• Journal of the Korean Society of Visualization
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• v.9 no.1
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• pp.36-41
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• 2011

It is highly needed to measure the dissolved oxygen (DO) concentration field in water for a variety of purposes such as biological, industrial, environmental monitoring and medical application. Application of PSP (Pressure Sensitive Paint) which is sensitive to oxygen concentration has been carried out to measure DO concentration field using PtOEP/PS film and intensity based method under the UV-LEDs illumination. A micro round water jet having 100% of DO was obliquely impinged on to a PtOEP/PS film coated plate placed in a 0% of DO water container. DO concentration fields on the impinging plate were quantitatively visualized with a $2.94\;{\mu}m$ of spatial resolution. Through pixel-by-pixel calibration, uncertainty of each pixel by different sensitivity, different dye concentration and non-uniformity of illumination was removed. It is demonstrated that the high DO concentration region was coincided with the impingement area. The DO concentration gradient due to DO diffusion was affected by Reynolds number.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.747-752
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• 2011

The parrotfish Oplegnathus fasciatus is a sub-tropical species that is difficult to culture during the winter in South Korea. As a result, a recirculating aquaculture system (RAS) was developed to rear parrotfish. This study investigated the effects of stocking density and dissolved oxygen (DO) concentration on the growth and hematology of the parrotfish in the RAS. The experimental stocking densities were 5 (SD05), 10 (SD10), 15 (SD15), and 20 kg/m3 (SD20) total body weight to tank water volume. As the stocking density increased, the mean weight gain, feed efficiency, and specific growth rate tended to decrease. However, SD10 and SD15 did not differ statistically from SD05 in feed efficiency (P>0.05). Although better growth was achieved in SD05, SD10 and SD15 appeared to be acceptable, practically and economically, in terms of feed efficiency. The experimental DO concentration ranges were 3-4 (DO3), 5-6 (DO5), and 7-8 mg/L (DO7). The mean weight gain and survival tended to increase with the DO concentration, but there were no differences among treatments (P>0.05). Although the feed efficiency did not differ among the treatments, the specific growth rates and daily feed intake increased with the DO concentration and were the highest in DO7 (P<0.05). The cortisol concentration was the highest in DO3 (P<0.05), while there was no difference between DO5 and DO7 (P>0.05).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.238-245
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• 2021

In this study, we carried out case study to predict dissolved oxygen (DO) concentration of Nakdong river estuary with LSTM model. we aimed to figure out a optimal model condition and appropriate predictor for prediction in dissolved oxygen concentration with model parameter and predictor as cases. Model parameter case study results showed that Epoch = 300 and Sequence length = 1 showed higher accuracy than other conditions. In predictor case study, it was highest accuracy where DO and Temperature were used as a predictor, it was caused by high correlation between DO concentration and Temperature. From above results, we figured out an appropriate model condition and predictor for prediction in DO concentration of Nakdong river estuary.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.4
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• pp.295-307
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• 2002

Water temperature, salinity, and DO concentration were measured vertically in the Chinhae-Masan Bay over the course of 1 year. The characteristics of the stratification were analysed using the measured water temperature and salinity data. The vertical DO concentration changes were also analysed through consideration of the degree of stratification and the level of sediment pollution. The results of the analyses show that the thermal stratification appears just before April and disappears after October. The salinity differences between the surface and the bottom were 3.9(equation omitted), 9.3 (equation omitted), 4.3(equation omitted) in April, August, and October, respectively. The DO concentration change averaged over water depth was 2.6(mg/L) in April; 8.3(mg/L) in June: 5.9(mg/L) in August; 7.2(mg/L) in September; and 4.4(mg/L) in October. The DO concentration changes were closely related to the levels of contamination and also to the effect of the mass-transfer inhibition between the surface and bottom layers due to the thermal and density stratification.

• Asian Journal of Atmospheric Environment
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• v.7 no.2
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• pp.85-94
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• 2013

Methane concentrations have been monitored at the Anmyeon-do Observatory, Korea, since 1999. In recent years, the methane concentration has increased, but the sources of this increase have yet to be identified. This study was designed to identify the major source contributing to the increase by using World Data Centre for Greenhouse Gases (WDCGG) data and the Greenhouse Gases Emission Presumption (GEP) method. The data were collected at Anmyeon-do between 2003 and 2009 (except 2008), and the analyses showed that the increase in methane concentration originated mainly in rice paddies around the observation point. The annual average methane concentration at Anmyeon-do was 1894 ppb, of which 100-103 ppb (5.3-5.4%) was shown to originate mainly from rice paddies. The seasonal fluctuation in methane concentration from May to October estimated by the GEP method was compared with experimental data of previous research conducted on rice paddies. The close match obtained through this comparison shows that the GEP method is effective. The difference in methane concentration was also analyzed in terms of land use and land cover. It was shown that although rice paddies account for only 14.7% of the area surveyed, they accounted for between 69 and 90% of the total increase in methane concentration. These results confirm that rice paddies are the main source of the increase in methane concentration observed at Anmyeon-do.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.385-398
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• 2007

