The Effect of Meteorological Conditions and Atmospheric Composition in the Occurrence and Development of New Particle Formation (NPF) Events in Europe

Abstract. Although new particle formation (NPF) events have been studied extensively for some decades, the mechanisms that drive their occurrence and development are yet to be fully elucidated. Laboratory studies have done much to elucidate the molecular processes involved in nucleation, but this knowledge has yet to be linked to NPF events in the atmosphere, except at very clean air sites. There is great difficulty in successful application of the results from laboratory studies to real atmospheric conditions, due to the diversity of atmospheric conditions and observations found, as NPF events occur almost everywhere in the world without following a clearly defined trend of frequency, seasonality, atmospheric conditions or event development. The present study seeks common features in nucleation events by applying a binned linear regression over an extensive dataset from 16 sites of various types (rural and urban backgrounds as well as roadsides) in Europe. A clear positive relation is found between the solar radiation intensity, temperature and atmospheric pressure with the frequency of NPF events, while relative humidity presents a negative relation with NPF event frequency. Wind speed presents a less consistent relationship which appears to be heavily affected by local conditions. While some meteorological variables appear to have a crucial effect on the occurrence and characteristics of NPF events, especially at rural sites, it appears that their role becomes less marked when at higher values. The analysis of chemical composition data presents interesting results. Concentrations of almost all chemical compounds studied (apart from O3) and the Condensation Sink (CS) have a negative relation with NPF event probability, though areas with higher average concentrations of SO2 had higher NPF event probability. Particulate Organic Carbon (OC), Volatile Organic Compounds (VOCs) and particulate phase sulphate consistently had a positive relation with the growth rate of the newly formed particles. As with some meteorological variables, it appears that at increased concentrations of pollutants or the CS, their influence upon NPF probability is reduced.

Download Full-text

The effect of meteorological conditions and atmospheric composition in the occurrence and development of new particle formation (NPF) events in Europe

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-3345-2021 ◽

2021 ◽

Vol 21 (5) ◽

pp. 3345-3370

Author(s):

Dimitrios Bousiotis ◽

James Brean ◽

Francis D. Pope ◽

Manuel Dall'Osto ◽

Xavier Querol ◽

...

Keyword(s):

Solar Radiation ◽

Radiation Intensity ◽

Particle Formation ◽

Meteorological Variables ◽

Atmospheric Conditions ◽

Laboratory Studies ◽

New Particle Formation ◽

Positive Relation ◽

Event Frequency ◽

Solar Radiation Intensity

Abstract. Although new particle formation (NPF) events have been studied extensively for some decades, the mechanisms that drive their occurrence and development are yet to be fully elucidated. Laboratory studies have done much to elucidate the molecular processes involved in nucleation, but this knowledge has yet to be conclusively linked to NPF events in the atmosphere. There is great difficulty in successful application of the results from laboratory studies to real atmospheric conditions due to the diversity of atmospheric conditions and observations found, as NPF events occur almost everywhere in the world without always following a clearly defined trend of frequency, seasonality, atmospheric conditions, or event development. The present study seeks common features in nucleation events by applying a binned linear regression over an extensive dataset from 16 sites of various types (combined dataset of 85 years from rural and urban backgrounds as well as roadside sites) in Europe. At most sites, a clear positive relation with the frequency of NPF events is found between the solar radiation intensity (up to R2=0.98), temperature (up to R2=0.98), and atmospheric pressure (up to R2=0.97), while relative humidity (RH) presents a negative relation (up to R2=0.95) with NPF event frequency, though exceptions were found among the sites for all the variables studied. Wind speed presents a less consistent relationship, which appears to be heavily affected by local conditions. While some meteorological variables (such as the solar radiation intensity and RH) appear to have a crucial effect on the occurrence and characteristics of NPF events, especially at rural sites, it appears that their role becomes less marked at higher average values. The analysis of chemical composition data presents interesting results. Concentrations of almost all chemical compounds studied (apart from O3) and the condensation sink (CS) have a negative relationship with NPF event frequency, though areas with higher average concentrations of SO2 had higher NPF event frequency. Particulate organic carbon (OC), volatile organic compounds (VOCs), and particulate-phase sulfate consistently had a positive relation with the growth rate of the newly formed particles. As with some meteorological variables, it appears that at increased concentrations of pollutants or the CS, their influence upon NPF frequency is reduced.

