10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Quantifying Initial Nanoparticle Growth of Organic and Inorganic Systems with the CLOUD Experiment
DOMINIK STOLZENBURG, Lukas Fischer, Martin Heinritzi, Mario Simon, Katrianne Lehtipalo, Chao Yan, Lubna Dada, Paul M. Winkler, University of Vienna
Abstract Number: 467 Working Group: Aerosol Physics
Abstract New particle formation and subsequent nanoparticle growth has been identified as the main contributor to the global budget of cloud condensation nuclei (CCN), significantly impacting the Earth’s radiative balance (Gordon et al. (2017), J. Geophys. Res.-Atmos., 122). In order to reach CCN sizes, high initial particle growth rates are crucial for the survival of freshly formed nanoparticles, at sizes below 10nm, as they rapidly coagulate with pre-existing aerosol. Characteristics of particle growth depend largely on the abundance of different condensable vapours and parameters such as temperature and relative humidity. Detailed studies exploring this wide parameter space are missing so far.
Here we present results from three measurement campaigns at the CERN CLOUD experiment (Duplissy et al. (2016) J. Geophys. Res. Atmos., 121, and references therein), exploring a wide range of parameters under precisely controlled conditions. Accurate quantification of sub-10 nm growth rates were achieved by using a DMA-train (Stolzenburg et al. (2017), Atmos. Meas. Tech., 10, 1639-1651) in combination with high-resolution mass spectrometry (Jokinen et al. (2012), Atmos. Chem. Phys., 12, 4117-4125; Breitenlechner et al. (2017), Anal. Chem., 89, 5824-5831).
Particle growth in several organic, inorganic and combined systems, including sulphuric acid, ammonia and highly oxidized molecules from alpha-pinene ozonolysis was measured in the temperature range between -50 and +25 °C. Moreover, experiments were performed for systems similar to those found in the atmosphere, by adding NOx and isoprene.
We find that the chemical system directly impacts the size-dependence of the growth rates and that especially the addition of NOx and isoprene influence the contribution of organics due to different resulting oxidation products. In this respect, also temperature plays a decisive role as volatility is the dominant parameter for the condensation of organic molecules. The resulting parametrization of growth rates with respect to condensable vapour concentrations will certainly help to improve the treatment of nanoparticle growth in global models. The insights gained into particle growth mechanisms by this set of experiments can possibly explain the occurrence of nanoparticle growth up to CCN sizes in various regions all over the globe.