SURFACE OZONE IN PISA (ITALY) - A 6-YEAR STUDY

The paper reports the results of ground level distribution of ozone in Pisa (Italy) in the periods May to September, 1986-1991. The recurren ce of relevant levels of photochemically produced ozone is described. The maximum hourly peak (M1) proved to be 128 ppb and the average of t he M1 peaks turned out to be 60 ppb. The threshold of 100 ppb was surp assed in 17 d. The average value of the ''daily highest consecutive 7- h mean concentrations'' (M7) was 53 ppb. M1 and M7 are closely correla ted and both show approximately a log-normal distribution. Monthly var iations are relatively low, with September showing the lowest values. The years 1986 and 1991 show values that are clearly higher than the o ther years, and no temporal trend has been verified. Ozone levels were positively correlated with temperature and solar radiation.