scholarly journals The simulations of sulfuric acid concentration and new particle formation in an urban atmosphere in China

2013 ◽  
Vol 13 (21) ◽  
pp. 11157-11167 ◽  
Author(s):  
Z. B. Wang ◽  
M. Hu ◽  
D. Mogensen ◽  
D. L. Yue ◽  
J. Zheng ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Acid Concentration ◽  
Sulfuric Acid Concentration ◽  
Lower Troposphere ◽  
Particle Growth ◽  
Particle Formation ◽  
Urban Atmosphere ◽  
Chemical Mechanism ◽  
New Particle Formation ◽  
Aerosol Formation

Abstract. Simulations of sulfuric acid concentration and new particle formation are performed by using the zero-dimensional version of the model MALTE (Model to predict new Aerosol formation in the Lower TropospherE) and measurements from the Campaign of Air Quality Research in Beijing and Surrounding areas (CAREBeijing) in 2008. Chemical reactions from the Master Chemical Mechanism version 3.2 (MCM v3.2) are used in the model. High correlation (slope = 0.72, R = 0.74) between the modelled and observed sulfuric acid concentrations is found during daytime (06:00–18:00). The aerosol dynamics are simulated by the University of Helsinki Multicomponent Aerosol (UHMA) model including several nucleation mechanisms. The results indicate that the model is able to predict the on- and offset of new particle formation in an urban atmosphere in China. In addition, the number concentrations of newly formed particles in kinetic-type nucleation including homogenous homomolecular (J=K[H2SO4]2) and homogenous heteromolecular nucleation involving organic vapours (J=Khet[H2SO4][Org]) are in satisfactory agreement with the observations. However, the specific organic compounds that possibly participate in the nucleation process should be investigated in further studies. For the particle growth, only a small fraction of the oxidized total organics condense onto the particles in polluted environments. Meanwhile, the OH and O3 oxidation mechanism contribute 5.5% and 94.5% to the volume concentration of small particles, indicating the particle growth is more controlled by the precursor gases and their oxidation by O3.

scholarly journals The simulations of sulfuric acid concentration and new particle formation in an urban atmosphere in China

2013 ◽  
Vol 13 (6) ◽  
pp. 14977-15005
Author(s):  
Z. B. Wang ◽  
M. Hu ◽  
D. Mogensen ◽  
D. L. Yue ◽  
J. Zheng ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Acid Concentration ◽  
Sulfuric Acid Concentration ◽  
Lower Troposphere ◽  
Particle Formation ◽  
Urban Atmosphere ◽  
Chemical Mechanism ◽  
New Particle Formation ◽  
Aerosol Formation ◽  
Surrounding Areas

Abstract. Simulations of sulfuric acid concentration and new particle formation are performed by using the zero-dimensional version of the model MALTE (Model to predict new Aerosol formation in the Lower TropospherE) and measurements from the Campaign of Air Quality Research in Beijing and Surrounding areas (CAREBeijing) in 2008. Chemical reactions from the Master Chemical Mechanism Version 3.2 (MCM v3.2) are used in the model. High correlation (slope = 0.72, R = 0.74) between the modelled and observed sulfuric acid concentrations is found during daytime (06:00–18:00). The aerosol dynamics are simulated by the University of Helsinki Multicomponent Aerosol (UHMA) model including several nucleation mechanisms. The results indicate that the model is able to predict the on- and offset of new particle formation in an urban atmosphere in China. In addition, the number concentrations of newly formed particles in kinetic-type nucleation including homogenous homomolecular (J=K[H2SO4]2) and homogenous heteromolecular nucleation involving organic vapours (J=Khet[H2SO4][Org]) are in satisfactory agreement with the observations. However, the specific organic compounds possibly participate in the nucleation process should be investigated in further studies.

scholarly journals Aerosol Surface Area Concentration: a Governing Factor for New Particle Formation in Beijing

2017 ◽  
Author(s):  
Runlong Cai ◽  
Dongsen Yang ◽  
Yueyun Fu ◽  
Xing Wang ◽  
Xiaoxiao Li ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Surface Area ◽  
Acid Concentration ◽  
Mass Concentration ◽  
Sulfuric Acid Concentration ◽  
Particle Formation ◽  
Atmospheric Environment ◽  
Geometric Standard Deviation ◽  
Growth Enhancement ◽  
New Particle Formation

