• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.9-15
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• 2019

Here, we present a facile route to fabricate a vertically stacked 3D porous structure-based triboelectric nanogenerator (TENG) that can be used to harvest energy from the friction in a repetitive contact-separation mode. The unit component of TENG consists of thin Al foil electrodes integrated with microstructured 3D foams such as Ni, Cu, and polyurethane (PU), which provide advantageous tribo-surfaces specifically to increase the friction area to the elastomeric counter contact surfaces (i.e., polydimethylsiloxane, PDMS). The periodic contact/separation-induced triboelectric power generation from a single unit of the 3D porous structure-based TENG was up to $0.74mW/m^2$ under a mild condition. To demonstrate the potential applications of our approach, we applied our TENGs to small-scale devices, operating 48 LEDs and capacitors. We envision that this energy harvesting technology can be expanded to the applications of sustainably operating portable electronic devices in a simple and cost-effective manner by effectively harvesting wasted energy resources from the environment.

• Journal of Wetlands Research
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• v.23 no.3
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• pp.213-223
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• 2021

To understand the sedimentary environment of Scirpus planiculmis habitat (Myeongji and Eulsuk tidal flats) in the Nakdong Estuary, this study analyzed the statistical parameters (sorting, skewness, and kurtosis) of grain size data and the major (Al, Fe, Mn, Mg, Ca, Na, K, Ti, and P), minor (Li, Sc, V, Cr, Co, Ni, Cu, Zn, Sr, Zr, Cs, Pb, Th, and U), and rare earth elements (REEs) in sediment cores. For Myeongji, the sediment structure of the upper part of the cores was poorly sorted, more finely skewed, and more leptokurtic due to construction of the West gate. By contrast, the Eulsuk cores all differed due to the contrasting floodgate operation patterns of the West and East gates. The linear discriminate function (LDF) results corresponded to the statistical parameters for grain size. At the Eulsuk tidal flat (sites ES05 and ES11), elemental distributions were representative of Al-, Fe- and Ca-associated profiles, in which the elements are largely controlled by the accumulation of their host minerals (such as Na- and K-aluminosilicate and ferromagnesium silicate) and heavy detrital minerals at the sites. Detrital minerals including the aluminosilicates are major factors in the elemental compositions at ES05, diluting the REE contents. However, clay minerals and Fe-oxyhydroxides, as well as REE-enriched heavy minerals, appeared to be controlling factors of the elemental composition at ES11. Therefore, the mineral fractionation process is important in determining the elemental composition during sedimentation, which reflects the depositional condition of riverine-saline water mixing at both sites.

• Clean Technology
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• v.28 no.4
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• pp.323-330
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• 2022

Microfluidic paper-based analytical devices (μPADs) have recently been in the spotlight for their applicability in point-of-care diagnostics and environmental material detection. This study presents a double-sided printing method for fabricating 3D-μPADs, providing simple and cost effective metal ion detection. The design of the 3D-μPAD was made into an acryl stamp by laser cutting and then coating it with a thin layer of PDMS using the spin-coating method. This fabricated stamp was used to form the 3D structure of the hydrophobic barrier through a double-sided contact printing method. The fabrication of the 3D hydrophobic barrier within a single sheet was optimized by controlling the spin-coating rate, reagent ratio and contacting time. The optimal conditions were found by analyzing the area change of the PDMS hydrophobic barrier and hydrophilic channel using ink with chromatography paper. Using the fabricated 3D-μPAD under optimized conditions, Ni²⁺, Cu²⁺, Hg²⁺, and pH were detected at different concentrations and displayed with color intensity in grayscale for quantitative analysis using ImageJ. This study demonstrated that a 3D-μPAD biosensor can be applied to detect metal ions without special analysis equipment. This 3D-μPAD provides a highly portable and rapid on-site monitoring platform for detecting multiple heavy metal ions with extremely high repeatability, which is useful for resource-limited areas and developing countries.

