The aerosol number spectrum and gas pollutants were measured and the new particle formation （NPF） events were discussed in Nanjing. The results showed that the size distributions of aerosol number concen- trations e...The aerosol number spectrum and gas pollutants were measured and the new particle formation （NPF） events were discussed in Nanjing. The results showed that the size distributions of aerosol number concen- trations exhibited distinct seasonal variations, implying the relations of particle sizes and their sources and sinks. The number concentrations of particles in the nuclei mode （10-30 nm）, Aitken mode （30-100 nm）, accumulation mode （100 -1000 nm） and coarse mode （〉1μm） varied in the order of summer 〉 spring 〉 autumn, summer 〉 autumn 〉 spring, autumn 〉 summer 〉 spring, and spring 〉 autumn 〉summer, re- spectively. The diurnal variation of total aerosol number concentrations showed three peaks in all observed periods, which corresponded to two rush hours and the photochemistry period at noon. In general, the NPF in summer occurred under the conditions of east winds and dominant air masses originating from marine areas with high relative humidity （50%-70%） and strong solar radiations （400 -700 W m-2）. In spring, the NPF were generally accompanied by low relative humidity （14%-30%） and strong solar radiations （400-600 W m-2）. The new particle growth rates （GR） were higher in the summertime in the range of 10- 16 nm h-1. In spring, the GR were 6.8-8.3 nm h-1. Under polluted air conditions, NPF events were seldom captured in autumn in Nanjing. During NPF periods, positive correlations between 10- 30 nm particles and 03 were detected, particularly in spring, indicating that NPF can be attributed to photochemical reactions.展开更多
Particle number size distribution(PNSD) between 10 nm and 20 μm were measured in the Pearl River Delta(PRD) region in winter 2011.The average particle number concentration of the nucleation mode(10-20 nm),Aitken mode...Particle number size distribution(PNSD) between 10 nm and 20 μm were measured in the Pearl River Delta(PRD) region in winter 2011.The average particle number concentration of the nucleation mode(10-20 nm),Aitken mode(20-100 nm),accumulation mode(100 nm-1μm) and coarse mode(1-20 μm) particles were 1 552,7 470,4 012,and 19 cm-3,respectively.The volume concentration of accumulation mode particles with peak at 300 nm accounted for over 70% of the total volume concentration.Diurnal variations and dependencies on meteorological parameters of PNSD were investigated.The diurnal variation of nucleation mode particles was mainly influenced by new particle formation events,while the diurnal variation of Aitken mode particles correlated to the traffic emission and the growth process of nucleation mode particles.When the PRD region was controlled by a cold high pressure,conditions of low relative humidity,high wind speed and strong radiation are favorable for the occurrence of new particle formation(NPF) events.The frequency of occurrence of NPF events was 21.3% during the whole measurement period.Parameters describing NPF events,including growth rate(GR) and source rate of condensable vapor(Q),were slightly larger than those in previous literature.This suggests that intense photochemical and biological activities may be the source of condensable vapor for particle growth,even during winter in the PRD.展开更多
To understand the contribution of new particle formation(NPF)events to ambient fine particle pollution,measurements of particle size distributions,trace gases and meteorological conditions,were conducted at a suburban...To understand the contribution of new particle formation(NPF)events to ambient fine particle pollution,measurements of particle size distributions,trace gases and meteorological conditions,were conducted at a suburban site(NJU)from October to December 2016 and at an industrial site(NUIST)from September to November 2015 in Nanjing.According to the temporal evolution of the particle size distributions,three types NPF events were observed:typical NPF(Type A),moderate NPF events(Type B)and strong NPF(Type C)events.The favorable conditions for Type A events included low relative humidity,low concentration of pre-existing particles,and high solar radiation.The favorable conditions of Type B events were similar to Type A,except for a higher concentration of pre-existing particles.Type C events were more likely to happen with the higher relative humidity,lower solar radiation and continuous growth of pre-existing particle concentration.The formation rate of 3 nm(J3)was the lowest for Type A events and highest for Type C events.In contrast,the growth rates of 10 nm and 40 nm particles were the highest for Type A,and lowest for Type C.Results show that NPF events with only higher J3 would lead to the accumulation of nucleation mode particles.Sulfuric acid was important for the formation of particles but had little effect on the growth of particle size.展开更多