Abstract. The predominating role of aerosol Fuchs surface area, AFuchs, in determining the occurrence of new particle formation (NPF) events in Beijing was elucidated in this study. Analysis was based on a field campaign from March 12th to April 6th, 2016, in Beijing, during which aerosol size distributions down to ~ 1 nm and sulfuric acid concentration were simultaneously monitored. The 26 days were classified into 11 typical NPF days, 2 undefined days, and 13 non-event days. A dimensionless factor, LΓ, characterizing the relative ratio of the coagulation scavenging rate over the condensational growth rate and predicting whether or not a NPF event would occur (Kuang et al., 2010), was applied. The three parameters determining LΓ are sulfuric acid concentration, the growth enhancement factor characterizing contribution of other gaseous precursors to particle growth, Γ, and AFuchs. Different from other atmospheric environment such as in Boulder and Hyytiälä, the variations of daily maximum sulfuric acid concentration and Γ in Beijing are in a narrow range with geometric standard deviations of 1.40 and 1.31, respectively. Positive correlation was found between estimated new particle formation rate, J1.5, and sulfuric acid concentration with a mean fitted exponent of 2.4. However, sulfuric acid concentration on NPF days is not significantly higher than that on non-event days. Instead, AFuchs varies greatly among days in Beijing with a geometric standard deviation of 2.56, while it is relatively stable at other locations such as Tecamac, Atlanta, and Boulder. Good correlation was found between AFuchs and LΓ in Beijing (R2 = 0.88). It appears that the abundance of gaseous precursors such as sulfuric acid in Beijing is high enough to have nucleation, however, it is AFuchs that determines the occurrence of NPF event in Beijing. 10 in 11 NPF events occurred when AFuchs is smaller than 200 μm2/cm3, and the NPF event was suppressed due to coagulation scavenging when AFuchs is larger than 200 μm2/cm3. Measured AFuchs is in good correlation with PM2.5 mass concentration (R2 = 0.85) since AFuchs in Beijing is mainly determined by particles in the size range of 50–500 nm that also contribute to PM2.5 mass concentration.

scholarly journals Molecular insights into new particle formation in Barcelona, Spain

2020 ◽  
Vol 20 (16) ◽  
pp. 10029-10045 ◽  
Author(s):  
James Brean ◽  
David C. S. Beddows ◽  
Zongbo Shi ◽  
Brice Temime-Roussel ◽  
Nicolas Marchand ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Organic Compounds ◽  
Radiative Forcing ◽  
Cloud Condensation Nuclei ◽  
Sulfuric Acid Concentration ◽  
Particle Growth ◽  
Particle Formation ◽  
Necessary Condition ◽  
New Particle Formation ◽  
High Concentrations

Abstract. Atmospheric aerosols contribute some of the greatest uncertainties to estimates of global radiative forcing and have significant effects on human health. New particle formation (NPF) is the process by which new aerosols of sub-2 nm diameter form from gas-phase precursors and contributes significantly to particle numbers in the atmosphere, accounting for approximately 50 % of cloud condensation nuclei globally. Here, we study summertime NPF in urban Barcelona in north-eastern Spain utilising particle counting instruments down to 1.9 nm and a Nitrate Chemical Ionisation Atmospheric Pressure interface Time of Flight Mass Spectrometer (CI-APi-ToF). The rate of formation of new particles is seen to increase linearly with sulfuric acid concentration, although particle formation rates fall short of chamber studies of H2SO4–DMA–H2O while exceeding those of H2SO4–BioOxOrg–H2O nucleation, although a role of highly oxygenated molecules (HOMs) cannot be ruled out. The sulfuric acid dimer : monomer ratio is significantly lower than that seen in experiments involving sulfuric acid and dimethylamine (DMA) in chambers, indicating that stabilisation of sulfuric acid clusters by bases is weaker in this dataset than in chambers, either due to rapid evaporation due to high summertime temperatures or limited pools of stabilising amines. Such a mechanism cannot be verified in these data, as no higher-order H2SO4–amine clusters nor H2SO4–HOM clusters were measured. The high concentrations of HOMs arise from isoprene, alkylbenzene, monoterpene and polycyclic aromatic hydrocarbon (PAH) oxidation, with alkylbenzenes providing greater concentrations of HOMs due to significant local sources. The concentration of these HOMs shows a dependence on temperature. The organic compounds measured primarily fall into the semivolatile organic compound (SVOC) volatility class arising from alkylbenzene and isoprene oxidation. Low-volatility organic compounds (LVOCs) largely arise from oxidation of alkylbenzenes, PAHs and monoterpenes, whereas extremely low-volatility organic compounds (ELVOCs) arise from primarily PAH and monoterpene oxidation. New particle formation without growth past 10 nm is also observed, and on these days oxygenated organic concentrations are lower than on days with growth by a factor of 1.6, and thus high concentrations of low-volatility oxygenated organics which primarily derive from traffic-emitted volatile organic compounds (VOCs) appear to be a necessary condition for the growth of newly formed particles in Barcelona. These results are consistent with prior observations of new particle formation from sulfuric acid–amine reactions in both chambers and the real atmosphere and are likely representative of the urban background of many European Mediterranean cities. A role for HOMs in the nucleation process cannot be confirmed or ruled out, and there is strong circumstantial evidence of the participation of HOMs across multiple volatility classes in particle growth.

