean Society on Water Environment
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• v.29 no.1
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• pp.19-28
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• 2013

Artificial neural networks were used for time series modelling of algal dynamics of whole year and by season at the Paldang dam station (confluence area). The modelling was based on comprehensive weekly water quality data from 1997 to 2004 at the Paldang dam station. The results of validation of seasonal models showed that the timing and magnitude of the observed chlorophyll a concentration was predicted better, compared with the ANN model for whole year. Internal weightings of the inputs in trained neural networks were obtained by sensitivity analysis for identification of the primary driving mechanisms in the system dynamics. pH, COD, TP determined most the dynamics of chlorophyll a, although these inputs were not the real driving variable for algal growth. Short-term prediction models that perform one or two weeks ahead predictions of chlorophyll a concentration were designed for the application of Harmful Algal Alert System in Lake Paldang. Short-term-ahead ANN models showed the possibilities of application of Harmful Algal Alert System after increasing ANN model's performance.

• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.2
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• pp.96-108
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• 1998

The management of water quality and fishery resources with a major environmental problem in eutrophic coastal sea is studied. The numerical experiments using the water-sediment quality model (WSQM) were carried out for the management of water quality at the Seto Inland Sea in Japan. The results of long-term water quality simulation showed responses of seawater quality to input loads to vary in different localities. A formula roughly forecasting water qualify to estimate the effect of loading abatement was proposed. The simulation for the improvement of seawater quality showed the abatements of nutrient loads such as total phosphorus (TP) and total nitrogen (TN) as well as organic loads such as chemical oxygen demand (COD) to be peformed in the eastern Seto Inland Sea from Bisan Seto to Osaka Bay. On the other hand, it is indicated that the increase of loading leads to the increase of primary production. while not straightly to the increase of fish production for the catch of fisheries.

• Journal of environmental and Sanitary engineering
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• v.3 no.1 s.4
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• pp.27-39
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• 1988

This investigation was carried out to evaluate the removal effect of biological contaminants for the municipal sewage treatment process at Cheonggye Cheon terminal plant which in the first plant for municipal sewage treatment in Seoul area. It was conducted in raw influent, primary treatment water and secondary treatment water from September, 1986 to July, 1987. The results were as follow; 1, The primary treatment could eliminate microbials for $65.38\%$ of total bacteria, $64.35\%$ of total coliform, $62.16\%$ of fecal coliform $69.48\%$ of pseudomonas and $64.70\%$ of fecal streptococci in averages for a year respectively. 2. The secondary treatment could eliminate microbials for $97.50\%$ of total bacteria, $97.30\%$of total coliform, $95.95\%$ of fecal coliform, $97.00\%$ of pseudomonas and $96.53\%$ of fecal streptococci in average for a year respectively. 3. In the detect rate of pathogenic agent, salmonella spp was decreased $12.5\%$ to $4.2\%$ in primary treatment and it was not detected in secondary treatment, shigella spp was detected $4.2\%$ in influent water but it was not detected in primary and secondary treatment. 4. In the seasonal variation of treatment effect, the removal of summer was the highest, and the removal of all item in winter was lower than the other seasons. 5. There was significant correlation between water temperature and microbal all items (P<0.05) $NH_3-N$ and Microbal items (P< 0.01) at raw water.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.295-305
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• 2009

The purpose of this study was to understand of water quality characteristics of lake Paldang, especially at a certain representative site, right in front of Paldang dam ($P_2$ site) and to propose the directions of water quality management of lake Paldang. Water characteristics at $P_2$ site was investigated by principle components analysis and the Pearson correlation coefficient analysis. Also, seasonality was identified by the Kruskal-Wallis test and long term trend of nutrients and chlorophyll-a was analyzed by seasonal decomposition method at lake Paldang statistically. The primary factor affecting on water quality at $P_2$ site was identified as nutrients, while physical parameters, such as rainfall and inflow rate were also important factors. At the result of linear regression analysis particulate organic phosphorus (POP) vs total phosphorus (TP) showed very high correlation of 0.78. TP loading was increased annually from 1995 to 2006. Chlorophyll-a and nutrients show seasonality at $P_2$ site. Long term trend of Chlorophyll-a was increased by increase of TP at lake Paldang.