Molecular Identification of Organic Vapors Driving Atmospheric Nanoparticle Growth
Organic aerosol formation, reactions, and chemical properties are complex and remain one of the most important uncertainties limiting our ability to predict and mitigate climate change. In particular, the condensation of organic vapors to form cloud particle nuclei has been the focus of intense recent research.
An international team of researchers used an iodide chemical ionization TOFMS to measure a wide suite of semi-volatile, low-volatility, and extremely low volatility organic compounds in ambient air above a boreal forest in Finland. These compounds are primarily responsible for particle growth, but are analytically challenging because of their very low concentrations and high functionalization. More than 1000 individual species were detected, quantified, and characterized in terms of their volatility and contribution to particle growth. Measurements from the Iodide CI-TOFMS were used to develop a model of particle growth rate that agreed well with observations.
Direct, real-time measurement of a broad range of species, the ability to determine their molecular formulas, and the application of a new, CI-specific calibration method were all key aspects of the CI-TOFMS instrumentation that enabled this research.