• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.90-103
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• 2014

Distribution characteristics of water masses, dissolved inorganic and organic nutrients were investigated in the southern part of the East Sea of Korea in September, 2011. On the basis of the vertical profiles of temperature, salinity and dissolved oxygen, water masses in the study area were divided into 4 major groups, such as WM (water mass)-I, WM-II, WM-III, WM-IV. Their characteristics were similar to Tsushima Surface Water (TSW), Tsushima Middle Water (TMW), North Korea Cold Water (NKCW) and East Sea Proper Water (ESPW), respectively. In the vertical profiles of dissolved nutrients, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) concentrations were highest in the WM-IV, followed by WM-III, WM-II, WM-I. On the contrary, distribution of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) were highest in the WM-I, followed by WM-II, WM-III, WM-IV. Although the DIN : DIP ratio in all of the water masses was similar to Redfield ratio(16), the DIN : DIP ratio in mixed layer was about 5.3, indicating that inorganic nitrogen is the limiting factor for the growth of phytoplankton. However, the DON proportion in dissolved total nitrogen (DTN) was about 70% in the mixed layer where inorganic nitrogen is limiting factor. Thus, enriched DON may play an important source of the nutrient for the growth of phytoplankon in the East Sea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.42-51
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• 2016

We investigated the distribution of dissolved nutrients, phytoplankton community structure and utilization of nitrogen compounds by dominant species in the southwestern part of East Sea in September, 2014. Dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) were lower in the surface layer, and concentrations were increased with depth. Dissolved organic nitrogen (DON) and dissolved organic phosphorus were the opposite of dissolved inorganic nutrients. Although DIN DIP ratio in all of the water masses was higher than Redfield ratio (16), DIN : DIP ratio in mixed layer was about 2, indicating that inorganic nitrogen is the limiting factor for the growth of phytoplankton. In particular, DON proportion in dissolved total nitrogen was about 88 % in the mixed layer where inorganic nitrogen is limiting factor. The dominant species Chaeotceros debilis and Prorocentrum minimum were able to grow using DIN as well as DON such as urea and amino acids. Therefore, DON utilization of phytoplankton may play a role as a survival strategy in the DIN-limited conditions of East Sea.

• KSBB Journal
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• v.18 no.2
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• pp.155-160
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• 2003

The effect of dissolved oxygen(DO) on microbial transglutaminase(mTG) production by Streptoverticillium morbaraense was studied in on-line computer controlled fermentation system. In order to control dissolved oxygen during fermentation, the agitation speed and aeration rate of 2.5 L fermenter ranged from 260 to 360 rpm and 0.3 to 3.9 L/min, respectively. The maximum microbial transglutaminase production was obtained at controlled 20% of dissolved oxygen among the various dissolved oxygen controlled batch cultures tested. The production of microbial transglutaminase at controlled 20% of dissolved oxygen was about 2.12 U/mL which was 1.1 times higher than that obtained in batch culture without control of dissolved oxygen. Also, the highest microbial transglutaminase production was obtained in fed-batch cultures in which dissolved oxygen was controlled at 20%, and it was improved almost 1.3 times in comparison with that without control of dissolved oxygen. Maximal dry cell weight and microbial transglutaminase production were 13.2 g/L and 2.6 U/mL, respectively. Finally, it was also found that fed-batch fermentation at controlled 20% of dissolved oxygen showed a good performance for the microbial transglutaminase production by on-line computer controlled fermentation system which may be generally applicable to other microbial cultures.

• Journal of Sensor Science and Technology
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• v.10 no.4
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• pp.259-265
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• 2001

FET-type dissolved oxygen sensor has the Pt working electrode around the pH-ISFET. Appling a voltage to the working electrode, the hydrogen ion which is proportional to the dissolved oxygen concentration occurs around the pH sensing gate and we can measure the dissolved oxygen concentration by detecting pH concentration through the pH-ISFET. In this paper, a dissolved oxygen measurement system using FET-type dissolved oxygen sensor array which adopt a specific algorithm to enhance the reliability has been developed and we compared its performance with the commercial dissolved oxygen measurement system.

• Journal of the Korean institute of surface engineering
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• v.50 no.4
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• pp.231-236
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• 2017

The present work addresses how to measure the amount of dissolved aluminum in phosphoric acid, based on volumetric and gravimetric measurements of the precipitates formed by reaction between the $H_3PO_4$ solution containing dissolved aluminum ions and 10 % KF solution. The volume of the precipitates increased with dilution of the dissolved aluminum-containing $H_3PO_4$ solution up to 1/4 dilution above which it decreased with further dilution. The lowered amounts of the precipitates at low dilution less than 1/4 and high dilution more than 1/4 are attributed to high acidity of the solution and decreased amount of dissolved aluminum in the solution, respectively. Volumetric measurement of the amount of precipitates was found not to be very reliable with the experiments, while weight measurement of the precipitates after drying for 80 min at $60^{\circ}C$ appeared to be very reproducible. In the present work, it is suggested that the amount of Al dissolved in 85 % $H_3PO_4$ solution can be calculated by multiplying 50 to the weight of precipitate obtained by reacting 8 ml of 1/4 diluted $H_3PO_4$ solution containing dissolved aluminum ions with 6 ml of 10 % KF solution.

