• The Journal of Fisheries Business Administration
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• v.52 no.2
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• pp.55-67
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• 2021

Global warming affects critical natural resources, one of which is the oceans that occupy 70% of the total cover of the earth. In other words, ocean warming is a subset of global warming which needs to be addressed urgently. Purple laver (pyropia spp.) is one of the most vulnerable items to climate change although it is a major export product of Korean fisheries. The purpose of this study is to analyze the causality of how climate change caused by global warming affects the increase or decrease of PLP (purple laver production). The target area for analysis was set to Maro-hae between Jindo-gun and Haenam-gun. We selected marine environmental factors and meteorologic factors that could affect PLP as variables, as well as co-integration tests to determine long-term balance, and the Granger causticity tests. As a result, PLP and marine environmental factors WT (water temperature), pH, and DO confirmed that long-term equilibrium relationships were established, respectively. However, there is only causality with WT and it is confirmed that there is only a correlation between pH and DO (dissolved oxygen). There was no long-term equilibrium relationship between PLP and HDD (heating degree days) and there is a causal effect that HDD affects PLP; however, it was less clear than that of WT. The relationship between PLP and RF (rainfall), WS (wind speed), SS (percentage of sunshine), and FF (farm facilities) was all balanced in the long term, and causality exists. Based on the results of the analysis, policy proposals were made.

• Journal of Korean Society on Water Environment
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• v.39 no.1
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• pp.46-60
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• 2023

Climate change causes fluctuations in water quality in the aquatic environment, which can cause changes in water circulation patterns and severe adverse effects on aquatic ecosystems in the future. Therefore, research is needed to predict and respond to water quality changes caused by climate change in advance. In this study, we tried to predict the dissolved oxygen (DO), chlorophyll-a, and turbidity of the Paldang reservoir for about two weeks using long short-term memory (LSTM) and gated recurrent units (GRU), which are deep learning algorithms based on recurrent neural networks. The model was built based on real-time water quality data and meteorological data. The observation period was set from July to September in the summer of 2021 (Period 1) and from March to May in the spring of 2022 (Period 2). We tried to select an algorithm with optimal predictive power for each water quality parameter. In addition, to improve the predictive power of the model, an important variable extraction technique using random forest was used to select only the important variables as input variables. In both Periods 1 and 2, the predictive power after extracting important variables was further improved. Except for DO in Period 2, GRU was selected as the best model in all water quality parameters. This methodology can be useful for preventive water quality management by identifying the variability of water quality in advance and predicting water quality in a short period.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.159-159
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• 2021

한국은 수자원 이용현황 중 농업용수가 차지하는 비중이 가장 크다. 농업용수의 60% 이상이 저수지에서 공급된다. 현재 한국의 약 18,797개의 저수지 중 대부분이 농업용 저수지로 사용될 만큼 많은 농업용 저수지를 보유하고 있다. 연간 강우량이 7월과 8월에 집중되고 강우의 유출이 빨라 하천의 이용 가능 수량이 한정되어있는 우리나라에서 관개용수 공급 및 하천유지 용수 공급의 기능을 하는 농업용 저수지는 용수원으로써 중요성을 가진다. 농업용 저수지의 수질은 수량과 더불어 작물생산량에 직접적인 영향을 미치며 저수지의 부영양화는 저수지 기능과 유지관리상의 문제점을 야기한다. 하지만 농업용 저수지의 수량 관리에 비해 수질관리 및 분석에 관한 연구는 비교적 부족한 실정이다. 본 연구에서는 우리나라 농업용 저수지의 수질 특성 파악과 건기, 우기와 여름, 겨울철에 따른 부영양화 정도의 차이에 대한 분석을 진행하고자 한다. 한국 농업용 저수지의 장기적인 영양상태 파악을 위해 과거 30년 (1991-2020) 연별, 월별 저수지 수질 모니터링 데이터를 활용하였다. 분석항목으로는 DO (Dissolved Oxygen), TN (Total Nitrogen), TP (Total Phosphorus), SS (suspended solid), SD (Secchi disk), TN/TP, pH를 지정하였다. 자연호가 많은 외국에 비해 대부분이 인공호인 우리나라 저수지는 자연호에 비해 낮은 수심과 작은 저수용량을 가지며 자연호보다 부영양화가 더 빠르게 진행된다. 때문에 부영양화 정도 평가를 위해 TSI와 더불어 한국형 부영양화지수(TSIKo)를 사용하였다. 또한 강우와 각 수질 측정항목 그리고 수온과 DO 간의 상관분석을 진행하였으며, 각 수질 측정항목에 대한 값을 한국 호수 수질 기준과 비교하였다. 이러한 한국 저수지의 부영양화 정도 평가와 화학적 특성에 대한 파악을 기반으로 한국의 농업용 저수지 특성에 따른 적합한 수질관리 방안을 결정할 수 있을 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.125-130
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• 2006

