Evaluation of the effect of various emission sources on ozone formation in Memphis, Tennessee

The Urban Airshed Model has been employed to predict the maximum impact of ozone formation in the atmosphere passing over Memphis, Tennessee during the period of 1986 to 1988. The wind direction was chosen from south-west to north-east. The model result was compared with the observed peak ozone concentration. The model result was within 7% of the observed ozone concentration. The effects of various emission sources on ozone formation were evaluated. Mobile and area sources had the most significant contribution to ozone formation and those sources were also the most significant contributor to NO_x emissions. NO_x emissions from a local power plant were also high. This source showed less of a contribution to ozone formation at the ground level due to the stack height. In spite of large VOC emissions from biogenic sources, this source category also showed little contribution to ozone formation. A sensitivity analysis was done by varying the VOCs emitted from mobile sources. Analysis showed that the ozone formation was NO_x limited. The peak ozone concentration did not change appreciably when VOC emissions from mobile sources were changed significantly. However, a reduction of NO_x emissions from mobile source caused a significant reduction in ozone formation based on the UAM modeling.