Abstract
Abstract. A new model for the formation of secondary organic aerosol (SOA) from isoprene was developed. This model uses surrogate molecular species (hydroxy-hydroperoxides, tetrols, methylglyceric acid, organic nitrates) to represent SOA formation. The development of this model used available experimental data on yields and molecular composition of SOA from isoprene and methacrolein oxidation. This model reproduces the amount of particles measured in smog chambers under both low-NOx and high-NOx conditions. Under low-NOx conditions, the model reproduces the transitional formation of hydroxy-hydroperoxides particles, which are photolyzed and lead to SOA mass decrease after reaching a maximum. Under high-NOx conditions, particles are assumed to be formed mostly from the photo-oxidation of a PAN-type molecule derived from methacrolein (MPAN). This model successfully reproduces the complex NOx-dependence of isoprene oxidation and suggests a possible yield increase under some high-NOx conditions. Experimental data correspond to dry conditions (RH < 10%). However, particles formed from isoprene are expected to be highly hydrophilic, and isoprene oxidation products would likely partition between an aqueous phase and the gas phase at high humidity in the atmosphere. The model was extended to take into account the hydrophilic properties of SOA, which are relevant under atmospheric conditions, and investigate the effect of particulate liquid water on SOA formation. An important increase in SOA mass was estimated for humid conditions due to the hydrophilic properties. Experiments under high relative humidity conditions should be conducted to confirm the results of this study, which have implications for SOA modeling.
Highlights
Atmospheric fine particles are known to have effects on health, atmospheric visibility, materials and climate
The model successfully reproduces the results of Kroll et al (2006) within the uncertainties of the experiments except for one experiment, (the lowest quantity of NOx, the model gives a result (7.0 μg m−3) close to the upper value, 6.9 μg m−3). This slight overestimation could be attributed to a calculated quantity of radical HO2 too important or the fact that some reactions are missing in the gas-phase mechanism
A model for secondary organic aerosols (SOA) formation from isoprene oxidation that takes into account different chemical regimes and the hydrophilic properties of SOA has been developed
Summary
Atmospheric fine particles are known to have effects on health, atmospheric visibility, materials and climate. Among those particles, particulate organic matter (POM) represents a large fraction of the particulate mass, typically between 20 and 60% (Kanakidou et al, 2005; Yu et al, 2007; Zhang et al, 2007a). Particulate organic matter (POM) represents a large fraction of the particulate mass, typically between 20 and 60% (Kanakidou et al, 2005; Yu et al, 2007; Zhang et al, 2007a) Those particles are either primary (directly emitted as particles) or secondary (particles formed by chemical reactions in the atmosphere). SOA formation is poorly understood due to the numerous and complex chemical phenomena involved (successive VOC oxidation steps, NOx chemistry, compounds partitioning between several phases, SOA degradation, interactions between compounds in the particle, oligomerization)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