In this research, possibility of sand capping was experimentally evaluated to control phosphorus release from lake sediment into water body. Three acrylic columns without and with 40 and 80 mm of sand capping were prepared. Phosphorus concentrations of overlying water in these columns were measured. Performances of sand capping were evaluated for 0, 40, and 80 mm of capping thickness by measuring DO, ORP, TP, and $PO_4$-P. For the case without capping, the releasing rate of total phosphorus was higher and dissolved oxygen decreased faster, comparing with those of columns with capping. Total phosphorus concentrations in overlying water were inversely proportional to capping thickness, while phosphate concentration showed no significant differences between both cases. The experiment results suggested that sand capping is effective to retard total phosphorus release from sediment.

• Journal of Wetlands Research
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• v.26 no.2
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• pp.127-138
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• 2024

The river ecosystems are influenced by numerous human activities such as agriculture and industrial operations, and benthic macroinvertebrates are utilized as important biological indicators. In this study, we aimed to assess the impact of land use surrounding rivers on river ecosystems in two industrial areas and two agricultural areas in Pyeongtaek city. We measured water temperature, dissolved oxygen (DO), and pH for physicochemical water quality assessment, and conducted water environment evaluation using benthic macroinvertebrates, cluster analysis, BMI, and ESB. Through water environment assessment, the environmental condition of rivers in agricultural areas was found to be more favorable compared to those in industrial areas. Consequently, it was observed that the impact on river ecosystems varied depending on the differences in anthropogenic activities.

• Journal of Environmental Impact Assessment
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• v.27 no.6
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• pp.582-594
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• 2018

In this study, the vertical and horizontal flow wetlands were combined in series to create conditions for flow in the exhalation and anaerobic state with the aim of monitoring the variability and reduction of dissolved organic matterin the bio-reactive artificial wetlands, and the performance assessment was conducted as acrylic reaction groups by designing artificial wetlands that filled the functionalresiduals. In case of artificial wetlands in vertical and horizontal planes, the concentration of dissolved oxygen (DO) in the reaction tank was measured as 2.7 mg/L in the vertical flow wetlands under exhalation, and N.D. in the horizontal flow artificial wetlands under anaerobic conditions. The test was carried out by changing the operation time to 140 min, 80 min, and 60 min. The test was conducted with the same natural operation time of 20 min depending on the operation time. All hours of operation were shown to be due to microbial activity. In 3D-EEM, it was found that the longer the driving time was taken, the more reduction the organic compounds in the areas of insoluble human resources, III and V. Further research on the mechanism analysis of future reduction effects is expected to be carried out, but the findings are expected to contribute to the development of technologies for reducing obfuscated substances using artificial wetlands in the future.

