Study of the evolution of air pollution in Salamanca (Spain) along a five-year period (1994–1998) using HJ-Biplot simultaneous representation analysis

Five-year data of SO2, PM10, NO, NO2, O3 and CO levels recorded at two air pollution monitoring stations in the city of Salamanca were analysed using a HJ-Biplot Simultaneous Representation analysis method in order to determine the possible relationships among the different pollutants and to gain insight into the temporal evolution of pollution in this city. Use of this statistical method proved to be very useful for such purposes. Current trends in the evolution of atmospheric pollution in Salamanca are shown, pointing to an important decrease in SO2 and PM10, and an increase in NOx and photochemical pollution, as indicated by O3 levels. Additionally, the increase in photochemical pollution has meant that this is more preponderant in the summer. In general, at the start of the study period pollution was mainly characterised by pollutants typically found in winter, thereafter evolving towards pollution characterised by nitrogen oxides and ozone towards the end of the period studied.