• Current Research on Agriculture and Life Sciences
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• v.16
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• pp.75-83
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• 1998

The purpose of this survey was to investigate the regional and seasonal characteristics of a water system and to obtain basic information of a water system at Andong bridge, Nakdan bridge, Kangjung, Waekwan bridge and Koryung bridge along Nakdong River. We surveyed the water quality in the Nakdong River for 2 years from Jan. 1996 to Dec. 1997. The results summarized were follows; 1) The pH in the Nakdong River on the basic of 2 years average were 6.5-8.6. 2) The DO, the COD and the BOD were low level in summer and high level in winter, respectively. 3) The suspended solids(SS) contents was high especially in summer. 4) The T-P and the T-N contents were higher than the lower level of nitrogen and phosphorous for algae growth and the contents were high especially in winter. 5) The $NH_4{^+}$-N and $NO_3{^-}$-N were also observed to be quite high.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.3
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• pp.95-120
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• 2023

Methane (CH₄) is a key greenhouse gas in the atmosphere with 85 times greater greenhouse potent relative to carbon dioxide (CO₂). The atmospheric concentration of CH₄ is rapidly increasing due to the intensive usage of CH₄ and the thawing of the cryosphere. Additionally, with the current warming of ocean water, the dissociation of gas hydrates, an ice-like compound and the largest reservoir of CH₄ on Earth, is expected to occur, resulting in the release of CH₄ from the seafloor into the overlying water and atmosphere. Moreover, bottom water hypoxia is another concern that potentially introduces greenhouse gases into the atmosphere. With ongoing global warming and eutrophication, the size and duration of bottom water hypoxia are rapidly increasing. These low-oxygen conditions would relocate the redox zone shallower in sediment or in the water column, causing the release of CH₄ into the atmosphere and thereby intensifying global warming. However, there exists a gap in the understanding of CH₄ dynamics including its generation in relation to bottom water hypoxia. Therefore, this review article aims to understand the relationship between CH₄ and bottom water hypoxia and to draw attention to CH₄ investigation in Korea.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.3
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• pp.219-227
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• 1993

Broadcast-seeded rice in submerged paddy frequently lodge in the field. In general, the causes of lodging in rice cultivation differ with different cultural methods. This study was conducted to investigate the causes of lodging in broadcast-seeded rice (BSR) and hand-transplanted rice (HTR) under four nitrogen (N) levels. Lodging in BSR was mainly a root lodging due to shallow root distribution, while that in HTR showed a bending type owing to deep rooting system. At the upper soil layer (0-5cm from the surface of ground) the root distribution of BSR (65.2%) was much larger than that of HTR (51.6%), whereas at the 5-10cm soil layer the root distribution of BSR (18.5%) was much smaller than that of HTR (28.0%). The depth of buried culm base was much shallower in BSR (1.2cm) than in HTR (4.0cm). The plant height, fresh weight, lodging index, culm diameter and thickness in HTR were much greater than those in BSR, and the breaking strength of lower internode was similar in the two cultivation methods indicating that HTR would have more lodging causes than BSR. In spite of . the more advantages to lodging resistance in BSR it severely lodged in the field. The main lodging-inducing factors of BSR were the shallow root distribution and shallow depth of buried culm base. Besides these, the higher ratio of gravity center of culm was an important factor. This result suggested that for the fundamental prevention of lodging in BSR, an ideotype of rice plant with ' a deep-rooted behavior ' should be developed.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.162-166
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• 2011

Phosphorous contaminated in the effluent from sewage treatment plants can cause the eutrophication in surface water bodies. In this study, a powder of titanium oxysulfate-sulfuric acid made of ion-exchange materials was immobilized in an alginate gel and this material was examined to evaluate its phosphorous removal efficiency. Equilibrium and kinetic studies were carried out to quantify the adsorption capacity and time dependent removal rate of phosphorous. Adsorption isotherms and kinetic parameters were obtained for the entrapped titanium beads with three different methods. Equilibrium data were analyzed using Langmuir adsorption isotherm model and found to be well fitted to the model. The maximum adsorption capacity for phosphorous by the titanium bead synthesized with the solution method was 92.26 mg/g. Kinetic data followed a pseudo-second-order kinetic model. Due to the low production cost and high adsorption capacity, the titanium bead synthesized by the solution method has a potential to be utilized for the cost-effective removal of phosphorous from wastewater.

