New Particle Formation Involving Charged Sulfuric Acid – Ammonia Clusters

Author(s):  
Vitus Besel ◽  
Jakub Kubečka ◽  
Theo Kurtén ◽  
Hanna Vehkamäki

<div> <p>The bulk of aerosol particles in the atmosphere are formed by gas-to-particle nucleation (Merikanto et al., 2009). However, the exact process of single molecules forming cluster, which subsequently can grow into particles, remains largely unknown. Recently, sulfuric acid has been identified to play a key role in this new particle formation enhanced by other compounds such as organic acids (Zhang, 2010) or ammonia (Anttila et al., 2005). To identify the characteristics of cluster formation and nucleation involving sulfuric acid and ammonia in neutral, positive and negative modes, we conducted a computational study. We used a layered approach for configurational sampling of the molecular clusters starting from utilizing a genetic algorithm in order to explore the whole potential energy surface (PES) with all plausible geometrical minima, however, with very unreliable energies. The structures were further optimized with a semi-empirical method and, then, at the ωB97X-D DFT level of theory. After each step, the optimized geometries were filtered to obtain the global minimum configuration. Further, a high level of theory (DLPNO-CCSD(T)) was used for obtaining the electronic energies, in addition to performing DFT frequency analysis, to calculate the Gibbs free energies of formation. These were passed to the Atmospheric Cluster Dynamics Code (ACDC) (McGrath et al., 2012) for studying the evolution of cluster populations. We determined the global minima for the following sulfuric acid - ammonia clusters: (H<sub>2</sub>SO<sub>4</sub>)<sub>m</sub>(NH<sub>3</sub>)<sub>n</sub> with m=n, m=n+1 and n=m+1 for neutral clusters, (H<sub>2</sub>SO<sub>4</sub>)<sub>m</sub>(HSO<sub>4</sub>)<sup>−</sup>(NH<sub>3</sub>)<sub>n</sub> with m=n and n=m+1 for positively charged clusters, and (H<sub>2</sub>SO<sub>4</sub>)<sub>m</sub>(NH<sub>4</sub>)<sup>+</sup>(NH<sub>3</sub>)<sub>n</sub> with m=n and m=n+1 for negatively charged clusters. Further, we present the formation rates, steady state concentrations and fluxes of these clusters calculated using ACDC and discuss how a new configurational sampling procedure, more precise quantum chemistry methods and parameters, such as symmetry and a quasiharmonic approach, impact these ACDC results in comparison to previous studies.</p> </div><div> <p><em>References:<br></em><em>J. Merikanto, D. V. Spracklen, G. W. Mann, S. J. Pickering, and K. S. Carslaw (2009). Atmos. Chem.  Phys., 9, 8601-8616. <br>R. Zhang (2010). Science, 328, 1366-1367. <br>T. Anttila, H. Vehkamäki, I. Napari, M. Kulmala (2005). Boreal Env. Res., 10, 523. <br>M.J. McGrath, T. Olenius, I.K. Ortega, V. Loukonen, P.  Paasonen, T. Kurten, M. Kulmala (2012). Atmos. Chem. Phys., 12, 2355. <br></em></p> </div>

2014 ◽  
Vol 14 (9) ◽  
pp. 13413-13464 ◽  
Author(s):  
S. Schobesberger ◽  
A. Franchin ◽  
F. Bianchi ◽  
L. Rondo ◽  
J. Duplissy ◽  
...  

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.


2015 ◽  
Vol 15 (2) ◽  
pp. 2305-2353 ◽  
Author(s):  
J. Größ ◽  
W. Birmili ◽  
A. Hamed ◽  
A. Sonntag ◽  
A. Wiedensohler ◽  
...  

Abstract. This paper revisits the atmospheric new particle formation (NPF) process in the polluted Central European troposphere, focusing on the diurnal evolution of the meteorological and gas phase parameters involved. Atmospheric aerosol observations include Neutral cluster and Air Ion Spectrometer (NAIS) measurements at the research station Melpitz, East Germany between 2008 and 2011. Particle formation events were classified by a new automated method based on the convolution integral of particle number concentration in the diameter range 2–20 nm. To study the relationship with gaseous precursors, a proximity measure was calculated for the sulfuric acid concentration on the basis of a one month intensive measurement campaign in May 2008. A major result was that the number concentration of fresh produced neutral particles correlated significantly with the amount of sulfur dioxide available as a main precursor of sulfuric acid. The condensation sink, a factor potentially inhibiting NPF events, played a subordinate role only. The same held for experimentally determined ammonia concentrations, which also represent a recognised precursor of aerosol particle nucleation. The analysis of meteorological parameters confirmed the absolute need for solar radiation to induce NPF events, and demonstrated the presence of significant turbulence during those events. Due to its tight correlation with solar radiation, however, an independent effect of turbulence for NPF could not be established with certainty. On the basis of observed diurnal cycles of aerosol, gas phase, and meteorological parameters near the ground, we conclude that particle formation is likely to be induced aloft, rather than near the ground.


2018 ◽  
Vol 20 (25) ◽  
pp. 17406-17414 ◽  
Author(s):  
Ling Liu ◽  
Hao Li ◽  
Haijie Zhang ◽  
Jie Zhong ◽  
Yang Bai ◽  
...  

