The impact of aerosols on solar ultraviolet radiation and photochemical smog.

Photochemical smog, or ground-level ozone, has been the most recalcitrant of air pollution problems, but reductions in emissions of sulfur and hydrocarbons may yield unanticipated benefits in air quality. While sulfate and some organic aerosol particles scatter solar radiation back into space and can cool Earth's surface, they also change the actinic flux of ultraviolet (UV) radiation. Observations and numerical models 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.

[1]  B. Holben,et al.  Urban/industrial aerosol: Ground‐based Sun/sky radiometer and airborne in situ measurements , 1997 .

[2]  P. Bhartia,et al.  Global distribution of UV-absorbing aerosols from Nimbus 7/TOMS data , 1997 .

[3]  D. H. Stedman,et al.  Direct measurements of ozone and nitrogen dioxide photolysis rates in the troposphere , 1980 .

[4]  Yoram J. Kaufman,et al.  Size distribution and scattering phase function of aerosol particles retrieved from sky brightness measurements , 1994 .

[5]  J. Houghton,et al.  Climate change 1995: the science of climate change. , 1996 .

[6]  David John Lary,et al.  Carbon aerosols and atmospheric photochemistry , 1997 .

[7]  J H Seinfeld,et al.  Urban Air Pollution: State of the Science , 1989, Science.

[8]  Stuart A. McKeen,et al.  Effect of anthropogenic aerosols on biologically active ultraviolet radiation , 1991 .

[9]  B. Finlayson‐Pitts,et al.  Tropospheric air pollution: ozone, airborne toxics, polycyclic aromatic hydrocarbons, and particles. , 1997, Science.

[10]  D. Hauglustaine,et al.  HNO3/NOx ratio in the remote troposphere During MLOPEX 2: Evidence for nitric acid reduction on carb , 1996 .

[11]  Rudolf B. Husar,et al.  Spatial and temporal pattern of eastern U.S. haziness: A summary , 1981 .

[12]  S. Madronich,et al.  Actinometric and radiometric measurement and modeling of the photolysis rate coefficient of ozone to O (^1D) during Mauna Loa Observatory Photochemistry Experiment 2 , 1996 .

[13]  S. Lal,et al.  Changes in surface ozone amount and its diurnal and seasonal patterns, from 1954–55 to 1991–93, measured at Ahmedabad (23 N), India , 1996 .

[14]  M. Khalil,et al.  The distribution of solar radiation in the earth's atmosphere : The effects of ozone, aerosols and clouds , 1996 .

[15]  M. Molina,et al.  Chemical kinetics and photochemical data for use in stratospheric modeling , 1985 .

[16]  J. Coakley,et al.  Climate Forcing by Anthropogenic Aerosols , 1992, Science.

[17]  P. Crutzen,et al.  Atmospheric aerosols: Biogeochemical sources and role in atmospheric chemistry , 1997 .

[18]  J. H. Seinfeld,et al.  The Atmospheric Aerosol-Forming Potential of Whole Gasoline Vapor , 1997, Science.

[19]  Paul J. Crutzen,et al.  On the disproportionate role of tropospheric ozone as a filter against solar UV‐B radiation , 1989 .

[20]  Teruyuki Nakajima,et al.  Modelling radiation quantities and photolysis frequencies in the troposphere , 1994 .

[21]  S. Madronich.  Photodissociation in the atmosphere: 1. Actinic flux and the effects of ground reflections and clouds , 1987 .

[22]  J. Peterson,et al.  The sensitivity of computed ozone concentrations to U.V. radiation in the Los Angeles area , 1976 .