Polycyclic aromatic hydrocarbons in bulk PM2.5 and size-segregated aerosol particle samples measured in an urban environment

To analyze polycyclic aromatic hydrocarbons (PAHs) at an urban site in Seoul, South Korea, 24-hr ambient air PM_2.5 samples were collected during five intensive sampling periods between November 1998 and December 1999. To determine the PAH size distribution, 3-day size-segregated aerosol samples were also collected in December 1999. Concentrations of the 16 PAHs in the PM_2.5 particles ranged from 3.9 to 119.9 ng m⁻³ with a mean of 24.3 ng m⁻³.An exceptionally high concentration of PAHs(∼120 ng m⁻³) observed during a haze event in December 1999 was likely influenced more by diesel vehicle exhaust than by gasoline exhaust, as well as air stagnation, as evidenced by the low carbon monoxide/elemental carbon (CO/EC) ratio of 205 found in this study and results reported by previous studies. The total PAHs associated with the size-segregated particles showed unimodal distributions. Compared to the unimodal size distributions of PAHs with modal peaks at < 0.12 μm measured in highway tunnels in Los Angeles (Venkataraman and Friedlander, 1994), four- to six-ring PAHs in our study had unimodal size distributions, peaking at the larger size range of 0.28–0.53 μm, suggesting the coagulation of freshly emitted ultrafine particles during transport to the sampling site. Further, the fraction of PAHs associated with coarse particles(> 1.8 μm) increased as the molecular weight of the PAHs decreased due to volatilization of fine particles followed by condensation onto coarse particles.     

Production of hydrogen-rich gas from methane by thermal plasma reform

This study investigated the reforming characteristics and optimum operating condition of the high-temperature plasma torch (so called plasmatron) for hydrogen-rich gas (syngas) production. At the optimum condition, the composition of produced syngas was 45.4% hydrogen (H2), 6.9% carbon monoxide (CO), 1.5% carbon dioxide (CO2), and 1.1% acetylene (C2H2). The H2/CO ratio was 6.6, hydrogen yield was 78.8%, and the energy conversion rate was 63.6%. To obtain the optimum operating condition, parametric studies were carried out examining the effects of O2/CH4 ratio, steam/CH4 ratio, and Ni catalyst addition in reactor. When the steam/CH4 ratio was 1.23, the production of hydrogen was maximized and the methane conversion rate was 99.7%. The syngas composition was determined to be 50.4% H2, 5.7% CO, 13.8% CO2, and 1.1% C2H2. The H2/CO ratio was 9.7, hydrogen yield was 93.7%, and the energy conversion rate was 78.8%. Hydrogen production with catalyst was effective, compared with no catalyst.     

Health risk assessment and source apportionment of PM2.5-bound toxic elements in the industrial city of Siheung,Korea

Environmental Science and Pollution Research - The emission sources and their health risks of fine particulate matter (PM2.5) in Siheung, Republic of Korea, were investigated as a middle-sized...     

Optimized thermochemical detoxification of asbestos-containing waste using chemical additives and microwave heat treatment

Journal of Material Cycles and Waste Management - Owing to the increasing ACW generation, asbestos detoxification and recycling technologies are required for environmental and economic reasons....