Trends of frequencies of the suspended particulates values classes in a metropolitan area

The mean daily concentrations of the total suspended particulates (TSP) and the inspirable particulates (IPs) from the air duality monitoring stations in Thessaloniki, are separated in classes (by means of the European Union and WHO air duality standards) and the appearance frequency of the values c lasses is examined statistically during the period 1987-95. The spatial and temporal distribution of these frequencies is also examined. The results a re correlated with the trends of pollution sources emissions, the technolog ical innovations and the environmental policy in the metropolitan area of T hessaloniki.