Impacts of an extreme flood event on the riparian vegetation of a monsoonal cobble-bed stream in southern Korea: A multiscale fluvial biogeomorphic framework

© 2022 John Wiley & Sons Ltd.With climate change increasing the magnitude and frequency of extreme precipitation events, there is a growing demand for investigations on the impacts of extreme flooding on the hydrological characteristics and vegetation of rivers, particularly in monsoonal areas. In this study, we examined multiscale relationships between hydrology, vegetation, and geomorphology after a record-breaking flood event along the Seomjin River of South Korea in the summer of 2020. We conducted numerical modeling at the broad scale to identify the flow characteristics (e.g., depth and shear stress) of the flood event. A field survey was performed to investigate the impact of the flood on individual plants at the fine scale. The results showed widespread devastation of all vegetation types, from reed and willow communities to large, late-successional trees taller than 10 m, which typically survive under ordinary flooding conditions. A higher threshold of shear stress was estimated for these trees (124 N m−2) than for willow (120 N m−2) and reed plants (26 N m−2), indicating that a greater level of stress is required to cause vegetation damage as ecological succession progresses. In the presence of vegetation, the average water depth increased by 9%–23% compared to the absence of vegetation. Many rivers in northeast Asia have undergone substantial vegetation expansion and succession due to the infrequency of extreme flood events. Our findings indicate that dense communities of large plants in these systems can raise the maximum water levels of flood events, thereby increasing the future flood risk to surrounding areas utilized for agriculture, transportation, industry, and housing.N

Biodistribution and toxicity of spherical aluminum oxide nanoparticles

With the rapid development of the nano-industry, concerns about their potential adverse health effects have been raised. Thus, ranking accurately their toxicity and prioritizing for in vivo testing through in vitro toxicity test is needed. In this study, we used three types of synthesized aluminum oxide nanoparticles (AlONPs): gamma-aluminum oxide hydroxide nanoparticles (gamma-AlOHNPs), gamma- and alpha-AlONPs. All three AlONPs were spherical, and the surface area was the greatest for gamma-AlONPs, followed by the alpha-AlONPs and gamma-AlOHNPs. In mice, gamma-AlOHNPs accumulated the most 24 h after a single oral dose. Additionally, the decreased number of white blood cells (WBC), the increased ratio of neutrophils and the enhanced secretion of interleukin (IL)-8 were observed in the blood of mice dosed with gamma-AlOHNPs (10 mg kg(-1)). We also compared their toxicity using four different in vitro test methods using six cell lines, which were derived from their potential target organs, BEAS-2B (lung), Chang (liver), HACAT (skin), H9C2 (heart), T98G (brain) and HEK-293 (kidney). The results showed gamma-AlOHNPs induced the greatest toxicity. Moreover, separation of particles was observed in a transmission electron microscope (TEM) image of cells treated with gamma-AlOHNPs, but not gamma-AlONPs or alpha-AlONPs. In conclusion, our results suggest that the accumulation and toxicity of AlONPs are stronger in gamma-AlOHNPs compared with gamma-AlONPs and alpha-AlONPs owing their low stability within biological system, and the presence of hydroxyl group may be an important factor in determining the distribution and toxicity of spherical AlONPs. Copyright (C) 2015 John Wiley & Sons, Ltd

Time-dependent bioaccumulation of distinct rod-type TiO2 nanoparticles: Comparison by crystalline phase

A complete understanding of the interaction between nanoparticles and biological systems, including nanoparticle uptake and distribution and the biological responses, could guide the design of safer and more effective nanoparticles than those currently available. In this study, we compared the distribution in mice over time of two rod-type titanium dioxide nanoparticles (TiNPs) that feature distinct phases, anatase (ATO) and brookite (BTO). Surface areas of BTO and ATO were estimated to be 102 and 268m(2)g(-1), respectively, and negative charge on the surface of ATO was higher than that of BTO in deionized water. Both TiNPs were rapidly distributed into tissues after injection. At 4weeks after injection, both TiNPs were maximally accumulated in the spleen, followed by the liver, but the total accumulation of ATO in tissues measured in this study was more than that of BTO. Moreover, the cellular antioxidant function was similar although the levels of Ti measured in tissues were distinct between the two TiNPs. Based on these results, we suggest that the fate of TiNPs in the body may differ according to the size and surface charge of the TiNPs even when their shape is the same. Copyright (c) 2014 John Wiley & Sons, Ltd

