摘要 :
In the last 10 yr,Beijing has made a great effort to improve its air quality.However,it is still suffering from regional coarse particulate matter (PM_(10)) pollution that could be a challenge to the promise of clean air during th...
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In the last 10 yr,Beijing has made a great effort to improve its air quality.However,it is still suffering from regional coarse particulate matter (PM_(10)) pollution that could be a challenge to the promise of clean air during the 2008 Olympics.To provide scientific guidance on regional air pollution control,the Mesoscale Modeling System Generation 5 (MM5) and the Models-3/Community Multiscale Air Quality Model (CMAQ) air quality modeling system was used to investigate the contributions of emission sources outside the Beijing area to pollution levels in Beijing.The contributions to the PM10 concentrations in Beijing were assessed for the following sources:power plants,industry,domestic sources,transportation,agriculture,and biomass open burning.In January,it is estimated that on average 22% of the PM10 concentrations can be attributed to outside sources,of which domestic and industrial sources contributed 37 and 31%,respectively.In August,as much as 40% of the PM_(10) concentrations came from regional sources,of which approximately 41% came from industry and 31% from power plants.However,the synchronous analysis of the hourly concentrations,regional contributions,and wind vectors indicates that in the heaviest pollution periods the local emission sources play a more important role.The implications are that long-term control strategies should be based on regional-scale collaborations,and that emission abatement of local sources may be more effective in lowering the PM_(10) concentration levels on the heavy pollution days.Better air quality can be attained during the Olympics by placing effective emission controls on the local sources in Beijing and by controlling emissions from industry and power plants in the surrounding regions.
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摘要 :
Motivated by the recent realization of graphene sensor to detect gas molecules that are harmful to the environment, the ammonia adsorption on graphene or graphene oxide (GO) was investigated using first-principles calculation. The...
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Motivated by the recent realization of graphene sensor to detect gas molecules that are harmful to the environment, the ammonia adsorption on graphene or graphene oxide (GO) was investigated using first-principles calculation. The optimal adsorption and orientation of the NH_3 molecules on the graphene surfaces were determined, and the adsorption energies (E_b) as well as the Mulliken charge transfers of NH_3 were calculated. The E_b for the graphene are small and seem to be independent of the sites and orientations. The surface epoxy or hydroxyl groups can promote the adsorption of NH_3 on the GO; the enhancement of the E_b for the hydroxyl groups is greater than that for the epoxy groups on the surface. The charge transfers from the molecule to the surfaces also exhibit the same trend. The Broensted acid sites and Lewis acid sites could stably exist on the GO with surface hydroxyl groups and on the basal, respectively.
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