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It is crucial to evaluate the effects of thinning on litterfall production, soil chemical properties, and fine root dynamics when implementing thinning as a silvilcultural technique to enhance tree growth and timber yield in Pinus koraiensis plantations. Thus, we determined the 10-year effects (2007–2017) of different thinning intensities on litterfall production, soil chemical properties, and fine root biomass and necromass within a P. koraiensis plantation in South Korea. The soil chemical parameters and fine root biomass and necromass were also compared across three soil depths (0–10, 10–20, and 20–30 cm). Three thinning treatments were employed: no thinning (CON), light thinning (32% removed, LT), and heavy thinning (64% removed, HT). Results revealed that litterfall was consistent across all thinning treatments, but broadleaf species had considerably higher litterfall production at HT stands than at CON/LT stands. Soil chemical properties, except exchangeable K+, were generally lower at LT stands, particularly at a depth of 20–30 cm soil. After ten years, there was a decrease in fine root biomass and necromass with increasing soil depth. Over 80% of fine roots were found in the upper layer (0–20 cm), while very fine roots (0–1 mm) consisted mainly of 47% pine and 53% other species and were concentrated in the 0–10 cm soil depth in HT. In conclusion, different thinning intensities had diverse effects on the parameters measured within the plantation. Future studies can explore how the effects of thinning intensities on litterfall production, soil chemistry, and fine root dynamics affect species diversity, carbon storage, and understory vegetation in P. koraiensis plantations. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate chemical-physical properties and apatite-forming ability of recently introduced premixed bioceramic sealers for endodontics. An epoxy-resin based was used as control. Three different premixed bioceramic sealers were used: Ceraseal (Meta Biomed Cheong-si, South Korea) NeoSealer Flo, (Avalon Nusmile, Houston, TX, USA) AH plus Bioceramic (Maruchi, Wonju-si, South Korea). An epoxy-resin based sealer (AH Plus Densply, DeTrey, Konstanz, Germany) was used as control. The chemical (calcium release, alkalising activity) and physical (radiopacity, initial and final setting times, solubility, apparent porosity, water adsorption, flowability, film thickness) properties were analyzed following ISO guidelines. The nucleation of calcium phosphates and/or apatite after 28 days aging was evaluated by ESEM-EDX and micro-Raman spectroscopy. Final setting time was higher for NeoSealer Flo, while AH Plus Bioceramic and Ceraseal showed the lowest values. Radiopacity, flowability and film thickness complied with ISO 6876/12 for all tested materials, AH Plus Bioceramic showed the highest values when compared to NeoSealer Flo and Ceraseal. Ceraseal and AH Plus revealed the lowest solubility while markedly higher values were observed for NeoSealer and AH Plus Bioceramic (p<0.05). All three bioceramic sealers revealed markedly higher water adsorption and apparent porosity values when compared to AH Plus (p<0.05). These sealers were able to leach Ca and to alkalinize the soaking water. AH Plus did not release calcium and provided slight acidification of soaking water. ESEM-EDX analyses after immersion in HBSS revealed a different surface morphology on the three compositions. A mineral layer covered the surface of the sealer, with a subsequent lower detection of the elements used as radiopacifier (Zirconium for Ceraseal and AH Plus Bioceramic, Tantalum for NeoSealer Flo) and an increase of Calcium, Phosphorous and Carbon. Micro-Raman revealed that the layer was mostly composed of calcium phosphates (b-type carbonated apatite) and calcium carbonate (calcite and aragonite), the thickness varied on the basis of the premixed bioceramic. This layer was not observed on AH Plus. Premixed bioceramic sealers met the required chemical and physical standards and released biologically relevant ions. These materials were able to nucleate apatite and calcium carbonate on their surface. [ABSTRACT FROM AUTHOR]

It is crucial for understanding the characteristics of fly ash, emitted from the incinerator of municipal solid waste, to properly diagnose its impact on air quality and human health. In this study, to precisely describe the chemical property of the fly ash and its effects on near ambient particles, an intensive measurement was conducted. Fly ash was collected in dry condition from the downstream of a bag filter dust collector which is installed at an incinerator located in Iksan City, Korea. Sampling of ambient particles was carried out at both near and far away sites from an incinerator. Elemental analyses of the pretreated samples were subsequently performed by a Particle Induced X-ray Emission (PIXE) and a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray Detector (EDX). Moreover, in order to estimate the residents' exposure to the fly ash and the effect of fly ash on the near ambient particles, Gaussian plume model was carried out. The high content of soluble S, Cl, K, and Ca in fly ash were detected. Small quantities of heavy elements including Zn, Br, and Pb were also detected in the water-soluble fraction. The scattering plots drawn by the ratios of Z/Zn (i.e., the ratio of mass concentration of each element (Z) to that of zinc) of ambient PM2.5 and that of fly ash reveal a good relationship regardless of the distance from an incinerator. A ternary plot drawn by the wt% concentrations of Na, K, and Cl in the individual ambient particles and fly ash powders indicates that a small portion of the fine and coarse ambient particles was directly influenced by the fly ashes. Modeling evaluation of fly ash diffusion suggests that the air quality at the incinerator nearby areas, especially 1.5 km points, was strongly influenced by the air pollution materials emitted from an incinerator. [ABSTRACT FROM AUTHOR]

