Earticle

Deep eutectic solvent (DES) can be considered a next-generation ionic solvent consisting of a mixture of two or more compounds, one of which is a salt. The formation of new liquid compounds at room temperature is due to the formation of hydrogen bonds between the hydrogen bond donor (HBD) and the hydrogen bond acceptor (HBA), generally the halide anions present in the salt. This DES is a fairly new kind of green solvent that can be applied to various fields, and attracts much attention as an alternative to IL. This study examines the choline chloride-based DES treatment as a new pretreatment for the production of cellulose nanofibers. In the Experiments, deep eutectic solvent systems having lactic acid, urea and glycerin as the second component were formed at 100 °C and then applied to decompose wood-derived cellulose fibers. DES-pretreated fibers were nanofibrillated by mechanical treatment using a blender and their properties were analyzed. Cellulose nanofibrils with a width of 4.7 to 5.4 nm were successfully produced from DES pretreatment under all conditions. As a result, choline chloride-based DES has shown high potential as an environmentally friendly solvent in the production of cellulose nanofibrils.

Once flourished across the Korean Peninsula, Amur leopard (Panthera pardus oritentalis) vanished from South Korea in late 20 century, and only 70 individuals survive in China-Russian border in a brink of extinction. With its ecological and cultural importance, its reintroduction to South Korea has been discussed. However, the reintroduction of large carnivores demands a considerable amount of time, money and human resources with handful successes and thus needs a careful and systematic approach in the planning. In our study, we used the Open Standard for the Practice of Conservation to identify biophysical indicators which help to assess the feasibility of the leopard restoration in South Korea. For the three conservation targets, Amur leopards, leopard prey, and habitat, of the restoration, we selected key ecological attributes for respected targets. Then, we identified one to four indicators for each key ecological attribute and 12 biophysical indicators in total based on the Amur leopard reintroduction program in the Russian Far East. The indicators include the number of breeding females for the population size of the leopards, roe deer density for major prey density, and connectivity for the habitat fragmentation. The viability assessment based on the indicators revealed a good ecological potential of the leopard restoration as well as uncertainties from research gaps. Although not all necessary information is available at this moment, our study provides a good starting point to understand the requirement of Amur leopard restoration in South Korea. Follow-up research is needed to focus on information gaps found during this study.

Recent climate change has led to an increase in the frequency of large-scale wildfires, causing extensive damage and generating substantial quantities of wildfire-damaged wood. While there is growing interest in the efficient utilization of this wood, the majority is currently used as fuel for power generation, a process that shortens its lifecycle and accelerates carbon emissions. In response to this issue, alternative high-value applications for wildfire-damaged wood have been suggested, including the cultivation of medicinal mushrooms, the creation of handicrafts, and its use as timber for wooden structures. However, these approaches typically only employ the non-charred portions of the wood, with the charred sections being removed and discarded. Therefore, this study aims to evaluate the fundamental properties of the charred portions of wildfire-damaged wood and provide foundational data for the development of functional materials from these components.

In this study, a novel zwitterion-decorated lignin (ZL) containing amine and sulfonic acid groups was synthesized and ZL/Nafion composite membranes was fabricated to evaluate its effectiveness as a membrane additive. Kraft lignin was modified using amino-silane and 1,3-propanesultone by continuous grafting reaction to provide zwiterionic moieties structures. Chemical structural analyses confirmed the successful introduction of zwitterion moieties structure onto lignin. Especially, the surface charge of ZL was positive in acidic medium, and negative in basic medium, suggesting that ZL exhibited zwitterionic material. The ZL, an additive, was incorporated with the Nafion to enhance excellent ion exchange capacity and hydrophilicity. The proton conductivity of the ZL/Nafion is slightly lower than that of pure Nafion. On the other hand, it was confirmed that the addition of ZL in Nafion was significantly effective for proton conductivity compared to the addition of unmodified lignin. The reason is that the presence of amine groups in ZL can contribute to good dispersion and the presence of sulfonic acid groups preserves and further improves the continuity of the proton pathway inside the Nafion matrix. In addition, ZL may play a role in enhancing thermal stability, hydrophilicity, ion exchange capacity, and proton conductivity. Therefore, ZL is expected to be utilized as a multifunctional additive and has potential in fuel cell applications.

Flexible and conductive hydrogels play an important role in the design and fabrication of wearable sensors. However, the preparation of high-performance hydrogel-based sensors that can work under extreme cold conditions is still challenging. Herein, we demonstrated the preparation of a novel composite hydrogel based on polyacrylamide (PAM), LiCl, and PEDOT:PSS coated cellulose nanofibrils (PEDOT:PSS/CNF). The introduction of PEDOT:PSS/CNF increased the hydrogen bonding between the molecular chains in the micro and enhanced the mechanical strength and the conductivity of the hydrogel in the macro. Moreover, the presence of LiCl endowed the hydrogel with excellent freezing tolerance. For example, the optimized hydrogel exhibited stable mechanical properties at extreme cold conditions (e.g., −40 ℃). Finally, the composite hydrogel was used to assemble a flexible sensor, which could detect a wide range of human movement and physiological activities in a stable, fast, and accurate manner. Overall, this work provided a simple and universal approach for the preparation of flexible and anti-freezing hydrogels that can be used for flexible electronic devices.

