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E. Karnezi et al.
59.1 Introduction
Organic aerosol is an important component of fine atmospheric particulate matter.
The physical properties of the OA and its formation mechanisms are still highly
uncertain. Using lumped species for the representation of the hundreds or even
thousands of different OA components in atmospheric chemical transport models
is computationally efficient and has been used in almost all previous studies. The
two-dimensional volatility basis set (2D-VBS) framework [1] lumps organic compounds into surrogates along two axes, the axis of volatility and the axis of oxygen
content (in this work expressed as O:C ratio), for the description of the OA chemical
aging reactions. Murphy et al. [2, 3] used a 2D-VBS module for the first time in
the one-dimensional Langrangian chemical transport model PMCAMx-Trj, with 12
volatility bins (effective saturation concentrations C
* varying from 10
−5 up to 10
6
µg m
−3 at 298 K) and 13 O:C bins (from 0 to 1.2 with a step equal to 0.1). They
evaluated various parameterizations with ground measurements at three European
sites and their results showed that the simplest parameterization for the chemical
aging reactions was the most successful.
59.2 Model Description
In this work, we use the one-dimensional PMCAMx-Trj model with the 2D-VBS
module [2, 3] simulating the air parcels that arrived at each PEGASOS monitoring
location: San Pietro Capofiume in Italy during 2012 and Hyytiälä during 2013.
59.2.1 The Seven OA Chemical Aging Parameterizations
In the simulations performed, we evaluated a series of OA chemical aging parameterizations. Two simple functionalization schemes, the 1-bin and 2-bin case, in which
there is either one or two bin volatility reduction for every reaction respectively with
50% probability for an increase of 1 or 2 oxygen atoms and a more rigorous scheme,
the detailed functionalization scheme, initially suggested by [1]. Two biogenic SOA
aging schemes and different fragmentation probabilities varying from zero (no fragmentation) to unity are explored. Seven aging schemes (out of approximately 200
tested) reproduced well the AMS ground and aloft O:C and OA measurements.
Table 59.1 summarizes the 7 parameterizations that were found to reproduce the OA
observations in Italy.
E. Karnezi et al.
59.1 Introduction
Organic aerosol is an important component of fine atmospheric particulate matter.
The physical properties of the OA and its formation mechanisms are still highly
uncertain. Using lumped species for the representation of the hundreds or even
thousands of different OA components in atmospheric chemical transport models
is computationally efficient and has been used in almost all previous studies. The
two-dimensional volatility basis set (2D-VBS) framework [1] lumps organic compounds into surrogates along two axes, the axis of volatility and the axis of oxygen
content (in this work expressed as O:C ratio), for the description of the OA chemical
aging reactions. Murphy et al. [2, 3] used a 2D-VBS module for the first time in
the one-dimensional Langrangian chemical transport model PMCAMx-Trj, with 12
volatility bins (effective saturation concentrations C
* varying from 10
−5 up to 10
6
µg m
−3 at 298 K) and 13 O:C bins (from 0 to 1.2 with a step equal to 0.1). They
evaluated various parameterizations with ground measurements at three European
sites and their results showed that the simplest parameterization for the chemical
aging reactions was the most successful.
59.2 Model Description
In this work, we use the one-dimensional PMCAMx-Trj model with the 2D-VBS
module [2, 3] simulating the air parcels that arrived at each PEGASOS monitoring
location: San Pietro Capofiume in Italy during 2012 and Hyytiälä during 2013.
59.2.1 The Seven OA Chemical Aging Parameterizations
In the simulations performed, we evaluated a series of OA chemical aging parameterizations. Two simple functionalization schemes, the 1-bin and 2-bin case, in which
there is either one or two bin volatility reduction for every reaction respectively with
50% probability for an increase of 1 or 2 oxygen atoms and a more rigorous scheme,
the detailed functionalization scheme, initially suggested by [1]. Two biogenic SOA
aging schemes and different fragmentation probabilities varying from zero (no fragmentation) to unity are explored. Seven aging schemes (out of approximately 200
tested) reproduced well the AMS ground and aloft O:C and OA measurements.
Table 59.1 summarizes the 7 parameterizations that were found to reproduce the OA
observations in Italy.