THE IMPACT OF AEROSOLS ON SOLAR ULTRAVIOLET-RADIATION AND PHOTOCHEMICAL SMOG

Photochemical smog, or ground-level ozone, has been the most recalcitr ant of air pollution problems, but reductions in emissions of sulfur a nd hydrocarbons may yield unanticipated benefits in air quality. While sulfate and some organic aerosol particles scatter solar radiation ba ck into space and can cool Earth's surface, they also change the actin ic flux of ultraviolet (UV) radiation. Observations and numerical mode ls show that UV-scattering particles in the boundary layer accelerate photochemical reactions and smog production, but UV-absorbing aerosols such as mineral dust and soot inhibit smog production. Results could have major implications for the control of air pollution.