• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1225-1230
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• 2008

A new approach based on the Seasonal Mann-Kendall Trend Analysis, was presented in this paper, in order to estimate effect of water quality management policy in Kyoungan Stream which is one of major tributaries into the Lake Paldang. The estimation was undertaken by comparing water quality trend slopes before and after implementation of the policy. The monthly water quality data of Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Nitrogen (TN) and Total Phosphorus (TP) measured from 1992 to 2005, were analyzed to determine the Kendall slopes before and after the Han River special policy implemented at 1998. The results indicated that the 1998 special policy would be effective in water quality improvement not at upstream but at downstream. This result agrees well with the previous water quality studies at Kyoungan stream. It was suggested that the presented approach could be an useful tool to estimate effect of a water quality management policy.

• Journal of Environmental Impact Assessment
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• v.10 no.3
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• pp.235-243
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• 2001

Since the middle of 1990s, in Korea a few researches on the optimal management technologies combining numerical model and GIS for the management of water environment in drinking watershed area and reservoir such as Paldang Lake have been carried out. In this study, the integrated water environment management system was been suggested to efficiently reflect the public awareness of the environment by integrating the web based distributed data collection system, GIS, public hearing system and water quality model. As all the components of the system have been developed using the World Wide Web and all data have been collected from the relevant agencies through the Internet, the water quality model could be implemented on the web directly. In consequence, the environmental geographic information in Paldang Lake could be acquired and analyzed through the Internet. The system can rapidly respond to the public right to know on environment, so the public will willingly participate in the governmental projects on environment. To verify the usability of the developed system, it has been applied to Paldang Lake. Especially when the web based model has been used, users can easily and confidentially get the prediction results by applying the minimum number of parameters for the water quality model. This model will provide clearness and scientific bases in the process of water quality prediction for the sensitive sites where there are critical conflicts between the residents and the developers. In this study, rapid water environment management technique without spatial and time limit has been suggested, which can contribute to the efforts on the government and the public participation.

• Korean Journal of Microbiology
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• v.31 no.1
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• pp.93-98
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• 1993

To investigate the organic matter transformation in aquatic environment, seasonal fluctuations of heterotrophic activity and microbia] extracellular enzyme activity were studied in Paldang Lake, Korea. The turnover time in the water column and the sediment at the station I fluctuated between 3 -I ,300 hrs and 17-170 hrs for glucose, 5 -1.900 hrs and 15-240 hrs for protein hydrolysate and 4-350 hrs and 15-230 hrs for acetic acid, respectively, indicating that the seasonal turnover time of organic substrates fluctuated drastically. The respiration ratios of glucose. protein hydrolysate and acetate were 23-32%, 38-41% and 22-28% in the water column and 34%, 61% and 41% in the sediment. respectively. These results showed that the respiration ratios in the sediment were higher than those in the water column regardless of kinds of organic substrates. The bacterial extracellular enzyme activities of $\alpha$-glucosidase. $\beta$-glucosidase, N-acetyl-$\beta$-D-glucosaminidase and aminopeptidase were 32-44%. 31-32%, 18-34% and 61-67% in the water column, and 34%. 40%, 23% and 65% in the sediment. respectively.

• Journal of Ecology and Environment
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• v.30 no.3
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• pp.231-236
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• 2007

This study examined the decomposition of blades and culms of aquatic emergent plant species, Zizania latifolia, Phragmites communis and Typha angustata, and changes in nutrient contents during decomposition. Z. latifolia, P. communis and T. angustata were the most frequently occurring species in Lake Paldang of Han River, Korea. Experiments were carried out from July 27 to December 14, 2005 in Lake Paldang using the litter bag method. The remaining masses of blade litter of each species at the end of experimental period were 21.2% of initial dry weight in Z. latifolia, 32.5% in P. communis, and 44.7% in T. angustata. In addition, the remaining mass of culm was 22.6% of initial dry mass in Z. latifolia, 56.4% in P. communis, and 38.1% in T. angustata. During the litter decomposition period, P, K, Na, and Mg concentration decreased rapidly within 10 days, but Ca and Mg concentration declined slowly. K contents remained below 10% of initial values in all litter samples retrieved during decomposition, whereas Ca and Mg concentration remained above 40% and 50% during decomposition in all three species. Na, P and Mn contents in litter varied among species and plant parts. P concentration in culms of P. communis remained at about 60% of initial concentration throughout the study, but the remaining P content in culms of Z. latifolia was only 10% of the original value at the end of the study period. The Mn concentration in blades of P. communis increased about 15-fold relative to the initial content by the end of experiment.

• Korean Journal of Ecology and Environment
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• v.35 no.4 s.100
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• pp.266-272
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• 2002

For analyzing function of a microbial ecosystem which was created under the artificial vegetation island (AVI) installed at Lake Paldang, zooplankton and bacterial numbers and exoenzyme activities (${\beta}$-glucosidase and phosphatase) were measured biweekly from 3 November 2()()1 to 20 April 2002 at AVI site and control site. Under the AVI, the water quality was worse than control site in term of comparing the environmental parameters. But, zooplankton number of AVI site was 25 times higher than that of control site. Respiratory active bacterial numbers were 3-8 times higher at AVI site. In addition, enzymatic activities were higher at AVI site than those of control site. These results suggest that the zooplankton-phytoplankton-bacteria relationships are closely coupled with each other and organic materials are eliminated by respiration of zooplankton and bacterial activities.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.1-13
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• 2020

