Variability of oxidants (OX = O3 + NO2), and preliminary study on ambient levels of ultrafine particles and VOCs, in an important ecological area in Spain

• Is the first study of OX, VOCs, UFPs and back trajectories air masses in this area.
• This area presents high background level of ozone with maximum in June.
• European limits to protect human health and vegetation were exceeded.
• [formaldehyde]/[benzene] indicates predominant contribution of BVOC.
• Average total concentration of UFPs was 3.5 × 103 #cm− 3.

This work reports the first study of photochemical air pollution inside the Cabañeros National Park, in the south-centre of the Iberian Peninsula. For this purpose, we analysed (i) the daily and seasonal variation of oxidant levels (OX = O3 + NO2), (ii) the particle number concentration and size distribution (for particle diameters in the range 6–560 nm), (iii) the volatile organic compounds (VOCs) and (iv) back trajectories of the air masses affecting this region.The ozone NO and NO2 data were collected from January to September 2011. NOx levels were very low during the measurement time. On the other hand, the threshold for the protection of human health defined in the European Ozone Directives was exceeded 2 times and the AOT40 parameters to protect vegetation and trees were also exceeded. Under the found conditions, photochemical production of ozone was NOx-limited and the ozone problem in this region is associated to transport of polluted air masses from remote areas, mainly from the eastern Mediterranean coast and the western Atlantic coast, according to the back trajectories data. The average total concentration of particles during our study was 3.5 × 103 #cm− 3 with the Aitken and accumulation modes as the main contributions.