• Ocean and Polar Research
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• v.42 no.3
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• pp.233-247
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• 2020

This study was carried out at 5 sites 11 times over two years to identify the variation of benthic environments and benthic polychaetous community and analyze the benthic healthiness in Dangdong Bay, a small semi-enclosed inner bay of Jinhae Bay. The temperature of bottom water showed the typical temporal fluctuation of a temperate zone and was in the range of 5.94 ~ 23.94℃. The salinity did not change significantly during the study period and was in the range of 32.93 ~ 35.72 psu. The concentration of dissolved oxygen of bottom water fluctuated a great deal and was in the range of 0.31 ~ 10.20 mg/L. The lowest DO value was recorded in July 2015, as 0.31±0.04 mg/L corresponding to the hypoxic water mass. The hypoxic water mass was formed continuously at some sites also in July and August 2016. The mean grain size was in the range of 7.57 ~ 9.81Ø and the average was 8.89±0.20Ø. The surface sediments were mainly composed of fine sediment (mud) above 85%. The mean of TOC was 3.09±0.22% and LOI was 13.30±0.47%, showing very high levels in Korean coastal waters. The concentration of AVS was in the range of 0.33 ~ 1.28 mgS/g-dry. The high values of organic contents and AVS indicated that there had been the serious organic enrichment in Dangdong Bay. The number of species and the density of the benthic polychaetous community in Dangdong Bay were in the range of 2 ~ 38 species and 2 ~ 2,185 ind./㎡ during the study period. The number of species and density were highly sustained in winter and spring, and then decreased gradually with the formation of a hypoxic water mass in summer, and the lowest number of species and density were recorded in autumn. In September and November 2015, the dead zone expanded to almost the whole study area. Dominant polychaetous species were Capitella capitata, Lumbrineris longifolia, Paraprionospio patiens and Sigambra tentaculata, each known as opportunistic species and potential organic pollutant indicator species. In particular, Paraprionospio patiens showed a very high population density of 2,019 ind./㎡ in December 2016. Polychaetous communities at each sampling time were classified into 4 temporal groups according to dominant species in each period by cluster analysis and nMDS. 'Period Group AI' was formed in winter and spring of 2015, dominated by Capitella capitata, 'Period AII' in summer dominated by Lumbrineris longifolia, 'Period B' in autumn with no fauna in the dead zone, and particularly 'Period C' in winter of 2016 dominated by Paraprionospio patiens. As a result of analysis of benthic healthiness, the study area was estimated to be in a Fair~Very Poor condition by AMBI and in a Poor~Very Poor condition by BPI during the study period. Both AMBI and BPI showed that the study area was in a Very Poor condition in September and November 2015, and when the dead zone occurred. In Dongdong Bay, the fact that the formation of a hypoxic water mass occurred in summer and a dead zone in autumn were confirmed. In addition, the dominance of opportunistic and organic pollutant indicator species was also observed clearly. The benthic healthiness indexes such as AMBI and BPI showed that organic enrichment was serious in Dangdong Bay.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.334-344
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• 2013

In order to understand the characteristics of oceanic environment in the coastal aquaculture waters of the East Sea, the observation of the CTD (temperature and salinity), dissolved oxygen, chlorophyll a and N/P (DIN ($NO_2$-N, $NO_3$-N, $NH_4$-N) : DIP($PO_4$-P)) ratio was carried out at Sokcho, Jukbyon and Gampo in February, April, June, August, October, December 2013. Based on T(temperature)-S(salinity) diagram analysis, the water masses in the study area were divided into 3 groups; Tsushima Surface Water (TSW: $20-28.3^{\circ}C$ temperatures and 31.04-33.75 salinities), Tsushima Middle Water (TMW: $8.1-16.3^{\circ}C$ and 33.00-34.49), and North Korean Cold Water (NKCW: $1.8-9.4^{\circ}C$ and 33.78-34.42). In winter, DO concentrations in the northern part were higher than those in southern part. In spring and fall, they were low in the surface layer, and increased in summer. Chl-a concentrations < $0.4{\mu}g/L$ dominated in February, April, October and December. Chl-a concentrations were higher in June and August. In particular, the highest Chl-a concentration > $2{\mu}g/L$ was observed in the middle layer of Gampo in August. In February, April, June and December, the N/P ratio in the most of the water masses was less than the Redfield ratio (16), indicating that nitrate did act as a limiting factor in phytoplankton growth. On the contrary, in August and October, the N/P ratio in surface and sub-surface layer was greater than the Redfield ratio, suggesting that phosphate was a limiting factor.

