• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.610-619
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• 2018

This study was carried out in August and September 2016 to investigate the species composition and biomass of benthic diatoms in Yubu Island, Gomso Bay, Imja Island, and Yeoja Bay tidal flat of Southwestern coast. There were 181 species of 48 genera in Yubu Island tidal flats, 194 species of 51 genera in Gomso Bay tidal flats, 224 species of 64 genera in Imja Island tidal flats and 188 species of 56 genera in Yeoja Bay tidal flats. A total of 274 species of 70 genera appeared. Pennales appeared more widely than Centrales and were dominated by Paralia sulcata and Navicula spp. Biomass of Yubu Island tidal flat ranged from $18.8-136.1mg\;m^{-2}$, $31.9-215.7mg\;m^{-2}$ in Gomso Bay, $2.9-120.2mg\;m^{-2}$ in Imja Island and $10.1-147.7mg\;m^{-2}$ in Yeoja Bay. The range of total biomass from 4 areas was $2.9-215.7mg\;m^{-2}$. The concentration of phaeopigment and degradation product of chlorophyll-a was $1.7-470.8mg\;m^{-2}$ in Yubu Island tidal flat, $52.3-277.2mg\;m^{-2}$ in Gomso Bay, $0.6-78.9mg\;m^{-2}$ in Imja Island and $39.1-346.3mg\;m^{-2}$ in Yeoja Bay. Compared with the results reported in this study area and the domestic tidal flats, it cannot be directly compared and evaluated due to various factors such as the timing of the survey, the frequency of the survey, the analysis method and geography. The southwestern coast of Korea has a variety of benthic diatoms and the high concentration of chlorophyll-a is the main determinant of primary productivity.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.181-190
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• 2019

Recently, Low impact development techniques, a form of nature-based solutions (NBS), were seen cost-efficient alternatives that can be utilized as alternatives for conventional stormwater management practices. This study evaluated the effectiveness of an infiltration trench (IT) and a small constructed wetland (SCW) in treating urban stormwater runoff. Long-term monitoring data were observed to assess the seasonal performance and cite the advantages and disadvantages of utilizing the facilities. Analyses revealed that the IT has reduced performance during the summer season due to higher runoff volumes that exceeded the facility's storage volume capacity and caused the facility to overflow. On the other hand, the pollutant removal efficiency of the SCW was impacted by the winter season as a result of dormant biological activities. Sediment data also indicated that fine and medium sand particles mostly constituted the trapped sediments in the pretreatment and media zones. Sediments in SCW exhibited a lower COD and TN load due to the phytoremediation and microbiological degradation capabilities of the system. This study presented brief comparison LID facilities equipped with pre-treatment zones. The identified factors that can potentially affect the performance of the systems were also beneficial in establishing metrics on the utilization of similar types of nature-based stormwater management practices.

• Clean Technology
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• v.29 no.2
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• pp.118-125
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• 2023

Once a site is contaminated with polychlorinated biphenyls (PCBs), serious environmental and human health risks are inevitable. Therefore, innovative but economical in situ remediation technologies must be immediately applied to the contaminated site. Recently, nanoscale zero-valent iron (nano-ZVI) particles have successfully been applied for the dechlorination of various chlorinated organic compounds like TCE, PCE and DDT, and they are considered to be environmentally safe due to the high abundance of iron in the earth's crust. Nano-ZVIs are much more reactive than granular ones, but tend to agglomerate due to their high surface energy and magnetic properties. In order to prevent them from being agglomerated toward larger particles, TiO₂ was used as a support to immobilize the nano-ZVI particles as much as possible. 10wt% ZVI/TiO₂ was prepared by adding NaBH₄ slowly into an FeSO₄/TiO₂ aqueous slurry. In spite of their non-uniformity in size, the nano-ZVI particles were quite successfully dispersed onto the exterior surface of a non-porous TiO₂ powder. The ZVI/TiO₂ was then employed to degrade Aroclor 1242, a kind of PCBs standard, in spiked soil, and its reactivity towards the degradation of Aroclor 1242 was investigated. The fabricated ZVI/TiO₂ degraded Aroclor 1242 in soil quite effectively, but the creation of remaining dechlorinated compounds, possibly high molecular weight hydrocarbons, in the soil was unavoidable.

