Urban air pollution monitoring with DOAS considering the local meteorological situation

The concentrations of ozone, NO2 and SO2, measured with a DOAS system 70 m above ground level in the city of Graz were compared with data from convent ional ground stations. The dependence of vertical trace-gas distributions o n stability categories and time of the day or year was investigated. Concer ning the maximum ozone concentrations in summer, the DOAS data are represen tative for the ground-level situation. In average, the concentrations 70 m above ground are more than twice the ground-level concentrations. It has be en shown that beside the reaction with NO, dry deposition is an important s ink for ozone near the surface. The DOAS NO2-concentrations are representat ive for ground-level conditions in summer, except for the morning maximum o f NO2. In winter the DOAS NO2-concentrations amount for 73% of the ground l evel values in average. Concerning the slow reacting trace gas SO2, the DOA S data are always representative for the ground-level conditions.