The measurements of atmospheric carbonyls concentrations in Beijing were conducted from 12 July to 8 October, 2008, covering the periods of the 2008 Olympic Games and Paralympic Games. Six carbonyls, including formald...The measurements of atmospheric carbonyls concentrations in Beijing were conducted from 12 July to 8 October, 2008, covering the periods of the 2008 Olympic Games and Paralympic Games. Six carbonyls, including formaldehyde, acetaldehyde, acetone, butyraldehyde, valeraldehyde, and hexaldehyde, were identified in all air samples. The total average concentrations of these carbonyls before, during, and after traffic restriction were （48.1 ± 15.2）, （36.6 ± 14.5） and （23.4± 12.3） μg/m^3, respectively. Compared with the period after traffic restriction, the distinct high concentrations of the carbonyls before and during traffic restriction were primarily ascribed to the remarkable contribution of photochemical reactions. With respect to our previous investigation in the summer of 2005, the reductions of formaldehyde, acetaldehyde and acetone during traffic restriction period were about 64%, 47% and 27%, respectively, indicating that the air cleaning actions adopted by the Chinese government for the two games were efficient. The lowest levels of atmospheric carbonyls and the extremely high composition proportion of acetone after the traffic restriction were mainly attributed to the long-term effect of the control measures for the two games.展开更多
The Large Eddy Simulation （LES） method has been used to solve the fluid momentum equations coupled with a convection,liffusion equation to study the formation of pollutant nanoparticles in a vehicular exhaust with i...The Large Eddy Simulation （LES） method has been used to solve the fluid momentum equations coupled with a convection,liffusion equation to study the formation of pollutant nanoparticles in a vehicular exhaust with impinging twin-jet. The functions of the space （S） between the two jets and the distance （H） from the exit of nozzle to the impingement plane are evaluated according to the distributions of pollutant nanoparticles. The results show that the nucleation produces a large number of nanoparticles, and gas-to-nanoparticle conversion mostly takes place in the interface region of the two jets, the circumambience of the jets, and region near the plane. The maximal particle size and maximal number concentration produced by both nucleation and coagulation appear around the region of free jet and the region near the plane, respectively. The significant differences for various spaces between the two jets are the number concentration and size distributions in the interface region of the two jets. For the case with larger space, more nanoparticles are produced by nucleation and coagulation The more the distance from the exit of nozzle to the impingement plane, the lower is the fewer the particles distribute distance from nozzle to plane is nanoparticle formation. the number concentration and near the plane. Increasing the beneficial to the reduction of展开更多
基金supported by the National Natural Science Foundation of China (No. 20977097,40830101, 41075094)the Chinese Academy of Sciences (No. KZCX2-YW-Q02-03)+1 种基金the Platform Construction of Introducing Central Resources in Beijing (No.PXM2008 178305 06995)the National Basic Research and Development Program (973) of China (No.2010CB732304)
文摘The measurements of atmospheric carbonyls concentrations in Beijing were conducted from 12 July to 8 October, 2008, covering the periods of the 2008 Olympic Games and Paralympic Games. Six carbonyls, including formaldehyde, acetaldehyde, acetone, butyraldehyde, valeraldehyde, and hexaldehyde, were identified in all air samples. The total average concentrations of these carbonyls before, during, and after traffic restriction were （48.1 ± 15.2）, （36.6 ± 14.5） and （23.4± 12.3） μg/m^3, respectively. Compared with the period after traffic restriction, the distinct high concentrations of the carbonyls before and during traffic restriction were primarily ascribed to the remarkable contribution of photochemical reactions. With respect to our previous investigation in the summer of 2005, the reductions of formaldehyde, acetaldehyde and acetone during traffic restriction period were about 64%, 47% and 27%, respectively, indicating that the air cleaning actions adopted by the Chinese government for the two games were efficient. The lowest levels of atmospheric carbonyls and the extremely high composition proportion of acetone after the traffic restriction were mainly attributed to the long-term effect of the control measures for the two games.
基金supported by the Ministry of Science and Technology of China(Grant No.2005CCA06900)
文摘The Large Eddy Simulation （LES） method has been used to solve the fluid momentum equations coupled with a convection,liffusion equation to study the formation of pollutant nanoparticles in a vehicular exhaust with impinging twin-jet. The functions of the space （S） between the two jets and the distance （H） from the exit of nozzle to the impingement plane are evaluated according to the distributions of pollutant nanoparticles. The results show that the nucleation produces a large number of nanoparticles, and gas-to-nanoparticle conversion mostly takes place in the interface region of the two jets, the circumambience of the jets, and region near the plane. The maximal particle size and maximal number concentration produced by both nucleation and coagulation appear around the region of free jet and the region near the plane, respectively. The significant differences for various spaces between the two jets are the number concentration and size distributions in the interface region of the two jets. For the case with larger space, more nanoparticles are produced by nucleation and coagulation The more the distance from the exit of nozzle to the impingement plane, the lower is the fewer the particles distribute distance from nozzle to plane is nanoparticle formation. the number concentration and near the plane. Increasing the beneficial to the reduction of
