• Ocean Science Journal
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• v.42 no.1
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• pp.9-17
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• 2007

The summer distributions of planktonic microbial communities (heterotrophic and phtosynthetic bacteria, phtosynthetic and heterotrophic nanoflagellates, ciliate plankton, and microphytoplankton) were compared between inner and outer areas of Lake Sihwa, divided by an artificial breakwater, located on the western coast of Korea, in September 2003. The semi-enclosed, inner area was characterized by hyposaline surface water (<17 psu), and by low concentrations of dissolved oxygen (avg. $0.4\;mg\;L^{-1}$) and high concentrations of inorganic nutrients (nitrogenous nutrients $>36\;{\mu}M$, phosphate $>4\;{\mu}M$) in the bottom layer. Higher densities of heterotrophic bacteria and nanoflagellates also occurred in the inner area than did in the outer area, while microphytoplankton (mainly diatoms) occurred abundantly in the outer area. A tiny tintinnid ciliate, Tintinnopsis nana, bloomed into more than $10^6\;cells\;L^{-1}$ at the surface layer of the inner area, while its abundance was much lower ($10^3-10^4\;cells\;L^{-1}$) in the outer area of the breakwater. Ciliate abundance was highly correlated with heterotrophic bacteria (r = 0.886, p < 0.001) and heterotrophic flagellates (r = 0.962, p < 0.001), indicating that rich food availability may have led to the T. nana bloom. These results suggest that the breakwater causes the eutrophic environment in artificial lakes with limited flushing of enriched water and develops into abundant bacteria, nanoflagellates, and ciliates.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.5
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• pp.313-318
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• 2014

The remote monitoring system of water salinity was assessed in Wando reclaimed land lake during a farming season in 2009. Increasing of water salinity in this lake used to bring about salt damage on rice plant occasionally. At the early stage of the rice growing period, rice growth was not damaged due to enough rainfall with more than 120 mm from the mid-May to the first ten days of June. Data collection using on-site water salinity measuring sensors every 2 hours and real-time transmission in system were carried out for the experiment. We compared the transmitted values from the sensor system with water sample values collected and analyzed by a local technical office. Salt concentrations measured by sensor in real-time monitoring system were available data. The regression equation between rainfall and water salinity was presented as (water salinity after rainfall) = $0.621{\times}$(water salinity before rainfall)${\times}exp(-0.0139{\times}rainfall)$, ($r^2=0.579$, p<0.01). It is suggested that the system is useful for stable farming in the area where farmer use water in reclaimed lakes as an irrigation source.

• Journal of Korean Society on Water Environment
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• v.29 no.4
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• pp.531-539
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• 2013

In order to apply a water quality indicator as a certain target pollutant, the indicator should have the representability of an index for the management of Total Maximum Daily Loads (TMDLs). Scientific groundwork and treatment technologies also should be provided for the application of the indicator. This study analyzed the applicability of major water quality indicators for target pollutants. The results showed that four water quality indicators of TOC, T-N, SS & T-Coli can be considered as target pollutants besides existing BOD and T-P. These indicators can be applied with the preparations such as essential basic data, pollution load estimation framework as well as legal criteria setting when the need is raised. As the importance of TOC, which is considered as a replacement of BOD, is emphasized, technical and institutional terms are being prepared in order to determine TOC as another target pollutant in the near future. It could be considered to combine TOC with BOD for the time being during the $3^{rd}$ stage of TMDLs in view of the present conditions for the management of TOC. TOC can be the most effective index for the organic matter and help to be managed more systematically in the waterbodies where rivers and lakes are mutually connected.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.393-398
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• 2005

Suspended fine mineral particles are deposited at the areas with low flow velocity and low transportation capacity in rivers, reservoirs and lakes. It can be contaminated by heavy metals. Examples of problem fields art dredging of sediment, water pollutants, and maintenance of navigation channels and construction works. To deal with the settling problems it is necessary to understand tile physico-chemical characteristics of cohesive sediment under varying density of particle and ion addition(NaOH, HCl, NaCl), which is dissolved in river, because fine-grained cohesive sediment can lead to flocculation with the physico-chemical influences and takes different characteristics. Experiments with fresh and saline water are followed with fine-grained sediments(alumina and quartz) in settling columns. Settling velocity of suspended fine particles in still water was measured with a pressure sensor(maximum 10 mbar). Until the initial concentration of 20,000 mg/1 of alumina and quartz the settling velocity was on the increase. Above this initial concentration was it on the decrease. In an acid condition, which causes strong flocculation, average settling velocity of quartz powder was high. In an alkaline water low average settling velocity of it was observed. However, alumina behaved exactly contrarily.

