• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.415-415
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• 2021

농업시설의 확장과 함께 수자원으로서 지하수의 중요성이 점차 커지면서 지하수 수질 특성을 설명하기 위하여 강수량과 지하수 그리고 전기전도도의 상관관계를 정확하게 이해하는 것이 매우 중요하다. 많은 연구에서 선행 강수를 고려한 누적이동강수량을 사용하여 지하수위와 강수량의 상관관계를 분석하였다. 최근 기후변화로 인해 줄어든 강수일수와 강수량으로 인하여 지하수 수질 변동의 장기간 분석이 어려워짐에 따라 지하수 수질변동에 대한 강수량의 단기간 영향을 규명하기 위하여 지하수위 변동량과 강수량의 상관관계를 이해할 필요가 있다. 지하수위 변동량은 지하수 함양률 산정 및 함양 특성 분석 등 지하수 변동 특성을 분석하는 데 있어서 매우 중요한 자료이다. 본 연구에서는 충남 예산 효교리에서 2019년 7월 1일부터 2020년 6월 30일까지 지하수위와 전기전도도를 관측하였고 지하수위와 전기전도도 변동량을 강수량과 비교 분석함으로써 단기적인 변동 특성을 해석하고 상관관계를 도출하였다. 먼저, 강수량과 지하수위, 전기전도도의 시계열 분석을 통한 교차상관분석(cross-correlation)을 수행하여 자료 간에 지연 시간(lag time)을 산정하였다. 다음, 지연 시간을 고려하여 강수량과 지하수위 변동량의 상관성 분석과 강수량과 전기전도도 변동량의 상관성 분석을 수행하였다.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.337-348
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• 2011

We examined temporal variations in and relationships among groundwater level, groundwater temperature, and electric conductivity, and estimated groundwater recharge at Jeju Island. The time lag and regulation time of groundwater level data revealed that monitoring well in Ansung (JM-AS) has the highest auto-correlation. The cross-correlations for electric conductivity-water level, precipitation-water level, and air temperature-water temperature revealed that monitoring well in Seogwi-2 (JR-SG2) (electric conductivity-water level), monitoring well in Hamo (JD-HM) (precipitation-water level), and monitoring well in Wonjongjang-2 (JT-WJJ2) (air temperature-water temperature) had the highest cross-correlations. The average groundwater recharge ratio was 39.61%, and the average groundwater recharge amount was 1,153,490,407 $m^3/yr$, which is consistent with the results of previous studies.

• Journal of Environmental Science International
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• v.30 no.7
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• pp.519-527
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• 2021

Moving average precipitation provides periodic precipitation patterns by solving precipitation irregularities. However, due to uncertain moving average periods, excessive data smoothing occurs, which limit the possibility to analyze groundwater levels in the short term. Nonetheless, groundwater level fluctuation can compensate these limitations as it can calculate appropriately for unit time and verify the effect of precipitation penetrated into groundwater in a short time period. In this study, the characteristics of groundwater level were evaluated using groundwater level fluctuation to compensate for limitations of groundwater level analysis using moving average precipitation. In addition, the groundwater quality was investigated using the electrical conductivity fluctuation. The study site was Hyogyo-ri, Yesan-si, Chungcheongnam-do. Four observation wells and an automated weather system were used. The correlation between groundwater level fluctuation and precipitation (Case 1) and the correlation between groundwater level and moving average precipitation (Case 3) were compared. In the analysis for 1 hour data, the correlation coefficient of Case 1 was higher than that of Case 3, and in the analysis for 1 day data, the correlation coefficient of Case 3 was higher than that of Case 1.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.13 no.3
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• pp.103-108
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• 1980

The contents of inorganic conservative constituents in Nagdong River water were determined at Mulgeum where the intake station for Busan city water is located. Samples were taken at intervals of one hour from 7 a.m. to 7 p.m. at spring and neap tides of every month from January 1979 to April 1980. Annual ranges and means of the chemical constituents were as follows: electrical conductivity $99-912\mu\mho/cm,\;200\mu\mho/cm;$ chlorides 6.0-256 ppm, 17.2 ppm; sulfates 4.1-37.9 ppm, 23.5 ppm; calcium 4.2-28 ppm, 13 ppm; magnesium 2.2-23 ppm, 5.6 ppm; sodium 5,0-126 ppm, 14 ppm; and potassium 1.2-10.8 ppm, 2.6 ppm respectively. At several times in this period, the concentrations of chloride ion exceeded 150 ppm that is the criteria for drinking water. The chloride ion concentration was higher at spring tides than that at neap tides and the contents of inorganic conservative constituents were higher in winter than those in summer. The chloride ion concentration showed the highest value at Mulgeum about 4 hors after the high water in Busan harbour.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.73-84
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• 2006

