Impact of stratospheric ozone depletion on photoproduction of hydrogen peroxide in Lake Ontario

Using a solar spectral irradiance model, the clear-sky ground-level ultravi olet irradiance spectra over Lake Ontario on the vernal/autumnal equinox an d the summer solstice were calculated for two concentrations of stratospher ic ozone. Using these UV spectra in conjunction with apparent spectral quan tum yield values appropriate for UV-generated hydrogen peroxide from all aq uatic photoreactions, the total photoproduction of H2O2 in Lake Ontario was estimated for clear sky conditions. It was determined that for a dramatic reduction of 37.5% in stratospheric ozone concentration, a) total photoprod uction of H2O2 in Lake Ontario would only increase by 3.5%, b) spectral pho toproduction of H2O2 dramatically increases by over a factor of 200 at 290 nm falling to about a factor of 6 at 300 nm, c) the enhanced ground-level U V-B radiation results in a 33% increase in its contribution to the total ph otoproduction of H2O2 in Lake Ontario, and d) although the increased UV-B i rradiance is the primary energy source for increased formation of H2O2, the essentially non-impacted UV-A irradiance remains the dominant factor in th e total formation of H2O2 Therefore, current reductions fi stratospheric oz one concentrations will have minimal effect on the photoproduction of H2O2 intake Ontario.