A 13-week repeated-dose oral toxicity and bioaccumulation of aluminum oxide nanoparticles in mice

Because of an increase in the commercial applications of manufactured nanoparticles, the issue of potential adverse health effects of nanoparticles following intended or unintended exposure is rapidly gaining attention. In this study, we evaluated the toxicity of aluminum oxide nanoparticles (AlNPs, rod-type, 1.5, 3, and 6 mg/kg) after oral administration to mice for 13 weeks. Compared with the control group, the consumption of diet and drinking water and body weight gain decreased in the group treated with AlNPs. The group treated with 6 mg/kg AlNPs also showed a marked elevation in the count of white blood cells that associated with a significant decrease and increase to the proportion of eosinophils and lymphocytes, respectively. In addition, the secretion of IL-6 and monocyte chemotactic protein-1 increased in a dose-dependent manner in the treated groups. Furthermore, AlNPs showed the highest accumulation in the liver and kidneys compared with the control group, increased the lactate dehydrogenase level in the blood, and induced the development of a pathological lesion in the liver and kidneys. Taken together, we suggest that the target organs of rod-type AlNPs may be the liver, kidneys and the immune system, and the not-observed adverse effect level may be lower than 6 mg/kg

An electrochemical approach to graphene oxide coated sulfur for long cycle life

Owing to the possibilities of achieving high theoretical energy density and gravimetric capacity, sulfur has been considered as a promising cathode material for rechargeable lithium batteries. However, sulfur shows rapid capacity fading due to the irreversible loss of soluble polysulfides and the decrease in active sites needed for conducting agents. Furthermore, the low electrical conductivity of sulfur hampers the full utilization of active materials. Here we report that graphene oxide coated sulfur composites (GO-S/CB) exhibit improved electrochemical stability as well as enhanced rate performance, evidenced by various electrochemical analyses. The cyclic voltammetry and the galvanostatic cycling analysis revealed that the GO plays key roles in homogenizing the nanocomposite structures of the electrodes, in improving the electrochemical contact, and in minimizing the loss of soluble polysulfide intermediates. An electrochemical impedance spectroscopy analysis also confirms the enhanced structural stability of the GO-S/CB composites after battery operation. As a result, the GO-S/CB exhibited excellent cycle stability and specific capacity as high as similar to 723.7 mA h g(-1) even after 100 cycles at 0.5 C

Toxic response of HIPCO single-walled carbon nanotubes in mice and RAW264.7 macrophage cells

In this study, we identified the toxic response of pristine single-walled carbon nanotubes (P-SWCNTs) synthesized by HIPCO method in mice and RAW264.7 cells, a murine peritoneal macrophage cell line. P-SWCNT contained a large amount of Fe ion (36 wt%). In the lungs of mice 24 h after intratracheal administration, P-SWCNTs increased the secretion of IL-6 and MCP-1, and the number of total cells, the portion of neutrophils, lymphocytes, and eosinophils, also significantly increased at a 100 mg/mL of concentration. In RAW264.7 cells, cell viability and ATP production decreased in a dose-dependent manner at 24 h after exposure, whereas the generations of ROS and NO were enhanced at all concentrations together with the activation of the MAP kinase pathway. Moreover, the levels of both apoptosis-and autophagy-related proteins and ER stress-related proteins clearly increased, and the concentrations of Fe, Cu, and Zn ions, but not of Mn ions, increased in a dose-dependent manner. TEM images also revealed that P-SWCNTs induced the formation of autophagosome-like vacuoles, the dilatation of the ER, the generation of mitochondrial flocculent densities, and the separation of organelle by disappearance of the cell membrane. Taken together, we suggest that P-SWCNTs cause acute inflammatory response in the lungs of mice, and induce autophagy accompanied with apoptosis through mitochondrial dysfunction and ER stress in RAW264.7 cells. Furthermore, further study is required to elucidate how the physicochemical properties of SWCNTs determine the cell death pathway and an immune response. (C) 2014 Elsevier Ireland Ltd. All rights reserved