Coal-based granular activated carbon was modified with acetates of sodium, potassium and lithium at concentrations of 10 and 15% and used as adsorbents to explore the adsorption mechanism of nickel ion in aqueous solution. Acetate treatment reduced surface area and pore volume of the activated carbons, but the adsorption amount of Ni(II) on the modified activated carbons (MAC) was greater than that on the virgin activated carbon. The adsorption depended on pH of the solution with an optimum at 4.5 and the adsorbed nickel could be fully desorbed by using 0.05 M HCl solution. The maximum adsorption capacity of nickel ion on Li (15 wt%) modified activated carbon was 151.3 mg/g and the adsorption isotherm follows Langmuir, Sips, and Redlich-Peterson isotherm models better than the Freundlich isotherm model. The kinetic data was better fitted by a non-linear form of the pseudo-first order than the pseudo-second order, but the difference between two kinetic models was small.
The concentrations of outdoor airborne bacteria measured in Seoul, Korea for one year (Jan. 2008~Dec. 2008 ranged from 500 CFU/m 3 to 7,500 CFU/m 3 . In monthly concentration distribution, the level of outdoor airborne bacteria was highest in September and October and lowest in March. In seasonal concentration distribution, the order of level of outdoor airborne bacteria was autumn¤winter¤spring¤summer. In regional concentration distribution, the highest level of outdoor airborne bacteria was generally found in the forest, followed by general area and traffic site. In distribution characteristics according to particle size, outdoor airborne bacteria showed 31% for ¤7.0 μm (stage 1), 21% for 4.7~7.0 μm (stage 2), 15% for 3.3~4.7 μm (stage 3), 19% for 2.1~3.3 μm (stage 4), 10% for 1.1~2.1 μm (stage 5), and 4% for 0.65~1.1 μm (stage 6) and its mean respirable fraction was 48%. In concentration distribution by yellow dust, the mean levels of outdoor airborne bacteria were 803 (±479) CFU/m 3 for period of yellow dust and 691 (±1,134) CFU/m 3 for period of non-yellow dust. Although the level of outdoor airborne bacteria was higher in period of yellow dust than period of non-yellow dust, there was no significant difference between period of yellow dust and non-yellow dust (p¤0.05). In correlation analysis between outdoor airborne bacteria and atmospheric factors (temperature and relative humidity), there was no significant correlation between outdoor airborne bacteria and atmospheric factors. The predominant airborne bacteria were identified to the Bacillus-derived species.
Against the backdrop of the COVID-19 pandemic, it is necessary to identify these risks and determine whether the current level of management is appropriate to respond to the risk of biological hazards depending on the occupation. In this study, the incidence and fatality rates of occupational diseases were calculated using industrial accident statistics of South Korea, and trends by year using joinpoint regression and relative risk by industry using k-means clustering were evaluated for infectious diseases. We found that infectious diseases had the third highest incidence and fourth highest fatalities among all occupational diseases. In the incidence rate, joinpoints appeared in 2009 and 2018, and the annual percent change changed to 7.79, −16.63, and 82.11. The fatality rate showed a consistent increase with an annual percent change of 4.37, but it was not significant. Industries were classified into five groups according to risk, and the legal control measures of certain industries were not sufficient. Follow-up studies are needed to rectify the structural limitations of industrial accident statistics.
Chemical accidents have affected the social-environmental system. For the regional vulnerability assessment, which is the baseline work to assess the impact on the environment, a meteorological field is needed to determine how chemicals from multiple adjacent companies are propagated. In this study, we present the method of meteorological field based on the spatial cluster which is the main component of vulnerability assessment on regional chemical accident scenario. To integrate spatially dense chemical companies into a cluster, we adopt spatial clustering algorithms. Experiment result shows that DBSCAN-based approach reduces 80.5% total area of the meteorological field against brute-force algorithm, and shows good performance on the average of the overlap ratio, and utility ratio for clustering results.
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