• Ecology and Resilient Infrastructure
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• v.4 no.3
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• pp.142-148
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• 2017

Nitrogen and phosphorus are key factors in causing eutrophication of water body. In this study, ceramics media was selected to increase the removal efficiency of nitrogen and phosphorus. We designed vertical, horizontal flow constructed wetlands to create aerobic and anaerobic flow conditions by using the media, then proceeded to performance evaluations after acrylic reactors were produced. In the case of vertical and horizontal flow constructed wetlands, we measured oxygen concentrations to evaluate aerobic and anaerobic conditions. we got the result of 2.7 mg/L in the aerobic condition, N.D in the anaerobic condition respectively, which suited our purpose. The result of the combined vertical and horizontal flow condition showed that the removal efficiency of SS was 94%, 91%, 61% at 140 min, 80 min, 60 min of running times, respectively, and the removal efficiency of T-P was 84%, 71%, 63% during each running time. In case of T-N, the removal efficiency was 63%, 49%, 42% during each running time. We found that the reactor exerted better removal efficiency when in the short time compared to 12 - 24 hr residence time of existing wetlands. In this study, we conducted experiments to explore functional effects after applying combined vertical and horizontal flow methods in the field. Further study will be carried out to identify its mechanism and administrative perspective.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.9
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• pp.482-496
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• 2016

Algal blooms of cyanobacteria (blue-green Algae) due to the eutrophication of rivers and lakes can cause not only the damage by its biological toxins but also the economic loss in drinking water treatment. The natural algae coagulant, a commercial product known as W.H. containing the algicidal and allelopathic material derived from oak, can control algal problems proactively through the coagulation flotation process. However, because there have been no applications of the process for pre-treatment in drinking water plants, we could find no report on the optimum injection dose of W.H.. In this study, we have conducted several sets of jar-tests while changing W.H. dose and concentration of chl-a for (1) Han-river samples and (2) subcultured cyanobacteria samples, and monitored the removal mechanisms of algae intensively. Based on these jar-test results, two linear equations with variables of chl-a and turbidity have been deduced to predict the optimal W.H. dose after the multiple regression analysis using IBM-SPSS. Also, prototypes of automatic control logic have been suggested to inject the optimal W.H. dose promptly in response to the variation of water quality.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.11
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• pp.589-595
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• 2016

This study evaluated the environmental impacts for landfill treatment of the wastewater treatment sludge (WTS) from petrochemical firms by life cycle assessment (LCA) and reviewed the impact reduction by landfill gas (LFG) utilization. The functional unit was 'landfill of 1 ton of WTS', and the system boundary included the process of input and treatment for WTS in landfill site. The impacts were high at landfill process (LP) and leachate treatment process (LTP). Global warming (GWP) and photochemical oxidants creation (POCP) were high at LP, while abiotic depletion (ADP), acidification (AP), eutrophication (EP), ozone depletion (ODP) were high at LTP. The major substances of various impact categories were crude oil (ADP), $NO_X$ (AP, EP), $CH_4$ (GWP, POCP), $Cl_2$ (ODP), respectively. The major factor of ADP, AP, EP was attributed from the generation of electricity used in LTP, and the methane within uncollected LFG was main factor of GWP and POCP. Therefore, electricity consumption reduction is identified to be an impact improvement option, and the flaring system installation or enhanced LFG recovery could be an alternative to reduce impacts. Among the various categories, GWP accounted the highest impact (${\geq}90%$) followed by ADP, POCP. In the avoidance impact resulted from the utilization of LFG, to substitute B-C oil or LNG showed the impact reduction of 32.7% and 12.0%, respectively.