Download Full-text

Kinetics of sulfuric acid-amine nucleation in the urban atmospheric environment

10.5194/egusphere-egu2020-8262 ◽

2020 ◽

Author(s):

Runlong Cai ◽

Chao Yan ◽

Jun Zheng ◽

Lin Wang ◽

Markku Kulmala ◽

...

Keyword(s):

Reaction Kinetics ◽

Urban Environment ◽

Formation Rate ◽

Particle Formation ◽

Atmospheric Environment ◽

Atmospheric Conditions ◽

Laboratory Studies ◽

New Particle Formation ◽

The Real ◽

Real Atmosphere

The formation of new secondary aerosols form gaseous precursors is a frequent phenomenon in various atmospheric environments and it impacts aerosol number concentration, cloud formation, and hence climate. There has been a considerable number of new particle formation (NPF) studies in various atmospheric environments, but current knowledge on NPF in the polluted atmospheric boundary layer (e.g., the urban environment in megacities) is still limited. The clustering of H2SO4 and amines is a possible mechanism driving the fast nucleation and initial growth of new particles in the polluted urban environment. Laboratory studies using typical ambient H2SO4 concentrations and theoretical calculations based on quantum chemistry have provided insights into H2SO4-amine nucleation. However, the molecular-level mechanism and governing factors for H2SO4-amine nucleation have not been quantitatively investigated in the real atmosphere. Some previous studies indicate that differently from clean environments, the coagulation scavenging is a governing factor for NPF in polluted environments. In the presence of a high aerosol concentration in the polluted environment, a considerable fraction of the newly formed particles are scavenged by coagulation within minutes and hence, NPF is significantly suppressed. Similarly, the coagulation scavenging may also impact the steady-state cluster concentrations and the new particle formation rate. Due to the differences in the coagulation scavenging and perhaps some gaseous precursor concentrations between laboratory and atmospheric conditions, the reaction kinetics determined in previous laboratory studies may not directly applicable to the real atmosphere. Herein, based on long-term atmospheric measurements from January 2018 to March 2019 in urban Beijing, we show the different reaction kinetics under laboratory and atmospheric conditions and how to unify them using proper normalization approaches. The influences of governing factors on particle formation rate are then quantitatively elucidated. Based on the synergistic effects of these factors, an indicator for the occurrence of NPF in the urban environment is proposed and verified.

Download Full-text

Evidence of an elevated source of nucleation based on model simulations and data from the NIFTy experiment

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-8021-2012 ◽

2012 ◽

Vol 12 (17) ◽

pp. 8021-8036 ◽

Cited By ~ 11

Author(s):

P. Crippa ◽

T. Petäjä ◽

H. Korhonen ◽

G. S. El Afandi ◽

S. C. Pryor

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Ultrafine Particle ◽

Ground Level ◽

Particle Formation ◽

Atmospheric Conditions ◽

New Particle Formation ◽

Near Surface ◽

Nocturnal Inversion

Abstract. New particle formation has been observed at a number of ground-based measurement sites. Prior research has provided evidence that this new particle formation, while observed in the near-surface layer, is actually occurring in atmospheric layers above the surface and appears to be focused in or close to the residual layer formed by the nocturnal inversion. Here, we present both observations and modeling for southern Indiana which support this postulate. Based on simulations with a detailed aerosol dynamics model and the Weather Research and Forecasting model, along with data from ground-based remote sensing instruments and detailed gas and particle phase measurements, we show evidence that (i) the maximum rate change of ultrafine particle concentrations as observed close to the surface is always preceded by breakdown of the nocturnal inversion and enhancement of vertical mixing and (ii) simulated particle size distributions exhibit greatest accord with surface observations during and subsequent to nucleation only when initialized with a particle size distribution representative of clear atmospheric conditions, rather than the in situ (ground-level) particle size distribution.

Download Full-text

On the formation of sulphuric acid-amine clusters in varying atmospheric conditions and its influence on atmospheric new particle formation

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-11485-2012 ◽

2012 ◽

Vol 12 (5) ◽

pp. 11485-11537 ◽

Cited By ~ 1

Author(s):

P. Paasonen ◽

T. Olenius ◽

O. Kupiainen ◽

T. Kurtén ◽

T. Petäjä ◽

...

