• Magazine of the Korean Society of Agricultural Engineers
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• v.13 no.1
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• pp.2162-2176
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• 1971

From the ancient times our forefathers settled down in this peninsular and cultivated the hills and waste-lands into fields. Instead of fertilizing the lands they moved to find other fertile lands and lived a feudal life of agriculture and various machines played a main role in the land reclamation. The best method of land clearing, the time and efficiency in the operation and the effect of growing crops should sysematically analized prior to the time of 3rd Five-year Economic Development(1972-1976) in order to cultivated 210,000 ha of waste-land or the modernization of our country. The present study was investigated to find out a new working-system of mechanical land clearing and development of fertile soil. The results are as follows: 1) The land reclamation in natural slope is much more encourageable in land clearing and farming when the slope is below ten grades than bench terrace. 2) Weeds were mixed with soil in the land clearing work in order to supply organic materials and to make soil swollen instead of burning of just removing. 3) The equipments such as bulldozers, harrows, power tillers and so on should be prepared in order to do a systematic work in the land clearing. 4) The work of pulling-up roots is dependent upon the forms of roots spreading under the ground. The work of the pulling-up the straight roots was most difficult. 5) The land clearing work of the wrinkled style blocks was easy in pulling up roots and in the time of first plowing. The harrowing work could also be simply done. 6) The amount of soil carried was $240m^3/10a$, 15.6% increased amount from the standard block, while the required time of clearing work was 2 hours 15 minutes 45 seconds/10a, the one third of time required for the standard block. 7) The time disc harrowing work increased 50%, or 15 minutes/10a compared to the harrowing work required in the cultivated soil. 8) The time of rotary tilling increased 2.4 times or 1 hour 47 minutes 43 seconds/10a compared to the time required in the cultivated soil. 9) The reclamed land should be fertilized according to the soil quality, especially added fertilizer should be more than 1,200kg/10a, limes 20kg/10a. In order to produce added fertilizer grass fields should be needed. 10) The experiment of pasture growing is now progressing and therefore the effect of land clearing and the degree of developed soil will be investigated before long.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.43-71
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• 1999

This research is an experimental work of developing a construction material using municipal wastewater sludge as liner and cover materials for waste disposal landfill. Weathered granite soil and flyash, produced as a by-product in the power plant, were used as the primary additives to improve geotechnical engineering properties of sludge. For secondary additives, bentonite and cement were mixed with sludge to decrease the permeability and to increase the shear strength, respectively. Various laboratory test required to evaluate the design criteria for liner and cover materials, were carried out by changing the mixing ratio of sludge with the additives. Basic soil properties such as specific gravity, grain size distribution, liquid and plastic limits were measured to analyze their effects on permeability, compaction, compressibility and shear strength properties of mixtures. Laboratory compaction tests were conducted to find the maximum dry densities and the optimum moisture contents of mixtures, and their effectiveness of compaction in field was consequently evaluated. Permeability tests of variable heads with compacted samples, and the stress-controlled consolidation tests with measuring permeabilities of samples during consolidation process were performed to obtain permeability, and to find the compressibility as well as consolidational coefficients of mixtures, respectively. To evaluate the long term stability of sludges, creep tests were also conducted in parallel with permeability tests of variable heads. On the other hand, for the compacted sludge decomposed for a month, permeability tests were carried out to investigate the effect of decomposition of organic matters in sludges on its permeability. Direct shear tests were performed to evaluate the shear strength parameters of mixed sludge with weathered granite, flyash and bentonite. For the mixture of sludge with cement, unconfined compression tests were carried out to find their strength with varying mixing ratio and curing time. On the other hand, CBR tests for compacted specimen were also conducted to evaluate the trafficability of mixtures. Various test results with mixtures were assessed to evaluate whether their properties meet the requirements as liner and cover materials in waste disposal landfill.

• Journal of Wetlands Research
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• v.21 no.4
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• pp.374-383
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• 2019

The Wangpo stream located in the Buyeo-gun was a small stream with both low water quality and quantity due to the cultivated land and settlement area through the stream. In order to restore ecosystem, the Sustainable Structured wetland Biotop system was applied to treat 1,500 to 7,000 ㎥/d amount of effluent water pumped from the Buyeo sewage treatment plant facility as well as inflowed from nonpoint pollution source of Wangpo stream. As a result of continuous monitoring for 2 years from 2016 to 2018 after completing restorative construction, the average BOD₅ as an index of organic pollution was 7.3 mg/L and the average effluent concentration became 2.1 mg/L, showing an improvement by 71.2%. The average inflow concentration of T-N was 7.953 mg/L and the average outflow concentration was 3.379 mg/L, showing 57.5% of improvement. The average inflow concentration of T-P was 0.177 mg/L and the average outflow concentration was 0.052 mg/L, showing about 70.7% improvement. The results of ecological monitoring after creating biotope by reuse of treated waste water and nonpoint pollution source of the Wangpo Stream are as follows. The plant taxa founded in water SSB(Sustainable Structured wetland Biotop) system of the Wangpo Stream was total 41 species in 21 families, showing a higher proportion of naturally introduced plant than that of artificially planted species. In case of other terrestrial animals, both amphibian and reptile group were confirmed as 3 species in 6 families, avian group was 25 species of 15 families, and mammal group observed 5 species in 5 families, respectively. All species have been created and enhanced through purified water inhabited in the SSB(Sustainable Structured wetland Biotop) system as a treatment wetland, eventually migrating to the Wangpo Stream.

