Environmental Engineering Reference
In-Depth Information
2.2 Application of CAMx Model in Switzerland
with the New SOA Mechanism
Ş. Andreani-Aksoyoğlu, D. Oderbolz, J. Keller, I. Barmpadimos,
A.S.H. Prévôt, and U. Baltensperger
Laboratory of Atmospheric Chemistry (LAC), Paul Scherrer Institute, Switzerland
Abstract
In this study, we report the preliminary results of the CAMx (Compre-
hensive Air quality Model with eXtensions) application in Switzerland using a
new secondary organic aerosol (SOA) module. The latest CAMx version includes
polymerization of SOA in addition to partitioning mechanism as well as other
SOA formation pathways such as from isoprene and sesquiterpenes. The aerosol
parameters were updated as well. The model was tested for two different periods
in winter and summer 2006. We compared the model results with the Aerosol
Mass Spectrometer (AMS) measurements. Simulations with earlier model version
underestimated organic aerosols and contradicted the measurements about the
fractions of SOA and POA (primary organic aerosols). A significant improvement
(20%) was achieved in SOA formation in winter using the new version. The SOA
concentrations increased by 11% for the summer episode. The improvements are
due to increased SOA production and polymerization from biogenic precursors.
Keywords
SOA, CAMx, aerosols, polymerization, biogenic emissions
1. Introduction
The current models often underestimate SOA concentrations (Volkamer et al.,
2006; Andreani-Aksoyoğlu et al., 2008). A recent model study by Morris et al.
(2006) showed that including mechanisms such as polymerization, SOA formation
from isoprene and sesquiterpenes led to increased SOA yields. Robinson et al.
(2007) indicated another pathway to SOA formation from primary organic-
particulate emissions. The authors showed experimentally that photo-oxidation of
diesel emissions rapidly generates organic aerosol, greatly exceeding the contri-
bution from known secondary organic-aerosol precursors. There were several
measurements in northern Switzerland during winter and summer 2006 investi-
gating the chemical composition of particles. In this study, winter and summer
episodes were simulated by two CAMx versions.