Keyword(s):

Relative Humidity ◽

Sulphuric Acid ◽

Acid Concentration ◽

Formation Rate ◽

Particle Formation ◽

Atmospheric Conditions ◽

New Particle Formation ◽

Atmospheric Particle ◽

Atmospheric Observations ◽

Sulphuric Acid Concentration

Abstract. Sulphuric acid is a key component in atmospheric new particle formation. However, sulphuric acid alone does not form stable enough clusters to initiate particle formation in atmospheric conditions. Strong bases, such as amines, have been suggested to stabilize sulphuric acid clusters and thus participate in particle formation. We modelled the formation rate of clusters with two sulphuric acid and two amine molecules (JA2B2) at varying atmospherically relevant conditions with respect to concentrations of sulphuric acid ([H2SO4]), dimethylamine ([DMA]) and trimethylamine ([TMA]), temperature and relative humidity (RH). The modelled formation rates JA2B2 were functions of sulphuric acid concentration with close to quadratic dependence, which is in good agreement with atmospheric observations of the connection between the particle formation rate and sulphuric acid concentration. The coefficients KA2B2 connecting the cluster formation rate and sulphuric acid concentrations as JA2B2 = KA2B2[H2SO4]2 turned out to depend also on amine concentrations, temperature and relative humidity. We tested how the model results change if the clusters with two sulphuric acid and two amine molecules are assumed to act as seeds for heterogeneous nucleation of organic vapours (other than amines) with higher atmospheric concentrations than sulphuric acid. We also compared the modelled coefficients KA2B2 with the corresponding coefficients calculated from the atmospheric observations (Kobs) from environments with varying temperatures and levels of anthropogenic influence. By taking into account the modelled behaviour of JA2B2 as a function of [H2SO4], temperature and RH, the atmospheric particle formation rate was reproduced more closely than with the traditional semi-empirical formulae based on sulphuric acid concentration only. The formation rates of clusters with two sulphuric acid and two amine molecules with different amine compositions (DMA or TMA or one of both) had different responses to varying meteorological conditions and concentrations of vapours participating to particle formation. The observed inverse proportionality of the coefficient Kobs with RH and temperature agreed best with the modelled coefficient KA2B2 related to formation of a~cluster with two H2SO4 and one or two TMA molecules, assuming that these clusters can grow in collisions with abundant organic vapour molecules. In case this assumption is valid, our results suggest that the formation rate of clusters with at least two of both sulphuric acid and amine molecules might be the rate-limiting step for atmospheric particle formation. More generally, our analysis elucidates the sensitivity of the atmospheric particle formation rate to meteorological variables and concentrations of vapours participating in particle formation (also other than H2SO4).

Download Full-text

The Role of Organic Acids in New Particle Formation from Methanesulfonic Acid and Methylamine

10.5194/acp-2021-831 ◽

2021 ◽

Author(s):

Rongjie Zhang ◽

Jiewen Shen ◽

Hong-Bin Xie ◽

Jingwen Chen ◽

Jonas Elm

Keyword(s):

Organic Acids ◽

Cluster Formation ◽

Methanesulfonic Acid ◽

Particle Formation ◽

Structural Factors ◽

Atmospheric Conditions ◽

New Particle Formation ◽

Free Energies ◽

Limited Temperature

Abstract. Atmospheric organic acids (OAs) are expected to enhance methanesulfonic acid (MSA)-driven new particle formation (NPF). However, the exact role of OAs in MSA-driven NPF remains unclear. Here, we employed a two-step strategy to probe the role of OAs in MSA-methylamine (MA) NPF. Initially, we evaluated the enhancing potential of 12 commonly detected OAs in ternary MA-MSA-OA cluster formation by considering the formation free energies of the (MSA)1(MA)1(OA)1 clusters and the atmospheric concentrations of the OAs. It was found that formic acid (ForA) has the highest potential to stabilize the MA-MSA clusters. The high enhancing potential of ForA results from its acidity, structural factors such as no intramolecular H-bonds and high atmospheric abundance. The second step is to extend the MSA-MA-ForA system to larger cluster sizes. The results indicate that ForA can indeed enhance MSA-MA NPF at atmospheric conditions (the upper limited temperature is 258.15 K), indicating that ForA might have an important role in MSA-driven NPF. The enhancing effect of ForA is mainly caused by an increased formation of the (MSA)2(MA)1 cluster, which is involved in the pathway of binary MSA-MA nucleation. Hence, our results indicate that OAs might be required to facilitate MSA-driven NPF in the atmosphere.

