A feasibility study on bioelectrokinetics for the removal of heavy metals from tailing soil

The combination of bioremediation and electrokinetics, termed bioelectrokinetics, has been studied constantly to enhance the removal of organic and inorganic contaminants from soil. The use of the bioleaching process originating from Fe- and/or S-oxidizing bacteria may be a feasible technology for the remediation of heavy metal-contaminated soils. In this study, the bioleaching process driven by injection of S-oxidizing bacteria, Acidithiobacillus thiooxidans, was evaluated as a pre-treatment step. The bioleaching process was sequentially integrated with the electrokinetic soil process, and the final removal efficiency of the combined process was compared with those of individual processes. Tailing soil, heavily contaminated with Cd, Cu, Pb, Zn, Co, and As, was collected from an abandoned mine area in Korea. The results of geochemical studies supported that this tailing soil contains the reduced forms of sulfur that can be an energy source for A. thiooxidans. From the result of the combined process, we could conclude that the bioleaching process might be a good pre-treatment step to mobilize heavy metals in tailing soil. Additionally, the electrokinetic process can be an effective technology for the removal of heavy metals from tailing soil. For the sake of generalizing the proposed bioelectrokinetic process, however, the site-specific differences in soil should be taken into account in future studies.     

Antecedents and consequences of satisfaction with work–family balance: A moderating role of perceived insider status

This study developed a moderated mediation model to investigate how family‐supportive paid leave and supervision affect employees' satisfaction with work–family balance and in turn their affective organizational commitment and supervisor‐directed organizational citizenship behavior depending on their perceived insider status in the organization. Our analysis of data collected from 118 employee–supervisor dyads in Korean organizations revealed that satisfaction with work–family balance mediated the linkages from family‐supportive supervision to affective organizational commitment and supervisor‐directed organizational citizenship behavior, and the linkage from family‐supportive paid leave to affective organizational commitment. Results further showed that the entire mediational process for family‐supportive supervision was more pronounced for those who perceived themselves to be an insider of their organizations, while the same pattern was not found for the meditational process related to family‐supportive paid leave. Our findings provide theoretical implications for work–family balance research and offer practical suggestions to make employees satisfied with work–family balance.     

Evaluation of PCDD/Fs characterization in animal feed and feed additives

Safety control of feed and feed additives is necessary to have safe food of animal origin. Based on media reports, nine incidents regarding dioxins and/or PCBs contaminations occurred worldwide during the last decade. Korea is a country which imports feed and feed additives. In this study, various kinds of feed and feed additives were analyzed to monitor the contamination level of dioxins. The level of PCDD/Fs in fish oil was the highest with a concentration of 23.33ngkg(-1), which is equivalent to a toxicological concentration of 4.68ngWHO-TEQ/kg. Feed from animals origin such as chicken meal, animal fat, fish meal, fish oil, and shell powder showed relatively higher concentrations of PCDD/Fs. Feed from plants origin, minerals, and additives ranged from non-detects for bit pulp and ethoxyquin to 8.28ngkg(-1) for dl-methionine. From a toxicological point of view, the highest concentration in vitamins was 0.08ngWHO-TEQ/kg among the feed additives. 2,3,4,7,8-PeCDF was the dominant congener in samples of fish oil, fish meal, and shell powder. Animal fat showed that the pattern of PCDD/Fs depends on the sources of contamination. A sample of animal fat showed 1,2,3,4,7,8-HxCDF and the other sample showed 1,2,3,4,7,8-HxCDD as a primary congener. Generally, low levels of PCDDs were detected in feed additives. Patterns of PCDD/Fs in choline chloride were different with that in choline chloride from an incident in Europe in 2000.     

Formation and emission status of PCDDs/PCDFs in municipal solid waste incinerators in Korea

This study was carried out to examine the formation and the emission status of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDDs/PCDFs) in the flue gases of commercial-scale municipal solid waste (MSW) incinerators, and thus to provide the engineering data for the reduction of PCDDs/PCDFs emitted from MSW incinerators. The formation concentrations of the PCDDs/PCDFs generated at the outlet of waste heat boilers (WHB) were in the range of 1.18-29.61 ng-TEQ/N m3 (average 5.75 ng-TEQ/N m3), while the emission concentrations at the stacks were in the range of 0.026-4.548 ng-TEQ/N m3 (average 0.924 ng-TEQ/N m3). Two major 2,3,7,8-substituted congeners were 2,3,4,7,8-PeCDF and 2,3,4,6,7,8-HxCDF, and their concentrations were up to 50% and 64% of total TEQ values at the outlet of WHB and the stack, respectively. From the results of multi-regression analysis, the formation concentration of PCDDs/PCDFs could be predicted as follows with the correlation factor of r2 = 0.962: PCDDs/PCDFs (ng-TEQ/N m3) = 3.036 (Cl) + 0.094 (T1) - 0.472 (Combustibles) + 0.059 (CO) - 0.039 (THC) - 3.366 (H) + 22.157, where T1 (degrees C) is the temperature at the outlet of the WHB. Cl, Combustibles and H are given as percentages and the others are in parts per million.     