scholarly journals Effect of ions on the measurement of sulfuric acid in the CLOUD experiment at CERN

2014 ◽  
Vol 7 (11) ◽  
pp. 3849-3859 ◽  
Author(s):  
L. Rondo ◽  
A. Kürten ◽  
S. Ehrhart ◽  
S. Schobesberger ◽  
A. Franchin ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Mass Spectrometer ◽  
Acid Concentration ◽  
Uv Light ◽  
Sulfuric Acid Concentration ◽  
Particle Formation ◽  
Galactic Cosmic Rays ◽  
Cloud Chamber ◽  
Proton Synchrotron ◽  
New Particle Formation

Abstract. Ternary aerosol nucleation experiments were conducted in the CLOUD chamber at CERN in order to investigate the influence of ions on new particle formation. Neutral and ion-induced nucleation experiments, i.e. without and with the presence of ions, respectively, were carried out under precisely controlled conditions. The sulfuric acid concentration was measured with a chemical ionisation mass spectrometer (CIMS) during the new particle formation experiments. The added ternary trace gases were ammonia (NH3), dimethylamine (DMA, C2H7N) or oxidised products of pinanediol (PD, C10H18O2). When pinanediol was introduced into the chamber, an increase in the mass spectrometric signal used to determine the sulfuric acid concentration (m/z 97, i.e. HSO4−) was observed due to ions from the CLOUD chamber. The enhancement was only observed during ion-induced nucleation measurements by using either galactic cosmic rays (GCRs) or the proton synchrotron (PS) pion beam for the ion generation, respectively. The ion effect typically involved an increase in the apparent sulfuric acid concentration by a factor of ~ 2 to 3 and was qualitatively verified by the ion measurements with an atmospheric-pressure interface-time of flight (APi-TOF) mass spectrometer. By applying a high-voltage (HV) clearing field inside the CLOUD chamber, the ion effect on the CIMS measurement was completely eliminated since, under these conditions, small ions are swept from the chamber in about 1 s. In order to exclude the ion effect and to provide corrected sulfuric acid concentrations during the GCR and PS beam nucleation experiments, a parameterisation was derived that utilises the trace gas concentrations and the UV light intensity as input parameters. Atmospheric sulfuric acid measurements with a CIMS showed an insignificant ion effect.

scholarly journals Aerosol surface area concentration: a governing factor in new particle formation in Beijing

2017 ◽  
Vol 17 (20) ◽  
pp. 12327-12340 ◽  
Author(s):  
Runlong Cai ◽  
Dongsen Yang ◽  
Yueyun Fu ◽  
Xing Wang ◽  
Xiaoxiao Li ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Surface Area ◽  
Acid Concentration ◽  
Mass Concentration ◽  
Sulfuric Acid Concentration ◽  
Particle Formation ◽  
Geometric Standard Deviation ◽  
Daily Maximum ◽  
Growth Enhancement ◽  
New Particle Formation

