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

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.148-149
• /
• 2021

Food waste has increasingly become a global issue of concern among the researchers and policymakers due to its significant environmental and economic impacts, and other associated unsustainable use of resources, including water resources. While food wastage occurs at each stage of the supply chain with food loss at the upstream and food waste at the downstream, the impacts of food waste occurring at the consumption side are enormous due to the accumulated added values. In this study, the embedded water resources, greenhouse gas emissions, and economic loss of household food waste were investigated. The primary granular data of household food waste was collected through direct sampling from 218 selected households of the Buk-gu community in Daegu, South Korea from July 2019 to May 2020. The water footprint, which was based on the water footprint concept, i.e., indirect water use, and GHG emission potential factor for each of the food items were adopted from the literature, while the retail prices and disposal cost were used to assess the economic cost of wasted food items. The water footprint, GHG emission associated with environmental impacts, and the economic cost of 42 major identified wasted food items were conducted. The findings showed that an average of 0.73 ± 0.06 kg/household/day edible food waste was generated among the sampled households, with leafy vegetable, watermelon, and rice responsible for 10, 9, and 4%, respectively, of the total weight of the 42 food wasted items. The water footprint and environmental impact of the household food waste resulted in 0.46 ± 0.04 m³ and 0.71±0.05 kg CO2eq, respectively. Beef, pork, poultry, and rice accounted for 52, 9, 5, and 4% of the total water footprint, while beef, pork, rice, tofu/cheese had 52, 8, 6, and 6% of the total emissions, respectively, embedded in the food wasted. Furthermore, the average estimated economic cost associated with wasted food items was 3855.93±527.27 Korean won, with beef, fish, and leafy vegetable responsible for 21, 13, and 10%, respectively, of the total economic cost. A combined assessment using water-environmental-economic nexus indicated that animal-based food had the highest footprint impacts, with beef, pork, and poultry indicating high indices of 0.3, 0.08, and 0.06 respectively, on a scale of 0 to 1, compared to corn and lettuce with lowest impacts of 0.02. Other food items had moderate impact values ranging from 0.03 to 0.05. This study, therefore, provides insight into the enormity of environmental and economic implications of household food waste among Korean households.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.43 no.4
• /
• pp.449-458
• /
• 2023

As an adsorption technology for dissolved organic matter, the adsorption capacity of granular activated carbon, GAC, can be applied, but activated carbon whose adsorption capacity is significantly reduced by use is inevitably replaced or regenerated. However, due to the economics of replacement cost, thermal regeneration method is used commercially, but high energy cost and loss of activated carbon occur under high temperature conditions above 800℃. In this study, the Sono-Fenton method, a multi-oxidation technology that combines Fenton oxidation and ultrasonic oxidation, was applied to improve the regeneration efficiency of spent GAC used to treat dissolved organic matter in combined sewer overflows (CSOs), and the regeneration efficiency of spent GAC by oxidant and ultrasonic frequency was investigated. In the applied Sono-Fenton treatment, the highest regeneration efficiency of 68.5% was obtained under the regeneration conditions of Fe²⁺ 10 mmol/L, H₂O₂ concentration 1,000 mmol/L, ultrasonic treatment time of 120 min, and ultrasonic frequency of 40 kHz. And similar efficiency was also obtained at 750 kHz, while ultrasonic waves of other frequencies had poor regeneration efficiency, and the magnitude of frequency and GAC regeneration efficiency did not show a linear relationship. In the case of continuous operation of the GAC adsorption tower with CSOs prepared by diluting raw sewage, about 700 hours of operation without regeneration was possible, and as a result of applying one Sono-Fenton treatment, 40-70% COD_cr removal efficiency was obtained during a total of 1,000 hours of GAC adsorption operation.

• Analytical Science and Technology
• /
• v.19 no.4
• /
• pp.290-300
• /
• 2006

Disinfection by-products(DBPs), such as volatile trihalomethanes and the nonvolatile organochlorine acids, created by chlorination have been extensively studied. However MX which contributes 20-50% of the mutagenic activity in drinking water began to people's attention since 1990. Its chemical name is 3-chloro-4-dichloromethyl-5-hydroxy-2(5H)-furanone. According to WHO guidelines its concentration should be controlled, but its value has not been set up. Due to analytical difficulties in measuring this compound at such a low concentrations and lack of information on toxicity to human. Because concentration (ng/L) of MX in drinking water is low traditional testing methods are ineffective. Therefore this study compared LLE and SPE and have chosen SPE to improve preconcentration. MX has been identified in chlorinated drinking water samples in several countries but not in korea Therefore this study analyzed concentration of MX in different water sources and in spring water. This study examined the causes of changing MX content. Chlorine dosage, seasons, water temperature and distance from the source was all discoverd to be relavant. MX was analyzed in various treatment to find optimum disinfection methods. The outcome was that the concentration of MX was minimized when using biological activated carbon-O3 and granular activated carbon.