Download Full-text

On the formation of sulphuric acid – amine clusters in varying atmospheric conditions and its influence on atmospheric new particle formation

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-9113-2012 ◽

2012 ◽

Vol 12 (19) ◽

pp. 9113-9133 ◽

Cited By ~ 88

Author(s):

P. Paasonen ◽

T. Olenius ◽

O. Kupiainen ◽

T. Kurtén ◽

T. Petäjä ◽

...

Keyword(s):

Relative Humidity ◽

Sulphuric Acid ◽

Acid Concentration ◽

Formation Rate ◽

Particle Formation ◽

Atmospheric Conditions ◽

New Particle Formation ◽

Atmospheric Particle ◽

Atmospheric Observations ◽

Sulphuric Acid Concentration

Abstract. Sulphuric acid is a key component in atmospheric new particle formation. However, sulphuric acid alone does not form stable enough clusters to initiate particle formation in atmospheric conditions. Strong bases, such as amines, have been suggested to stabilize sulphuric acid clusters and thus participate in particle formation. We modelled the formation rate of clusters with two sulphuric acid and two amine molecules (JA2B2) at varying atmospherically relevant conditions with respect to concentrations of sulphuric acid ([H2SO4]), dimethylamine ([DMA]) and trimethylamine ([TMA]), temperature and relative humidity (RH). We also tested how the model results change if we assume that the clusters with two sulphuric acid and two amine molecules would act as seeds for heterogeneous nucleation of organic vapours (other than amines) with higher atmospheric concentrations than sulphuric acid. The modelled formation rates JA2B2 were functions of sulphuric acid concentration with close to quadratic dependence, which is in good agreement with atmospheric observations of the connection between the particle formation rate and sulphuric acid concentration. The coefficients KA2B2 connecting the cluster formation rate and sulphuric acid concentrations as JA2B2=KA2B2[H2SO4]2 turned out to depend also on amine concentrations, temperature and relative humidity. We compared the modelled coefficients KA2B2 with the corresponding coefficients calculated from the atmospheric observations (Kobs) from environments with varying temperatures and levels of anthropogenic influence. By taking into account the modelled behaviour of JA2B2 as a function of [H2SO4], temperature and RH, the atmospheric particle formation rate was reproduced more closely than with the traditional semi-empirical formulae based on sulphuric acid concentration only. The formation rates of clusters with two sulphuric acid and two amine molecules with different amine compositions (DMA or TMA or one of both) had different responses to varying meteorological conditions and concentrations of vapours participating in particle formation. The observed inverse proportionality of the coefficient Kobs with RH and temperature agreed best with the modelled coefficient KA2B2 related to formation of a cluster with two H2SO4 and one or two TMA molecules, assuming that these clusters can grow in collisions with abundant organic vapour molecules. In case this assumption is valid, our results suggest that the formation rate of clusters with at least two of both sulphuric acid and amine molecules might be the rate-limiting step for atmospheric particle formation. More generally, our analysis elucidates the sensitivity of the atmospheric particle formation rate to meteorological variables and concentrations of vapours participating in particle formation (also other than H2SO4).

Download Full-text

Analysis of new particle formation (NPF) events at nearby rural, urban background and urban roadside sites

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-5679-2019 ◽

2019 ◽

Vol 19 (8) ◽

pp. 5679-5694 ◽

Cited By ~ 8

Author(s):

Dimitrios Bousiotis ◽

Manuel Dall'Osto ◽

David C. S. Beddows ◽

Francis D. Pope ◽

Roy M. Harrison

Keyword(s):