The cluster formation mechanism indicates that nitric acid can connect the smaller and larger clusters, enhancing sulfuric acid–ammonia cluster formation rates.


2016 ◽  
Vol 16 (4) ◽  
pp. 1919-1935 ◽  
Author(s):  
Jenni Kontkanen ◽  
Emma Järvinen ◽  
Hanna E. Manninen ◽  
Katrianne Lehtipalo ◽  
Juha Kangasluoma ◽  
...  

Abstract. The concentrations of neutral and charged sub-3nm clusters and their connection to new particle formation (NPF) were investigated during the PEGASOS campaign (7 June–9 July 2012) at the San Pietro Capofiume measurement station in the Po Valley, Italy. Continuous high concentrations of sub-3nm clusters were detected during the measurement period, although the condensation sink was relatively high (median value 1.1 × 10−2 s−1). The median cluster concentrations were 2140 and 7980 cm−3 in the size bins of 1.5–1.8 and 1.8–3 nm, and the majority of them were electrically neutral. NPF events were observed during the measurement period frequently, on 86 % of the days. The median growth rates of clusters during the events were 4.3, 6.0 and 7.2 nm h−1 in the size ranges of 1.5–3, 3–7 and 7–20 nm. The median formation rate of 1.6 nm clusters was high, 45 cm−3 s−1, and it exceeded the median formation rate of 2 nm clusters by 1 order of magnitude. The ion-induced nucleation fraction was low; the median values were 0.7 % at 1.6 nm and 3.0 % at 2 nm. On NPF event days the neutral cluster concentration had a maximum around 09:00 (local winter time), which was absent on a non-event day. The increase in the cluster concentrations in the morning coincided with the increase in the boundary layer height. At the same time radiation, temperature and SO2 concentration increased, and RH and condensation sink decreased. The concentrations of neutral and charged clusters were observed to have a positive correlation with sulfuric acid proxy, indicating the significance of sulfuric acid for the cluster formation in San Pietro Capofiume. The condensation sink had a negative correlation with the concentration of charged clusters but no clear relation to the neutral cluster concentration. This finding, together with back-trajectory analysis, suggests that the precursor vapors of the clusters and background aerosol particles, acting as their sink, have possibly originated from the same sources, including e.g., power plants and industrial areas in the Po Valley.


2015 ◽  
Vol 15 (1) ◽  
pp. 55-78 ◽  
Author(s):  
S. Schobesberger ◽  
A. Franchin ◽  
F. Bianchi ◽  
L. Rondo ◽  
J. Duplissy ◽  
...  

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 (0.1 to 56 pptv), 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/Δ n), where n is in the range 4–18 (negatively charged clusters) or 1–17 (positively charged clusters). For negatively charged clusters, Δ m/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 electrically neutral NH3–H2SO4 clusters, unobservable in this study, have generally the same composition as ionic clusters 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.


2021 ◽  
Author(s):  
James Brean ◽  
Manuel Dall’Osto ◽  
Rafel Simó ◽  
Zongbo Shi ◽  
David C. S. Beddows ◽  
...  

2012 ◽  
Vol 12 (8) ◽  
pp. 3591-3599 ◽  
Author(s):  
O. Kupiainen ◽  
I. K. Ortega ◽  
T. Kurtén ◽  
H. Vehkamäki

Abstract. The substitution of ammonia by dimethylamine in sulfuric acid – ammonia – dimethylamine clusters was studied using a collision and evaporation dynamics model. Quantum chemical formation free energies were computed using B3LYP/CBSB7 for geometries and frequencies and RI-CC2/aug-cc-pV(T+d)Z for electronic energies. We first demonstrate the good performance of our method by a comparison with an experimental study investigating base substitution in positively charged clusters, and then continue by simulating base exchange in neutral clusters, which cannot be measured directly. Collisions of a dimethylamine molecule with an ammonia containing positively charged cluster result in the instantaneous evaporation of an ammonia molecule, while the dimethylamine molecule remains in the cluster. According to our simulations, a similar base exchange can take place in neutral clusters, although the overall process is more complicated. Neutral sulfuric acid – ammonia clusters are significantly less stable than their positively charged counterparts, resulting in a competition between cluster evaporation and base exchange.


2018 ◽  
Vol 18 (16) ◽  
pp. 11779-11791 ◽  
Author(s):  
Ximeng Qi ◽  
Aijun Ding ◽  
Pontus Roldin ◽  
Zhengning Xu ◽  
Putian Zhou ◽  
...  

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.


2016 ◽  
Author(s):  
Oona Kupiainen-Määttä

Abstract. Evaporation rates of small negatively charged sulfuric acid–ammonia clusters are determined by combining detailed cluster formation simulations with cluster distributions measured at CLOUD. The analysis is performed by varying the evaporation rates with Markov chain Monte Carlo (MCMC), running cluster formation simulations with each new set of evaporation rates and comparing the obtained cluster distributions to the measurements. In a second set of simulations, the fragmentation of clusters in the mass spectrometer due to energetic collisions is studied by treating also the fragmentation probabilities as unknown parameters and varying them with MCMC. This second set of simulations results in a better fit to the experimental data, suggesting that a large fraction of the observed HSO4− and HSO4− ⋅ H2SO4 signals may result from fragmentation of larger clusters, most importantly the HSO4− ⋅ (H2SO4)2 trimer.


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