New particle formation is a key process in shaping the size distribution of aerosols in the atmosphere.We present here the measurement results of number and size distribution of aerosol particles （10–10000 nm in dia...New particle formation is a key process in shaping the size distribution of aerosols in the atmosphere.We present here the measurement results of number and size distribution of aerosol particles （10–10000 nm in diameter） obtained in the summer of 2008,at a suburban site in Beijing,China.We firstly reported the pollution level,particle number size distribution,diurnal variation of the particle number size distribution and then introduced the characteristics of the particle formation processes.The results showed that the number concentration of ultrafine particles was much lower than the values measured in other urban or suburban areas in previous studies.Sharp increases of ultrafine particle count were frequently observed at noon.An examination of the diurnal pattern suggested that the burst of ultrafine particles was mainly due to new particle formation promoted by photochemical processes.In addition,high relative humidity was a key factor driving the growth of the particles in the afternoon.During the 2-month observations,new particle formation from homogeneous nucleation was observed for 42.7% of the study period.The average growth rate of newly formed particles was 3.2 nm/hr,and varied from 1.2 to 8.0 nm/hr.The required concentration of condensable vapor was 4.4×10 7 cm-3,and its source rate was 1.2×10 6 cm-3 sec-1.Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rates was 28.7%.展开更多
Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to e...Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO2, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO2/NOx significantly. The results of smoke emissions and particle number （PN） emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter （PM） and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO2/NOx. The PN emission results from two CRDPFs indicated that more NO2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO2 exposure in atmosphere.展开更多
基金supported by the National Department Public Benefit Research Foundation of China (No.201009001)the National Natural Science Foundation of China (No.41005065)the Basic Foundation for Public Benefit-Research Academies from the Central Government (No.2008KYYW01)
文摘New particle formation is a key process in shaping the size distribution of aerosols in the atmosphere.We present here the measurement results of number and size distribution of aerosol particles （10–10000 nm in diameter） obtained in the summer of 2008,at a suburban site in Beijing,China.We firstly reported the pollution level,particle number size distribution,diurnal variation of the particle number size distribution and then introduced the characteristics of the particle formation processes.The results showed that the number concentration of ultrafine particles was much lower than the values measured in other urban or suburban areas in previous studies.Sharp increases of ultrafine particle count were frequently observed at noon.An examination of the diurnal pattern suggested that the burst of ultrafine particles was mainly due to new particle formation promoted by photochemical processes.In addition,high relative humidity was a key factor driving the growth of the particles in the afternoon.During the 2-month observations,new particle formation from homogeneous nucleation was observed for 42.7% of the study period.The average growth rate of newly formed particles was 3.2 nm/hr,and varied from 1.2 to 8.0 nm/hr.The required concentration of condensable vapor was 4.4×10 7 cm-3,and its source rate was 1.2×10 6 cm-3 sec-1.Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rates was 28.7%.
基金supported by the National Natural Science Foundation of China (No. 50876013)
文摘Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO2, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO2/NOx significantly. The results of smoke emissions and particle number （PN） emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter （PM） and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO2/NOx. The PN emission results from two CRDPFs indicated that more NO2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO2 exposure in atmosphere.