It was analysed that spatial and temporal change patterns of general water quality constituents were measured monthly from 2002 to 2005 in Jumunjin Harbour. The measured constituents are temperature, salinity, pH, SS and DO. Concentration difference of upper lower layer for general water quality constituents was small. Temperature and DO concentration show the clear difference at temporal concentration change pattern, but SS, pH and salinity have irregular change pattern. Also, water quality improvement effect of seawater exchange facilities and sewage treatment plants is analysed quantitatively using averaged spatial and temporal data set. From this result, it is found that effect of sewage treatment plants is small and seawater exchange facilities at zone 1 and 2 is clear concentration reduction effect to be about 26% and 16%, respectively. After sewage treatment plants operation, DO concentration reduced about 10% at inner zone of Jumunjin Harbour, the other side, after seawater exchange facilities concentration DO concentration increased about 10%. DO concentration at 2005 estimated little than that of 2002, it is concluded that a yearly change of DO concentration has about 10%.

• Journal of environmental and Sanitary engineering
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• v.17 no.2
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• pp.63-70
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• 2002

We investigated the concentration degree of VOCs for ambient air in the air environment control area of Kyonggi-do in 2001. The VOCs showing higher concentration were in the ascending order of Toluene > n-Butane > 1-Butene > Benzene > n-Hexane. The concentration distribution ratio mentioned above showed almost same pattern in each city. The relative concentration ratio of Benzene, Toluene, Ethylbenzene, Xylenes which are aromatic VOCs were 1 : 6.3 : 0.6 : 1.6. It was similar to the pattern in 1999 but different from the pattern in 2000. In the aspect of seasons, the highest B.T.E.X concentration was indicated in fall and in the aspect of areas, the higher concentration showed in the ascending order of Buchon > Ansan > Kwangmyong > Shihung > Sungnam. The average concentration of target VOCs for ambient air in the air environment control area of Kyonggi-do showed lower concentration than the metropolis of Seoul but higher concentration than Kwang-ju city and Dae-gu city. The amount of total VOCs was increasing, comparing with it last year and the more increasing tendency is anticipated so that it will need to establish the proper regulative criteria.

• Korean Journal of Organic Agriculture
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• v.19 no.spc
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• pp.131-134
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• 2011

• Journal of Environmental Health Sciences
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• v.9 no.1
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• pp.1-13
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• 1983

This study was carried out to investigate nitrification in the main stream of the Naktong river for two times, 12-13 August and 23-26 September 1982. The results of this study were as follows : 1. The increase of nitrogen concentration was due to inflow of Geumho river, which was polluted by the municipal and industrial wastewater of Daegu city. 2. The rate constant of ammonia calculated for three reaches was high according to the stream flow and was eminently low in the reach from Goroung to Gangjung. (0.068-0.116 $day^{-1}$). This phenomena might be attributed to the sublethal or even lethal effect upon aquatic life by relatively low DO concentration and high heavy metal concentration. 3. DO consumption rate by nitrification was highest for the reach from Goroung to Daeam where was affected by Geumho river. (56.7-147.8%). This phenomena might be attributed to low DO concentration and high nitrogen concentration. Especially, the less stream flow was, the higher DO consumption was. And so, nitrification in the station where is low DO concentration, especially under the low flow condition, might cause more serious water quality management problem. Therefore, for the purpose of effective conservation of water quality in the Naktong river, it was suggested that We have more concern about the nitrogen compound, and more study on the nitrification phenomena.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.355-358
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• 2002

In this study, we have tried to find the maximum microbial efficiency at the various dissolved oxygen (DO) concentration conditions in the treatment of pharmaceutical wastewater. Experiments of activated sludge process were performed to examine the relation between microbial activity and DO concentration in a continuous bioreactor. The reduction rate of COD (chemical oxygen demand) was low at the DO concentration between 0 ppm and 1.0 ppm, but it went higher and showed maximum between 1.5 ppm and 3.0 ppm. Then the COD reduction rate was quickly decreased above the DO concentration of 3.0 ppm.