The Ebre Delta atmospheric station (DEC3) was installed in Eastern Spain, within the framework of the ClimaDat project of the Institut Català de Ciències del Clima (IC3). This station offers continuous measurements of greenhouse gases and tracers concentrations (CO2, CH4, CO, N2O and SF6), along with atmospheric concentrations of the natural radioactive gas 222Rn. Meteorological parameters, such as humidity, temperature, wind speed and wind direction are also measured at DEC3 site. This qualitative analysis aims to use the FLEXPART and the HYSPLIT models, with meteorological input of ECMWF and with spatial resolution of 0.2 degrees, to perform back trajectories at DEC3 station and qualitatively analyze how different air masses coming from the Northern Western Europe or from the Mediterranean Sea influence observed gases concentrations.