Regional variations in extreme weather events, such as droughts, is expected to increase and they will have significant impacts on forest ecosystem carbon cycles. In particular, the frequency of spring droughts has been increasing in Korea, and the effects of drought on carbon balance in forests may vary depending on the presence of leaves during spring droughts. In this study, a total of 4 years from 2015 to 2018, net ecosystem production (NEP) of evergreen Korean pine (Pinus koraiensis) and nearby oak dominant deciduous forests were examined using eddy-covariance systems. As a result, the intensity of drought at the study site weakened in the order of 2015, 2017, and 2016, and the drought ended in 2018. In deciduous forests, the annual NEP during the growing season was negatively correlated with the intensity of drought (p-value <0.001, R2 = 0.99) and the recovery index was 1.34 ± 0.13. On the other hand in Korean pine forests, the annual NEP in 2017 was the lowest throughout the study period and the recovery index was 1.16 ± 0.10. This caused by severe drought from the fall of 2016 to the spring of 2017, and during this period, the moisture content of the soil of Korean pine stand was lower than that of deciduous broadleaved forest due to the more evaporation and canopy interception during the winter and early spring. In addition, the recovery of NEP after the drought was slower in Korean pine than deciduous forests due to the legacy effect of extreme moisture stress. Our study could provide useful information for sustainable forest management, especially considering the increase of forest damage caused by climate change including drought.

Valuable applications of lignin are restricted by its heterogeneous features such as structural heterogeneity, high polydispersity, complex functional group distribution, solubility and etc. Solvent fractionation of lignin is one of the useful ways to increase its utilization by taking more uniform lignin. In this study, the crude lignin extracted from Quercus mongolica as treated in supercritical water oxidation was subjected to sequential fractionation with four organic solvents and five lignin fractions (F1~F5) were obtained. The yields of five fractions F1, F2, F3, F4, and F5 were 30.6%, 4.3%, 41.7%, 2.0%, and 3.7%, respectively. As fractionation proceeded, the carbon content gradually increased from 57.6% (F2) to 67.0% (F5). In addition, molecular weights and polydispersity (PDI) of fractionated lignins gradually decreased from F2 to F5. However, the content of methoxyl groups tended to be opposite to the molecular weights. The FT-IR spectra of crude lignin and fractionated lignins were very similar. Additional chemical structures of lignin such as phenolic hydroxyl and aliphatic hydroxyl content were investigated by 1H NMR. Moreover, TGA/DSC was conducted to analyze thermal stabilities and degradation behavior of the fractionated lignins.

Paulownia tomentosa is the fastest growth species in south korea and has been used for furniture and musical instruments for very long time due to its low warping excellent abrasion resistance and excellent acoustic properties. However, the basis of such use is qualitative evaluation and experience based guesswork, but there are not many studies that provide specific and quantitative data. Therefore in this study, we evaluated the termite resistance of the paulownia species. In addition, the termites resistance of Populus tomentiglandulosa (dominant species) and Pinus densiflora were evaluated and compared with paulownia. Three species samples were prepared with 1 × 1 × 2cm (L × R × T) size after heat treatment at Control, 160 ° C, 180 ° C, 200 ° C and 220 ° C. 200 worker ants were placed in a bottle containing one piece of wood sample and kept under conditions of 70% relative humidity and 28 ° C for 3 weeks. After 3 weeks, we measured the mortality rate of termites and the weight loss rate of the specimens. As a result, paulownia control sample showed lower weight loss and higher termite mortality than poplar and pine. And heat treatment reduced the resistance of termites.

This study was carried out to provide the effect of the site factor on the growth of Japanese larch(Larix kaempferi), which is one of major coniferous species in Korea. In 2013, in order to find out the growth of Japanese larch, permanent plot established in Eastern, Northern and Southern Region of Korea. The permanent plot investigation was repeated every three years, starting with the first investigation when the site was installed, and the fourth investigation is in progress as of 2022. The investigation was performed to measure tree factor (age of tree, DBH(diameter breast height), total height, clear height, number of tree) and site factor(slope, aspect, elevation). In order to provide the effect of the site factor on the growth of the species, one-way ANOVA was performed by site factor. The slope was classified and analyzed into six categories (slope<15°, 15°slope<20°, 20°slope<25°, 25°slope<30°, 30° slope<40°, 40°slope) and the aspect was classified and analyzed into eight categories (north, northeast, east, southeast, south, southwest, west, northwest). The Elevation was classified and analyzed into six categories (Elevation<200m, 200mElevation<400m, 400mElevation<600m, 600mElevation<800, 800mElevation<1000m, 1000mElevation). As a result to one-way variance of analysis, the DBH was not significantly dfferent according to elevation, aspect and slope(p>0.05). Also, the height was not significantly different according to slope and aspect(p>0.05), whereas the height was significantly different according to elevation (p<0.05).