• Journal of Korea Society of Waste Management
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• v.34 no.2
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• pp.205-213
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• 2017

The current study was performed to investigate the effect of recycling coir substrates on the growth, fruit yield, and quality of strawberry plants. Analysis of physical properties revealed that the pH of a fresh coir substrate was 5.04 while those of substrates reused for one and two years were 5.20 and 5.33, respectively. The electrical conductivity (EC) of a new substrate was as high as $4.58dS{\cdot}m^{-1}$. This can cause salt stress after transplanting. The EC tended to decrease as the substrate was recycled, and the EC of a two-year recycled substrate was $1.48dS{\cdot}m^{-1}$. The fresh substrate had lower nitrogen and calcium concentrations, but higher phosphate, potassium, and sodium concentrations than the recycled coir substrate. The coir substrates recycled for one or two years maintained better chemical properties for plant growth than the fresh substrate. Strawberry growth varied depending on the number of years that the coir substrate was recycled. In general, strawberries grown in substrates that had been reused for two years did better than those grown in substrates that had been reused once or were fresh. Ninety days after transplanting, a plant grown in a substrate that had been reused for two years contained 25 leaves, which was 3.6 more than with a fresh substrate. In addition, the plants grown in a substrate that had been reused for two years exhibited larger leaf areas than those grown in other substrates. Coir substrates that had been reused for one year increased the number and area of leaves, but not as much as the substrate that had been reused for two years. One- and two-year reused coir substrates increased the weight of strawberries produced relative to the unused substrate, but the difference was not statistically significant. The plants grown in two-year reused substrates were longer and wider, as well. Also, the number of fruits per plant was higher when substrates were reused. Specifically, the number of fruits per plant was 28.7 with a two-year reused substrate, but only 22.2 with a fresh substrate. The fruit color indices (as represented by their Hunter L, a, b values) were not considerably affected by recycling of the coir substrate. The Hunter L value, which indicates the brightness of the fruit, did not change significantly when the substrate was recycled. Neither Hunter a (red) nor b (yellow) values were changed by recycling. In addition, there were no significant changes in the hardnesses, acidities, or soluble solid-acid ratios of fruits grown in recycled substrates. Thus, it is thought that recycling the coir substrate does not affect measures of fruit quality such as color, hardness, and sugar content. Overall, reuse of coir substrates from hydroponic culture as high-bed strawberry growth substrates would solve the problems of new substrate costs and the disposal of substrates that had been used once.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.421-433
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• 2023

The final disposal of spent nuclear fuel(SNF) from nuclear power plants takes place in a deep geological repository. The metal canister encasing the SNF is made of cast iron and copper, and is engineered to effectively isolate radioactive isotopes for a long period of time. The SNF is further shielded by a multi-barrier disposal system comprising both engineering and natural barriers. The deep disposal environment gradually changes to an anaerobic reducing environment. In this environment, sulfide is one of the most probable substances to induce corrosion of copper canister. Stress-corrosion cracking(SCC) triggered by sulfide can carry substantial implications for the integrity of the copper canister, potentially posing a significant threat to the long-term safety of the deep disposal repository. Sulfate can exist in various forms within the deep disposal environment or be introduced from the geosphere. Sulfate has the potential to be transformed into sulfide by sulfate-reducing bacteria(SRB), and this converted sulfide can contribute to the corrosion of the copper canister. Bentonite, which is considered as a potential material for buffering and backfilling, contains oxidized sulfate minerals such as gypsum(CaSO4). If there is sufficient space for microorganisms to thrive in the deep disposal environment and if electron donors such as organic carbon are adequately supplied, sulfate can be converted to sulfide through microbial activity. However, the majority of the sulfides generated in the deep disposal system or introduced from the geosphere will be intercepted by the buffer, with only a small amount reaching the metal canister. Pyrite, one of the potential sulfide minerals present in the deep disposal environment, can generate sulfates during the dissolution process, thereby contributing to the corrosion of the copper canister. However, the quantity of oxidation byproducts from pyrite is anticipated to be minimal due to its extremely low solubility. Moreover, the migration of these oxidized byproducts to the metal canister will be restricted by the low hydraulic conductivity of saturated bentonite. We have comprehensively analyzed and summarized key research cases related to the presence of sulfates, reduction processes, and the formation and behavior characteristics of sulfides and pyrite in the deep disposal environment. Our objective was to gain an understanding of the impact of sulfates and sulfides on the long-term safety of high-level radioactive waste disposal repository.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.737-760
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• 2022

