ESTIMATED CONTRIBUTION OF POWER-PLANTS TO AMBIENT NITROGEN-OXIDES MEASURED IN ATLANTA, GEORGIA IN AUGUST 1992

Since gasoline and coal vary in sulfur content, plumes from mobile and point sources can be identified by their characteristic sulfur dioxid e to nitrogen oxides ratios. In this study this fingerprint ratio is u sed to estimate what percentage of the total ambient nitrogen oxides i ntercepted by a chemical measurement station in Atlanta is attributabl e to specific point sources. Emission estimates of nitrogen oxides fro m point and mobile sources were approximately equal for a 160 x 160 km grid centered around Atlanta. Using the present method, point sources represented 15% of the total ambient nitrogen oxides for the period a t the measurement site. However, this average may be misleading becaus e nitrogen oxides from point sources were found to be regularly affect ing the station most probably through the process of fumigation, typic ally during the peak ozone producing hours of the day. For instance, o n 31 August an ozone exceedence day, a large percentage of the total a mbient nitrogen oxides were from point sources at 3 p.m. (92%). On the other hand, 10 August showed no significant evidence of point source contribution, yet exceeded the ozone standard. The importance of fumig ation to ozone production in Atlanta will be the subject of future wor k.