• Fisheries and Aquatic Sciences
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• v.25 no.12
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• pp.626-636
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• 2022

Shellfish are exoskeleton-bearing aquatic invertebrates that consume various organic and inorganic substances floating in seawater through filter feeding. Heavy metals are known as absorbed and accumulated in seawater. Some of the toxic heavy metals are highly accumulated in seawater, and exposure to them can cause a variety of risks to the human body. Since Koreans like to eat seafood, they are more likely to be exposed to contaminated seafood with heavy metals. In this study, nine types of heavy metals were analyzed on ten different shellfish species in the coastal area of South Korea. The risk assessment was also done on shellfish in which heavy metals were detected. Zinc (Zn) and copper (Cu) were identified at an average of 56.7 mg/kg (6.70 to 466 mg/kg) and 13.2 mg/kg (0.064 to 143 mg/kg), respectively. Lead (Pb) average of 0.208 mg/kg (0.000750 to 1.02 mg/kg), cadmium (Cd) average of 0.454 mg/kg (0.0388 to 1.56 mg/kg) and mercury (Hg) average of 0.0266 mg/kg (0.00548 to 0.174 mg/kg) were identified. Additionally, arsenic (As), chromium (Cr), nickel (Ni), and silver (Ag) were also identified as average concentrations of 4.02 (0.460 to 15.0 mg/kg), 0.167 (< limit of quantification [LOQ] to 0.820 mg/kg), 0.281 (< LOQ to 1.46 mg/kg), and 0.158 mg/kg (< LOQ to 1.15 mg/kg). The result indicates that the monitoring results of heavy metals in most shellfish satisfied the Korean standard. However, Pb and Cd have exceeded some foreign standards, such as the United States and the EU. The permissible human exposure calculated using the heavy metal intake and detection amount was lower than the Joint FAO/WHO Expert Committee on Food Additives human safety standard, and the risk of heavy metals from shellfish consumption was at an acceptable level.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.799-816
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• 2023

Mineralogical and geochemical studies of shales within the Lower Anambra Basin was conducted to unravel the depositional environment, provenance, maturity, paleo-weathering conditions, and tectonic settings. Mineralogical studies conducted using X-ray diffraction analysis revealed that the samples were composed of kaolinite, montmorillonite, chlorite, and illite. KaolinIite is the dominant mineral, constituting approximately 41.5% of the bulk composition, whereas the non-clay minerals are quartz, ilmenite, and sillimanite. Geochemical analysis showed a predominance of SiO₂, Al₂O₃, and Fe₂O₃ contents of the shale samples with mean values of 52.29%, 14.09%, and 6.15% for Imo Shale (IS); 52.31%, 16.70%, and 7.39% for Mamu Shale (MS); 43.21%, 21.33%, and 10.36% for Enugu Shale (ES); 53.35%, 15.64%, and 7.17% for Nkporo Shale (NS); and 51.24%, 17.25%, and 7.78% for Agwu Shale (AS). However, the shales were depleted in Na₂O, MgO, K₂O, MnO, TiO₂, CaO, and P₂O₅. The trace element ratios of Ni/Co and Cu/Zn of the shale suggest an oxic depositional environment. The average SiO₂ vs. Al₂O₃ ratio of the shales indicated textural maturity. Compared to the PAAS standard, the shales plot below the PAAS value of 0.85, suggesting a high degree of maturity and intensive chemical weathering, further confirmed on a CIA vs. PIA plot. On log (K₂O/Na₂O) against SiO₂ and tectonic setting discriminant function diagrams, the shales plot mostly in the field of passive continental margin tectonic setting. The discriminant function diagrams as well as Al₂O₃/TiO₂ ratio of the shales showed that they were derived from a mixed source (mafic and intermediate igneous rocks).