For the geological disposal of high-level radioactive wastes (HLW), an understanding of deep subsurface environment is essential through geological, hydrogeological, geochemical, and geotechnical investigations. Although South Korea plans the geological disposal of HLW, only a few studies have been conducted for characterizing the geochemistry of deep subsurface environment. To guide the hydrogeochemical research for selecting suitable repository sites, this study overviewed the status and trends in hydrogeochemical characterization of deep groundwater for the deep geological disposal of HLW in developed countries. As a result of examining the selection process of geological disposal sites in 8 countries including USA, Canada, Finland, Sweden, France, Japan, Germany, and Switzerland, the following geochemical parameters were needed for the geochemical characterization of deep subsurface environment: major and minor elements and isotopes (e.g., ³⁴S and ¹⁸O of SO₄^2-, ¹³C and ¹⁴C of DIC, ²H and ¹⁸O of water) of both groundwater and pore water (in aquitard), fracture-filling minerals, organic materials, colloids, and oxidation-reduction indicators (e.g., Eh, Fe²⁺/Fe³⁺, H₂S/SO₄^2-, NH₄⁺/NO₃^-). A suitable repository was selected based on the integrated interpretation of these geochemical data from deep subsurface. In South Korea, hydrochemical types and evolutionary patterns of deep groundwater were identified using artificial neural networks (e.g., Self-Organizing Map), and the impact of shallow groundwater mixing was evaluated based on multivariate statistics (e.g., M3 modeling). The relationship between fracture-filling minerals and groundwater chemistry also has been investigated through a reaction-path modeling. However, these previous studies in South Korea had been conducted without some important geochemical data including isotopes, oxidationreduction indicators and DOC, mainly due to the lack of available data. Therefore, a detailed geochemical investigation is required over the country to collect these hydrochemical data to select a geological disposal site based on scientific evidence.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.68 no.2
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• pp.81-89
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• 2023

Lime-treated fertilizer (LTF) is manufactured using the lime stabilization method with food waste. LTF is effective in neutralizing acidic soil, improving nutrient and organic matter content in soil, and increasing crop productivity. However, excessive use of LTF in agricultural land can have undesirable effects, such as reduced crop growth and nutrient accumulation in soil. This study was evaluated the effect of different application ratios of LTF on the crop yield index (%), nutrient (N, P₂O₅, K₂O) uptake index (%), and soil chemical properties. The following treatments were applied: untreated (UT), NPK (NPK), NPK+calcium hydroxide (CH), and NPK+1-, 2-, 4-, and 8-times of LTF (LTF1, 2, 4, and 8). The yield index for LTF1 was the highest among different LTF treatments. Moreover the yield index for spring and winter cabbage in LTF1 treatment was 10% and 21% higher, respectively, than that in NPK treatment. The yield and nutrient indices were decreased with the increase in LTF application ratio. The soil pH and EC tended to increase with the increase in LTF ratio, and were the highest at 8.2 and 2.1, respectively, after cultivation for LTF8 (P<0.05). With the increase in soil pH, the soil inorganic nitrogen (NH₄-N, NH₃-N) and available phosphate (Av. P₂O₅) levels were decreased (P<0.05). Our results suggest that LTF1 (643 kg 10a^-1) is an appropriate ratio for improving soil chemical properties and increasing crop yield.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.3
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• pp.77-91
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• 2015