Abstract. The predominating role of aerosol Fuchs surface area, AFuchs, in determining the occurrence of new particle formation (NPF) events in Beijing was elucidated in this study. The analysis was based on a field campaign from 12 March to 6 April 2016 in Beijing, during which aerosol size distributions down to  ∼  1 nm and sulfuric acid concentrations were simultaneously monitored. The 26 days were classified into 11 typical NPF days, 2 undefined days, and 13 non-event days. A dimensionless factor, LΓ, characterized by the relative ratio of the coagulation scavenging rate over the condensational growth rate (Kuang et al., 2010), was applied in this work to reveal the governing factors for NPF events in Beijing. The three parameters determining LΓ are sulfuric acid concentration, the growth enhancement factor characterized by contribution of other gaseous precursors to particle growth, Γ, and AFuchs. Different from other atmospheric environments, such as in Boulder and Hyytiälä, the daily-maximum sulfuric acid concentration and Γ in Beijing varied in a narrow range with geometric standard deviations of 1.40 and 1.31, respectively. A positive correlation between the estimated new particle formation rate, J1.5, and sulfuric acid concentration was found with a mean fitted exponent of 2.4. However, the maximum sulfuric acid concentrations on NPF days were not significantly higher (even lower, sometimes) than those on non-event days, indicating that the abundance of sulfuric acid in Beijing was high enough to initiate nucleation, but may not necessarily lead to NPF events. Instead, AFuchs in Beijing varied greatly among days with a geometric standard deviation of 2.56, whereas the variabilities of AFuchs in Tecamac, Atlanta, and Boulder were reported to be much smaller. In addition, there was a good correlation between AFuchs and LΓ in Beijing (R2 = 0.88). Therefore, it was AFuchs that fundamentally determined the occurrence of NPF events. Among 11 observed NPF events, 10 events occurred when AFuchs was smaller than 200 µm2 cm−3. NPF events were suppressed due to the coagulation scavenging when AFuchs was greater than 200 µm2 cm−3. Measured AFuchs in Beijing had a good correlation with its PM2.5 mass concentration (R2 = 0.85) since AFuchs in Beijing was mainly determined by particles in the size range of 50–500 nm that also contribute to the PM2.5 mass concentration.

scholarly journals Ion-induced sulfuric acid–ammonia nucleation drives particle formation in coastal Antarctica

2018 ◽  
Vol 4 (11) ◽  
pp. eaat9744 ◽  
Author(s):  
T. Jokinen ◽  
M. Sipilä ◽  
J. Kontkanen ◽  
V. Vakkari ◽  
P. Tisler ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Particle Growth ◽  
Field Studies ◽  
Particle Formation ◽  
New Particle Formation ◽  
Aerosol Formation ◽  
Radiative Balance ◽  
Secondary Aerosol

Formation of new aerosol particles from trace gases is a major source of cloud condensation nuclei (CCN) in the global atmosphere, with potentially large effects on cloud optical properties and Earth’s radiative balance. Controlled laboratory experiments have resolved, in detail, the different nucleation pathways likely responsible for atmospheric new particle formation, yet very little is known from field studies about the molecular steps and compounds involved in different regions of the atmosphere. The scarcity of primary particle sources makes secondary aerosol formation particularly important in the Antarctic atmosphere. Here, we report on the observation of ion-induced nucleation of sulfuric acid and ammonia—a process experimentally investigated by the CERN CLOUD experiment—as a major source of secondary aerosol particles over coastal Antarctica. We further show that measured high sulfuric acid concentrations, exceeding 107 molecules cm−3, are sufficient to explain the observed new particle growth rates. Our findings show that ion-induced nucleation is the dominant particle formation mechanism, implying that galactic cosmic radiation plays a key role in new particle formation in the pristine Antarctic atmosphere.

scholarly journals Sulfuric acid and OH concentrations in a boreal forest site

2009 ◽  
Vol 9 (19) ◽  
pp. 7435-7448 ◽  
Author(s):  
T. Petäjä ◽  
R. L. Mauldin, III ◽  
E. Kosciuch ◽  
J. McGrath ◽  
T. Nieminen ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Gas Phase ◽  
Acid Concentration ◽  
Sulfuric Acid Concentration ◽  
Particle Formation ◽  
Daily Maximum ◽  
Ionization Mass ◽  
Forest Site ◽  
Aerosol Formation ◽  
Atmospheric Particle

