*Marine background particles from the Pacific Ocean make the single largest contribution to the light extinction coefficient. They act as a site for the accumulation of secondary particulate species, such as ammonium nitrate, producing transformed particles with a size and composition that scatters light very efficiently.
*The particles who have a diameter in the range of 0.1 mm � 10 mm are the ones who contribute to light scattering. Smaller or larger particles do not have a significant contribution to light scattering.
Control 1: The complete elimination of all anthropogenic primary particle emissions in the South Coast Air Basin, surrounding L.A. All other emissions sources are held constant.
Results of Control 1:
There was accumulation of secondary particulate matter onto the marine background particles, which caused significant light extinction. The visual range increased from 9.5km, (under 1987 historical conditions), to 14.5 km under controlled conditions; an increase in visual range of 53%.
Control 2: Background sulfate particles that are advected into the South Coast Air Basin from the marine environment are removed before entry, holding other emissions sources constant.
Results of Control 2:
Caused redistribution of secondary aerosol mass to smaller particle sizes. However, only improved visual range by 11% at Claremont, Aug 28, 1987.
Control 3: Balanced control: reductions in the emission rate of anthropogenic particles, gaseous oxides of sulfur, oxides of nitrogen, VOC�s, and ammonia.
Results of Control 3:
Caused significant reductions in primary and secondary particulate matter concentrations at all particle sizes. The light extinction coefficient was significantly reduced. In conclusion, this emissions control program could more than double visual range at Claremont on Aug. 28, 1987.