• Ocean and Polar Research
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• v.39 no.1
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• pp.35-43
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• 2017

Concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphate (DOP), and colored dissolved organic matter (CDOM) were measured in the coastal sea off inland aqua farms in northeastern Jeju Island in summer 2015. The highest concentrations of DOC, DON, and DOP were revealed in the surface water off Hado-ri where the lowest salinity conditions prevailed (31.6). The concentrations of DOC, DON, and DOP in the surface water were lower in the inner stations (SH1-1, 1-2, and 1-3) near the aqua farms of the Haengwon-ri than in the outer stations. The concentrations of DOC, DON, and DOP negatively correlated with salinity. These results indicate that the contribution of dissolved organic matter (DOM) from the aqua farms seems to be not significant. On the other hand, the higher concentrations of DON and DOP in the inner stations of Hado-ri (HD 1-1) seem to be attributed to excrement of migrating birds. The three components of CDOM (T, M, and C peaks) showed no relationship with salinity, perhaps due to various in situ productions by marine organisms and decomposition by ultraviolet radiation. The observed lower C:M ratio, an indicator of terrestrial source, and the higher biological index (BIX) of CDOM in the station off Hado-ri indicate that DOM is produced mainly by biological activity. Based on the higher humification index (HIX) of CDOM and the higher DOC:DON ratio off Haengwon-ri, refractory DOM in the inland aqua farms is likely transported to the coastal sea.

• Journal of Environmental Science International
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• v.4 no.3
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• pp.259-267
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• 1995

This study was conducted to evaluate the effects of pressure and dissolved oxygen concentration on the activated slut비e and to determine the optimum depth of deep shaft process. Some results from this study were summarized as follows. 1. It is considered that low sludge product in the activated sludge system maintaining high dissolved oxygen concentration is attributed to the increase of endogeneous respiration rate caused by the increase of aerobic zone in the sludge floe. 2. The increase of dissolved oxygen concentration does not affect to the increase of organic removal efficiency greatly and therefore the limiting factor is the substrate transfer into the inner part of floe. 3. The yield coefficient, Y is decreased in proportion to the increase of oxygen concentration. In this study, Y values arre ranged from 0.70 to 0.41 according to the variation of dissolved oxygen concentration from 18.0mg/$\ell$ to 258 mg/$\ell$. 4. The optimum depth of deep shaft process should be determined within the limits of non-toxicity to the microorganism and it is about loom in this study.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.375-381
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• 2002

Measuring of the dissolved oxygen is widely used for the environmental control of natural waters, sewage waste treatment, medical and biochemical studies, soil husbandry, food and drug process control, and prevention of corrosion in boilers. Especially, a power plants need special management for preventing accidents from corrosion, therefore, it is essential to measure the concentration of dissolved oxygen in real-time. In this paper we present a method of measuring dissolved oxygen very accurately up to pub units. This method, called polarograph method, is based on the measures of the electric current generated by the oxidation process in cathode and de-oxidation process in anode, assuming that the amount of the current is proportional to the density of dissolved oxygen.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.197-201
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• 2001

Measuring of the dissolved oxygen is widely used for the environmental control of natural waters, sewage waste treatment, medical and biochemical studies, soil husbandry, food and drug process control, and prevention of corrosion in boilers. Especially, a power plants need special management for preventing accidents from corrosion, therefore, it is essential to measure the concentration of dissolved oxygen in real-time. In this paper we present a method of measuring dissolved oxygen very accurately up to ppb units. This method, called polarographic method, is based on the measures of the electric current generated by the oxidation process in cathode and de-oxidation process in anode, assuming that the amount of the current is proportional to the density of dissolved oxygen.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.428-433
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• 2009

Dissolved oxygen is considered as one of the important water-quality constituents in streams from one century ago and fishes perish in low dissolved oxygen concentration. Environmental scientists and engineers have introduced the deterministic model to estimate dissolved oxygen concentration of streams and recommended the use of the Delta Method (DM), Approximate Delta Method (ADM), Extreme Value Method (EVM) and Optimization Method (OPT) which can be applied in no spatial variation of dissolved oxygen. The diurnal or annual variation of dissolved oxygen is mainly determined from the parameters such as reaeration rate, 1st production rate and respiration rate which are related to dissolved oxygen. Each method was briefly introduced and applied to two sampling sites of Anseong Stream watershed in this paper. The limitation, advantages and disadvantages of each method were reviewed and analyzed after running the each method. From these analyses, the benefit-cost approach to estimate dissolved oxygen effectively in streams was recommended.