MOLECULAR COMPOSITION OF ORGANIC AEROSOLS FORMED IN THE ALPHA-PINENE O-3 REACTION - IMPLICATIONS FOR NEW PARTICLE FORMATION PROCESSES/

The molecular composition of particle phase ozonolysis products of alp ha-pinene is investigated to comprehend the aerosol formation process following the VOC oxidation, focusing on an understanding of new parti cle formation. Two analytical approaches are applied to identify low-v olatile oxidation products in the particle phase; off-line investigati ons using preconcentration on Tenax TA(R) followed by solvent extracti on and liquid chromatography/mass spectrometry as well as an on-line t echnique, in which the organic aerosols are introduced directly into t he ion source of a mass spectrometer (atmospheric pressure chemical io nization/mass spectrometry (APCI/MS)). Both techniques showed the form ation of difunctional carboxylic acids, compounds whose physico-chemic al properties will govern most of their mass into the particle phase. Furthermore, stable binary diacid adducts could be identified by MSn-e xperiments. These observations might give insight into the process of new particle formation by heteromolecular homogeneous nucleation, indi cating that the initial cluster formation cannot be described by macro scopic properties of single oxidation products. Instead, strong interm olecular forces between different diacids might play a key role in the formation of initial nuclei and their subsequent growth.