Emission of particulate and gaseous pollutants from household laser processing machine

Indoor air quality (IAQ) directly affects the health of occupants. Household manufacturing equipment (HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment (HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration (PNC) and particle emission rate (PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 mW, the mode diameters of particles were <150 nm, and PNCs were >2.0 × 10⁴ particles/cm³. Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C₈ aromatics (ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles (UFPs) was >5 × 10⁴ particles/cm³ during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.     

Applying mass transfer models for controlling organic compounds in ozonation process

Mass transfer plays a significant role in the ozonation process. The prediction models associated with the volumetric overall mass transfer coefficient (K_La) and initial fractional ozone absorption (FOA₀) during the ozonation process were developed through the use of dimensional analysis. It was found that the volumetric overall mass transfer coefficient is the function of diffusivity, agitation speed, and gas flow rate, and the parameters in the K_La equation are determined. Application of the prediction models for K_La and FOA₀ would yield information to choose the most practically feasible operating parameters. The removability of total organic carbon (TOC) can be estimated based on the mass balance relationship and kinetic expression of TOC oxidation, during continuous laboratory ozonation of humic acid solution. The reaction rate constant averaged 0.0291 L/mg·min. The developed model in combination with the mass transfer and reaction kinetics can be used successfully in forecasting the most efficient agitation speed to control the formation of organic compounds. Also, the critical value of ozone partial pressure to achieve the highest TOC removability can be determined through the use of the above developed model.     

Modeling of road traffic noise and estimated human exposure in Fulton County, Georgia, USA

Environmental noise is a major source of public complaints. Noise in the community causes physical and socio-economic effects and has been shown to be related to adverse health impacts. Noise, however, has not been actively researched in the United States compared with the European Union countries in recent years. In this research, we aimed at modeling road traffic noise and analyzing human exposure in Fulton County, Georgia, United States. We modeled road traffic noise levels using the United States Department of Transportation Federal Highway Administration Traffic Noise Model implemented in SoundPLAN?. After analyzing noise levels with raster, vector and fa?ade maps, we estimated human exposure to high noise levels. Accurate digital elevation models and building heights were derived from Light Detection And Ranging survey datasets and building footprint boundaries. Traffic datasets were collected from the Georgia Department of Transportation and the Atlanta Regional Commission. Noise level simulation was performed with 62 computers in a distributed computing environment. Finally, the noise-exposed population was calculated using geographic information system techniques. Results show that 48% of the total county population [N=870,166 residents] is potentially exposed to 55 dB(A) or higher noise levels during daytime. About 9% of the population is potentially exposed to 67 dB(A) or higher noises. At nighttime, 32% of the population is expected to be exposed to noise levels higher than 50 dB(A). This research shows that large-scale traffic noise estimation is possible with the help of various organizations. We believe that this research is a significant stepping stone for analyzing community health associated with noise exposures in the United States.     

Photocatalytic decomposition of N<Subscript>2</Subscript>O over g-C<Subscript>3</Subscript>N<Subscript>4</Subscript>/WO<Subscript>3</Subscript> photocatalysts

Although the nitrous oxide belongs among three of the most contributing greenhouse gases to global warming, it is quite neglected by photocatalytic society. The g-C₃N₄ and WO₃ composites were therefore tested for the photocatalytic decomposition of N₂O for the first time. The pure photocatalysts were prepared by simple calcination of precursors, and the composites were prepared by mixing of suspension of pure components in water followed by calcination. The structural (X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy), textural (N₂ physisorption), and optical properties (diffuse reflectance spectroscopy, photoluminescence spectroscopy, photoelectrochemical measurements) of all composites were correlated with photocatalytic activity. The experimental results and results from characterization techniques confirmed creation of Z-scheme in the WO₃/g-C₃N₄ composites, which was confirmed by hydroxyl radicals’ trapping measurements. The photocatalytic decomposition of N₂O was carried out in the presence of UVA light (peak intensity at 365 nm) and the 1:2 WO₃/g-C₃N₄ composite was the most active one, but the photocatalytic activity was just negligibly higher than that of pure WO₃. This is caused by relatively weak interaction between WO₃ and g-C₃N₄ which was revealed from XPS.     

Estimation of the liability to detonating of prilled ammonium nitrate fertiliser grade

The statistical analysis of the results of testing liability to detonation of coated and uncoated prilled ammonium nitrate was performed. The correlation between the crushing of the lead cylinders as a result of the so-called 4″ tube test and the chemical as well as the physical properties of ammonium nitrate were determined. The results demonstrated that the liability to detonation of ammonium nitrate may be estimated by use of mathematical equations, which employ easily obtainable experimental values relating to the chemical composition and physical properties of the tested fertilisers.     

Work-related injuries of educational support staff in schools

This study aims to describe the characteristics of occupational injuries to educational support staff (service worker) in schools. In this research, 803 injured workers registered in 2015 were analyzed in terms of their gender, age, work experience, school type, work type, accident type, agency of accident, nature of injury and injured part of the body for each occupation. The workers were classified into after-school instructor, custodian and cooking staff. Accidents occurred mainly due to slips (35.6%) on floor/stair or contact with high temperature (18.1%). Also, the workers mostly fractured (41.2%) or had burns (19.3%) on their leg/foot (37.1%) or arm/hand/finger (29.8%). The results showed the difference in characteristics and injury pattern of injured persons for each occupation type, addressing the need for customized preventative measures for each situation. The results of this study can be a baseline in devising policies and guidelines for preventing accidents of service workers in schools.     