• Korean Journal of Ecology and Environment
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• v.34 no.3 s.95
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• pp.206-214
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• 2001

Water quality and Pollution state of Lake Chungcho were evaluated during three years from 1998 to 2000. We surveyed physicochemical parameters, and TSI (trophic state index) was calculated using TP, Chl. a, and SD (secchi disc transparency) data of growing season average. Water samples were collected bimonthly except freezing season. During the study period, total annual precipitation in 1998, 1999 and 2000 year was 1,797,1,722 and 1,345 mm, respectively. Salinity and conductivity were high($29.3{\pm}5.5\;ppt$, and $45,105{\pm}7,585\;{\mu}S/cm$) then other lagoons in the Eastern Coast of Korea. Chemocline was formed by salinity at $0.5{\sim}1.5\;m$ water depth. As a result of this, DO concentration of hypolimnion was below $3.0\;mgO_2/L$. Especially, when intense chemocline was formed, temperature of hypolimnion was higher than epilimnion. Secchi disc transparency, chlorophyll a, and COD were $1.8{\pm}0.3\;m$, $15.7{\pm}20.7\;mg/m^3$, and $3.1{\pm}0.8\;mgO_2/L$, respectively. Most of TN/TP ratios below 20, but concentration of TN and TP was high. Values of TSI ranged between 59 and 77, indicating a eutrophic condition in this system.

• Korean Journal of Environmental Biology
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• v.31 no.3
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• pp.213-224
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• 2013

Between May 2006 and November 2009, we investigated the relationship between fluctuations in environmental factors and phytoplankton communities in Saemangeum Artificial Lake, South Korea. Nutrient concentrations in the lake increased because of the inflow of water from Mankyung and Dongjin Rivers during the summer rainy season; in particular, high concentrations were detected at an inner zone close to the estuaries. During the summer rainy season, salinity at the inner zone reduced more rapidly than that at the other zones, and it was similar to the changes in nutrient concentrations. Variations in phytoplankton communities were caused by fluctuations in environmental factors: the abundance of phytoplankton at the inner zone was higher than that at the other zones. Diatoms were the dominant species in the phytoplankton communities. A small centric diatom, Skeletonema costatum like species, was predominant, with a mean abundance of 19.5% in Saemangeum lake. Because of accelerated eutrophication in the lake, phytoplankton abundance increased continuously and the total number of species present in the community decreased. In particular, some dinoflagellates could intermittently cause red tides during low temperature and salinity conditions (at the inner zone). In 2006~2007, a red tide-forming dinoflagellate, Prorocentrum minimum, was the predominant species, while Heterocapsa triquetra, Karlodinium veneficum, and Heterocapsa rotundata were the newly recorded species in late 2008 to early 2009. Therefore, the dynamics of phytoplankton communities under the perennially eutrophic conditions in Saemangeum lake appear to be primarily affected by changes in water temperature and salinity. In particular, the growth of harmful algae may have been accelerated by the low salinity and temperature conditions during the spring season at the inner zone.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.882-895
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• 1997

Changes in the benthic communities have been studied to investigate the environmental effects before and after the construction of Shihwa Dike in the West coast of Korea. It is suggested that sequential changes in macrofaunal assemblages progressed in two sucressional directions. In the Shihwa lake under the influence of organic enrichment. First, the appearance of 'azoic tone' or 'grossly polluted zone' developed in the area of less than 6 m in depth resulted from the severe dissolved oxygen depletion due to the eutrophication from the increased organic loading. Second, the 'polluted zone' characterized by the proliferation of the opportunistic species in organically enriched area, was found in the vicinity of the industrial discharges and nearby fluvial inputs. This benthic community succession in the Shihwa lake seemed to be caused by the various ecological events such as an eutrophication in this organically enriched environment after construction of the dike and other physico-chemical parameters like salinity and dissolved oxygen in the bottom water, which may be influenced by the irregular surface water discharge and dilution by outer seawater inflow through the water gate of the dike. On the other hand, the benthic communities in the outside of the dike showed that the species richness was more than doubled and the abundance increased almost seven times more than that before the dike construction. This may be a typical characteristics of the initial phase in benthic eutrophication, suggesting that an increased organic input area may have been reponsible for this faunal change in the study area.