CONCENTRATION AND SIZE DISTRIBUTION OF ATMOSPHERIC PARTICULATE MATTERON A FORESTED AREA IN THE BASQUE COUNTRY (SPAIN)

Throughout the period going from October 1989 to September 1990, we me asured the air concentrations of both SO2 gas and of the atmospheric p articulate fraction, both in total and split into in size ranges, by m eans of a Denuder-filter system and of a cascade impactor, respectivel y, all of it for a forested area located in the centre of the Basque C ountry in northern Spain. The results thrown when the Denuder-filter s ystem was used, show the SO42-. and NH4+ ions, with 4.6 mu g m(-3) of each, as being the most important species in the particulate traction, whereas the NO3 ion would come second in the scale, with 0.9 mu g m(- 3). The average concentration of SO2 gas was 3.2 mu g m(-3) The levels of SO2 gas and those of the SO42- ion, both calculated for Summer and Winter, are related in such a way that their correlation shows the co nsiderable effect of local emissions on the actual air concentrations for both species during the Winter season. Likewise, after an assessme nt of the above correlation, according to the backtrajectory followed by the air mass, we infer that the greatest correlation for both these species is given by those air masses coming from the NW.