COBRA: A Computational Brewing Application for Predicting the Molecular Composition of Organic Aerosols
Atmospheric organic aerosols (OA) represent a significant fraction of airborne particulate matter and can impact climate, visibility, and human health. These mixtures are difficult to characterize experimentally due to the enormous complexity and dynamic nature of their chemical composition. We introduce a novel Computational Brewing Application (COBRA) and apply it to modeling oligomerization chemistry stemming from condensation and addition reactions of monomers pertinent to secondary organic aerosol (SOA) formed by photooxidation of isoprene. COBRA uses two lists as input: a list of chemical structures comprising the molecular starting pool, and a list of rules defining potential reactions between molecules. Reactions are performed iteratively, with products of all previous iterations serving as reactants for the next one. The simulation generated thousands of molecular structures in the mass range of 120-500 Da, and correctly predicted ~70% of the individual SOA constituents observed by high-resolution mass spectrometry (HR-MS). Selected predicted structures were confirmed with tandem mass spectrometry. Esterification and hemiacetal formation reactions were shown to play the most significant role in oligomer formation, whereas aldol condensation was shown to be insignificant. COBRA is not limited to atmospheric aerosol chemistry, but is broadly applicable to the prediction of reaction products in other complex mixtures for which reasonable reaction mechanisms and seed molecules can be supplied by experimental or theoretical methods.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1047365
- Report Number(s):
- PNNL-SA-85407; ESTHAG; 39957; KP1704020; TRN: US201216%%224
- Journal Information:
- Environmental Science & Technology, 46(11):6048-6055, Vol. 46, Issue 11; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Atmospheric Oxidation of Squalene: Molecular Study Using COBRA Modeling and High-Resolution Mass Spectrometry
Direct Aqueous Photochemistry of Isoprene High-NOx Secondary Organic Aerosol
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AEROSOLS
CHEMICAL COMPOSITION
CHEMISTRY
DYNAMICS
ESTERIFICATION
FORECASTING
ISOPRENE
MASS
MASS SPECTROSCOPY
MATTER
MIXTURES
MOLECULAR STRUCTURE
MOLECULES
MONOMERS
PARTICULATES
POTENTIALS
RANGE
REACTION KINETICS
SEEDS
SIMULATION
USES
VISIBILITY
Environmental Molecular Sciences Laboratory