• Molecules and Cells
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• v.46 no.9
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• pp.545-557
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• 2023

Sphingomyelinase (SMase) catalyzes ceramide production from sphingomyelin. Ceramides are critical in cellular responses such as apoptosis. They enhance mitochondrial outer membrane permeabilization (MOMP) through self-assembly in the mitochondrial outer membrane to form channels that release cytochrome c from intermembrane space (IMS) into the cytosol, triggering caspase-9 activation. However, the SMase involved in MOMP is yet to be identified. Here, we identified a mitochondrial Mg²⁺-independent SMase (mt-iSMase) from rat brain, which was purified 6,130-fold using a Percoll gradient, pulled down with biotinylated sphingomyelin, and subjected to Mono Q anion exchange. A single peak of mt-iSMase activity was eluted at a molecular mass of approximately 65 kDa using Superose 6 gel filtration. The purified enzyme showed optimal activity at pH of 6.5 and was inhibited by dithiothreitol and Mg²⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Fe²⁺, and Fe³⁺ ions. It was also inhibited by GW4869, which is a non-competitive inhibitor of Mg²⁺-dependent neutral SMase 2 (encoded by SMPD3), that protects against cytochrome c release-mediated cell death. Subfractionation experiments showed that mt-iSMase localizes in the IMS of the mitochondria, implying that mt-iSMase may play a critical role in generating ceramides for MOMP, cytochrome c release, and apoptosis. These data suggest that the purified enzyme in this study is a novel SMase.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.27 no.3
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• pp.45-56
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• 2024

Heavy metals emitted from urban development do not decompose in the soil and remain for long periods, continually impacting the environment. Since the mid-1990s, there has been increasing societal concern in South Korea regarding soil contamination, prompting various legislative revisions to reduce pollution. This study utilizes the Environmental Impact Assessment Support System (EIASS) to investigate projects in the metropolitan area that have exceeded the Ministry of Environment's soil contamination concern levels from 1989 to 2022 and to examine improvements in the environmental impact assessment (EIA) process. The results reveal that the average concentrations of nine contaminants-cadmium (Cd), copper (Cu), arsenic (As), mercury (Hg), lead (Pb), hexavalent chromium (Cr6+), zinc (Zn), nickel (Ni), and fluoride (F)-have all increased over the years. Among these, Zn had the highest relative proportion, with 37.5% of the 40 sites exceeding environmental concern levels. Investigation of 19 specific projects at these exceedance sites showed that only 7 had documented analyses of contamination causes and remediation plans, and just one had contracted additional remediation services, though results from these efforts were found to be lacking. Furthermore, since 2019, a significant proportion of these sites were involved in residential developments, likely due to government initiatives in new city development and extensive housing supply plans. This research emphasizes the importance of public disclosure of the processes and outcomes of remediation efforts on historically contaminated soils prior to project development. It discusses improvements to the EIA by reviewing current legislation and international examples. The findings of this study are expected to heighten public awareness about heavy metal contamination and enhance transparency in soil remediation efforts, contributing to sustainable environmental management and development.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.1
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• pp.51-56
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• 2007

