Surface ozone study in Campinas, Sao Paulo, Brazil

The first results of the surface ozone study in Campinas, Sao Paulo state, Brazil, are presented. During the local winter (dry season) the photochemical ozone production is found to be a regular process with the afternoon ozone mixing ratio maximum ranging from 10 to 15 ppbv during totally cloudy days to 40-60 ppbv during clear sky weather. Several high-value ozone episodes with ozone mixing ratios from 80 to 140 ppbv have been registered. At the beginning of the wet season the ozone concentration in Campinas did not decrease significantly as in the Amazonia forest region, but diurnal variations became more Complicated with sharp dropouts during the days with rainfall and other fast changes of meteorological conditions. The fast irregular pulsations of ozone concentration with periods from the first tens of seconds to tens of minutes have been registered. Possible explanations of the nature of pulsations are briefly discussed. Photochemical ozone production by urban plumes of Campinas or Sao Paulo is named as a first possible source of the elevated ozone concentration and a local biomass burning is suggested as an alternative or an additional source. (C) 1996 Elsevier Science Ltd