10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Investigation of New Particle Formation from Aromatic Hydrocarbons: Impact of OH and NOx on Highly Oxidized Multifunctional Compounds
HOUSSNI LAMKADDAM, Mao Xiao, Christopher R. Hoyle, Lubna Dada, Mingyi Wang, Dominik Stolzenburg, Lukas Fischer, Andrea Baccarini, Chuan Ping Lee, Ruby Marten, Imad El Haddad, Josef Dommen, Urs Baltensperger, CLOUD Collaboration, Paul Scherrer Institute
Abstract Number: 684 Working Group: Aerosol Chemistry
Abstract Aerosol particles in the atmosphere are ubiquitous. Despite their tiny size, aerosols exert an important impact on human health, clouds and global climate. Understanding new particle formation (NPF) is an essential step since nucleated particles might contribute to 50% of the cloud condensation nuclei (CCN) (Merikanto et al. 2009; Dunne et al. 2016).
Our current knowledge of the physical and chemical mechanisms controlling NPF is still poorly constrained. This lack of a robust framework on NPF processes results in a large uncertainty of model outputs – i.e. long-term prediction of CCN – and hence past and future change in climate.
Recently, laboratory and field campaigns have shown evidence for NPF from highly oxidized multifunctional compounds (HOMs) in the absence of sulfuric acid (H2SO4) while that molecule was thought to be absolutely required (Kirkby et al. 2016; Bianchi et al. 2016). However, studies highlighting the role of HOMs in the aerosols growth and NPF were predominantly performed on anthropogenic-free activities, i.e. experiments carried out with biogenic precursors and without NOx (Riccobono et al. 2014; Kirkby et al. 2016; Frege et al. 2018). Therefore the representation of NPF in urban environment is an area of research where data are urgently needed.
In this context, the aim of this work is to study NPF from aromatic hydrocarbons (ArHCs) which represents a dominant source of emitted volatile organic compounds in urban areas. The project aims also at building a NPF database by providing a parameterization which represents the physical and chemical processes (NOx, NH3, H2SO4…) leading to NPF in air quality model.
The CERN CLOUD (Cosmic Leaving Outdoor Droplets) chamber was used to study the HOMs production from individual and mixtures of ArHCs under atmospherically relevant concentration of NOx, NH3 and H2SO4. Selected ArHCs are toluene, 1,2,4-trimethylbenzene and naphthalene.
We will present to which extent the HOMs production yields and particle formation rates are impacted by NOx and OH level for each precursor and their respective mixture.
The research is supported by the Swiss National Science Foundation and the MSCA-ITN project CLOUD-MOTION no. 764991. We thank CERN for supporting CLOUD with important technical and financial resources, and for providing a particle beam from the Proton Synchrotron. We acknowledge tofTools software for mass spectrometry analysis.
References: 1. Bianchi F., et al. (2016) Science 352 : 8962. 2. Dunne E., et al. (2016) Science 354 : 6316. 3. Frege C., et al. (2018) Atmos. Chem. Phys., 18: 65-79. 4. Kirkby J., et al. (2016) Atmos. Chem. Phys., 9: 8601-16. 5. Merikanto J., et al. (2009) Atmos. Chem. Phys., 9(21): 8601-8616. 6. Riccobono F., et al. (2014) Science, 344: 717-21.