Abstract. As demonstrated in a number of investigations, gaseous sulfuric acid plays a central role in atmospheric aerosol formation. Using chemical ionization mass spectrometer the gas-phase sulfuric acid and OH concentration were measured in Hyytiälä, SMEAR II station, Southern Finland during 24 March to 28 June 2007. Clear diurnal cycles were observed as well as differences between new particle formation event days and non-event days. Typically, the daily maximum concentrations of gas phase sulfuric acid varied from 3×105 to 2×106 molec cm−3 between non-event and event days. Noon-time OH concentrations varied from 3-6×105 molec cm−3 and not a clear difference between event and non-events was detected. The measured time series were also used as a foundation to develop reasonable proxies for sulfuric acid concentration. The proxies utilized source and sink terms, and the simplest proxy is radiation times sulfur dioxide divided by condensation sink. Since it is still challenging to measure sulfuric acid in ambient concentrations, and due to its significant role in atmospheric particle formation, reasonable proxies are needed. We use all together three different proxies and one chemical box model and compared their results to the measured data. The proxies for the sulfuric acid concentration worked reasonably well, and will be used to describe sulfuric acid concentrations in SMEAR II station, when no measured sulfuric acid data is available. With caution the proxies could be applied to other environments as well.

scholarly journals Modelling studies of HOMs and their contributions to new particle formation and growth: comparison of boreal forest in Finland and a polluted environment in China

2018 ◽  
Vol 18 (16) ◽  
pp. 11779-11791 ◽  
Author(s):  
Ximeng Qi ◽  
Aijun Ding ◽  
Pontus Roldin ◽  
Zhengning Xu ◽  
Putian Zhou ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Boreal Forest ◽  
Environmental Conditions ◽  
Eastern China ◽  
Particle Growth ◽  
Particle Formation ◽  
Forest Site ◽  
Polluted Environment ◽  
New Particle Formation ◽  
Multifunctional Compounds

Abstract. Highly oxygenated multifunctional compounds (HOMs) play a key role in new particle formation (NPF), but their quantitative roles in different environments of the globe have not been well studied yet. Frequent NPF events were observed at two “flagship” stations under different environmental conditions, i.e. a remote boreal forest site (SMEAR II) in Finland and a suburban site (SORPES) in polluted eastern China. The averaged formation rate of 6 nm particles and the growth rate of 6–30 nm particles were 0.3 cm−3 s−1 and 4.5 nm h−1 at SMEAR II compared to 2.3 cm−3 s−1 and 8.7 nm h−1 at SORPES, respectively. To explore the differences of NPF at the two stations, the HOM concentrations and NPF events at two sites were simulated with the MALTE-BOX model, and their roles in NPF and particle growth in the two distinctly different environments are discussed. The model provides an acceptable agreement between the simulated and measured concentrations of sulfuric acid and HOMs at SMEAR II. The sulfuric acid and HOM organonitrate concentrations are significantly higher but other HOM monomers and dimers from monoterpene oxidation are lower at SORPES compared to SMEAR II. The model simulates the NPF events at SMEAR II with a good agreement but underestimates the growth of new particles at SORPES, indicating a dominant role of anthropogenic processes in the polluted environment. HOMs from monoterpene oxidation dominate the growth of ultrafine particles at SMEAR II while sulfuric acid and HOMs from aromatics oxidation play a more important role in particle growth. This study highlights the distinct roles of sulfuric acid and HOMs in NPF and particle growth in different environmental conditions and suggests the need for molecular-scale measurements in improving the understanding of NPF mechanisms in polluted areas like eastern China.

scholarly journals New particle formation in the sulfuric acid–dimethylamine–water system: reevaluation of CLOUD chamber measurements and comparison to an aerosol nucleation and growth model

2018 ◽  
Vol 18 (2) ◽  
pp. 845-863 ◽  
Author(s):  
Andreas Kürten ◽  
Chenxi Li ◽  
Federico Bianchi ◽  
Joachim Curtius ◽  
António Dias ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Detection Threshold ◽  
Sulfuric Acid Concentration ◽  
Water System ◽  
Particle Formation ◽  
New Particle Formation ◽  
Flow Tube ◽  
Aerosol Model ◽  
Wide Range ◽  
Good Agreement

