Hydrogen peroxide measurements made aboard the NOAA WP-3D aircraft in the summer of 1995 as part of the Southern Oxidants Study revealed loss of hydrogen peroxide within fossil fuel power plant plumes and the Nashville urban plume. On July 7 the Cumberland power plant plume was intercepted at five different downwind distances. H2O2 mixing ratios within the plume decreased with increasing distance from the plant. Conversely, ozone mixing ratios increased. The H2O2 loss was likely a result of the lowered rate of formation due to suppression of HO2 radical concentrations in the high NOx environment and subsequent removal of H2O2 by photolysis, reaction with HO, and dry deposition. From steady state model estimates of the chemical loss rates in the plume and an analytical approximation of the influx of H2O2 into the plume center due to horizontal dispersion, a simple budget for H2O2 was formulated, from which a dry deposition lifetime of 19 hours ¿55% was inferred. ¿ 1998 American Geophysical Union