The article presents a study concerning the effectiveness of composted oyster shell compared to fresh oyster shell as lime fertilizer in soybean cultivation in South Korea. The study involves the observation in the physio-chemical changes in oyster through atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM). It shows that composted oyster shell is more effective than fresh oyster shell as lime fertilizer due to the higher yield of soybean obtained.

Based on water chemistry data, a rockfill dam in South Korea was investigated to identify major parts of substantial dam water leakage. Sinkholes in the dam crest and abnormal water leakage through the dam were observed since the first impounding of the dam. Previous investigations, including observational drillings, hydraulic tests, geophysical surveys, and tracer tests, revealed the development of a high permeability zone in the clay core and an abnormally high phreatic line zone in the left embankment. Sequential tracer tests provided further evidence of locations of preference and rapid water leakage pathways. In this study, we examined the usefulness of water chemistry data to confirm previous findings of water leakage. Factor analysis of the water chemistry data revealed major processes controlling the chemical composition, which include the wash-out and successive dissolution of fill materials in the dam interior, interaction between percolating water and dam core materials, and contamination of seeping water by grouting materials and previous tracer tests. Distinct spatial distribution of similar chemical groups was illustrated by cluster analysis and confirmed the location of major water leakage at the left abutment adjoining the spillway. [ABSTRACT FROM AUTHOR]

South Korea is one of the largest consumers of flame-retardants worldwide. In this study, water, sediment, and biota samples were collected from a highly industrialized lake to investigate contamination, isomeric profiles, source, and the bioaccumulation potential of hexabromocyclododecanes (HBCDDs). Almost all of the sediments were severely contaminated by HBCDDs, which were some of the highest global levels compared to those found in previous studies. The highest concentrations and similar profiles to those of technical mixtures of HBCDDs were observed in creeks passing through industrial complexes, indicating on-going contamination by high consumption of HBCDDs from industrial activities. γ -HBCDD was dominant in water and sediment, whereas α -HBCDD was dominant in fish and shellfish. The diastereoisomeric profiles of HBCDDs in multiple matrices were influenced by proximity to industry and chemical properties. In-situ biota-sediment accumulation factors of α -HBCDDs were > 1 in benthic species, implying that HBCDDs are of great concern in sedimentary environments. • HBCDD isomers were detectable in multiple matrices from an industrialized lake. • Severe HBCDD contamination was identified in creeks near industrialized complexes. • Different diastereoisomeric distributions were observed in multiple matrices. • Diastereoisomeric HBCDD profiles were governed by sources and chemical properties. • In-situ BSAFs of α -HBCDD exceeded 1 for benthic species. [ABSTRACT FROM AUTHOR]

This paper reviews the scientific literature concerning urushi lacquers. Urushi has been used by skilled lacquer artists for thousands of years, predominantly in the East Asian countries of Japan, Korea and China, where there is an abundance of urushi-producing trees. Spectacular lacquered artefacts still exist due to the stability of the material, and numerous conservation efforts endeavour to preserve these pieces. This review discusses the chemical properties of this complex material, with particular reference to its stability and durability, and the conditions that contribute to its deterioration. The importance of understanding these properties is discussed with regard to the conservation of urushi-based objects. [ABSTRACT FROM AUTHOR]

Compared to the bottom ash obtained by a water-cooling system (wBA), dry process bottom ash (dBA) makes hardly any unburnt carbon because of its stay time at the bottom of the boiler and contains less chloride because there is no contact with seawater. Accordingly, to identify the chemical stability of dBA as a lightweight aggregate for construction purposes, the chemical properties of dBA were evaluated through the following process of the reviewing engineering properties of a lightweight aggregate (LWA). Typically, river gravel and crushed gravel have been used as coarse aggregates due to their physical and chemical stability. The coal ash and LWA, however, have a variety of chemical compositions, and they have specific chemical properties including SO3, unburnt coal and heavy metal content. As the minimum requirement to use the coal ash and lightweight aggregate with various chemical properties for concrete aggregate, the loss on ignition, the SO3 content and the amount of chloride should be examined, and it is also necessary to examine heavy metal leaching even though it is not included in the standard specifications in Korea. Based on the results, it is believed that there are no significant physical and chemical problems using dBA as a lightweight aggregate for concrete. [ABSTRACT FROM AUTHOR]