The mechanisms of new particle formation(NPF)events that occurred under high aerosol loadings(“polluted”NPF)in the atmosphere have been unclear,which has inhibited the precision of particlepollution control.To deepe...The mechanisms of new particle formation(NPF)events that occurred under high aerosol loadings(“polluted”NPF)in the atmosphere have been unclear,which has inhibited the precision of particlepollution control.To deepen the understanding of how the“polluted”NPF events occur,a one-monthcomprehensive measurement was conducted in the atmosphere of Beijing during the summer of2016.The“clean”NPF events(frequency=22%)(condensation sink,CS<0.015 s^(-1))were found to becaused by local nucleation and growth.The“polluted”NPF events(frequency=28%)(CS>0.015 s^(-1))were influenced by both local nucleation-growth and regional transport,and the contributions from thetwo factors to 6e25 nm particle number concentration were 60%and 40%,respectively.This studyemphasized the importance of the transport for nanoparticles in relatively polluted atmospheres,and forthat the regional joint particle pollution control would be an essential policy.展开更多
Number concentration and distribution of airborne particles in the size range 5.6 to 560 nm diameter were measured in Beijing for a 15-d period in winter 2005. Dally average number concentrations of nucleation mode （...Number concentration and distribution of airborne particles in the size range 5.6 to 560 nm diameter were measured in Beijing for a 15-d period in winter 2005. Dally average number concentrations of nucleation mode （5.6-20 um）, Aitken mode （20-100 um）, and accumulation mode （100-560 um） particles, and total particles were 17500, 32000, 4000, and 53500 cm^-3, respectively. Average particle size distribution was monomodal with a mode diameter of about 40 um at night and bimodal with mode diameters of about 10 and about 40 um during the daytime. New particle formation events, which were connected to diurnal variation of nucleation mode particles, were observed in more than half of the observation days. The events often started around 10：00-11：00 Chinese Standard Time （CST） and ended up after 3-4 h. Concentrations of Aitken and accumulation mode particles increased from midnight and reached their maxima at about 10：00 CST, and then decreased and became the lowest in the afternoon. Analysis of diurnal cycles in traffic volume and meteorological parameters revealed that the accumulation of the particles in Aitken and accumulation modes in the morning was influenced by formation of an inversion and increase in vehicle emission, and dispersion of such particles in the afternoon was associated with more effective vertical mixing and higher wind speed.展开更多
Particle number size distribution from 10 to 10,000 nm was measured by a wide-range particle spectrometer （WPS-1000XP） at a downwind site north of downtown Lanzhou, western China, from 25 june to 19 July 2006. We fi...Particle number size distribution from 10 to 10,000 nm was measured by a wide-range particle spectrometer （WPS-1000XP） at a downwind site north of downtown Lanzhou, western China, from 25 june to 19 July 2006. We first report the pollution level, diurnal variation of particle concentration in different size ranges and then introduce the characteristics of the particle formation processes, to show that the number concentration of ultrafine particles was lower than the values measured in other urban or suburban areas in previous studies, However, the fraction of ultrafine particles in total aerosol number concentration was found to be much higher. Furthermore, sharp increase of ultrafine particle concentration was frequently observed at noon. An examination of the diurnal pattern suggests that the burst of the ultrafine particles was mainly due to nucleation process. During the 25-day observation, new particle formation （NPF） from homogeneous nucleation was observed during 33% of the study period. The average growth rate of the newly formed particles was 4.4 nm/h, varying from 1.3 to 16,9 nm/h. The needed concentration of condensable vapor was 6.1 × 10^7 cm-3, and its source rate was 1.1× 10^6 cm-3 s 1. Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rate was 68.3%.展开更多
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
