Sulfuric acid nucleation: power dependencies, variation with relative humidity, and effect of bases

Abstract

Nucleation of particles composed of sulfuric acid, water, and nitrogen base molecules was studied using a continuous flow reactor. The particles formed from these vapors were detected with an ultrafine condensation particle counter, while vapors of sulfuric acid and nitrogen bases were detected by chemical ionization mass spectrometry. Variation of particle numbers with sulfuric acid concentration yielded a power dependency on sulfuric acid of 5 ± 1 for relative humidities of 14–68% at 296 K; similar experiments with varying water content yielded power dependencies on H<sub>2</sub>O of ~7. The critical cluster contains about 5 H<sub>2</sub>SO<sub>4</sub> molecules and a new treatment of the power dependency for H<sub>2</sub>O suggests about 12 H<sub>2</sub>O molecules for these conditions. Addition of 2-to-45 pptv of ammonia or methyl amine resulted in up to millions of times more particles than in the absence of these compounds. Particle detection efficiencies, sulfuric acid and nitrogen base detection, wall losses, and the extent of particle growth are discussed with the help of a recent computational fluid dynamics study that simulated the flow and chemistry in the flow reactor. Results are compared to previous laboratory nucleation studies and they are also discussed in terms of atmospheric nucleation scenarios

Stabilization of sulfuric acid dimers by ammonia, methylamine, dimethylamine, and trimethylamine

“…The blue squares are the baseline measurements from Petäjä et al [], i.e., those without added base and at a residence time of 32 s. Their results can be directly compared to our baseline measurement at 40 s, given as a dashed black line in Figure . This residence time is determined from the point of sulfuric acid injection into the flow reactor [see Zollner et al , ] and is different from the 3 s reaction time where the base is injected (see Figure ). The solid black curve is the steady state collision‐controlled limit (no cluster evaporation and no base reaction, but with coagulation and wall losses for the Augsburg flow reactor).…”

“…Each day, prior to the addition of base, [ A 1 ] and [ A 2 ] were measured to serve as the “baseline” measurement for the flow reactor and MCC [cf. Zollner et al , ]. The primary origin of the baseline measured [ A 2 ] is due to IIC and is further explained in the supporting information.…”

“…At the point of injection, the centerline base concentration was ~10 times greater than at the MCC sampling point [ Freshour et al ., ]. A well‐mixed concentration, called no loss dilution concentration (NLD), of basic gas was determined a priori [ Zollner et al , ] from the permeation rate and dilution ratios, assuming no losses to the walls. The MCC in positive ion mode measured the base concentration and is within 20% of NLD (see supporting information).…”

“…The greatest experimental challenge for such investigations is the extraordinary cleanliness required to isolate and study particular chemical systems. This study utilizes a previously characterized glass flow reactor at Augsburg College [ Panta et al , ; Zollner et al , ]. This flow reactor has been continuously purged over a period of 2 years with about 2 million liters of nitrogen from the head space of a liquid nitrogen tank; a portion of this flow carries sulfuric acid vapor which coats all the surfaces within the reactor.…”

Size resolved chemical composition of nanoparticles from reactions of sulfuric acid with ammonia and dimethylamine

“…Sulfuric acid (H 2 SO 4 ) is well recognized to be critical in many NPF events (Weber et al 1996(Weber et al , 1997McMurry et al 2000;Weber et al 2001;Kulmala et al 2006;Sipil€ a et al 2010). Amines and ammonia (NH 3 ) can bond strongly with H 2 SO 4 , and greatly enhance NPF (Ball et al 1999;Korhonen et al 1999;Yu 2006;Kurt en et al 2008;Benson et al 2009;Berndt et al 2010;Erupe et al 2011;Kirkby et al 2011;Zollner et al 2012;Almeida et al 2013;Glasoe et al 2015). Recent studies suggest that organic acids such as methanesulfonic acid (Kreidenweis et al 1989;Wyslouzil et al 1991;Dawson et al 2012;Chen et al 2016), and highly oxidized, low-volatility organic compounds Schobesberger et al 2013;Bianchi et al 2014;Ehn et al 2014;Riccobono et al 2014;Jokinen et al 2015;Bianchi et al 2016;Tr€ ostl et al 2016) also play an important role in NPF.…”