DOAS measurements above an urban street canyon in a medium sized city

The concentrations of ozone, NO2 and SO2 measured by a Differential Optical Absorption
Spectroscopy (DOAS) system in the city of Kozani in Northwestern Greece are presented and
compared against data from a conventional ground station. This was made in order to assess
DOAS performance in a complicated area in terms of sources variety, terrain complexity and
meteorological conditions. Measurements of aromatic hydrocarbon substances (benzene,
toluene, styrene and xylene) are also presented for air quality purposes.
Results between the conventional station and the DOAS system indicated the existence of
significant correlations among some of the monitored trace gases, confirming this way the
strong compatibility between the two systems. The low values of sulfur dioxide especially
during the winter were attributed to the absence of central heating in the most of the buildings
due to the use of district heating provided by the Greek Public Power Corporation. The
averaged annual benzene and daily toluene concentrations exceeded their legislated limits.
Meteorological parameters remain vital in the development of a clear understanding in DOAS
performance due to its ability to cover a wide spatial scale over the open path length.