A study of O3 and NO2 vertical structure in a coastal wooded zone near a metropolitan area, by means of DOAS measurements

The possible influence on the Castel Porziano Presidential Estate pine forest (Italy) of pollutant-rich air masses from the neighboring metropolitan area of Rome is analyzed. This study aims to highlight the consequences which this natural reserve located along the coast may suffer due to the vicinity of the metropolitan area. Two case studies, one representative of synoptic and the other of breeze patterns, are presented and analyzed to evaluate how the local wind circulation can influence these processes of mutual interaction between the wooded and the urban area nearby. This is a common situation in many other places around the world. s end an up-to-date version of a method for gas profile retrieval in the lower troposphere, developed by the authors, is exploited to study the time evolution of the vertical structure of O3 and NO2 concentrations on the Estate. The method consists of applying an inversion technique, based on the weighted Chahine algorithm, to DOAS (Differential Optical Absorption Spectroscopy) remote-sensing measurements. alysis of the retrieved vertical profiles shows that the degradation process associated with the arrival of air masses rich in photo-chemical pollutants, due to breeze circulation modified by the Coriolis Effect, is more apparent at upper levels than near the surface, affecting to a greater degree the higher branches of the trees. The paper also examines the impact of O3 on the wooded part of the Castel Porziano Estate. The incidence of this effect is evaluated with the analysis of the so-called AOT40 parameter.