Ozone yields and production efficiencies in a large power plant plume

The plume of Tennessee Valley Authorityʹs coal-fired Cumberland power plant was sampled during four different days in the summer of 1998 and 1999 from an instrumented helicopter. The extent of formation of ozone and various secondary NOy species in the plume was measured and the rates of loss processes estimated. The rates of these processes were found to be similar during three of the four sampling days. On the fourth day conversion and removal processes within the plume were significantly slower apparently due to lower ambient temperatures, and poor dispersion conditions. On the three more ‘reactive’ days ozone yield (Y) was found to be in the range of 1.5–2.6 molecules of O3 produced per molecule of NOx emitted. The ozone production efficiency, estimated from Y and the average chemical age of the farthest distance sampled, varied from 2.3 to 5.4.