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 mino r pollutant species as nitrogen oxides and sulphur dioxide: these species a re correlated to motor vehicle traffic and to heating system activities, an d their distribution can provide information on both urban and industrial f actors affecting the air quality. Air pollutant concentration trends make i t possible to distinguish three types of areas: (i) the 'town-centre' areas display nitrogen oxide contents higher than sulphur dioxide; (ii) the 'ind ustrial' 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 d istribution is affected by winds. Industrial source-points of sulphur dioxi de were detected. In town centre, sulphur dioxide has its minimum in summer , when home heating systems stop: this decrease is not observed in sites ne arby industrial areas.