• Applied Biological Chemistry
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• v.23 no.2
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• pp.131-139
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• 1980

TOK (2,4-Dichlolo-4'-nitrodiphenyl ether) was applied to two Korean soils possessing different physico-chemical properties at a certain concentration and incubated for a certain time under flooded conditions. The metabolites and the soil microorganisms involved in the degradation of TOK are studied. Chong Ju and Chung Ju soils treated with TOK at a concentration of 500 ppm and incubated for two, four, and six months at $30^{\circ}C$ yielded 4-chloro-4'-amino diphenyl ether, 2, 4-dichloro-4'-amino diphenyl ether(amino-TOK), N-[4'-(4-chloro-phenoxy)] phenyl acetamide, and N-[4'-(4-chloro-phenoxy)] phenyl formamide as the major metabolites. TOK underwent the reduction of nitrogroup to amino group, dechlorination, acetylation, and formylation. No cleavage at the ether linkage was recognized. TOK was more readily degraded in Chung Ju soil which is characterized by the higher pH (PH 6.43), clay loam in textural class, and the higher cation exchange capacity. The toxicity of TOK as a possible environmental contaminant is expected to be considerably reduced as a result of the above degradation Twelve strains of soil bacteria were isolated from the TOK-treated Chong Ju and Chung Ju soils. As a result of the incubation of TOK in pure cultures of the isolates, T-1-1 strain isolated from Chong Ju soil had almost no degradability, whereas T-2-3 strain turned out to be the most potent. The degradation of TOK by the isolates constituted mostly the reduction of the nitro group to amino group. The citrate buffer extract of Chung Ju soil reduced TOK more readily to amino-TOK than that of Chong Ju soil.

• Korean Journal of Ecology and Environment
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• v.44 no.3
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• pp.272-279
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• 2011

Copper cyanide is a chemical produced in large quantities with 2,500 tonnes being produced in 2006. It is mainly used for electroplating copper, particularly alkali-Cu plate and brass plating. The purpose of this study is to reassess the physicochemical properties and environmental fate of copper cyanide based on reliable data and and to conduct an ecotoxicity test according to the OECD test guidelines as an initial environmental risk assessment (need to state where this was done). Metal containing inorganic substances are not subject to degradation, biodegradation or hydrolysis. Aquatic toxicity tests of copper cyanide were conducted according to OECD test guideline 201, 202 and 203 for green algae, daphnia, and fish, respectively. The following acute toxicity test results were obtained for aquatic species: 0.089 mg $L^{-1}$ (Algae, 72 Hr-$EC_{50}$); 0.21 mg $L^{-1}$ (flea, 48 Hr-$LC_{50}$); 0.62 mg $L^{-1}$ (Fish, 96 Hr-$ErC_{50}$). The chemical possesses properties indicating a hazard for the aquatic environment (acute toxicity in fish, daphnia and algae below 1.0 mg $L^{-1}$). As a result of this study, copper cyanide has become a candidate for detailed risk assessment. Countries that produce this chemical in significant quantities are recommended to perform specific assessments.

• Journal of Soil and Groundwater Environment
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• v.10 no.3
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• pp.38-45
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• 2005

The feasibility of stimulating in situ aerobic cometabolic activity of indigenous microorganisms was investigated in a trichloroethylene (TCE)-contaminated aquifer. A series of single-well natural drift tests (SWNDTs) was conducted by injecting site groundwater amended with a bromide tracer and combinations of toluene, oxygen, nitrate, ethylene and TCE into an existing monitoring well and by sampling the same well over time. Three field tests, Push-pull Transport Test, Drift Biostimulation Test, and Drift Surrogate Activity Test, were performed in sequence. Initial rate of toluene degradation was much faster than the rate of bromide dilution resulting from natural groundwater drift, indicating stimulation of indigenous toluene-oxidizing microorganisms. Transformation of ethylene, a surrogate probing overall activity of TCE transformation, was also observed, and its transformation results in the production of ethylene oxide, suggesting that some tolueneoxidizing microorganisms stimulated may express a orthomonooxygenase enzyme. Also in situ transformation of TCE was confirmed by greater retardation of TCE than bromide after the stimulation of toluene-oxidizing microorganisms. These results indicate that, in this environment, toluene and oxygen additions stimulated the growth and aerobic cometabolic activity of indigenous microorganisms expressing orthomonooxygenase enzymes. The simple, low-cost field test method presented in this study provides an effective method for conducting rapid field assessments and pilot testing of aerobic cometabolism, which has previously hindered application of this technology to groundwater remediation.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.311-321
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• 2018

