HYDROGEN-PEROXIDE DRY DEPOSITION LIFETIME DETERMINED FROM OBSERVED LOSS RATES IN A POWER-PLANT PLUME

Hydrogen peroxide measurements made aboard the NOAA WP-3D aircraft in the summer of 1995 as part of the Southern Oxidants Study revealed los s of hydrogen peroxide within fossil fuel power plant plumes and the N ashville urban plume. On July 7 the Cumberland power plant plume was i ntercepted at five different downwind distances. H2O2 mixing ratios,wi thin the plume decreased with increasing distance from the plant. Conv ersely, ozone mixing ratios increased. The H2O2 loss was likely a resu lt of the lowered rate of formation due to suppression of HO2 radical concentrations in the high NOx environment and subsequent removal of H 2O2 by photolysis, reaction with HO, and dry deposition. From steady s tate model estimates of the chemical loss rates in the plume and an an alytical approximation of the influx of H2O2 into the plume center due to horizontal dispersion, a simple budget for H2O2 was formulated, fr om which a dry deposition lifetime of 19 hours +/- 55% was inferred.