• Journal of Korea Water Resources Association
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• v.40 no.9
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• pp.723-734
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• 2007

This study was to investigate the settling velocity which is an important factor for the prediction of cohesive deposition under the various densities of particle and dissolved ion addition$(Na^+,\;Cl^-,\;OH^-,\;H^+)$ in rivers, ports, reservoirs and lakes. Settling velocity of suspended fine particles in still water was measured with a pressure sensor (maximum 10 mbar). At the initial concentration of 20g/l of alumina and quartz the average settling velocities were high due to the aggregation behaviour of particles. At this point it was 0.185 mm/s (alumina) and 0.022 mm/s (quartz). Above this initial concentration it was on the decrease owing to the hindered settling. The higher the salinity is, the faster the settling velocity of alumina and quartz is. Furthermore, in an acid condition the average settling velocity of alumina was on the decrease. In an alkaline water, which causes strong flocculation, the average settling velocity of alumina it was observed on the increase. However, in an alkaline medium the low average settling velocity of quartz powder was measured.

• The Korean Journal of Ecology
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• v.16 no.3
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• pp.261-273
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• 1993

The nitrogen assimilation rate of nitrogenous nutrients by reservior phytoplankton was masured in the in situ condition in the euphotic layer of Lakes Soyang, Chuncheon and Uiam located on the upper reaches of the North Han River System in August, 1983, Korea. The assimilation rate of ammonia, nitrate and urea nitrogen in surface water was 13, 2 and $13{\mu}g$ at. $N{\cdot}m^{-3}{\cdot}(12:10~18:15)^{-1}$ in Lake Soyang, 325, 27 and $59{\mu}g$ at. $N{\cdot}m^{-3}{\cdot}(12:30~18:30)^{-1}$ in Lake Chuncheon, and 174, 12 and $45{\mu}g$ at. $N{\cdot}m^{-3}{\cdot}(12:30~19:30)^{-1}$ in Lake Uiam. Ammonia and urea were perferntially utilized by reservoir phytoplankton. The dark/light ratios of nitrate assimilation were much lower than those of ammonia and urea assimilation of nitrate showed little contribution. The primary productuin was estimated as 59mg $C{\cdot}m^{-2}{\cdot}day^{-1}$ and 6.9mg $N{\cdot}m^{-2}{\cdot}day^{-1}$ in Lake Spyang, 217mg C{\cdot}m^{-2}{\cdot}day^{-1}$ and 26mg N{\cdot}m^{-2}{\cdot}day^{-1}$ in Lake Chuncheon, and 110mg C{\cdot}m^{-2}{\cdot}day^{-1}$ and 13mg N{\cdot}m^{-2}{\cdot}day^{-1}$ in Lake Uiam, with production ratios of 8.6, 8.4 and 8,4, respectively. The turnover time o ammonia and urea in the upper euphotic layer was 2 to 47 days and 4 to 38 days, respectively. Nitrate required much longer periods. In the euphotic layer of reservoirs, ammonia and urea played signigicant roles in the biogeoKDICical nitrogen metabolism.

• Parasites, Hosts and Diseases
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• v.56 no.2
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• pp.205-210
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• 2018

Waterborne parasitic protozoa, particularly Giardia lamblia and Cryptosporidium spp., are common causes of diarrhea and gastroenteritis worldwide. The most frequently identified source of infestation is water, and exposure involves either drinking water or recreation in swimming pools or natural bodies of water. In practice, studies on Cryptosporidium oocysts and Giardia cysts in surface water are challenging owing to the low concentrations of these microorganisms because of dilution. In this study, a 3-year monitoring of Cryptosporidium parvum, Giardia lamblia, and Naegleria fowleri was conducted from August 2014 to June 2016 at 5 surface water sites including 2 lakes, 1 river, and 2 water intake plants. A total of 50 water samples of 40 L were examined. Cryptosporidium oocysts were detected in 22% of samples and Giardia cysts in 32%. Water at the 5 sampling sites was all contaminated with Cryptosporidium oocysts (0-36/L), Giardia cysts (0-39/L), or both. The geometric mean concentrations of Cryptosporidium and Giardia were 1.14 oocysts/L and 4.62 cysts/L, respectively. Thus, effective monitoring plans must take into account the spatial and temporal parameters of contamination because they affect the prevalence and distribution of these protozoan cysts in local water resources.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.2
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• pp.1-15
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• 2006

