Enhancement of atmospheric H<sub>2</sub>SO<sub>4</sub> / H<sub>2</sub>O nucleation: organic oxidation products versus amines

Abstract

Abstract. Atmospheric H 2 SO 4 / H 2 O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research -Laminar Flow Tube) at 293 ± 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a possible background amine concentration in the order of 10 7 -10 8 molecule cm −3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, α-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H 2 SO 4 formation starting from SO 2 . The oxidant generation is inevitably associated with the formation of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H 2 SO 4 concentrations higher than ∼ 10 7 molecule cm −3 . Also the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products in line with the expected growth by organic products using literature data. An additional, H 2 SO 4 -independent process of particle (nano-CN) formation was observed in the case of α-pinene and limonene ozonolysis for H 2 SO 4 concentrations smaller than ∼ 10 7 molecule cm −3 . Furthermore, the findings confirm the appearance of an additional oxidant for SO 2 beside OH radicals, very likely stabilized Criegee Intermediates (sCI). A second set of experiments has been performed in the presence of added amines in the concentrations range of a few 10 7 -10 10 molecule cm −3 applying photolytic OH radical generation for H 2 SO 4 production without addition of other organics. All amines showed significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H 2 SO 4 cluster stabilization by amines due to strong H 2 SO 4 ↔ amine interactions. On the other hand, this study indicates that for organic oxidation products (in presence of the possible amine background as stated) a distinct H 2 SO 4 / H 2 O nucleation enhancement can be due to increased H 2 SO 4 formation caused by additional organic oxidant production (sCI) rather than by stabilization of H 2 SO 4 clusters due to H 2 SO 4 ↔ organics interactions.

Sulfuric acid nucleation: An experimental study of the effect of seven bases

“…Comparison with the flow reactor DMA results of Berndt et al . [] show a factor of ~100 disparity from equation . A likely contributing factor to this difference is the loss of clusters to the wall before they are counted by the particle counter.…”

“…As shown for pyridine by Berndt et al . [], our results for TEA show that the structure of the amine plays a role in addition to its gas‐phase basicity.…”

Detection of dimethylamine in the low pptv range using nitrate chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry

“…Participation of amines in nucleation was studied in the laboratory for the amine-sulfuric acid-water system (e.g., Berndt et al, 2010;Erupe et al, 2011;Zollner et al, 2012;Almeida et al, 2013;Berndt et al, 2014;Kürten et al, 2014;Bianchi et al, 2014;Jen et al, 2015;Glasoe et al, 2015). Almeida et al (2013) showed for dimethylamine (DMA, (CH 3 ) 2 NH) that the presence of a few pptv enhances the aerosol formation rates of sulfuric acid by several orders of magnitude, and formation rates that are typical for atmospheric nucleation events are observed.…”

Measurement-model comparison of stabilized Criegee Intermediate and Highly Oxygenated Molecule production in the CLOUD chamber

“…Other important aerosol precursors identified in several laboratory studies include ammonia and amines (Almeida et al, 2013;Ball et al, 1999;Murphy et al, 2007). Laboratory measurements (Almeida et al, 2013;Berndt et al, 2010Berndt et al, , 2014bJen et al, 2014;Kirkby et al, 2011) and computational studies (Kurtén et al, 2008;Paasonen et al, 2012) suggest that ammonia and amines can enhance particle formation but it is challenging to estimate their importance in the ambient atmosphere without comprehensive measurements of 20 their concentration in the atmosphere. Neutral sulphuric acid -amine clusters have been observed in the CLOUD chamber experiments (Kürten et al, 2014) but similar neutral clusters have not yet been detected in the atmosphere.…”