The impact of aerosols on the climate and atmospheric environment depends on the water uptake ability of particles;namely,hygroscopic growth and activation into cloud condensation nuclei(CCN).The size-resolved activat...The impact of aerosols on the climate and atmospheric environment depends on the water uptake ability of particles;namely,hygroscopic growth and activation into cloud condensation nuclei(CCN).The size-resolved activation ratios(SRAR),characterizing the fraction of aerosol particles that act as CCN at different particle sizes and supersaturations,can be measured using a combination of differential mobility analyzers(DMA) and particle counters.DMA-based measurements are influenced by the multiply charged particles and the quasi-mono-dispersed particles(effect of DMA transfer function) selected for each prescribed particle size.A theoretical study,assuming different particle number size distributions and hygroscopicity of aerosols,is performed to study the effects of the DMA transfer function and multiple charging on the measured SRAR and the derived hygroscopicity.Results show that the raw SRAR can be significantly skewed and hygroscopicity may be highly biased from the true value if the data are not corrected.The effect of the transfer function is relatively small and depends on the sample to sheath flow ratio.Multiply charged particles,however,can lead to large biases of the SRAR.These results emphasize that the inversion algorithm,which is used to correct the effects of the DMA transfer function and multiple charging,is necessary for accurate measurement of the SRAR.展开更多
The Greater Casablanca, like the other large cities, has experienced significant urban and industrial development in recent years, this development has certainly helped develop the productive fabric, generate signific...The Greater Casablanca, like the other large cities, has experienced significant urban and industrial development in recent years, this development has certainly helped develop the productive fabric, generate significant employment opportunities for hundreds of thousands of families, but at the expense of the mobility and quality of the environment particularly those of the air. The deterioration of the air quality affects more and more the population＇s health with significant cost and damage to the community, this study aims to quantify the degree of aerosols pollution damage and also its health effects.展开更多
There is an increasing interest in understanding ambient bioaerosols due to their roles both in health and in climate. Here, we deployed an Ultraviolet Aerodynamic Particle Sizer to monitor viable （fluorescent） bioa...There is an increasing interest in understanding ambient bioaerosols due to their roles both in health and in climate. Here, we deployed an Ultraviolet Aerodynamic Particle Sizer to monitor viable （fluorescent） bioaerosol concentration levels at city centers （highly polluted） and their corresponding suburbs （near pristine） （total 40 locations） in 11 provinces featuring different climate zones in China between July 16 and 28, 2013. The concentration levels of viable bioaerosol particles （BioPM） of 〉0.5 μm were measured, and corresponding percentages of BioPM% （biological fraction of total PM） and BioPM2.5% （biological fraction of PM2.5） in particulate matter （PM） and BioPM, respectively, were determined. For some key cities, indoor viable bioaerosol levels were also obtained. In addition, bacterial structures of the air samples collected across these monitoring locations were studied using pyrosequencing. BioPM concentration levels ranged from 2.1 ×10^4 to 2.4 × 10^5/m3 for city centers [BioPM% = 6.4 % （4-6.3 %）] and 0.5 × 10^4 to 4.7 × 10^5/m3 for suburbs [BioPM% = 10 % （4-8.7 %）]. Distinctive bioaerosol size distribution patterns were observed for different climate zones, e.g., some had fluorescence peaks at 3 μm, while the majority had peaks at 1 μm. Ambient bacterial aerosol community structures were also found different for different geophysical locations. Results suggest that there was a poor overall relationship between PM and BioPM across 40 monitoring locations （R2= 0.081, two-tailed P value = 0.07435）. Generally, city centers had higher PM concentrations than suburbs, but not BioPM and BioPM%. Indoor bioaerosol levels were found at least tenfold higher than those corresponding outdoors. Bacillus was observed to dominate the bacterial aerosol community in the air sample.展开更多
基金supported by the National Natural Science Foundation of China (NSFC) (Grant Nos.41205098 and 41305114)the "Strategic Priority Research Program" of the Chinese Academy of Sciences (Grant No.XDA05100000)
文摘The impact of aerosols on the climate and atmospheric environment depends on the water uptake ability of particles;namely,hygroscopic growth and activation into cloud condensation nuclei(CCN).The size-resolved activation ratios(SRAR),characterizing the fraction of aerosol particles that act as CCN at different particle sizes and supersaturations,can be measured using a combination of differential mobility analyzers(DMA) and particle counters.DMA-based measurements are influenced by the multiply charged particles and the quasi-mono-dispersed particles(effect of DMA transfer function) selected for each prescribed particle size.A theoretical study,assuming different particle number size distributions and hygroscopicity of aerosols,is performed to study the effects of the DMA transfer function and multiple charging on the measured SRAR and the derived hygroscopicity.Results show that the raw SRAR can be significantly skewed and hygroscopicity may be highly biased from the true value if the data are not corrected.The effect of the transfer function is relatively small and depends on the sample to sheath flow ratio.Multiply charged particles,however,can lead to large biases of the SRAR.These results emphasize that the inversion algorithm,which is used to correct the effects of the DMA transfer function and multiple charging,is necessary for accurate measurement of the SRAR.
文摘The Greater Casablanca, like the other large cities, has experienced significant urban and industrial development in recent years, this development has certainly helped develop the productive fabric, generate significant employment opportunities for hundreds of thousands of families, but at the expense of the mobility and quality of the environment particularly those of the air. The deterioration of the air quality affects more and more the population＇s health with significant cost and damage to the community, this study aims to quantify the degree of aerosols pollution damage and also its health effects.
基金supported by the National Natural Science Foundation of China(21277007,21477003,and 41121004)the Ministry of Science and Technology of China(2015DFG92040,2015CB553401)Ministry of Education(20130001110044)
文摘There is an increasing interest in understanding ambient bioaerosols due to their roles both in health and in climate. Here, we deployed an Ultraviolet Aerodynamic Particle Sizer to monitor viable （fluorescent） bioaerosol concentration levels at city centers （highly polluted） and their corresponding suburbs （near pristine） （total 40 locations） in 11 provinces featuring different climate zones in China between July 16 and 28, 2013. The concentration levels of viable bioaerosol particles （BioPM） of 〉0.5 μm were measured, and corresponding percentages of BioPM% （biological fraction of total PM） and BioPM2.5% （biological fraction of PM2.5） in particulate matter （PM） and BioPM, respectively, were determined. For some key cities, indoor viable bioaerosol levels were also obtained. In addition, bacterial structures of the air samples collected across these monitoring locations were studied using pyrosequencing. BioPM concentration levels ranged from 2.1 ×10^4 to 2.4 × 10^5/m3 for city centers [BioPM% = 6.4 % （4-6.3 %）] and 0.5 × 10^4 to 4.7 × 10^5/m3 for suburbs [BioPM% = 10 % （4-8.7 %）]. Distinctive bioaerosol size distribution patterns were observed for different climate zones, e.g., some had fluorescence peaks at 3 μm, while the majority had peaks at 1 μm. Ambient bacterial aerosol community structures were also found different for different geophysical locations. Results suggest that there was a poor overall relationship between PM and BioPM across 40 monitoring locations （R2= 0.081, two-tailed P value = 0.07435）. Generally, city centers had higher PM concentrations than suburbs, but not BioPM and BioPM%. Indoor bioaerosol levels were found at least tenfold higher than those corresponding outdoors. Bacillus was observed to dominate the bacterial aerosol community in the air sample.