This study aims to suggest adequate soil management through the analysis of physicochemical properties of soil in the planting grounds of Incheon International Airport, which was constructed on a massive land reclamation site. Study areas were 5 sites at the international business complex, the passenger terminal, the airport support complex, the free trade zone, and the access road. Soil profile analysis showed that 9 plots out of the 27 plots were hardpan and heterospere within 80cm from the soil surface. The earth laid on the ground was categorized as gravel based soil(4 plots), dredged soil from the sea bottom and mixed reclamation materials(2 plots), clay with poor permeability(3 plots) and waste construction material(1 plot). Average soil hardness was $11.5kg/cm^2$ and soil textures were sandy soil, sandy loam and loamy sand. Average soil pH was 6.7 and average organic matter content was 0.7%. Electrical conductivity was 0.0dS/m and exchangeable cation concentrations were $Ca^{2+}$ 3.4cmol/kg, $Mg^{2+}$ 1.5cmol/kg, $K^+$ 0.3cmol/kg and $Na^+$ 1.0cmol/kg. Average cation exchange capacity was 11.0cmol/kg. Although average figures in Solum mostly meet the landscape design criteria, properties of each soil layer showed various values sometimes over the limit. Base saturations were $Ca^{2+}$ 29.9%, $Mg^{2+}$ 13.3% and $K^+$ 3.7% for lower soil, $Ca^{2+}$ 33.3%, $Mg^{2+}$ 17.0% and $K^+$ 2.7% for mid-soil and $Ca^{2+}$ 32.6%, $Mg^{2+}$ 12.2% and $K^+$ 1.9% for upper soil. Exchangeable sodium percentages were 16.4% for lower soil, 7.5% for mid-soil and 4.7% upper soil. Sodium adsorption rates were 0.8 for lower soil, 0.3 for mid-soil and 0.2 for upper soil. Factors affecting to the vegetation growth were heterogeneity and poorness of solum, disturbance of dredged soils, high soil hardness including hardpan in the subsurface soil layer and shallow effective soil depth, high soil acidity, imbalance of base contents, low organic matter content and low available phosphate levels in the soil.

• Korean Journal of Environmental Biology
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• v.24 no.3
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• pp.230-239
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• 2006

Nutrient over-enrichment as a consequence of anthropogenic loading leads to eutrophication, which has the detrimental effects on river and stream ecosystems. To examine dynamics of factors causing cultural eutrophication in a over-licked mountain stream due to anthropogenic loading, physicochemical parameters were measured from 5 stations in the upper Daecheon stream, Busan, from January 2002 to May 2003. The five study sites were located along the stream gradient. DC1 is upper most clean site, and DC5 is located at the lowest area. Wastewater was released into the stream from just upstream of DC2 site. Water column ammonium and phosphate concentrations were higher during winter than other seasons, while water column nitrate +nitrite concentration did not show clear seasonal variation. Water column ammonium, nitrate+nitrite and phosphate concentrations were lowest at DC1 and highest at DC2 in which waste water loading occurred. TOC and DOC, conductivity, turbidity, and BOD in the water column were also increased drastically at DC2, and then decreased at DC5. Sediment pore water phosphate concentrations during winter and spring were higher than those in summer and fall, while sediment pore water ammonium and nitrate +nitrite concentrations showed no seasonal trend. Sediment pore water ammonium and phosphate concentration were also increased at DC2 and slightly decreased at DC5, while sediment pore water nitrate+nitrite concentration was highest at DC5. Organic matter and inorganic nutrients at up-stream of Daechon stream significantly increased as a result of wastewater discharge, and the nutrient concentrations decreased at low-stream suggesting self-purification ability of the stream.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2047-2058
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• 2000

The effects of operating parameters on performance of upflow anaerobic sludge blanket(UASB). anaerobic filter(AF), and two-stage anaerobic sludge bed filter (ASBF) bioreactors in treating swine wastewater were evaluated by operating the lab-scale bioreactors upto hydraulic retention time(HRT) of 1 day and organic loading rate (OLR) of $5.1kg-COD/m^3{\cdot}d$ for 200 days. Swine wastewaters of which characteristics were affected by types of hog raising and seasons contained high concentrations of COD, SS, and ammonia. Inoculation of the bioreactors with waste sludge from anaerobic treatment facility of local municipal wastewater treatment plant was effective in developing biomass in the bioreactors. Acclimation period of the bioreactors with swine wastewaters required approximately 40 days, but that for AF and two-stage ASBF, which were filled with media, was faster than VASB. The bioreactors showed high and stable COD removal efficiency of 77~91% at influent T-N concentrations of 370~800mg/L but low and unstable COD removal efficiency of 24~94% at influent T-N concentrations of 760~1,310mg/L. It is essential to remove ammonia prior to anaerobic treatment since the concentrations of ammonia in swine wastewaters showed toxic effects to methanogenic bacteria. The bioreactors were effective in treating swine wastewaters with COD removal efficiency of 78.9~81.5% and biogas generation rate of $0.39{\sim}0.59m^3/kg-COD_r$ at OLR of $1.1{\sim}2.2kg-COD/m^3{\cdot}d$: however, an increase of OLR by reducing HRT and increasing influent COD caused decrease of COD removal efficiency. The extent of decrease in COD removal efficiency was higher in UASB than AF and two-stage ASBF. AF and two-stage ASBF anaerobic bioreactors were effective in treating varing characteristics of swine wastewaters since they showed high and stable COD removal efficiency at high OLR due to effective retention of biomass by media and staging.