Objectives: This analysis seeks to evaluate the impact of environmental health factors (EHF; e.g. hospital beds per capita, employees of medical institutions) on extreme-heat vulnerability assessment in Busan Metropolitan City during 2006-2010. Methods: According to the vulnerability concept suggested by the Intergovernmental Panel on Climate Change (IPCC), extreme-heat vulnerability is comprised of the categories of Exposure, Sensitivity, and Adaptive Capacity (including EHF). The indexes of the Exposure and Sensitivity categories indicate positive effects, while the Adaptive capacity index indicates a negative effect on extreme-heat vulnerability. Variables of each category were standardized by the re-scaling method, and then each regional relative vulnerability was computed with the vulnerability index calculation formula. Results: The extreme-heat vulnerability index (EVI) excepting EHF was much higher in urban areas than in suburban areas within the metropolitan area. When EHF was considered, the difference in the EVI between the two areas was reduced due to the increase of the Adaptive capacity index in urban areas. The low EVI in suburban areas was induced by a dominant effect of natural environmental factors (e.g. green area) within the Adaptive capacity category. Conclusions: To reduce the vulnerability to extreme heat in urban areas, which were more frequently exposed to extreme heat than others areas, public health and natural environments need to be improved in sensitive areas.
Abstract Noble gases possess extremely low reactivity because their valence shells are closed. However, previous studies have suggested that these gases can form molecules when they combine with other elements with high electron affinity, such as fluorine. Radon is a naturally occurring radioactive noble gas, and the formation of radon-fluorine molecules is of significant interest owing to its potential application in future technologies that address environmental radioactivity. Nevertheless, because all isotopes of radon are radioactive and the longest radon half-life is only 3.82 days, experiments on radon chemistry have been limited. Here, we study the formation of radon molecules using first-principles calculations; additionally, possible compositions of radon fluorides are predicted using a crystal structure prediction approach. Similar to xenon fluorides, di-, tetra-, and hexa-fluorides are found to be stabilized. Coupled-cluster calculations reveal that RnF 6 stabilizes with O h point symmetry, unlike XeF 6 with C 3V symmetry. Furthermore, relativistic effects are considered to calculate physical properties, such as bond length, bond angle, and vibrational spectra, and the results suggest that relativistic effects should be considered to describe properly many-electrons of Rn. The molecular stability of radon fluoride obtained through calculations may lead to advances in radon chemistry research.
Noble gases possess extremely low reactivity because their valence shells are closed. However, previous studies have suggested that these gases can form molecules when they combine with other elements with high electron affinity, such as fluorine. Radon is a naturally occurring radioactive noble gas, and the formation of radon-fluorine molecules is of significant interest owing to its potential application in future technologies that address environmental radioactivity. Nevertheless, because all isotopes of radon are radioactive and the longest radon half-life is only 3.82 days, experiments on radon chemistry have been limited. Here, we study the formation of radon molecules using first-principles calculations; additionally, possible compositions of radon fluorides are predicted using a crystal structure prediction approach. Similar to xenon fluorides, di-, tetra-, and hexafluorides are found to be stabilized. Coupled-cluster calculations reveal that RnF6 stabilizes with Oh point symmetry, unlike XeF6 with C3v symmetry. Moreover, we provide the vibrational spectra of our predicted radon fluorides as a reference. The molecular stability of radon di-, tetra-, and hexafluoride obtained through calculations may lead to advances in radon chemistry.
Traffic-related pollutants such as NO, NO2, PM and O3 which is indirectly produced through photochemical reaction are widely known as a serious hazard for human health. In this study, we estimate the contribution of traffic-related pollutants to ambient concentrations using CMAQ model and examine the "double count" of the same traffic emissions for applying a hybrid modeling approach, which is to combine the regional-scale air quality model and local dispersion model for linking the model-predicted gridded concentrations with population exposure model. Busan, the target area in this study, is the second largest metropolis located on the southeastern tip of the Korean Peninsula with a population of around 3.6 million. The main emission sources in the city are on-road mobile sources (50.5%), followed by non-road mobile sources such as shipping around port areas (17.6%) and solvent utilization (17.4%). In this study, to evaluate the impact of the traffic-related pollutants on outdoor ambient concentrations were quantified by analyzing the difference between model-predicted concentrations derived from two sets of simulation scenarios : (1) the WRF-SMOKE-CMAQ simulation for a 1 month (May, 2011) with (i.e., BASE case) and (2) without the traffic emissions (i.e., CNTL case). To evaluate the model validation for the BASE case, a statistical comparison was made between the observed and simulated values of both meteorological variables (air temperature, wind speed and direction) and air pollutants (O3 and NO2) at several monitoring sites. Overall, the simulated values show good correlation with the observations and indicate that O3-NO2 dynamics are generally well captured by the CMAQ (MBE of -7.4 ppb and 3.4 ppb for NO2 and O3, respectively). The differences between two simulations (BASE case minus CNTL case) are the range from -4 ppb to 60 ppb for NO2 and -44 ppb to 17 ppb for O3. This result reveals that traffic-related pollutants contribute negatively to O3 concentrations due to NOx increase under the NOx-saturated environment.
