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91026 
Journal Article 
Comparison of the carbon bond and SAPRC photochemical mechanisms under conditions relevent to southeast Texas 
Faraji, M; Kimura, Y; McDonald-Buller, E; Allen, D 
2008 
1 
Atmospheric Environment
ISSN: 1352-2310
EISSN: 1873-2844 
42 
23 
5821-5836 
English 
WOS:000258365300008 
is also published as 1756670 Comparison of the carbon bond and SAPRC photochemical mechanisms under conditions relevant to southeast Texas
Gridded, regional photochemical models use simplified photochemical reaction mechanisms, and two commonly used mechanisms are the SAPRC and the carbon bond (CB) mechanism. Versions of the mechanisms currently in use include SAPRC99 and the CB-IV mechanism. For most urban areas, the CB-IV and SAPRC mechanisms yield similar results, but for the modeling done of the summer of 2000 in southeast Texas, the SAPRC mechanism leads to concentrations of ozone that are 30–45 ppb higher than with CB-IV. The differences are due to differences in both reaction rate/stoichiometry parameters and condensation methods in the mechanisms. Major reasons for the differences are: (1) the products of the reactions of aromatics with hydroxyl radical, which are more reactive in the SAPRC formulation, (2) the overall balancing of radical generation and termination reactions, which lead to higher radical concentrations in the SAPRC formulation,
and (3) the production of higher aldehydes, which is greater in the SAPRC formulation. The differences between the mechanisms is particularly relevant for evaluating attainment with the National Ambient Air Quality Standard (NAAQS) for ozone concentrations averaged over 8 h. 
Photochemical mechanisms; Atmospheric chemistry; Ozone; Air quality models 
NAAQS
• ISA-NOx (2016)
     2008 Final