Observations of aminium salts in atmospheric nanoparticles and possible climatic implications

Abstract

We present laboratory studies and field observations that explore the role of aminium salt formation in atmospheric nanoparticle growth. These measurements were performed using the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) and Ultrafine Hygroscopicity Tandem Differential Mobility Analyzers. Laboratory measurements of alkylammonium-carboxylate salt nanoparticles show that these particles exhibit lower volatilities and only slightly lower hygroscopicities than ammonium sulfate nanoparticles. TDCIMS measurements of these aminium salts showed that the protonated amines underwent minimal decomposition during analysis, with detection sensitivities comparable to those of organic and inorganic deprotonated acids. TDCIMS observations made of a new particle formation event in an urban site in Tecamac, Mexico, clearly indicate the presence of protonated amines in 8-10 nm diameter particles accounting for about 47% of detected positive ions; 13 nm particles were hygroscopic with an average 90% RH growth factor of 1.42. Observations of a new particle formation event in a remote forested site in Hyytiälä, Finland, show the presence of aminium ions with deprotonated organic acids; 23% of the detected positive ions during this event are attributed to aminium salts while 10 nm particles had an average 90% RH growth factor of 1.27. Similar TDCIMS observations during events in Atlanta and in the vicinity of Boulder, Colorado, show that aminium salts accounted for 10-35% of detected positive ions. We conclude that aminium salts contribute significantly to nanoparticle growth and must be accounted for in models to accurately predict the impact of new particle formation on climate.amine | atmosphere | new particle formation | Thermal Desorption Chemical Ionization Mass Spectrometer

SOA Formation Potential of Emissions from Soil and Leaf Litter

“…A more comprehensive soil and litter SOA composition data set needs to be generated to determine whether or not the dominant SOA precursors are constant over time or if there are bursts in emissions not measured here that may contribute to variability. Amines have been suggested as potential aerosol precursors from soil and litter previously, 42,43 and would not have been detectable with the analytical equipment used here. Neither the PTR-MS nor the GC-MS-FID measured sesquiterpenes in significant amounts, but these compounds are known to have high losses in sampling lines 44,45 and previous work has indicated that aerosol yields can be very sensitive to the presence of sesquiterpenes.…”

Ozonolysis of Trimethylamine Exchanged with Typical Ammonium Salts in the Particle Phase

“…For example, aliphatic amines contributed 23% to the NPF events at a remote forested site in Hyytiala, Finland in March, 2006 and 47% to that at an urban site in Tecamac, Mexico in April, 2007. 12 Amines observed in Marshall Field Site, Colorado (2007), 13 North Boulder, Colorado (2009), and Atlanta, Georgia (2009) 14 have also been confirmed to play the same role in NPF events. 12 In laboratory studies, NPF was observed when amines were added into a smog chamber or flow tube reactor containing a certain concentration of nitric acid, 15 sulfuric acid, 16 or methanesulfonic acid (MSA).…”

“…12 Amines observed in Marshall Field Site, Colorado (2007), 13 North Boulder, Colorado (2009), and Atlanta, Georgia (2009) 14 have also been confirmed to play the same role in NPF events. 12 In laboratory studies, NPF was observed when amines were added into a smog chamber or flow tube reactor containing a certain concentration of nitric acid, 15 sulfuric acid, 16 or methanesulfonic acid (MSA). 17,18 Density functional theory (DFT) calculations indicated that amine molecules act as cluster stabilizers for nucleation precursors, 19,20 and therefore promote nuclei formation.…”

“…Although the typical concentration of amines is from several pptv to tens of pptv, 63,64 it has been well recognized that amines contribute to both new particle formation 12,16 and brown carbon. 65 For example, nucleation rates with 5 pptv of DMA were enhanced more than 1000-fold compared with 250 pptv ammonia at ambient concentration of sulfuric acid.…”

Molecular understanding of sulphuric acid–amine particle nucleation in the atmosphere

“…in the continental boundary layer have been reported 17,19,20 , suggesting that sulphuric acid-amine nucleation is likely to be an important atmospheric process. However, atmospheric observations indicate both the presence 10,11,16 and the absence 22 of a significant amine fraction in newly formed particles, which suggests considerable variability of ambient amine levels. Although amines are volatile vapours, our measurements show that sulphate particles constitute an almost perfect sink (negligible evaporation).…”