The chemical and meteorological effects on the concentration variations of ozone ($O_3$) were evaluated based on the intensive air quality measurement (5 pollutants and aromatic volatile organic compounds (AVOCs)) in and out-side an urban valley during spring and summer of 2006. The 5 pollutants measured in the study area include $O_3$, $NO_2$, NO, $PM_{10}$, and CO; the AVOCs include benzene (BEN), toluene (TOL), ethylbenzene (EB), m,p-xylene (MPX), and o-xylene (OX). For the purpose of this study, study areas were classified into two categories: valley area (VA) with a semi-closed topography covering a number of industrial complex, public building, and mountains and non-valley area (NVA) surrounding the suburban and residential areas. In general, the mean concentration levels of most pollutants (except for $PM_{10}$) in the VA were higher than those in the NVA. It was found that the average $O_3$ increase in the VA during spring might result from the combined effects such as the photochemical production from diverse anthropogenic sources and the $O_3$ accumulation due to geographical features (e.g., the semi-closed topography) and wind conditions (e.g., a low wind speed). In addition, the nocturnal $O_3$ increase in the VA during spring was primarily caused by local wind conditions (e.g., mountain and valley winds) with the low wind speed (approximately $1{\sim}2\;m\;s^{-1}$). On the other hand, the $O_3$ difference between the two areas during summer might be because of the photo-chemical production with the $O_3$ precursors (especially the AVOCs) rather than the contribution of wind conditions.
Objectives : Secondary wastewater is generated as the soil washing process proceeds to restore contaminated soil near the nuclear power plants (NPPs). In this study, we tried to evaluate the possibility of removing radioactive cesium from secondary wastewater through the adsorption process using illite.Methods : To treat radioactive cesium present in wastewater, as an adsorbent, we used illite collected from Yeongdong, Chungbuk, and weathering illite artificially weathered by high temperature and acid treatment (60℃, 0.01 M HCl). Before and after weathering, the adsorption rate of illite at low concentrations of cesium and the desorption rate of adsorbents were compared and evaluated using a 1.5 ppm of competitive potassium ion similar to that of groundwater.Results and Discussion : When the illite was artificially weathered, the amount of frayed edge sites increased as the interlayer ions in the illite eluted. As a result of the adsorption and desorption experiments, it was confirmed that the adsorption rate of weathering illite increased by about 11% in acid condition (pH 3) and about 26% in neutral condition (pH 6.2), and the desorption rate of weathering illite decreased by about 6% in acid and neutral conditions, compared to Yeongdong illite. Yeongdong illite and weathering illite showed higher adsorption rate under neutral condition than acidic condition, because the surface of the illite became negatively charged at high pH so the reactivity with cesium present as a cation increased.Conclusions : The artificial weathering process has improved the performance of illite as an adsorbent. We expect that weathering illite can be used as an effective adsorbent for the removal of radioactive cesium from NPP.
The exposed population of a vulnerable group to high ozone episodes (exceeding 60 ppb/8h) was estimated in Busan metropolitan city from 2000 to 2010. The frequency of high ozone days at monitoring sites and the number of the population aged over 65 were used to calculate the accumulated (total, seasonal, and yearly) number of the exposed older population (EOP) to high ozone episodes during the study period based on administrative areas, by interpolation and zonal mean methods in ArcGIS software. The older population in this city had increased significantly from 2000 to 2010 (representing over 10% of the total population in 2010). The vulnerable areas (e.g. the eastern area of the city) of the EOP to high ozone episodes were different from the areas with frequent high ozone episodes (e.g., the western area) due to the increase of the older population in particular areas. The difference was more significant in spring than in any other season, and in 2010 than in previous years (2000 and 2005).
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