Abstract. A recent CLOUD (Cosmics Leaving OUtdoor Droplets) chamber study showed that sulfuric acid and dimethylamine produce new aerosols very efficiently and yield particle formation rates that are compatible with boundary layer observations. These previously published new particle formation (NPF) rates are reanalyzed in the present study with an advanced method. The results show that the NPF rates at 1.7 nm are more than a factor of 10 faster than previously published due to earlier approximations in correcting particle measurements made at a larger detection threshold. The revised NPF rates agree almost perfectly with calculated rates from a kinetic aerosol model at different sizes (1.7 and 4.3 nm mobility diameter). In addition, modeled and measured size distributions show good agreement over a wide range of sizes (up to ca. 30 nm). Furthermore, the aerosol model is modified such that evaporation rates for some clusters can be taken into account; these evaporation rates were previously published from a flow tube study. Using this model, the findings from the present study and the flow tube experiment can be brought into good agreement for the high base-to-acid ratios (∼ 100) relevant for this study. This confirms that nucleation proceeds at rates that are compatible with collision-controlled (a.k.a. kinetically controlled) NPF for the conditions during the CLOUD7 experiment (278 K, 38 % relative humidity, sulfuric acid concentration between 1 × 106 and 3 × 107 cm−3, and dimethylamine mixing ratio of ∼ 40 pptv, i.e., 1 × 109 cm−3).

scholarly journals Climatology of new particle formation at Izaña mountain GAW observatory in the subtropical North Atlantic

2014 ◽  
Vol 14 (8) ◽  
pp. 3865-3881 ◽  
Author(s):  
M. I. García ◽  
S. Rodríguez ◽  
Y. González ◽  
R. D. García
Keyword(s):  
Sulfuric Acid ◽  
North Atlantic ◽  
Growth Rates ◽  
Particle Growth ◽  
Particle Formation ◽  
Dust Particles ◽  
New Particle Formation ◽  
Data Set ◽  
Mean Values ◽  
Condensation Sink

Abstract. A climatology of new particle formation (NPF) events at high altitude in the subtropical North Atlantic is presented. A 4-year data set (June 2008–June 2012), which includes number size distributions (10–600 nm), reactive gases (SO2, NOx, and O3), several components of solar radiation and meteorological parameters, measured at Izaña Global Atmosphere Watch (GAW) observatory (2373 m above sea level; Tenerife, Canary Islands) was analysed. NPF is associated with the transport of gaseous precursors from the boundary layer by orographic buoyant upward flows that perturb the low free troposphere during daytime. On average, 30% of the days contained an NPF event. Mean values of the formation and growth rates during the study period were 0.46 cm−3 s−1 and 0.42 nm h−1, correspondingly. There is a clearly marked NPF season (May–August), when these events account for 50–60% of the days per month. Monthly mean values of the formation and growth rates exhibit higher values in this season, 0.49–0.92 cm−3 s−1 and 0.48–0.58 nm h−1, respectively. During NPF events, SO2, UV radiation and upslope winds showed higher values than during non-events. The overall data set indicates that SO2 plays a key role as precursor, although other species seem to contribute during some periods. Condensation of sulfuric acid vapour accounts for most of the measured particle growth during most of the year (~70%), except for some periods. In May, the highest mean growth rates (~0.6 nm h−1) and the lowest contribution of sulfuric acid (~13%) were measured, suggesting a significant involvement of other condensing vapours. The SO2 availability seems also to be the most influencing parameter in the year-to-year variability in the frequency of NPF events. The condensation sink showed similar features to other mountain sites, showing high values during NPF events. Summertime observations, when Izaña is within the Saharan Air Layer, suggest that dust particles may play a significant role acting as coagulation sink of freshly formed nucleation particles. The contribution of dust particles to the condensation sink of sulfuric acid vapours seems to be modest (~8% as average). Finally, we identified a set of NPF events in which two nucleation modes, which may evolve at different rates, occur simultaneously and for which further investigations are necessary.

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