The toxicities of contaminated soils with 8 consecutive year applications of three levels (12.5, 25.0, and $50.0t\;dry\;matter\;ha^{-1}yr^{-1}$) of four organic sludge [municipal sewage sludge (MSS), industrial sewage sludge (ISS), alcohol fermentation processing sludge (AFPS) and leather processing sludge (LPS)] on earthworm (Eisenia fetida) were examined by using microcosm container in the laboratory. Results were compared with those of pig manure compost (PMC) treated soil. In tests with three treatment levels (12.5, 25.0, and 50.0 t per plot), ISS treated soil showed higher contents of Cu (18.9~26.2 fold), Cr (7.7~34.7 fold), and Ni (14.8~18.8 fold) at 8 years post treatment, than PMC treated soil. LPS treated soil showed higher contents of Cr (35.7~268.0 fold) and Ni (4.5~7.6 fold) than PMC treated soil. There were no great differences in heavy metal contents among MSS, AFPS, and PMC treated soils. In these contaminated soils, earthworm mortalities of MSS and AFPS treated soils at 8 weeks post-exposure were similar to those of PMC treated soil regardless of each treatment level. Toxic effect (26.7~96.7 mortality) on the ISS and LPS treated soils was significantly higher than one of PMC treated soil, with an exception of LPS soil treated with 25.0 t per plot. At 16 weeks post-exposure, earthworm mortalities of AFPS' 12.5 and 25.0 t treated soils were similar to those of PMC treated soil. Toxic effect (53.3~100 mortality) on the 12.5, 25.0, and 50.0 t treated soils of MSS, ISS and LPS, and AFPS' 50.0 t treated soils was significantly higher than those of PMC treated soil. The data suggested that the 12.5, 25.0, and 50.0 t of MSS, ISS and LPS, and AFPS' 50.0 t treated soils were evaluated to have toxicity on earthworm.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.2
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• pp.189-196
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• 1998

Swage sludge cakes produced from domestic wastewater treatment plants were collected from 21 different sites throughout Korea, and chemical properties of the sludge samples were determined. Inorganic nutrient contents did not indicate great differences among swage sludges from each sites, whereas the toxic heavy metal contents differed greatly. T-N, $NH_4{^+}-N$ and $NO_3{^-}-N$ contents from 21 sites sludges ranged 2.3-6.0, 291-4284, $1.4-58.8mg\;kg^{-1}$, respectively. Heavy metal (Cd, Cu, Pb and Zn) contents ranged 2.86-58.22, 144.0-5417.3, N.D.-943.5, and $N.D.-8,083mg\;kg^{-1}$, respectively. One of the sludges was treated to soils at rates of 12.5, 25, 50. and 100, $Mg\;ha^{-1}$ and incubated for 12 weeks to determine nitrogen materialization rate. Ammoniun nitrogen content decreased sharply at higher rates of sludge treatment up to 8 weeks after treatment and did not change much, while $NO_3{^-}$ increased at all treatment levels. The net amount of mineralized N of sludge treatment rates (12.5, 25, 50, and $100Mg\;ha^{-1}$) during 12weeks incubation were 189.0, 277.2, 303.8 and $376.6mg\;kg^{-1}$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.1
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• pp.129-135
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• 2012

This study was to investigate the heavy metal content of 55 commercial salts in the Seoul area. There were 22 types of solar sea salt, 17 types of processed salt and 16 types of reworked salt. Looked at another way, there were 22 types of domestic salt and 33 types of salt imported from France, the U.S., Japan, Australia, New Zealand, and Argentina. The samples were measured using both a mercury analyzer and an Inductively-Coupled Plasma Optical Emission Spectrometer (ICP-OES). The average heavy metal contents for commercial salts were Pb $0.281{\pm}0.344$, Cd $0.035{\pm}0.221$, Cr $0.364{\pm}0.635$, Cu $0.182{\pm}0.313$, As $0.046{\pm}0.062$, Ni $0.155{\pm}0.247$, Al $5.753{\pm}10.746$, Co $0.028{\pm}0.211$ and Hg $0.001{\pm}0.001$ mg/kg. The leads were detected highly in solar sea salt rather than in processed salt or reworked salt. Also chrome, arsenic and nickel were found more in processed salt. There were large differences in aluminum content between imported solar sea salt and processed salt. Aluminum was highly detected in French products, showing that salt can be affected by regional differences. The weekly average intakes of Pb, Cd, Cr, Cu, and Hg from commercial salt were 1.652% (0.000~6.754), 0.372% (0.000~7.214), 3.177% (0.000~26.279), 0.008% (0.001~0.049), and 0.031% (0.000~0.094) respectively compared with Provisional Tolerable Weekly Intakes established by the Joint FAO/WHO Expert Committee for the evaluation of food safety. The content of heavy metals from commercial salts was determined to be at safe levels.