The sea breeze/land breeze circulation system in the Los Angeles area results in transport of pollutants seaward at night followed by return of aged material inland the next day. This characteristic wind reversal pattern both
increases the retention time available for the oxidation of SO_2 to form sulfates and causes individual air parcels to make multiple passes over large coastal emissions sources. As a result, the Los Angeles atmosphere exhibits high peak day and high annual mean sulfate concentrations in spite
of the fact that sulfate concentrations in marine background or desert air are low