Aerosols that are transported long distances to the Korean Peninsula due to seasonal weather conditions can affect the local air quality of South Korea. In general, the long-range transported aerosols are widely distributed and variable with respect to time and space. In this aspect, geostationary satellites can be used as a powerful tool for providing temporal and spatial variation of aerosols by sequentially observing a target area. In this study, select events of high-concentration aerosols transported to Seoul, the capital of South Korea, were identified and analyzed using aerosol optical properties retrieved from geostationary ocean color imager (GOCI) for the cold season (October–March) from 2015 to 2018. In addition to the satellite data, ground-based observations of particulate matter (PM) and backward trajectory models were used. Based on the trajectories of air masses simulated with the backward trajectory models, events of the long-range transported high-concentration aerosols (hereafter referred to as "LRT events") were selected and classified into three types: yellow dust, PM traversing over the Yellow Sea (PM-YS), and PM passing through North Korea (PM-NK). Optical and chemical properties of the three LRT events were analyzed, and significantly different features were found. Yellow dust showed a relatively high mean depolarization ratio at 1020 nm (0.26), a low Ångström exponent between 440 nm and 870 nm (0.27), fine mode fraction at 500 nm (0.26), single scattering albedo at 440 nm (0.93), and lidar ratio at 675 nm (37 sr) compared with those during the other PM events. Moreover, the proportions of Ca+ concentrations to the water-soluble ions in PM 2.5 and concentrations of Ca and Fe among inorganic elements in PM 2.5 significantly increased during the yellow dust event. On the contrary, the PM events (PM-YS and PM-NK) had relatively high mean Ångström exponent (1.28 and 1.38), fine mode fraction (0.94 and 0.81), single scattering albedo (0.96 and 0.94), lidar ratio (66 sr and 44 sr), and low depolarization ratios (0.035 and 0.066). The ratios of NO 3 − and SO 4 2− to water-soluble ions in PM 2.5 were significantly increased during the high PM events. By comparing the two PM events, the volume median radius of fine mode particles and fine mode fraction of PM-YS were found to be considerably higher compared with those of PM-NK. Such different characteristics found in this study for the three LRT events indicate that optical and chemical analyses of aerosols using satellite and ground-based observations can give us the possibility of roughly identifying aerosol types (yellow dust or PM) and trajectories (passing through the Yellow Sea or North Korea). • Long-range transported (LRT) aerosols to South Korea were detected and classified. • Significantly different optical and chemical properties of aerosols were found depending on the LRT events. • An analysis of optical and chemical properties of aerosols can be used to investigate their types and trajectories. [ABSTRACT FROM AUTHOR]

Denitrification is a major biological source or sink of N 2 O, an important greenhouse gas, which is a multi-step respiratory process that converts nitrate (NO 3 −) to gaseous forms of nitrogen (N 2 or N 2 O). In aquatic ecosystems, the residence time and flow length within the streambed can modulate denitrification, which is highly affected by micro-topography of streambed. For the reason, various restoration projects targeting streams and rivers incorporate the installment of dune-shaped streambed, but its role in ecosystem functions and key controlling variables are still elusive. In this study, N 2 O fluxes according to streambed micro-topography were measured at four locations in two streams with dune-shaped streambeds in Korea. We found that micro-topographical variations influenced N 2 O fluxes, chemical properties, and denitrifier abundances, but that this effect was highly constrained by carbon availability. In sites with relatively higher DOC, N 2 O fluxes increased along the flow direction, and the highest flux of each site (19.1 ± 5.67 μg N 2 O-N m−2 h−1 and 16.2 ± 0.896 μg N 2 O-N m−2 h−1, respectively) was observed in the slope on the back side of the dune, followed by decreases afterward. In contrast, streams with low DOC concentration did not exhibit micro-topographical variations. This study suggests that the presence of small dunes in streams can substantially enhance N 2 O fluxes when carbon availability was appropriate. The variations of N 2 O flux highlight the importance of micro-topography and DOC concentration of sediment for the accurate estimation of uncertainty of N 2 O flux. This has further implication for stream restoration where installment or management of dune-shaped streambed is of importance in the removal of inorganic N in water. • Micro-topography affected N 2 O flux, which is intermediate product of denitrification. • Abundances of denitirfier were substantially influenced by micro-topography in stream. • Carbon availability is a key controlling factor of the effects of micro-topography. [ABSTRACT FROM AUTHOR]