Anthropogenic emissions in China have been controlled for years to improve ambient air quality. However, severe haze events caused by atmospheric aerosols with aerodynamic diameter less than or equal to 2.5 µm (PM 2.5) have continued to occur, especially in the Beijing-Tianjin-Hebei (BTH) region. The Chinese government has set an ambitious goal to reduce urban PM 2.5 concentrations by 25% in BTH by 2017 relative to the 2012 levels. Source apportionment (SA) is necessary to the development of the effective emission control strategies. In this work, the Comprehensive Air Quality Model with extensions (CAMx) with the Particulate Source Apportionment Technology (PSAT) is applied to the China domain for the years 2006 and 2013. Ambient surface concentrations of PM 2.5 and its components are generally well reproduced. To quantify the contributions of each emission category or region to PM 2.5 in BTH, the total emissions are divided into 7 emission categories and 11 source regions. The source contributions determined in this work are generally consistent with results from previous work. In 2013, the industrial (44%) and residential (27%) sectors are the dominant contributors to urban PM 2.5 in BTH. The residential sector is the largest contributor in winter; the industry sector dominates in other seasons. A slight increasing trend (+3% for industry and +6% for residential) is found in 2013 relative to 2006, necessitating more attention to these two sectors. Local emissions make the largest contribution (40%-60%) for all receptors. Change of source contribution of PM 2.5 in Beijing and northern Hebei are dominate by change of local emission. However, for Tianjin, and central and southern Hebei, change of meteorology condition are as important as change of emission, because regional inflow in these areas is more important than in Beijing and northern Hebei and can increase under unfavorable weather conditions, indicating a strong need for regional joint emission control efforts. 3 The results in this study enhance the quantitative understanding of the source-receptor relationships and provide an important basis for policymaking to advance the control of PM 2.5 pollution in China.
A review of the major issues surrounding the postuse disposal of polymer composite materials is presented. Composites are compared to unreinforced plastics in terms of production volume and the technologies available for reprocessing. Not surprisingly, composites comprise a very small fraction of the plastics waste stream. In highvolume applications such as automobiles, however, there are reasons to be concerned about composites recycling. The fundamental categories of dealing with waste (burning, burying, reusing, or using less in the first place) are described in relation to plastics and composites. Reprocessing technologies with applications for composites are reviewed. For thermosetmatrix composites, processes involving regrinding waste materials and using them as filler for other polymer processes show promise. For thermoplasticmatrix composites, processes involving grinding and remolding by injection or compression molding are promising. Applications for recycled composites, without which reprocessing is futile, are also reviewed.
China's oil imports and greenhouse gas (GHG) emissions have grown rapidly over the past decade. Addressing energy security and GHG emissions is a national priority. Replacing conventional vehicles with electric vehicles (EVs) offers a potential solution to both issues. While the reduction in petroleum use and hence the energy security benefits of switching to EVs are obvious, the GHG benefits are less obvious. We examine the current Chinese electric grid and its evolution and discuss the implications for EVs. China's electric grid will be dominated by coal for the next few decades. In 2015 in Beijing, Shanghai, and Guangzhou, EVs will need to use less than 14, 19, and 23 kWh/100 km, respectively, to match the 183 gCO2/km WTW emissions for energy saving vehicles. In 2020, in Beijing, Shanghai, and Guangzhou EVs will need to use less than 13, 18, and 20 kWh/100 km, respectively, to match the 137 gCO2/km WTW emissions for energy saving vehicles. EVs currently demonstrated in China use 24-32 kWh/100 km. Electrification will reduce petroleum imports; however, it will be very challenging for EVs to contribute to government targets for GHGs emissions reduction.
A series of monolithic silica/resorcinol–formaldehyde (silica/RF) aerogels have been prepared by a simple one‐step sol–gel process of 3‐aminopropyltriethoxysilane (APTES), resorcinol (R), and formaldehyde (F) in ethanol, followed by drying with supercritical CO2. The silica/carbon composite aerogels were obtained by pyrolysis of the silica/RF aerogels under N2 atmosphere. The silica/carbon composite aerogels exhibit low densities (0.1241–0.2751 g/cm3) and high porosities (>84%). The pore morphologies of the composite aerogels have been investigated in detail by nitrogen sorption measurements, scanning electron microscopy, and transmission electron microscopy. The surface areas of these composite aerogels result from the contribution of macropores, mesopores, and micropores. Combustion in air or etching in HF solution can remove carbon or silica from the silica/carbon composite aerogels and yields monolithic or cracked unitary silica or carbon aerogels. The study indicates that when the starting APTES/R molar ratio is high (sample 3SiOC–C and 2SiOC–C), the silica framework is the supporting framework; and for low starting APTES/R ratio samples (sample SiOC–3C, SiOC–2C, and SiOC–C), the carbon framework is the supporting framework. Remarkably, carbon aerogels with high surface areas of 2000 m2/g can be obtained after removing silica frameworks of composite aerogels of 3SiOC–C and 2SiOC–C.
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