SENSITIVITY OF OZONE CONCENTRATIONS TO VOC AND NOX EMISSIONS IN THE CANADIAN LOWER FRASER VALLEY

The SAPRC90 chemical mechanism module implemented in CALGRID is update d for the specific emissions and applications of the Lower Fraser Vall ey (LFV) of British Columbia, Canada. The kinetic and mechanistic para meters of lumped VOC reactions recalculated using the LFV emissions pr ofiles are noticeably different from those based on default emissions profiles, indicating the importance of tailoring the parameters to spe cific regions. The sensitivities of ozone concentrations to total and speciated VOC and NOx emissions as well as to the NO2/NOx ratios are d etermined. Significant VOC model species are identified based on the i mpact of their emissions on ozone formation in the LFV. Of note is the importance of the emissions of a lumped class of aromatics, ARO2, whi ch contains mostly isomers of xylene and trimethylbenzene and is deriv ed chiefly from the use and distribution of gasoline fuels. The ARO2 e missions make the largest contribution of all model VOC species to the ozone levels in the urban plume. The results indicate that reduction of ARO2 emissions alone could achieve significant reduction of ozone l evels in the LFV. Base case emissions of NOx(NO or NO2) in the LFV con tribute negatively to the ozone formation. Any overestimation of NOx o r underestimation of VOC in the emissions inventory could cause undere stimations of ozone levels by photochemical models. Crown copyright (C ) 1996 Published by Elsevier Science Ltd