• The Korean Journal of Zoology
• /
• v.21 no.1
• /
• pp.29-39
• /
• 1978

The authors observed the ultrastructure of the mucous glandular epithelial cells in the amphibian skin by mean of electron microscope. The specimens from the experimental animals were fixed in 2.5% glutaraldehyde-oaraformaldehyde fixative in phosphate buffer at pH 7.2 prior to fixation in 1% osmium tetroxide, dehydrated in graded ethanol and acetone, embedded in Epon 812 mixture, and sectioned with Sorvall MT-2 ultramicrotome. The ultrasections were contrasted with uranyl acetate and lead citrate and observed with a JEOL-100B electron microscope. The results were as follows: 1. The cutaneous mucous glands in amphibia consisted of the glandular epithelial and the myoepithelial cells. 2. Several different cells in ultrastructure were observed in the mucous glandular epithelium of the adult amphibian skin. a. The dark and the light cells were observed in Hynobius leechi. b. The mitochondria-rich and the round secretory granule-containing cells were observed in Bombina orientalis. c. The round secretory granule-containing and the foam-like granule mass-containing cells were observed in Kaloula tornieri. d. The cutaneous mucous gland of Rana nigromaculata were divided into two types: A and B-type glands. In the A-type mucous gland, the mitochondria-rich and the round secretory granule-containing cells and in the B-type mucous gland, the mitochondria-rich, the secretory granule-containing and the ER-rich cells were observed. 3. Based upon the above findings, the authors infer that the mucous granular epithelium of the amphibian skin consists of the mitochondria-rich undifferentiated, the secetory granule-containing and mature, and the ER-rich evacuated cells.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.58.1-59
• /
• 2021

Exploration of asteroids' internal structure is essential for understanding their evolutional history. It also provides a fundamental information about the history of coalescence and collision of the solar system. Among several models of the internal structures, the rubble-pile model, confirmed by the near-Earth asteroid (25143) Itokawa by Hayabusa mission [1], is now widely regarded as the most common to asteroids with size ranging from 200 m to 10 km [2]. On the contrary, monolithic and core-mantle structures are also possible for small asteroids [3]. It is, however, still challenging to look through the interior of a target object using remote-sensing devices. In this presentation, we introduce our ongoing research conducted at Seoul National and propose an idea to infer the internal structure of Apophis using available instruments. Itokawa's research provides an important benchmark for Apophis exploration because both asteroids have similar size and composition [4][5]. We have conducted research on Itokawa's evolution in terms of collision and space weathering. Space weathering is the surface alteration process caused by solar wind implantation and micrometeorite bombardment [6]. Meanwhile, resurfacing via a collision acts as a counter-process of space weathering by exposing fresh materials under the matured layer and lower the overall degree of space weathering. Therefore, the balance of these two processes determine the space weathering degrees of the asteroid. We focus on the impact evidence on the boulder surface and found that space weathering progresses in only 100-10,000 years and modifies the surface optical properties (Jin & Ishiguro, KAS 2020 Fall Meeting). It is important to note that the timescale is significantly shorter than the Itokawa's age, suggesting that the asteroid can be totally processed by space weathering. Accordingly, our result triggers a further discussion about why Itokawa indicates a moderately fresh spectrum (Sq-type denotes less matured than S-type). For example, Itokawa's smooth terrains show a weaker degree of space weathering than other S-type asteroids [7]. We conjecture that the global seismic shaking caused by collisions with >1 mm-sized interplanetary dust particles induces granular convection, which hinders the progression of space weathering [8]. Note that the efficiency of seismic wave propagation is strongly dependent on the internal structure of the asteroid. Finally, we consider possible approaches to investigate Apophis's internal structure. The first idea is studying the space weathering age, as conducted for Itokawa. If Apophis indicates a younger age, the internal structure would have more voids [9]. In addition, the 2029 close encounter with Earth provides a rare natural opportunity to witness the contrast between before and after the event. If the asteroid exhibits a slight change in shape and space weathering degree, one can determine the physical structure of the internal materials (e.g., rubble-pile monolithic, thick or thin regolith layer, the cohesion of the materials). We will also consider a possible science using a seismometer.

