Remote Sensing Measurements for Evaluation of Air Quality in an Urban Area

Abstract

The Differential Optical Absorption Spectrometry (DOAS) is a remotesensing technique finding greater consents in these last years. The analytical principle of the DOAS system is based on the light absorption in the near—UV and Vis regions of those pollutants with fine vibrational structures such as SO₂, NO₂, O₃, nitrous acid, formaldehyde, benzene, toluene, etc. The relationship among the adsorbed light intensity and the xompound concentrations is ruled by the Lambert—Beer's law. The DOAS analysis allows to study and to interpretate the complex mechanisms of the formation and transformation of the pollutants and particularly of those of secondary origin. In this paper we have reported and discussed the behaviors of NO₂, O₃, HNO₂, formaldehyde, benzene and toluene measured by this system during the 2000—2003 period in the Rome area (an area highly influenced by anthropogenic sources) and in Pietracupa (Molise) area (considered as remote site). The results show how the DOAS system highlight very well the secondary pollution evolution; this, described by the profiles of NO₂ and O₃ being at the same time products and precursors of the photochemical smog, is not influenced by the emission flow intensity and consequently assumes homogeneous values in the whole urban area.