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Science in the News
Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health
- A novel method of microwave heating mixed liquid-assisted regeneration of V 2 O 5 –WO 3 /TiO 2 commercial SCR catalysts 2015-10-01
An experimental study on the regeneration of deactivated SCR catalysts was carried out using a microwave-assisted method containing three steps of washing with mixed liquid of ethanol and water, impregnating, and drying. After the regeneration treatment, NO conversion at 320 °C increased from 39 to 90 % and vanadium content increased by 62.2 %, which were much higher than those regenerated by the traditional method. The more impregnated vanadium was due to the fact that the rapid evaporation of mixed liquid inside the catalyst channels led to the enlargement of surface areas by creating more pores on the catalysts. Meanwhile, with the increasing concentrations of ethanol, the heating rate of the mixed liquid increased, and the volume after complete evaporation of the mixed liquid was gradually reduced. Since higher heating rate and lager volume after the liquid evaporation could help to create more pores, therefore, when the volume ratio of ethanol/mixed solution was 20 %, the catalyst obtained the maximum specific surface area, which significantly increased to ca. 123 % compared with the deactivated catalyst. In addition, the catalyst dried by microwave exhibited better catalytic activity than that dried in conventional oven. Therefore, this method showed great potential in industrial applications.
- Particle size distribution and air pollution patterns in three urban environments in Xi’an, China 2015-10-01
Three urban environments, office, apartment and restaurant, were selected to investigate the indoor and outdoor air quality as an inter-comparison in which CO2, particulate matter (PM) concentration and particle size ranging were concerned. In this investigation, CO2 level in the apartment (623 ppm) was the highest among the indoor environments and indoor levels were always higher than outdoor levels. The PM10 (333 µg/m3), PM2.5 (213 µg/m3), PM1 (148 µg/m3) concentrations in the office were 10–50 % higher than in the restaurant and apartment, and the three indoor PM10 levels all exceeded the China standard of 150 µg/m3. Particles ranging from 0.3 to 0.4 µm, 0.4 to 0.5 µm and 0.5 to 0.65 µm make largest contribution to particle mass in indoor air, and fine particles number concentrations were much higher than outdoor levels. Outdoor air pollution is mainly affected by heavy traffic, while indoor air pollution has various sources. Particularly, office environment was mainly affected by outdoor sources like soil dust and traffic emission; apartment particles were mainly caused by human activities; restaurant indoor air quality was affected by multiple sources among which cooking-generated fine particles and the human steam are main factors.
- Polycyclic aromatic hydrocarbons (PAHs) in atmospheric dustfall from the industrial corridor in Hubei Province, Central China 2015-10-01
Thirty atmospheric dustfall samples collected from an industrial corridor in Hubei Province, central China, were analyzed for 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) to investigate their concentrations, spatial distributions, sources, and health risks. Total PAH concentrations (ΣPAHs) ranged from 1.72 to 13.17 µg/g and averaged 4.91 µg/g. High molecular weight (4–5 rings) PAHs averaged 59.67 % of the ΣPAHs. Individual PAH concentrations were not significantly correlated with total organic carbon, possibly due to the semi-continuous inputs from anthropogenic sources. Source identification studies suggest that the PAHs were mainly from motor vehicles and biomass/coal combustion. The incremental lifetime cancer risks associated with exposure to PAHs in the dustfall ranged from 10−4 to 10−6; these indicate potentially serious carcinogenic risks for exposed populations in the industrial corridor.