• Knowledge Management Research
• /
• v.24 no.3
• /
• pp.95-125
• /
• 2023

As the aviation industry has rapidly been grown, there are more factors for customers to consider when choosing an airline. In response, airlines are trying to increase customer value by providing high-quality services and differentiated experiential value. While early customer value research centered on utilitarian value, which is the trade-off between cost and benefit in terms of utility for products and services, the importance of experiential value has recently been emphasized. However, experiential value needs to be studied in a specific context that fully represents customer preferences because what constitutes customer value changes depending on the product or service context. In addition, customer value has an important influence on customers' decision-making, so it is necessary for airlines to accurately understand what constitutes customer value. In this study, we collected customer reviews and ratings from Skytrax, a website specializing in airlines, and utilized the BERTopic technique to derive factors of customer value. The results revealed nine factors that constitute customer value in airlines, and six of them are related to customer satisfaction. This study proposes a new methodology that enables a granular understanding of customer value and provides airlines with specific directions for improving service quality.

• Korean Journal of Remote Sensing
• /
• v.39 no.6_1
• /
• pp.1477-1482
• /
• 2023

This study examines marine heat wave (MHW) in the Northeast Asia region from 2012 to 2021, utilizing geostationary satellite Communication, Ocean, and Meteorological Satellite (COMS)/Meteorological Imager sensor (MI) and GEO-KOMPSAT-2A (GK-2A)/Advanced Meteorological Imager sensor (AMI) Sea Surface Temperature (SST) data. Our analysis has identified an increasing trend in the frequency and intensity of MHW events, especially post-2018, with the year 2020 marked by significantly prolonged and intense events. The statistical validation using Optimal Interpolation (OI) SST data and satellite SST data through T-test assessment confirmed a significant rise in sea surface temperatures, suggesting that these changes are a direct consequence of climate change, rather than random variations. The findings revealed in this study serve the necessity for ongoing monitoring and more granular analysis to inform long-term responses to climate change. As the region is characterized by complex topography and diverse climatic conditions, the insights provided by this research are critical for understanding the localized impacts of global climate dynamics.

• Land and Housing Review
• /
• v.15 no.1
• /
• pp.167-177
• /
• 2024

This study aimed to assess the efficacy of an adsorption process in removing organic matter and micropollutant residuals. After a full-scale water circulation system, the adsorption process was considered a post-treatment step. The system, treating anthropogenically impacted surface waters, comprises a hydro-cyclone, coagulation, flocculation, and dissolved air flotation unit. While the system generally maintained stable and satisfactory effluent quality standards over months, it did not meet the highest standard for organic matter (as determined by chemical oxygen demands). Adsorption experiments utilized two granular activated carbon types, GAC 830 and GCN 830, derived from coal and coconut-shell feedstocks, respectively. The assessment encompassed organic materials along with two notable micropollutants: acetaminophen (APAP) and acid orange 7 (AO7). Adsorption kinetics and isotherm experiments were conducted to determine adsorption rates and maximum adsorption amounts. The quantitative findings derived from pseudo-second-order kinetics and Langmuir isotherm models suggest the effectiveness of the adsorption process. The findings of this study propose the potential of employing the adsorption process as a post-treatment to enhance the treatment of contaminants that are not satisfactorily treated by conventional water circulation systems. This enhancement is crucial for ensuring the sustainability of urban water cycles.

• Economic and Environmental Geology
• /
• v.38 no.6 s.175
• /
• pp.675-687
• /
• 2005

The rocks of the five storied stone pagoda in the Jeongrimsaji temple site are 149 materials in total with porphyritic biotite granodiorite. They include pegmatite veinlet, basic xenolith and evenly developed plagioclase porphyry. This stone pagoda has comparably small fracture and cracks which are farmed in the times of rock properties, but surface exfoliation and granular decomposition are in process actively since the rocks are generally weakened from the influence of air contaminants and acid rain. Structural instability of constituting rocks in the 4th roof materials are observed to occur from distortion and tilt. Such instability is judged to threat stability of the upper part of the stone pagoda. Also, chemical weathering is operating even more as the contaminants, ferro-manganese hydroxides eluted from water-rock interaction on the rock surface. Most of the rock surface is covered with yellowish brown, dark black and light gray contaminants, and especially occur in the lower part of the roof rocks on each floor. The roof underpinning rocks are severe in surface pigmentation from manganese hydroxides and light gray contaminants. The surface of rocks lives bacteria. algae, lichen, or moss and diverse productions in colors of light gray, dark Bray and dark green. Grayish white crustose lichen grows thick on the surface with darkly discolored by fungi and algae in the first stage on basement rocks, and weeds grows wild on the upper part of each roof rocks. This stone pagoda must closely observe the movements of the upper part rock materials through minute safety diagnosis and long term monitoring for structural stability. Especially since the surface discoloration of rocks and pigmentation of secondary contaminants are severe, establishment of general restoration and scientific conservation treatment are necessary through more detailed study for this stone pagoda.