Long-term continuous measurements of particle number size distributions with mobility diameter sizes ranging from 3 to 800 nm were pertbrmed to study new particle formation （NPF） events at Shangdianzi （SDZ）, Mt. T...Long-term continuous measurements of particle number size distributions with mobility diameter sizes ranging from 3 to 800 nm were pertbrmed to study new particle formation （NPF） events at Shangdianzi （SDZ）, Mt. Tai （TS）, and Lin＇an （LAN） stations representing the background atmospheric conditions in the North China Plain （NCP） Central East China （CEC） and Yangtze River Delta （YRD） regions, respectively. The mean formation rate of 3-nm particles was 6.3, 3.7, and 5.8 cm -3 .s-1, and the mean particle growth rate was 3.6, 6.0, and 6.2 nm. h at SDZ, TS, and LAN, respectively. The NPF, event characteristics at the three sites indicate that there may be a stronger source of low volatile vapors and higher condensational sink of pre-existing particles in the YRD region. The formation rate of NPF events at these sites, as well as the condensation sink, is approximately 10 times higher than some results reported at rural/urban sites in western countries. However, the growth rates appear to be 1 2 times higher. Approximately 12%-17% of all NPF events with nucleated particles grow to a climate- relevant size （〉50 nm）. These kinds of NPF events were normally observed with higher growth rate than the other NPF cases. Generally, the cloud condensation nuclei （CCN） number concentration can be enhanced by approximately a factor of 2 6 on these event days. The mean value of the enhancement factor is lowest at LAN （2-3） and highest at SDZ （-4）. NPF events have also been found to have greater impact on CCN production in China at the regional scale than in the other background sites worldwide.展开更多
This study discusses the evolution of particle number size distribution during episodes of heavy pollution and new particle formation in the urban atmosphere of Beijing to quantify the effects of dynamic processes (co...This study discusses the evolution of particle number size distribution during episodes of heavy pollution and new particle formation in the urban atmosphere of Beijing to quantify the effects of dynamic processes (coagulation and condensation) on the particle number size distribution.During a heavy-pollution event,an extremely low number concentration of 3-10 nm particles (on average 46 cm-3) was observed.This is because nucleation-mode particles were easily removed by strong coagulational scavenging of larger particles under this condition.In addition,a large condensation sink (on average 0.13 s-1) restrained nucleation,which is one of the major sources of nucleation-mode particles.Conversely,during a new-particle formation event,the small condensation sink (0.01 s-1) of precursor facilitated nucleation.At the same time,preexisting particles had little ability to scavenge newly formed particles (around 1 nm) and allowed them to grow to a detectable size (larger than 3 nm currently).We suggest that the effects of dynamic processes (coagulation and condensation) on particle size distribution should be stressed under some extreme conditions of the relatively polluted urban atmosphere in addition to traffic and meteorological factors.展开更多
Knowledge of particle number size distribution（PND） and new particle formation（NPF）events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air q...Knowledge of particle number size distribution（PND） and new particle formation（NPF）events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air quality,haze,and human health.In this study,seven field measurement campaigns were conducted from December 2013 to May 2015 using a scanning mobility particle sizer（SMPS） at four sites in Southern China,including three urban sites and one background site.Particles were measured in the size range of15-515 nm,and the median particle number concentrations（PNCs） were found to vary in the range of 0.3× 10~4-2.2 × 10~4 cn^（-3） at the urban sites and were approximately 0.2 × 10~4 cm^（-3） at the background site.The peak diameters at the different sites varied largely from 22 to 102 nm.The PNCs in the Aitken mode（25-100 nm） at the urban sites were up to 10 times higher than they were at the background site,indicating large primary emissions from traffic at the urban sites.The diurnal variations of PNCs were significantly influenced by both rush hour traffic at the urban sites and NPF events.The frequencies of NPF events at the different sites were0%-30%,with the highest frequency occurring at an urban site during autumn.With higher SO_2 concentrations and higher ambient temperatures being necessary,NPF at the urban site was found to be more influenced by atmospheric oxidizing capability,while NPF at the background site was limited by the condensation sink.This study provides a unique dataset of particle number and size information in various environments in Southern China,which can help understand the sources,formation,and the climate forcing of aerosols in this quickly developing region,as well as help constrain and validate NPF modeling.展开更多