The objective of this study was to analyze long-term temporal trends of water chemistry and spatial heterogeneity for 10 sampling sites of the Yeongsan River watershed using water quality dataset during 1995 to 2004 (obtained from the Ministry of Environment, Korea). The water quality, based on multi-parameters of biological oxygen demand (BOD), chemical oxygen demand (COD), conductivity, dissolved oxygen (Do), total phosphorus (TP), total nitrogen (TN) and total suspended solids (TSS), largely varied depending on the sampling sites, seasons and years. Largest seasonal variabilities in most parameters occurred during the two months of July to August and these were closely associated with large spate of summmer monsoon rain. Conductivity, used as a key indicator for a ionic dilution during rainy season, and nutrients of TN and TP had an inverse function of precipitation (absolute r values> 0.32, P< 0.01, n= 119), whereas BOD and COD had no significant relations(P> 0.05, n= 119) with rainfall. Minimum values in conductivity, TN, and TP were observed during the summer monsoon, indicating an ionic and nutrient dilution of river water by the rainwater. In contrast, major inputs of total suspended solids (TSS) occurred during the period of summer monsoon. BOD values varied with seasons and the values was closely associated (r=0.592: P< 0.01) with COD, while variations of TN were had high correlations (r=0.529 : P< 0.01) with TP. Seasonal fluctuations of DO showed that maximum values were in the cold winter season and minimum values were in the summer seasons, indicating an inverse relation with water temperature. The spatial trend analyses of TP, TN, BOD, COD and TSS, except for conductivity, showed that the values were greater in the mid-river reach than in the headwater and down-river reaches. Conductivity was greater in the down-river sites than any other sites. Overall data of BOD, COD, and nutrients (TN, TP) showed that water quality was worst in the Site 4, compared to those of others sites. This was due to continuous effluents from the wastewater treatment plants within the urban area of Gwangju city. Based on the overall dataset, efficient water quality management is required in the urban area for better water quality.

• Korean Journal of Ecology and Environment
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• v.35 no.1 s.97
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• pp.36-44
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• 2002

The spatial and temporal trends of water qualities in Lake Soyang was statistically analyzed in this study. The water qualities include nutrients, ionic contents and chlorophyll-a (Chl-a) measured during 1993${\sim}$2000. The rainfall intensity and runoff from the catchment appeared to play an important role in water quality trends in the lake. According to seasonal Mann-Kendall test, conductivity, TP, and Ctl-a did not show any trends of increase or decrease over the 8 year period, while TN declined slightly. It was found that the variation of TP was a function of interannual inflow and rainfall. In the analyses of spatial trend, conductivity, based on the mean by site, showed a downlake decline over the eight year period. Minimum conductivity was found in the headwaters during summer monsoon of July to August and near the dam during October. This result indicates a time-lag phenomenon that the headwater is diluted by rainwater immediately after summer monsoon rain and then the lake water near the dam is completely diluted in October. During summer period, TP and TN had an inverse relation with conductivity values. Concentrations of TP peaked during July to September in the headwaters and during September in the downlake. Also, TN increase during the summer and was more than 1.5 mg/L regardless of season and location, indicating a consistent eutrophic state. Values of Chl-a varied depending on location and season, but peaked in the midlake rather than in the headwaters during the monsoon. Regression analyses of log-transformed seasonal Chl-a against TP showed that value of $R^2$ was below 0.003 in the premonsoon and monsoon seasons but was 0.82 during the postmonsoon, indicating a greater algal response to the phosphorus during the postmonsoon. In contrast, TN had no any relations with Chl-a during all seasons.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.614-623
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• 1993

Electrical characteristics of LiF-$Li_{2}O-B_{2}O_{3}-P_{2}O_5$ glasses with fixed $Li_2O$ content have been investigated by using AC impedance spectroscopy. Part of the total lithium ions present in these glasses contributes to conduction, and the changes in electrical conductivity with composition was inconsistent with the weak electrolyte model. The power law could not be used to determine the hopping ion concentration in these glasses. Both mobile carrier density and mobility have been modified as Li were added in the form of LiF. The formation of $(B-O-P)^-,di^-$, and metaborate group gave additional available sites for Li+ diffusion causing the enhancement of conductivity. The observed maximum conductivity was $2.43 \times 10^{-4}$S/cm at $150^{\circ}C$ at the composition containing 8mol% LiF. The decomposion potential amounted to 5.94V. The Li/glass electrolyte/$TiS_2$ solid-state cell showed open circuit voltage of 3.14V and energy density of 22 Wh/Kg at $150^{\circ}C$.

