Development of a Chemical Ionization Time-of-flight Mass Spectrometer for Characterizing the Role of Organic Amines in New Particle Formation

Description

Aerosol particles affect global climate through cloud formation. Globally, potentially 50% of all cloud condensation nuclei (CCN) originate from new particle formation and growth. Gas-phase sulfuric acid plays a key role in new particle formation, though detailed mechanisms remain unclear. Recent experiments have shown that part-per-trillion (pptv) levels of organic amines can enhance particle nucleation by 1000 times or more compared to sulfuric acid plus water or sulfuric acid plus water and ammonia. Evaluation of atmospheric nucleation rates is limited by sparse amine measurements and the resulting lack of knowledge of atmospheric amine budgets. At the same time, atmospheric amine source budgets are potentially sensitive to climate change, through natural biological reactivity (e.g., soil carbon decomposition) and anthropogenic agricultural activity. Furthermore, the proposed use of amines for carbon dioxide (CO2) sequestration has significant implications for aerosol CCN budgets and their cloud interactions. The first step in determining the importance of amines in nucleation is reliable measurements of ambient amine concentrations. Due to their rapid uptake into aerosol particles and high photochemical reactivity, ambient amine mixing ratios are typically at pptv or sub-pptv levels. Ambient measurements of amines are sparse because high levels of background contamination are a significant obstacle for pptv measurements. Through DoE SBIR funding, Aerodyne Research, Inc. (ARI) is developing and characterized an effectively wall-less ionization source that uses a sulfuric acid cluster ionization (SACI) scheme to selectively measure organic amines using a field-portable chemical ionization time-of-flight mass spectrometer (ToF-CIMS). The Phase I results along with a discussion of design improvements for Phase II are presented here.