The mixing and segregation characteristics of rice straw in a cylindrical bubbling fluidized bed

In the present study, an experiment was performed to investigate the mixing and segregation characteristics of standard sand and rice straw particles in a cylindrical bubbling fluidized bed. The mass ratio (rice straw/standard sand = 0.5–1.25 %) of two particles and superficial gas velocity (0.13–0.18 m/s) were changed as experimental variables. The pressure drop curve and Kramer’s equation were used to determine the minimum fluidization velocity and mixing index, respectively. In all cases, the mixing index was the lowest at U/U _mf = 1.15. Based on the point of U/U _mf = 1.15, the segregation region and mixing region were observed. In the segregation region, mass ratio of 0.75 % showed the lowest mixing index. At the U/U _mf = 1.23 which was selected as the starting of fast pyrolysis considering residence time and the previous fast pyrolysis experiment, mass ratio of 1.25 % showed the highest mixing index which was 0.90.     

Optical and microphysical properties of severe haze and smoke aerosol measured by integrated remote sensing techniques in Gwangju,Korea

Aerosol optical and microphysical parameters from severe haze events observed in October 2005 at Gwangju, Korea (35.10°N, 126.53°E) were determined from the ground using a multi-wavelength Raman lidar, a sunphotometer, and a real-time carbon particle analyzer and from space using satellite retrievals. Two different aerosol types were identified based on the variability of optical characteristics for different air mass conditions. Retrievals of microphysical properties of the haze from the Raman lidar indicated distinct light-absorbing characteristics for different haze aerosols originating from eastern and northern China (haze) and eastern Siberia (forest-fire smoke). The haze transported from the west showed moderately higher absorbing characteristics (SSA = 0.90 ± 0.03, 532 nm) than from the northern direction (SSA = 0.96 ± 0.02). The organic/elemental carbon (OC/EC) ratio varied between 2.5 ± 0.4 and 4.1 ± 0.7.     

Aging estimation of reactor pressure vessel in the field using magnetic properties

Many researchers have been interested in the nondestructive measurement methods for estimating components damage in order to assure the safe service of steel structures. It is recognized that the evaluating techniques based on magnetic measurement can offer a great potential because of high susceptibility to the change of several metallurgical factors. Magnetic property such as coercive force was measured. The coercive force at room temperature monotonously increased with the increase of frequency. The correlation between the magnetic properties of used material and that of un-used material was studied. The coercive force gradient at room temperature increased with the increase of aging. Hence the estimating method using magnetic properties allows one to evaluate the extent of material aging for reactor pressure vessel.     

Implication of the cluster analysis using greenhouse gas emissions of Asian countries to climate change mitigation

Climate change caused by excessive emission of greenhouse gases (GHGs) into the atmosphere has gained serious attention from the global community for a long time. More and more countries have decided to propose their goals such as Paris agreements, to reduce emitting these heat trapping compounds for sustainability. The Asian region houses dramatic changes with diverse religions and cultures, large populations as well as a rapidly changing socio-economic situations all of which are contributing to generating a mammoth amount of GHGs; hence, they require calls for related studies on climate change strategies. After pre-filtering of GHG emission information, 24 Asian countries have been selected as primary target countries. Hierarchical cluster analysis method using complete linkage technique was successfully applied for appropriate grouping. Six groups were categorized through GHG emission properties with major and minor emission sectors based on the GHG inventory covering energy, industrial processes, agriculture, waste, land use change, and forestry and bunker fuels. Assigning six groups using cluster analysis finally implied that the approach to establish GHG emission boundaries was meaningful to develop further mitigation strategies. Following the outcome of this study, calculating amount of reduction potential in suitable sectors as well as determining best practice, technology, and regulatory framework can be improved by policy makers, environmental scientists, and planners at the different levels. Therefore, this work on reviewing a wide range of GHG emission history and establishing boundaries of emission characteristics would provide further direction of effective climate change mitigation for sustainability and resilience in Asia.     

Correction to: Biosolids application affects the competitive sorption and lability of cadmium,copper, nickel,lead, and zinc in fluvial and calcareous soils

Environmental Geochemistry and Health - Unfortunately, in the original publication of the article, Prof. Yong Sik Ok’s affiliation was incorrectly published.