New particle formation(NPF)events are an increasingly interesting topic in air quality and climate science.In this study,the particle number size distributions,and the frequency of NPF events over Hefei were investiga...New particle formation(NPF)events are an increasingly interesting topic in air quality and climate science.In this study,the particle number size distributions,and the frequency of NPF events over Hefei were investigated from November 2018 to February 2019.The proportions of the nucleation mode,Aitken mode,and accumulation mode were 24.59%,53.10%,and 22.30%,respectively,which indicates the presence of abundant ultrafine particles in Hefei.Forty-six NPF events occurred during the observation days,accounting for 41.82%of the entire observation period.Moreover,the favorable meteorological conditions,potential precursor gases,and PM_(2.5)range of the NPF events were analyzed.Compared to non-NPF days,the NPF events preferentially occurred on days with lower relative humidity,higher wind speeds,and higher temperatures.When the PM_(2.5) was 15–20,70–80,and105–115μg/m^(3),the frequency of the NPF events was higher.Nucleation mode particles were positively related to atmospheric oxidation indicated by ozone when PM_(2.5) ranged from 15 to 20μg/m^(3),and related to gaseous precursors like SO_(2) and NO_(2) when PM_(2.5)was located at 70-80 and 105–115μg/m^(3).On pollution days,NPF events did not directly contribute to the increase in the PM_(2.5) in the daytime,however,NPF events would occur during the night and the growth of particulate matter contributes to the nighttime PM_(2.5) contents.This could lead to pollution that lasted into the next day.These findings are significant to the improvement of our understanding of the effects of aerosols on air quality.展开更多
基金funded by the Special Fund for Public Welfare Industrial(Meteorology)Research of China(Grant No.GYHY20120602104)National Natural Science Foundation of China(Grant Nos.41030962 and 41005089)+1 种基金Jiangsu"333"Program,Jiangsu"Qinglan"program,Graduate Cultivation Innovative Project of Jiangsu province(Grant No.CXZZ110616)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions
文摘The aerosol number spectrum and gas pollutants were measured and the new particle formation （NPF） events were discussed in Nanjing. The results showed that the size distributions of aerosol number concen- trations exhibited distinct seasonal variations, implying the relations of particle sizes and their sources and sinks. The number concentrations of particles in the nuclei mode （10-30 nm）, Aitken mode （30-100 nm）, accumulation mode （100 -1000 nm） and coarse mode （〉1μm） varied in the order of summer 〉 spring 〉 autumn, summer 〉 autumn 〉 spring, autumn 〉 summer 〉 spring, and spring 〉 autumn 〉summer, re- spectively. The diurnal variation of total aerosol number concentrations showed three peaks in all observed periods, which corresponded to two rush hours and the photochemistry period at noon. In general, the NPF in summer occurred under the conditions of east winds and dominant air masses originating from marine areas with high relative humidity （50%-70%） and strong solar radiations （400 -700 W m-2）. In spring, the NPF were generally accompanied by low relative humidity （14%-30%） and strong solar radiations （400-600 W m-2）. The new particle growth rates （GR） were higher in the summertime in the range of 10- 16 nm h-1. In spring, the GR were 6.8-8.3 nm h-1. Under polluted air conditions, NPF events were seldom captured in autumn in Nanjing. During NPF periods, positive correlations between 10- 30 nm particles and 03 were detected, particularly in spring, indicating that NPF can be attributed to photochemical reactions.
基金Natural Science Foundation of China(41375156)Natural Science Foundation of Guangdong Province,China(S2013010013265)+2 种基金Special R&D fund for research institutes(2014EG137243)National Key Project of Basic Research(2011CB403403)Science and Technology Planning Project for Guangdong Province(2012A061400012)
文摘Particle number size distribution(PNSD) between 10 nm and 20 μm were measured in the Pearl River Delta(PRD) region in winter 2011.The average particle number concentration of the nucleation mode(10-20 nm),Aitken mode(20-100 nm),accumulation mode(100 nm-1μm) and coarse mode(1-20 μm) particles were 1 552,7 470,4 012,and 19 cm-3,respectively.The volume concentration of accumulation mode particles with peak at 300 nm accounted for over 70% of the total volume concentration.Diurnal variations and dependencies on meteorological parameters of PNSD were investigated.The diurnal variation of nucleation mode particles was mainly influenced by new particle formation events,while the diurnal variation of Aitken mode particles correlated to the traffic emission and the growth process of nucleation mode particles.When the PRD region was controlled by a cold high pressure,conditions of low relative humidity,high wind speed and strong radiation are favorable for the occurrence of new particle formation(NPF) events.The frequency of occurrence of NPF events was 21.3% during the whole measurement period.Parameters describing NPF events,including growth rate(GR) and source rate of condensable vapor(Q),were slightly larger than those in previous literature.This suggests that intense photochemical and biological activities may be the source of condensable vapor for particle growth,even during winter in the PRD.