Urban Environment ◽

Growth Rates ◽

General Pattern ◽

Particle Growth ◽

Particle Formation ◽

Atmospheric Conditions ◽

New Particle Formation ◽

Urban Background ◽

Air Masses ◽

Condensation Sink

Abstract. New particle formation (NPF) events have different patterns of development depending on the conditions of the area in which they occur. In this study, particle size distributions in the range of 16.6–604 nm (7 years of data) were analysed and NPF events occurring at three sites of differing characteristics – rural Harwell (HAR), urban background North Kensington (NK), urban roadside Marylebone Road (MR), London, UK – were extracted and studied. The different atmospheric conditions in each study area not only have an effect on the frequency of the events, but also affect their development. The frequency of NPF events is similar at the rural and urban background locations (about 7 % of days), with a high proportion of events occurring at both sites on the same day (45 %). The frequency of NPF events at the urban roadside site is slightly less (6 % of days), and higher particle growth rates (average 5.5 nm h−1 at MR compared to 3.4 and 4.2 nm h−1 at HAR and NK respectively) must result from rapid gas-to-particle conversion of traffic-generated pollutants. A general pattern is found in which the condensation sink increases with the degree of pollution of the site, but this is counteracted by increased particle growth rates at the more polluted location. A key finding of this study is that the role of the urban environment leads to an increment of 20 % in N16–20 nm in the urban background compared to that of the rural area in NPF events occurring at both sites. The relationship of the origin of incoming air masses is also considered and an association of regional events with cleaner air masses is found. Due to lower availability of condensable species, NPF events that are associated with cleaner atmospheric conditions have lower growth rates of the newly formed particles. The decisive effect of the condensation sink in the development of NPF events and the survivability of the newly formed particles is underlined, and influences the overall contribution of NPF events to the number of ultrafine particles in an area. The other key factor identified by this study is the important role that pollution, both from traffic and other sources in the urban environment (such as heating or cooking), plays in new particle formation events.

Download Full-text

On the composition of ammonia-sulfuric acid clusters during aerosol particle formation

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-13413-2014 ◽

2014 ◽

Vol 14 (9) ◽

pp. 13413-13464 ◽

Cited By ~ 1

Author(s):

S. Schobesberger ◽

A. Franchin ◽

F. Bianchi ◽

L. Rondo ◽

J. Duplissy ◽

...

Keyword(s):

Boundary Layer ◽

Sulfuric Acid ◽

Gas Phase ◽

Particle Formation ◽

Atmospheric Conditions ◽

New Particle Formation ◽

Acid Base ◽

Wide Range ◽

Charged Clusters ◽

Positively Charged

Abstract. The formation of particles from precursor vapors is an important source of atmospheric aerosol. Research at the Cosmics Leaving OUtdoor Droplets (CLOUD) facility at CERN tries to elucidate which vapors are responsible for this new particle formation, and how in detail it proceeds. Initial measurement campaigns at the CLOUD stainless-steel aerosol chamber focused on investigating particle formation from ammonia (NH3) and sulfuric acid (H2SO4). Experiments were conducted in the presence of water, ozone and sulfur dioxide. Contaminant trace gases were suppressed at the technological limit. For this study, we mapped out the compositions of small NH3-H2SO4 clusters over a wide range of atmospherically relevant environmental conditions. We covered [NH3] in the range from <2 to 1400 pptv, [H2SO4] from 3.3 × 106 to 1.4 × 109 cm−3, and a temperature range from −25 to +20 °C. Negatively and positively charged clusters were directly measured by an atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometer, as they initially formed from gas-phase NH3 and H2SO4, and then grew to larger clusters containing more than 50 molecules of NH3 and H2SO4, corresponding to mobility-equivalent diameters greater than 2 nm. Water molecules evaporate from these clusters during sampling and are not observed. We found that the composition of the NH3-H2SO4 clusters is primarily determined by the ratio of gas-phase concentrations [NH3] / [H2SO4], as well as by temperature. Pure binary H2O-H2SO4 clusters (observed as clusters of only H2SO4) only form at [NH3] / [H2SO4]<0.1 to 1. For larger values of [NH3] / [H2SO4], the composition of NH3-H2SO4 clusters was characterized by the number of NH3 molecules m added for each added H2SO4 molecule n (Δm / Δn), where n is in the range 4–18 (negatively charged clusters) or 1–17 (positively charged clusters). For negatively charged clusters, Δm / Δn saturated between 1 and 1.4 for [NH3] / [H2SO4]>10. Positively charged clusters grew on average by Δm / Δn = 1.05 and were only observed at sufficiently high [NH3] / [H2SO4]. The H2SO4 molecules of these clusters are partially neutralized by NH3, in close resemblance to the acid-base bindings of ammonium bisulfate. Supported by model simulations, we substantiate previous evidence for acid-base reactions being the essential mechanism behind the formation of these clusters under atmospheric conditions and up to sizes of at least 2 nm. Our results also suggest that yet unobservable electrically neutral NH3-H2SO4 clusters grow by generally the same mechanism as ionic clusters, particularly for [NH3] / [H2SO4]>10. We expect that NH3-H2SO4 clusters form and grow also mostly by Δm / Δn>1 in the atmosphere's boundary layer, as [NH3] / [H2SO4] is mostly larger than 10. We compared our results from CLOUD with APi-TOF measurements of NH3-H2SO4 anion clusters during new particle formation in the Finnish boreal forest. However, the exact role of NH3-H2SO4 clusters in boundary layer particle formation remains to be resolved.

