Effect of sea breeze on air pollution in the Greater Athens Area. Part II:Analysis of different emission scenarios

The Mediterranean Campaign of Photochemical Tracers-Transport and Chemical Evolution that took place in the greater Athens area from 20 August to 20 S eptember 1994 has confirmed the role of sea-breeze circulation in photochem ical smog episodes that had been suggested already by a number of experimen ts and numerical studies. The meteorological and photochemical modeling of this campaign were discuss ed in Part I. Part II focuses on the study of the 14 September photochemica l smog event associated with a sea-breeze circulation. The objective of the study is to identify and to understand better the nonlinear processes that produce high ozone concentrations. In particular, the effect of land and s ea breezes is investigated by isolating the effect of nighttime and daytime emissions on ozone concentrations. The same principle then is used to isol ate the effect on ozone concentrations of the two main sources of emissions in the greater Athens area: the industrial area around Elefsis and the Ath ens urban area. Last, the buildup of ozone from one day to another is inves tigated. From this study, it comes out that ozone production in the Athens area is m ainly a 1-day phenomenon. The increased values of photochemical pollutant ( up to 130 ppb at ground level) reached during summertime late afternoons on mountain slopes to the north and northeast of the city are related mainly to the current-day emissions. Nevertheless, the recirculation of old pollut ants can have an important effect on ozone concentrations in downtown Athen s, the southern part of the peninsula, and over the sea, especially near Ai gina Island.