基金sponsored by the National Natural Science Foundation of China(Nos.41922052 and 42177080)。
文摘To understand the contribution of new particle formation(NPF)events to ambient fine particle pollution,measurements of particle size distributions,trace gases and meteorological conditions,were conducted at a suburban site(NJU)from October to December 2016 and at an industrial site(NUIST)from September to November 2015 in Nanjing.According to the temporal evolution of the particle size distributions,three types NPF events were observed:typical NPF(Type A),moderate NPF events(Type B)and strong NPF(Type C)events.The favorable conditions for Type A events included low relative humidity,low concentration of pre-existing particles,and high solar radiation.The favorable conditions of Type B events were similar to Type A,except for a higher concentration of pre-existing particles.Type C events were more likely to happen with the higher relative humidity,lower solar radiation and continuous growth of pre-existing particle concentration.The formation rate of 3 nm(J3)was the lowest for Type A events and highest for Type C events.In contrast,the growth rates of 10 nm and 40 nm particles were the highest for Type A,and lowest for Type C.Results show that NPF events with only higher J3 would lead to the accumulation of nucleation mode particles.Sulfuric acid was important for the formation of particles but had little effect on the growth of particle size.
基金This study is funded by the National Natural Science Foundationof China(NSFC)(grant No.91844301)the NSFC e Creative ResearchGroup Fund(grant No.22221004)+1 种基金the National Key Research andDevelopment Program of China(grant No.2022YFC3701000,Task1)the bilateral SwedeneChina framework program“Photochemical smog in China:formation,transformation,impactand abatement strategies”(grant No.639-2013-6917).
文摘The mechanisms of new particle formation(NPF)events that occurred under high aerosol loadings(“polluted”NPF)in the atmosphere have been unclear,which has inhibited the precision of particlepollution control.To deepen the understanding of how the“polluted”NPF events occur,a one-monthcomprehensive measurement was conducted in the atmosphere of Beijing during the summer of2016.The“clean”NPF events(frequency=22%)(condensation sink,CS<0.015 s^(-1))were found to becaused by local nucleation and growth.The“polluted”NPF events(frequency=28%)(CS>0.015 s^(-1))were influenced by both local nucleation-growth and regional transport,and the contributions from thetwo factors to 6e25 nm particle number concentration were 60%and 40%,respectively.This studyemphasized the importance of the transport for nanoparticles in relatively polluted atmospheres,and forthat the regional joint particle pollution control would be an essential policy.
基金Project supported by the National Natural Science Foundation of China(No.20477020)the National Science Fund for Distinguished Young Scholars(No.20625722).
文摘Number concentration and distribution of airborne particles in the size range 5.6 to 560 nm diameter were measured in Beijing for a 15-d period in winter 2005. Dally average number concentrations of nucleation mode （5.6-20 um）, Aitken mode （20-100 um）, and accumulation mode （100-560 um） particles, and total particles were 17500, 32000, 4000, and 53500 cm^-3, respectively. Average particle size distribution was monomodal with a mode diameter of about 40 um at night and bimodal with mode diameters of about 10 and about 40 um during the daytime. New particle formation events, which were connected to diurnal variation of nucleation mode particles, were observed in more than half of the observation days. The events often started around 10：00-11：00 Chinese Standard Time （CST） and ended up after 3-4 h. Concentrations of Aitken and accumulation mode particles increased from midnight and reached their maxima at about 10：00 CST, and then decreased and became the lowest in the afternoon. Analysis of diurnal cycles in traffic volume and meteorological parameters revealed that the accumulation of the particles in Aitken and accumulation modes in the morning was influenced by formation of an inversion and increase in vehicle emission, and dispersion of such particles in the afternoon was associated with more effective vertical mixing and higher wind speed.