• Korean Journal of Ecology and Environment
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• v.46 no.4
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• pp.488-498
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• 2013

A three-dimensional hydrodynamic model was applied to the Lake Euiam. The lake has three inflows, of which Gongji Stream has the smallest flow rate and poorest water. The dam-storage volume, watershed area, lake shape and discharge type of the Chuncheon Dam and the Soyang Dam are different. Therefore, it is difficult to analyze the water plume and mixing pattern due to the difference of the two dams regarding the amount of outflow and water temperature. In this study, we analyzed the effects of different characteristics on temperature and conductivity using the model appropriate for the Lake Euiam. We selected an integrated system supporting 3-D time varying modeling (GEMSS) to represent large temporal and spatial variations in hydrodynamics and transport of the Lake Euiam. The model represents the water temperature and hydrodynamics in the lake reasonably well. We examined residence time and spreading patterns of the incoming flows in the lake based on the results of the validated model. The results of the water temperature and conductivity distribution indicated that characteristics of upstream dams greatly influence Lake Euiam. In this study, the three-dimensional time variable water quality model successfully simulated the temporal and spatial variations of the hydrodynamics in the Lake Euiam. The model may be used for efficient water quality management.

• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.14-24
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• 2001

In order to study the long-term change of water quality, water analysis for 9 items was conducted at 13 sites surrounding the Kumho river system for 18 times from September 1993 to August 1999. Analytical items for the study of water quality are as follows; water temperature, pH, BOD, COD, DO, SS, electrical conductivity, oil and grease, ABS and phenol. The six year term was divided into Part I(second study) and Part Ⅱ(third study), which covers the term from September 1993 to August 1996 and the term from September 1996 to August 1999, respectively. The mean values obtained for three years for water temperature, pH, BOD, COD, DO, SS, electrical conductivity, oil and grease, ABS and phenol for the Part I period showed 18.4$^{\circ}C$, 7.9, 4.88 ppm, 9.66 ppm, 9.0 ppm, 618.0 umho/cm, 6.9 ppm, 2.63 ppm, 3.57 ppm and 0.98 ppm, respectively. The mean values obtained for water temperature, pH, BOD, COD, DO, SS, electrical conductivity, oil and grease, ABS and phenol for the Part Ⅱ period showed 18.0$^{\circ}C$, 8.0, 2.86 ppm, 7.40 ppm, 8.94 ppm, 541.0 umho/cm, 6.0 ppm, 5.43 ppm, 0.94 ppm and 0.01 ppm respectively. The values of BOD, COD, SS, electrical conductivity, ABS and phenol in the second period were found to be decreased by 1/1.71, 1/1.31, 1/4.15, 1/3.80 and 1/98, respectively. The values of water temperature, pH and DO were nearly constant. However, the concentrations of oil and grease were found to be increased about 2.06 times in the second period.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.640-651
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• 2019

The study analyzed the relationship between harmful cyanobacteria and physicochemical factors in Lake Juam from 2005 to 2018. The research locations were designated St. 1 (Juam-Dam) and St. 2 (Sinpyong). Harmful cyanobacteria was found in four genera (Microcystis sp., Anabaena sp., Aphanizomenon sp., Oscillatoria sp.). The average standing crops of harmful cyanobacteria in both locations were 2,575 cells mL^-1 and 2,557 cells mL^-1 from 2005 to 2011. Since 2012, there has been a significant decrease that the measurements were 42 cells mL^-1 and 82 cells mL^-1 from 2012 to 2018. To analyze the reason for the decrease in harmful cyanobacteria, Pearson's correlation and t-tests were performed on data collected during the summer period (June-September). Pearson's correlation showed a significantly positive correlation with total nitrogen(TN), outflow, and storage and a negative correlation with electrical conductivity. T-tests were conducted in two different periods and showed decreases in total nitrogen, electrical conductivity, and residence time. The average rainfall was decreased from 263.3 mm (2005-2011) to 219.9 mm (2012-2018) and total nitrogen was decreased from 0.912 mg L^-1 (2005-2011) to 0.811 mg L^-1 (2012-2018) and the same variability was seen in TP (total phosphorus). Therefore, it seems that the low-rainfall decreased the nutrients (TN) and variability in the TP, resulting in a decrease in harmful cyanobacteria in Lake Juam.