Time variations of the air quality in reference sites of an urban and industrial environment (province of Trieste)

The air quality in Province of Trieste has been considered in terms of minor pollutant species as nitrogen oxides and sulphur dioxide: these species are correlated to motor vehicle traffic and to heating system activities, and their distribution can provide information on both urban and industrial factors affecting the air quality. Air pollutant concentration trends make it possible to distinguish three types of areas: (i) the town-centre' areas display nitrogen oxide contents higher than sulphur dioxide; (ii) the industrial' areas have instead sulphur dioxide contents similar or higher than nitrogen oxides; (iii) the peripheral ones, less affected by urban traffic and industrial sources, display the lowest pollutant contents. Pollutant distribution is affected by winds. Industrial source-points of sulphur dioxide were detected. In town centre, sulphur dioxide has its minimum in summer, when home heating systems stop: this decrease is not observed in sites nearby industrial areas