The purpose of this study was to investigate the thermal and chemical stratification in Lake Paldang 2013-2018 weekly using Schmidt's stability index (SSI) and the index of chemical stratification (IC-i). The annual average for SSI was 19.1 g cm/㎠ with the maximum value of 45.3 g cm/㎠ in the summer and the minimum value of 4.8 g cm/㎠ in fall-winter showing seasonal differences as well as increased vertical mixing in the summer. The lake stability increased higher in 2016 as compared with the other period. The most influential factors of thermal stratification were temperature and heavy rainfall. Especially, high water temperature and a prolonged residence duration caused by reduced rainfall and inflows could result in an increase of the stratification period. While decreasing inflow and outflow at the end of the rainfall, the thermal stratification was restrengthened within 7-14 days, and then stabilized rapidly before the rainfall. IC-DO increased with high air temperature in the spring and fall-winter. However increasing sunshine duration and residence time and decreasing rate of outflow caused an increase of IC-DO in the summer. Rainfall (less than 800 mm/year) and discharge (less than 200 CMS) significantly declined in 2015 resulting in IC-DO (0.77) increased more than three times over the other years and bottom water hypoxia occurred. The SSI and IC-i used in this study could be applied to other lakes to understand changes in stratification and mixing dynamics.

• Journal of Korean Society on Water Environment
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• v.35 no.1
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• pp.28-34
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• 2019

This study analyzed the occurrence pattern of Dolichospermum (= Anabaena) in the Bukhan river from March 2012 to December 2014 in order to identify the genotypes of Dolichospermum. Furthermore, 16S rRNA were analyzed to identify the genotypes of Dolichospermum that occurred in 2015 which were then compared to the reference sequence deposited at NCBI. During this period, the occurrence of Dolichospermum was highly correlated to water temperature. In the year 2012 and 2013, Dolichospermum appeared in Lake Cheongpyeong (CP), Sambong (SB), and Lake Paldang (P2) between July and August. However, in 2014, it appeared in SB and P2, but not in CP. This reduction in appearance was attributed to the decreased inflow to Lake Uiam as a result of low rainfall in 2014 as compared to 2012. In July 2015, the Dolichospermum 16S rRNA genotype was confirmed in five locations; Lake Cheongpyeong (CP), Seojong (SJ), Songchon Sewage Treatment Plant (SC), Joan (P4), and Lake Paldang (PD). Anabaena crassa of spiral clone, A. planctonica of linear clone, and A. circinalis of spiral clone exhibited high genetic similarity with the reference sequence. The 16r RNA genotype showed approximately 3 % sequence variation between the locations and were more similar to each other in locations that were closer.

• Korean Journal of Ecology and Environment
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• v.46 no.1
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• pp.135-144
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• 2013

Blue-green algae blooms occurred during early winter in the North-Han River, Korea. Among blue-green algae, Anabaena spiroides were observed for approximately 33 consecutive days, between 28 November and 30 December, 2011. A. spiroides emerged from Lake Uiam to Lake Paldang, depending on the flow of the river has spread downstream. Changes of physical water environment like rising water temperature and increasing hydraulic retention time influenced the A. spiroides bloom. The A. spiroides bloom showed a very rapid increase in cell density, and a slow decrease: the cell density increased to a maximum of $11,325cells\;mL^{-1}$ in Lake Paldang (st. 5), and was completely disappeared after the water temperature dropped below $4^{\circ}C$. A decrease in water temperature was the most influential factor among all environmental parameters, for the reduction of A. spiroides cell density. The A. spiroides bloom was accompanied with the occurrence of very high concentrations of the odor metabolite geosmin. Geosmin reached the peak value of $1,640ng\;L^{-1}$ in Lake Paldang (st. 4). The geosmin concentration was very strongly correlated with cell numbers of A. spiroides.

• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.129-135
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• 2011

The possibility of nutrient removal during Scenedesmus sp. growth in Lake Paldang, Geongan cheon stream, and the outflow from a wastewater treatment system was examined. Scenedesmus sp. grew well in Lake Paldang water when total nitrogen (TN) and total phosphorus (TP) values were 1.9 and 0.02 mg $L^{-1}$, respectively, and 50% of the nutrients were removed. In Geongan cheon stream, the TN and TP was 3.0 mg $L^{-1}$ and 0.09 mg $L^{-1}$, respectively, chlorophyll-${\alpha}$ reached a maximum of 239~259 $m^{-3}$, and 50% of the nutrients were removed. In the wastewater treatment outflow, where Scenedesmus sp. already existed, the organism grew well without inoculation. Scenedesmus sp. can grow with proper inoculation and physical turbulence in natural waters, such as lake and stream water, and nutrients can be eliminated as phytoplankton growth occurs.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.866-881
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• 2012

Han River is a complex water system consisting of many lakes. The water quality of Lake Paldang is significantly affected by incoming flows, which are the South and North branches of the Han River, and the Kyungan Stream. In order to manage the water quality of the Lake Paldang, we should consider the entire water body where the incoming flows are included. The objectives of this study are to develop an integrated river and lake modeling system for Han River system using a multidimensional dynamic model and evaluate the model's performance against field measurement data. The integrated model was calibrated and verified using field measurement data obtained in 2007 and 2008. The model showed satisfactory performance in predicting temporal variations of water level, flow rate and temperature. The Root Mean Square Error (RMSE) for water temperature simulation were $0.88{\sim}2.13^{\circ}C$ (calibration period) and $1.05{\sim}2.00^{\circ}C$ (verification period) respectively. And Nash-Sutcliffe Efficiency (NSE) for water temperature simulation were 1089~0.98 (calibration period) and 0.90~0.98 (verification period). Utilizing the validated model, we analyzed the spatial and temporal distributions of temperature within Han River system. The variations of temperature along the river reaches and vertical thermal profiles for each lakes were effectively simulated with developed model. The suggested modeling system can be effectively used for integrated water quality management of water system consisting of many rivers and lakes.