Concentration and size distribution of atmospheric particulate matter on a forested area in the basque country (Spain).

Abstract Throughout the period going from October 1989 to September 1990, we measured the air concentrations of both SO2 gas and of the atmospheric particulate fraction, both in total and split into in size ranges, by means of a Denuder‐filter system and of a cascade impactor, respectively, all of it for a forested area located in the centre of the Basque Country in northern Spain. The results thrown when the Denuder‐filter system was used, show the SO4 2‐and NH4 + ions, with 4.6 μg m‐3 of each, as being the most important species in the particulate fraction, whereas the NO3 ‐ ion would come second in the scale, with 0.9 μg m‐3. The average concentration of SO2 gas was 3.2 μg m‐3. The levels of SO2 gas and those of the SO4 2‐ ion, both calculated for Summer and Winter, are related in such a way that their correlation shows the considerable effect of local emissions on the actual air concentrations for both species during the Winter season. Likewise, after an assessment of the above correlation, according ...