As the imports of foreign agricultural products are liberalized and the consumption of agricultural products declines, abandoned rice paddy fields continues to rise. However, such abandoned rice paddy fields has not been precisely surveyed yet. In this backdrop, a necessity to develop technology to utilize such abandoned rice paddy fields has emerged. Utilization of abandoned rice paddy fields as wetlands may be a good example. This study aimed to survey the current status and characteristics of wetlands created within abandoned rice paddy fields by selecting abandoned rice paddy fields throughout the nation and conducting field surveys on the sites that had transformed into wetlands. The abandoned rice paddy fields almost transformed into wetland and the types of wetlands transformed from abandoned rice paddy fields were mainly Inland/Moutain/Depression/Abandoned rice paddy fields/Marsh/Phragmites communis community and Inland/Moutain/Depression/Abandoned rice paddy fields/Swamp/Salix koreensis community. Abandoned rice paddy fields that had transformed into wetlands was depending heavily on waterways for water supply than other reservoirs and lakes do. Abandoned rice paddy fields transformed into wetlands was most observed in mountainous area. Abandoned rice paddy fields are because agricultural land is no longer profitable due to international and social changes and is not cultivated as government policy. Wetland period and dimension originated from abandoned rice paddy fields are very various and its surrounding land its mostly forest and the next largest follow roads and rural community. The abandoned rice paddy fields transformed into wetlands is mostly deserted currently. Despite their value as wetlands, no restoration and utilization efforts are made in Korea today. Therefore, it is imperative to conduct a precise current status survey on these areas and introduce management and restoration plans at the government level in the case of important habitats.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.8
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• pp.441-448
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• 2017

A method for measuring the concentration of surfactant in water was developed. In this technique, microbubbles were used as light scatterers. The polarization change of light scattered by microbubbles was analyzed by Mueller matrix analysis. $M_{11}$, one of the Mueller matrix elements, was found to be a key parameter inferring the surfactant concentration within the concentration range of 0 ppm to 60 ppm. The best results for this measurement were obtained when the scattering angle was $150^{\circ}$ and the extinction ratio was 56.2. This experimental result shows that the EPLS can be effectively used as a real time inspection method for water quality monitoring in lakes or rivers.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.4
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• pp.111-122
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• 1989

A multiple box model which is suitable for the prediction of water quality in shallow lakes with active mixing is a water quality model expected to be used widely in estuary reservoir. In this study, a multiple box water quality model for estuary reservoirs (MBQER) was developed arid the applicability of the MBQER was tested by applying data obtained from Asan-estuary reservoir. The results of this study can be summarized as follows. 1. The MBQER, dynamic water quality model, was developed to estimate 10-day water qualities of estuary reservoirs. For the proper analysis and the application of hydraulics needed to build a model, lake hydraulics was simplified by condisering only hydrological inflow and lake mixing currents. The box division in the MBQER is longitudinal one dimension for upper and middle part, and two layers for lower part of the reservoir. 2. The methods of box division for the multiple box model were ekamined and applied to Asan-estuary reservoir. For determining the number of boxes, Pe number and Pk number were used. In case of three boxes, the error by the model simplification would be estimated about 5 % Therefore, in Asan reservoir, the proper number of boxes was three. 3. The MBQER was calibrated and verified using measured data in Asan-estuary reservoir from 1986 to 1988. The Root Mean Squares(RMS) for the differences between measured data and simulated results by the MBQER were 1.10$^{\circ}$C C for water temperature, 75.8mg/1 for salinity, 0.082mg/1 for total-phosphorus showing good estimations. 4. Through the simulation of water temperature and salinity by the MBQER, the exchange flow and the mixing coefficients for the estuary lake were determined. As a result of simulation, the horizontal mixing coefficients in Asan-estuary reservoir were in the range of 1.07X 105 to 1.12X 105 cm$^2$/sec and vertical mixing coefficient was 2.90X 10-1 cm$^2$/sec.