• Journal of Life Science
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• v.20 no.3
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• pp.416-423
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• 2010

In this study, the properties and gene expression of the lactate dehydrogenase (EC 1.1.1.27, LDH) isozyme were studied in angelfish (Pterophyllum scalare) - known for their adaptation to the low oxygen environment of the tropics - which were acclimated to acute temperature change ($27{\pm}0.5{\rightarrow}18{\pm}0.5^{\circ}C$) and dissolved oxygen (DO) change ($6{\pm}1{\rightarrow}18\;ppm$) for 2 hours. The properties of the LDH isozymes were confirmed in the native-polyacrylamide gel electrophoresis, Western blot analysis and enzyme activity measurement. Liver- and eye-specific Ldh-C gene were expressed in liver, eye and brain tissues. Through Western blot analysis, the LDH $A_4$ isozyme was shown to have a more cathodal mobility relative to the $B_4$ isozyme. In the liver tissue, the LDH $A_4$ isozyme increased with temperature drop while the $B_4$ isozyme decreased. The LDH $A_4$ and $C_4$ isozymes increased with DO increment, while the $B_4$ isozyme decreased. In the eye tissue, the LDH $A_4$ and B4 isozymse increased with temperature drop while the $B_4$ isozyme decreased. The LDH $A_4$ and $B_4$ isozymes increased with DO increment, but the $C_4$ isozyme and isozymes including the subunit C decreased. In the heart tissue, LDH activity increased with DO increment, as well as the LDH $B_4$ isozyme. In the brain tissue, the LDH $A_4$ and $B_4$ isozymes increased with temperature drop. The LDH $B_4$ isozyme increased with DO increment. Accordingly, since the liver- and eye-specific Ldh-C are influenced by changes in DO and the LDH $B_4$ and $C_4$ isozymes are relatively controlled in the liver and eye tissues, the $C_4$ isozyme can be considered to have a lactate oxidase function.

• Journal of Korean Society of Forest Science
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• v.86 no.1
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• pp.56-68
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• 1997

This study was carried out to evaluate the capacity of environment purification of forest and to reveal formation processes of stream water quality by evaluating water quality variations in forest hydrological processes. Water quantity, pH, electric conductivity(EC), dissolved oxygen(DO), and dissolved matter concentrations were monitored in open rainfall, throughfall, stemflow, litter flow and short-term stream flow for one unit storm, and also for those were monitored in long-term stream flow in Palgong, Yongsung, and Daedong catchments. The results were summarized as follows; 1. pH and DO values of stream flow were increased as the flux increased but EC values were decreased. 2. pH values of stemflow and throughfall were decreased with the lapse of rainfall time with lower values than open rainfall. Arid EC values were higher in initial rainfall period but lower gradually with the lapse of time than open rainfall. In litter flow, pH values were lower than open rainfall but EC values were higher. In stream flow, pH values of stream flow showed a high level in initial rainfall period and decreased remarkably with the lapse of time, but it recovered after the rainfall stopped. And however, the values of EC showed almost reverse tendency. DO values of litter flow and stream flow were decreased gradually with the lapse of time in litter flow and stream flow but there were no any tendency in open rainfall, stemflow and throughfall. 3. pH values of stemflow and throughfall in Quercus acutissima were higher than in Pinus densiflora, but EC values were lower. Total amount of canons in stemflow was higher in Pinus densiflora than in Quercus acutissima. 4. pH, DO, EC and total amount of cation values in hydrological processes were in the order of; litter flow