AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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New Particle Formation from BVOCs and Sulphuric acid in the CLOUD Chamber at Different Levels of NH3 and NOx
KATRIANNE LEHTIPALO, Chao Yan, Robert Wagner, Lubna Dada, Jenni Kontkanen, Tuomo Nieminen, Jonathan Duplissy, Hamish Gordon, Jasper Kirkby, Urs Baltensperger, Markku Kulmala, University of Helsinki
Abstract Number: 284 Working Group: Effects of NOx and SO2 on BVOC Oxidation and Organic Aerosol Formation
Abstract Both sulphuric acid and oxidation products of biogenic volatile organic compounds (BVOCs) have been previously identified as important precursors for new particle formation in the atmosphere. However, the processes leading to cluster formation and growth are not completely understood in the simultaneous presence of multiple precursor vapors and oxidation pathways. During the CLOUD10 experiment we aimed to replicate the new particle formation process as it is observed at the Hyytiälä SMEAR II station, which is one of the most studied field sites regarding in this respect. Using the CLOUD chamber at CERN we could use atmospherically relevant concentrations of precursors and maintain a high degree of control and a low level of contaminants.
Particle formation in the CLOUD chamber was started from a mixture of the two most abundant monoterpenes found in the boreal forest: alpha-pinene and delta-3-carene. The total monoterpene volume mixing ratios varied from about 150 to 1200 ppt. The experiments were conducted at varying levels of sulphuric acid (from less than 1e5 cm-3 up to 5e7 cm-3) and NOx (from 0 to 5 ppb). The first experiment series were carried out without ammonia to ensure clean conditions, and later ammonia (up to 3ppb, but mostly at the level of some hundreds of ppts) was added to the chamber. All the experiments were done first in neutral conditions (without ions present) and then repeated with ionization from galactic cosmic rays (GCR) and/or with additional ionization from the CERN pion-beam to study the fraction of ion-induced nucleation.
A comprehensive suite of instruments including state-of-the-art particle counters, size spectrometers and mass spectrometers were used to detect the forming particles and their precursors. We will present the first results from the “Hyytiälä simulation” in CLOUD and investigate the interactions between different particle formation pathways.