The purpose of this study is to investigate effect of stream channel naturalness on ecological health by using environmental factors and Fish Assessment Index (FAI) in the Han River of South Korea. These samples and data have been released from the research project titled Stream/River Ecosystem Survey and Health Assessment, which was conducted in 444 sites in the Han river watershed from 2008 to 2016. All samples were classified into five groups according to a degree of morphological changes of stream. Water chemistry analyses indicated a decline in water quality by decreasing stream channel naturalness, it is assumed that channelized stream was vulnerable to aquatic pollution compared to the natural meandering stream. In the result of frequency of dominant species, sensitive species and insectivore such as Zacco koreanus, Rhynchocypris kumgangensis and Pungtungia herzi were frequently dominated in the natural meandering stream while tolerant species and omnivores such as Carassius auratus and Cyprinus carpio were more dominated in the channelized streams. The FAI in the channelized stream shows decline to average of $46{\pm}25$ compared with that of the natural meandering stream ($80{\pm}20$). The decrease in FAI was highly influenced by changes in matrixes of fish assemblage structure such as number of sensitive species (M3), portion of omnivores (M5) and insectivores (M6). Moreover, annual average FAIs from 2008 to 2016 were significantly correlated with water chemistry, especially TN, TP and BOD ($r^2=0.59$, p<0.0001). Taken together, all the results suggest that the stream channelization could negatively impact on the water quality and fish assemblage structure, leading to degradation in aquatic ecosystem health.

• Journal of Environmental Impact Assessment
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• v.31 no.3
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• pp.141-160
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• 2022

The harbor construction projects can lead to various marine environmental problems including habitat degradation and loss, marine water pollution, change of flow patterns, erosion, scour, sedimentation, and so on. The EIA is a measure to prevent various environmental problems in advance from examining and minimizing the environmental impacts before the proposed developments are implemented. In addition, institutions reviewing EIA reports have made efforts to conduct scientific and standardized EIA by applying EIA guidelines for each project. This study aims to create a EIA guideline focusing on the harbor construction projects. Based on the review comments of the harbor construction EIA reports for the past 13 years (2009-2021) and the EIA guidelines of different types of projects, we identified the marine environmental problems and provided the appropriate guideline. This guideline summarizes and presents the contents which must be reviewed in the baseline condition survey, impact assessment, mitigation, and post-environmental impact investigation in the fields of marine fauna and flora, marine physics, and marine water and sediment quality. In the case of a baseline condition survey of marine fauna and flora, a method for selecting survey points considering the characteristics of sea area and project was presented. When estimating the impact of marine fauna and flora, we presented methods for predicting the impact on them due to the spread of suspended sediments and the damage to benthic habitats due to dredging and reclamation. In consideration of the characteristics of the sea area, we divided the survey items of the marine physics into essential items and supplementary items. In predicting the impact of marine physics, various methods for major issues such as seawater circulation, suspended sediment and bottom sediment transport, water temperature and salinity diffusion, seawater exchange, wave transformation, harbor tranquility, and shoreline change were presented. The research results will contribute to protect the marine environment by inducing more systematic and scientific surveys, impact assessments, and mitigation in the EIA process.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.2081-2091
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• 2013

Recently, the demand on the practical application of life-cycle cost effectiveness for design and rehabilitation of civil infrastructure is rapidly growing unprecedently in civil engineering practice. Accordingly, in the 21st century, it is almost obvious that life-cycle cost together with value engineering will become a new paradigm for all engineering decision problems in practice. However, in spite of impressive progress in the researches on the LCC, the most researches have only focused on the Deterministic or Probabilistic LCC analysis approach and general bridge at design stage. Thus, the goal of this study is to develop a practical and realistic methodology for the Life-Cycle Cost LCC-effective optimum decision-making based on reliability analysis of bridges at design stage. The proposed updated methodology is based on the concept of Life Cycle Performance(LCP) which is expressed as the sum of present value of expected direct/indirect maintenance costs with expected optimal maintenance scenario. The updated LCC methodology proposed in this study is applied to the optimum design problem of an actual highway bridge with Cable Stayed Bridges. In conclusion, based on the application of the proposed methods to an actual example bridge, it is demonstrated that a updated methodology for performance-based LCC analysis proposed in this thesis, shown applicably in practice as a efficient, practical, process LCC analysis method at design stage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.405-413
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• 2015

In the US, the number of cases of subterranean water contamination from tritium leaking through a damaged buried nuclear power plant pipe continues to increase, and the degradation of the buried metal piping is emerging as a major issue. A pipe blocked from corrosion and/or degradation can lead to loss of cooling capacity in safety-related piping resulting in critical issues related to the safety and integrity of nuclear power plant operation. The ASME Boiler and Pressure Vessel Codes Committee (BPVC) has recently approved Code Case N-755 that describes the requirements for the use of polyethylene (PE) pipe for the construction of Section III, Division 1 Class 3 buried piping systems for service water applications in nuclear power plants. This paper contains tensile and slow crack growth (SCG) test results for high-density polyethylene (HDPE) pipe welds under the environmental conditions of a nuclear power plant. Based on these tests, the fracture surface of the PENT specimen was analyzed, and the fracture mechanisms of each fracture area were determined. Finally, by using 3D finite element analysis, limit loads of HDPE related to premature failure were verified.