The sorption of hydrogen sulfide from hot syngas by metal oxides over supports

Six 5 wt.% metal sorbents including Mn, Fe, Cu, Co, Ce and Zn supported on gamma-Al2O3, prepared by the incipient wetness impregnation method with calcination at 700 degrees C for 2 h, have been investigated for sorption of hydrogen sulfide in the temperature range of 500-700 degrees C. The sorption experiments were conducted in a fixed-bed reactor in terms of breakthrough curves and characterized by X-ray powder diffraction. The results reveal that the copper and manganese sorbents exhibit the best performance because they provide nearly 100% utilization, but the copper sorbent has a lower sulfur sorption capacity compared with the manganese sorbent. The zinc and cerium sorbents are not good candidates attributed to the vaporization of zinc and unexpected product for cerium. Effects of support materials on 5 wt.% manganese were also investigated by using gamma-Al2O3, SiO2 and TiO2 in this study. Five weight percent Mn/gamma-Al2O3 shows the best performance among support candidates. On the basis of XRPD and BET surface area analysis, TiO2 appears a huge loss in BET surface area associated with a significant formation of rutile form.     

End-of-life batteries management and material flow analysis in South Korea

Analysis of collection and recycling system of end-of-life batteries was examined. Relatively limited fractions of portable batteries were collected by EPR system. More effective and diverse collection pathways should be developed. Consumers increasingly have worn-out batteries as electrical and electronic equipment with new technical developments are introduced into the market and quickly replace older models. As a result, large amounts of end-of-life (EOL) or waste batteries are generated. Such batteries may contain a variety of materials that includes valuable resources as well as toxic elements. Thus, the proper recycling and management of batteries is very important from the perspective of resource conservation and environmental effect. The collection and recycling of EOL batteries is relatively low in South Korea compared to other countries, although an extended producer responsibility (EPR) policy was adopted for battery recycling in 2003. In this study, the management and material flow of EOL batteries is presented to determine potential problems and quantitative flow, based on literature review, site visits to battery recycling facilities, and interviews with experts in the Korea Battery Recycling Association (KBRA), manufacturers, and regulators in government. The results show that approximately 558 tons of manganese-alkaline batteries, the largest fraction among recycling target items, was disposed in landfills or incinerators in 2015, while approximately 2,000 tons of batteries were recovered at a recycling facility by simple sorting and crushing processes. By raising environmental awareness, more diverse and effective collection systems could be established for consumers to easily dispose of EOL batteries in many places. Producers, retailers and distributors in South Korea should also play an important role in the collection of EOL batteries from consumers. Lithium-ion batteries from many electronic devices must be included in the EPR system for resource recovery.     

Stabilization of Cu-contaminated army firing range soils using waste oyster shells

A stabilization/solidification (S/S) process was used to immobilize Cu in contaminated soils obtained from two army firing ranges sites (A and B) with total Cu concentrations of 520 and 380 mg/kg, respectively. Both waste oyster shells (WOS) and pretreated oyster shells (POS) were used to immobilize Cu in the contaminated soils. Waste oyster shells passing the #10 mesh and #20 mesh were used for the Sites A and B, respectively. WOS- and POS-treated soil samples cured for 28 days were evaluated for Cu leaching by the Korean Standard Leaching Test (KSLT) method. Slurry suspensions were prepared to investigate the Cu immobilization mechanism using X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDX) analyses. The treatment results showed that the POS treatment was more effective than the WOS treatment of 28 days. For Site A, 10 wt% WOS and 3 wt% POS dosages were required to pass the Korean warning standard of 50 mg/kg, while 10 wt% WOS and 5 wt% POS dosages were required for the Site B treatment. The XRPD and SEM-EDX results showed that Cu immobilization was strongly linked to both CSH/CAH and ettringite. Overall, the POS treatment was effective at immobilizing the Cu in the contaminated soils, very likely due to its CaO content.     

Stabilization of the As-contaminated soil from the metal mining areas in Korea

The stabilization efficiencies of arsenic (As) in contaminated soil were evaluated using various additives such as limestone, steel mill slag, granular ferric hydroxide (GFH), and mine sludge collected from an acid mine drainage treatment system. The soil samples were collected from the Chungyang area, where abandoned Au–Ag mines are located. Toxicity characteristic leaching procedure, synthetic precipitation leaching procedure, sequential extraction analysis, aqua regia digestion, cation exchange capacity, loss on ignition, and particle size distribution were conducted to assess the physical and chemical characteristics of highly arsenic-contaminated soils. The total concentrations of arsenic in the Chungyang area soil ranged up to 145 mg/kg. After the stabilization tests, the removal percentages of dissolved As(III) and As(V) were found to differ from the additives employed. Approximately 80 and 40% of the As(V) and As(III), respectively, were removed with the use of steel mill slag. The addition of limestone had a lesser effect on the removal of arsenic from solution. However, more than 99% of arsenic was removed from solution within 24 h when using GFH and mine sludge, with similar results observed when the contaminated soils were stabilized using GFH and mine sludge. These results suggested that GFH and mine sludge may play a significant role on the arsenic stabilization. Moreover, this result showed that mine sludge can be used as a suitable additive for the stabilization of arsenic.