基金funded by the National Basic Research Program of China (2005CB422203, 2005CB422208)National Department Public Benefit Research Foundation (No.201009001)National Natural Science Foundation of China(Grant No. 41005065)
文摘Particle number size distribution from 10 to 10,000 nm was measured by a wide-range particle spectrometer （WPS-1000XP） at a downwind site north of downtown Lanzhou, western China, from 25 june to 19 July 2006. We first report the pollution level, diurnal variation of particle concentration in different size ranges and then introduce the characteristics of the particle formation processes, to show that the number concentration of ultrafine particles was lower than the values measured in other urban or suburban areas in previous studies, However, the fraction of ultrafine particles in total aerosol number concentration was found to be much higher. Furthermore, sharp increase of ultrafine particle concentration was frequently observed at noon. An examination of the diurnal pattern suggests that the burst of the ultrafine particles was mainly due to nucleation process. During the 25-day observation, new particle formation （NPF） from homogeneous nucleation was observed during 33% of the study period. The average growth rate of the newly formed particles was 4.4 nm/h, varying from 1.3 to 16,9 nm/h. The needed concentration of condensable vapor was 6.1 × 10^7 cm-3, and its source rate was 1.1× 10^6 cm-3 s 1. Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rate was 68.3%.
文摘鉴于新粒子生成(New particle formation,NPF)对气候的重要效应,过去很多研究重点关注持续增长型NPF事件;但新粒子生长过程中时常也伴随着非持续型生长,如生长粒径先增长后下降的收缩型以及粒径明显不增长的团块型NPF事件,对于这类NPF事件的生长机制尚不清楚。基于此,本研究于2019年夏季在中国科学院北京森林生态系统定位研究站(39.96°N,115.43°E,1170 m a.s.l.,以下简称北京山地森林站)进行了NPF事件的野外观测,发现了4次持续生长型NPF事件和3次非持续生长型NPF事件。本文借助WRF-Chem模式进一步探究非持续生长型NPF事件的生长机制,发现其主要成因有三个:首先,北京山地森林站与成核相关的气态前体物充足,但颗粒物中SO_(4)^(2-)、NO_(3)^(-)、NH_(4)^(+)等无机盐浓度较低,削弱了新粒子的后续增长能力;其次,后向轨迹显示非持续生长型NPF事件的气团来源于清洁的北方地区;最后,通过过程分析发现水平和垂向输送是非持续生长型NPF事件的重要物理过程。本研究对非持续增长新粒子传输来源和生长机制的解释,对于完善新粒子增长的物理化学机制的理解具有重要意义。
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This work was supported by National Basic Research Program of China （No. 2011CB403401）, the National Natural Science Foundation of China （Grant Nos. 41175113 and 41405132）, CAMS Basis Research Project （Nos. 2013Z007 and 2013Y004）. This paper is partially supported by the CMA Innovation Team for Haze-fog Observation and Forecasts. The authors would also like to thank the staff at Shangdianzi, Linan and Mr. Tai for operating and maintaining the instruments and the Leibniz Institute for Tropospheric Research for providing the TDMPS used at the SDZ station.
文摘Long-term continuous measurements of particle number size distributions with mobility diameter sizes ranging from 3 to 800 nm were pertbrmed to study new particle formation （NPF） events at Shangdianzi （SDZ）, Mt. Tai （TS）, and Lin＇an （LAN） stations representing the background atmospheric conditions in the North China Plain （NCP） Central East China （CEC） and Yangtze River Delta （YRD） regions, respectively. The mean formation rate of 3-nm particles was 6.3, 3.7, and 5.8 cm -3 .s-1, and the mean particle growth rate was 3.6, 6.0, and 6.2 nm. h at SDZ, TS, and LAN, respectively. The NPF, event characteristics at the three sites indicate that there may be a stronger source of low volatile vapors and higher condensational sink of pre-existing particles in the YRD region. The formation rate of NPF events at these sites, as well as the condensation sink, is approximately 10 times higher than some results reported at rural/urban sites in western countries. However, the growth rates appear to be 1 2 times higher. Approximately 12%-17% of all NPF events with nucleated particles grow to a climate- relevant size （〉50 nm）. These kinds of NPF events were normally observed with higher growth rate than the other NPF cases. Generally, the cloud condensation nuclei （CCN） number concentration can be enhanced by approximately a factor of 2 6 on these event days. The mean value of the enhancement factor is lowest at LAN （2-3） and highest at SDZ （-4）. NPF events have also been found to have greater impact on CCN production in China at the regional scale than in the other background sites worldwide.
