Measurements of Aerosol Chemistry during New Particle Formation Events at a Remote Rural Mountain Site

Abstract

Determining the major sources of particles that act as cloud condensation nuclei (CCN) represents a critical step in the development of a more fundamental understanding of aerosol impacts on cloud formation and climate. Reported herein are direct measurements of the CCN activity of newly formed ambient particles, measured at a remote rural site in the Sierra Nevada Mountains of Northern California. Nucleation events in the winter of 2009 occurred during two pristine periods following precipitation, with higher gas-phase SO(2) concentrations during the second period, when faster particle growth occurred (7-8 nm/h). Amines, as opposed to ammonia, and sulfate were detected in the particle phase throughout new particle formation (NPF) events, increasing in number as the particles grew to larger sizes. Interestingly, long-range transport of SO(2) from Asia appeared to potentially play a role in NPF during faster particle growth. Understanding the propensity of newly formed particles to act as CCN is critical for predicting the effects of NPF on orographic cloud formation during winter storms along the Sierra Nevada Mountain range. The potential impact of newly formed particles in remote regions needs to be compared with that of transported urban aerosols when evaluating the impact of aerosols on clouds and climate.

Single particle analysis of amines in ambient aerosol in Shanghai

“…Creamean et al reported an amine-OC particle burst episode with decreased mean particle sizes after a precipitation in Northern California, which was explained by amine-assisted particle growth after a particle nucleation event. [29] Precipitation can effectively remove airborne particles and leave a pristine ambient environment with less surface area, which is favoured for particle nucleation. However, new particle formation processes cannot explain our observation.…”

“…[13,[18][19][20] De Haan et al [21,22] observed that reactions between glyoxal and amines or amino acids can produce light-absorbing, nitrogen-containing imidazoles and oligomers. Particle phase amines have been extensively observed in many areas [9,17,[23][24][25] especially in ultrafine particles during nucleation [26][27][28] and particle growth [29] events. Compared with ammonia, amines have higher molecular weights and present stronger alkalinity that make them perfect candidates in new particle formation and growth.…”

“…Several studies have deployed single particle mass spectrometry to investigate particulate amines in laboratory and ambient environments. [17,29,[44][45][46] Pratt et al studied seasonal variations of aminium and ammonium salts with an aerosol time-of-flight mass spectrometer (ATOFMS) coupled with an automated thermodenuder, revealing the influence of particle acidity on determining the amine morphology in fine particles. [44] Creamean et al employed an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS) to study the components of freshly formed particles (100 # D va # 1000 nm), indirectly testifying to amine's participation in new particle formation.…”

“…[44] Creamean et al employed an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS) to study the components of freshly formed particles (100 # D va # 1000 nm), indirectly testifying to amine's participation in new particle formation. [29] Rehbein et al combined field and laboratory work to demonstrate that high relative humidity (RH) greatly enhances the gas-to-particle partitioning and subsequent aqueous acid-base reaction of amines. [45] In a field measurement in urban Shanghai, our group found that under low ambient oxidant levels of amines (or ammonia), formaldehyde and carbonylcontaining compounds, Mannich reactions occur to form highmolecular-weight aminiums, accounting for a substantial fraction of organic aerosol mass.…”

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).…”