Download Full-text

Observations of New Particle Formation events during summertime in Helsinki

10.5194/egusphere-egu21-13408 ◽

2021 ◽

Author(s):

Roseline Thakur ◽

Lubna Dada ◽

Lisa Beck ◽

Tommy Chan ◽

Juha Sulo ◽

...

Keyword(s):

Sulfuric Acid ◽

Urban Areas ◽

Boreal Forests ◽

Cloud Condensation Nuclei ◽

Cyanobacterial Bloom ◽

Particle Formation ◽

Capital City ◽

Atmospheric Conditions ◽

New Particle Formation ◽

Iodic Acid

Aerosols can originate from different sources and undergo various formation pathways. New Particle formation (NPF) events occur when precursor vapors nucleate and vapors with low volatility condense on the critical nuclei enabling them to grow to cloud condensation nuclei (CCN) relevant sizes. As CCN, these aerosols affect the occurrence of clouds and their lifetime on local, regional and global level. &#160;Many studies have investigated new particle formation events from various sites ranging from urban areas, boreal forests to pristine locations; however, there is still a dearth of studies investigating coastal new particle formation, which is a complex phenomenon due to the dynamic and ever-changing atmospheric conditions at the coast.&#160; A comprehensive study of particle number distributions and aerosol forming precursor vapors was carried out in a coastal capital city of Finland, Helsinki, during the summer of 2019. The experimental setup comprising of a nitrate-based chemical ionization atmospheric pressure interface time of flight mass spectrometer (CI-APi-TOF), a neutral cluster-air ion spectrometer (NAIS) and a particle size magnifier (PSM) were housed in and around the SMEAR III station in Kumpula Science campus. SMEAR III is a unique site situated in a semi-urban yet coastal location. The period of experiment coincided with the cyanobacterial bloom in the coastal areas of Finland and in the Baltic Sea region. Our study recorded several regional NPF and aerosol burst events during this period. High concentrations of sulfuric acid was found to be associated with the regional NPF events whereas increasing iodic acid concentrations was mostly associated with the initiation of burst events. The sources of sulfuric acid and iodic acid has been carefully evaluated in this study.&#160;

Download Full-text

The effect of COVID-19 restrictions of human activities on atmospheric chemical cocktail, new particle formation and air quality in in Eastern and Northern China

10.5194/egusphere-egu21-12589 ◽

2021 ◽

Author(s):

Markku Kulmala ◽

Chao Yan ◽

Lubna Dada ◽

Federico Bianchi ◽

Tom Kokkonen ◽

...

Keyword(s):

Anthropogenic Activities ◽

Substantial Reduction ◽

Northern China ◽

Particle Formation ◽

Urban Environments ◽

Atmospheric Composition ◽

New Particle Formation ◽

Continental Scale ◽

Aerosol Mass ◽

Haze Formation

The pandemic of SARS-CoV-2 has led to a substantial reduction in anthropogenic activities globally. This is particularly true for traffic, which was reduced by 40-80 % in Eastern and Northern China. The imposed lockdown provides a unique opportunity to investigate the direct and indirect effects of anthropogenic activities (particularly traffic) on atmospheric new particle formation, atmospheric chemical cocktail and haze formation in polluted urban environments in the case when the emissions were substantially lower. Here, we utilize comprehensive, long term ground-based and satellite observations to investigate changes in the atmospheric composition and connect them with a continental scale gas-to-particle conversion producing both fresh particles and new aerosol mass. &#160;We show &#160;that despite the reductions in emissions, both new particle formation (NPF) and haze events still occur. The observational evidence confirms that the main NPF mechanism remains similar because of non-linear response of NPF and growth to local and regional vehicle emission reductions. Furthermore we are able follow the growth from NPF to haze and show, in the case study, that regional NPF makes a dominating contribution to the haze.

Download Full-text