基金supported by National Natural Science Foundation of China (Grant No. 20977001,21025728)
文摘This study discusses the evolution of particle number size distribution during episodes of heavy pollution and new particle formation in the urban atmosphere of Beijing to quantify the effects of dynamic processes (coagulation and condensation) on the particle number size distribution.During a heavy-pollution event,an extremely low number concentration of 3-10 nm particles (on average 46 cm-3) was observed.This is because nucleation-mode particles were easily removed by strong coagulational scavenging of larger particles under this condition.In addition,a large condensation sink (on average 0.13 s-1) restrained nucleation,which is one of the major sources of nucleation-mode particles.Conversely,during a new-particle formation event,the small condensation sink (0.01 s-1) of precursor facilitated nucleation.At the same time,preexisting particles had little ability to scavenge newly formed particles (around 1 nm) and allowed them to grow to a detectable size (larger than 3 nm currently).We suggest that the effects of dynamic processes (coagulation and condensation) on particle size distribution should be stressed under some extreme conditions of the relatively polluted urban atmosphere in addition to traffic and meteorological factors.
基金supported by the National Natural Science Foundation of China(Nos.U1301234,21277003)the Shenzhen Science&Technology Plan,and the Ministry of Science and Technology of China(No.2013CB228503)
文摘Knowledge of particle number size distribution（PND） and new particle formation（NPF）events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air quality,haze,and human health.In this study,seven field measurement campaigns were conducted from December 2013 to May 2015 using a scanning mobility particle sizer（SMPS） at four sites in Southern China,including three urban sites and one background site.Particles were measured in the size range of15-515 nm,and the median particle number concentrations（PNCs） were found to vary in the range of 0.3× 10~4-2.2 × 10~4 cn^（-3） at the urban sites and were approximately 0.2 × 10~4 cm^（-3） at the background site.The peak diameters at the different sites varied largely from 22 to 102 nm.The PNCs in the Aitken mode（25-100 nm） at the urban sites were up to 10 times higher than they were at the background site,indicating large primary emissions from traffic at the urban sites.The diurnal variations of PNCs were significantly influenced by both rush hour traffic at the urban sites and NPF events.The frequencies of NPF events at the different sites were0%-30%,with the highest frequency occurring at an urban site during autumn.With higher SO_2 concentrations and higher ambient temperatures being necessary,NPF at the urban site was found to be more influenced by atmospheric oxidizing capability,while NPF at the background site was limited by the condensation sink.This study provides a unique dataset of particle number and size information in various environments in Southern China,which can help understand the sources,formation,and the climate forcing of aerosols in this quickly developing region,as well as help constrain and validate NPF modeling.
基金supported by grants from the National Key Research and Development Program of China(Nos.2017YFC0210002,2018YFC0213104,2016YFC0203302 and 2017YFC0212800)the National Natural Science Foundation of China(Nos.41722501,51778596,and 41977184)+5 种基金the Anhui Science and Technology Major Project(No.18030801111)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(Nos.DQGG0102 and DQGG0205)the Natural Science Foundation of Anhui Province(No.1908085QD170)the Key Research and Development Project of Anhui Province(No.202004i07020002)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(No.CERAE202004)。
文摘New particle formation(NPF)events are an increasingly interesting topic in air quality and climate science.In this study,the particle number size distributions,and the frequency of NPF events over Hefei were investigated from November 2018 to February 2019.The proportions of the nucleation mode,Aitken mode,and accumulation mode were 24.59%,53.10%,and 22.30%,respectively,which indicates the presence of abundant ultrafine particles in Hefei.Forty-six NPF events occurred during the observation days,accounting for 41.82%of the entire observation period.Moreover,the favorable meteorological conditions,potential precursor gases,and PM_(2.5)range of the NPF events were analyzed.Compared to non-NPF days,the NPF events preferentially occurred on days with lower relative humidity,higher wind speeds,and higher temperatures.When the PM_(2.5) was 15–20,70–80,and105–115μg/m^(3),the frequency of the NPF events was higher.Nucleation mode particles were positively related to atmospheric oxidation indicated by ozone when PM_(2.5) ranged from 15 to 20μg/m^(3),and related to gaseous precursors like SO_(2) and NO_(2) when PM_(2.5)was located at 70-80 and 105–115μg/m^(3).On pollution days,NPF events did not directly contribute to the increase in the PM_(2.5) in the daytime,however,NPF events would occur during the night and the growth of particulate matter contributes to the nighttime PM_(2.5) contents.This could lead to pollution that lasted into the next day.These findings are significant to the improvement of our understanding of the effects of aerosols on air quality.
