MATHEMATICAL-MODELING OF THE CONCENTRATIONS OF VOLATILE ORGANIC-COMPOUNDS - MODEL PERFORMANCE USING A LUMPED CHEMICAL MECHANISM

An Eulerian photochemical model is used to predict the transport and reactions of organic gas emissions to the atmosphere. The model is applied to the Los Angeles area for the August 27-29, 1987, intensive monitoring period of the Southern California Air Quality Study (SCAQS), and predictions for each of the lumped organic species in the model are evaluated using speciated organic gas concentration measurements made at nine sites. Model calculations using the official State of California emission inventory accurately predicted the observed concentrations of ethene, monoalkylbenzenes, and formaldehyde, and underpredicted the concentrations of other organic species. When the on-road vehicle hot exhaust emissions of organic gases was scaled up to approximate the actual emission rates measured in a local roadway tunnel and revisions were made to the chemical composition profiles for the organic gas emissions, model performance for both ozone and most lumped organic classes improved.