This project is aimed to give a strong leap forward into the understanding of the changes in chemical composition of atmospheric organic pollutants under temperature inversion. These episodes often involve precautionary health warnings or contaminant emission restrictions in urban areas as they encompass strong increases of atmospheric pollutants. Organic pollutants generated under several types of temperature inversions in urban, rural and high mountain environments will be studied. Urban areas will involve distinct examples such as Madrid and Barcelona. The former represents continental environments where soil radiative forcing is the main driver of the vertical structure. The second constitutes an example of coastal environments with significant breeze regime influence, involving eventual photo-oxidation in the marine atmosphere and inland transport. Rural environments will be represented by the temperature inversions in the area of Osona where highest summer O3 concentrations have been observed among those recorded in the Iberian Peninsula. The temperature inversions in the mountain-plain systems and their associated transport of organic pollutants uphill (day) and downhill (night), prior and after respective photo-oxidation will also be considered.