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PM 2.5 is the particulate matter with aerodynamic diameter lower than 2.5 µm; it is mainly produced by combustion processes (vehicle traffic, heating, industrial plants, etc.) and by gas-to-particle conversion processes during dilution of exhaust gases. In the last years PM 2.5 has been widely studied because of its negative effects on health 1 but there is still little information on its physicochemical properties. Due to its dimensions, TEM (Transmission Electron Microscopy) coupled with EDS (Energy Dispersive Spectroscopy) is a very suitable method for its characterization 2 . The aim of this work was to investigate morphology and composition of PM 2.5 produced by diesel vehicles with different fuels and at different working conditions, with a particular attention for its smallest fraction (<100 nm).The observations were done with a High Resolution Transmission Electron Microscope (Jeol JEM 3010: acceleration voltage 300 kV; resolution 1.7 Å) equipped with EDS microanalysis (Link Isis 200ATW, detecting elements from C) and a CCD camera for digital image acquisition. Dimensional ranges were determined by manual image analysis (IA). In order to collect the soot without introducing artefacts and to conserve its original morphology and composition, on-line sampling was used 3 : 3mm diameter copper support grids were deposited on paper filters and the particulate was collected directly upon them from the tailpipe, with short collecting times (1-10 minutes) and without any manipulation. This procedure is a very good alternative to thermophoretic sampling, that requires a very expensive apparatus 4 . To separate the different sizes before the observation, PM 2.5 was collected from ELPI (Electric Low Pressure Impactor) plates with a special procedure.Samples from different sources (EuroI and EuroII common rail engines) and fuels (diesel, biodiesel, etc.), taken at different speeds (32 km/h, 120 km/h), were examined. All of them have the same basic structure: PM 2.5 is formed by aggregates of small, amorphous elementary particles. They are mostly spherical and contain only carbon. The dimensions vary in the range 10-20 nm. With the new lowemissions engines, their size and composition are not significantly affected by changing the fuel or the operating conditions. The aggregates, 0.1-3 µm in size, have bizarre shapes: they can be monodimensional (like chains or branches), bidimensional (like flakes) or tridimensional (like sponges). They are made only by elementary particles and do not have any condensation nucleus inside. The aggregate shapes vary with their dimensions (Figure 1-3). If metal-containing additives are added in the fuel, they form oxide particles, separated from the carbonaceous ones (Figure 4).

ResumenEspaña es un país de castillos. La estampilla española nos revela una colección de imá-genes evolutiva de este edificio. Se trata de una iconografía que pasa de lo simbólico a lo figurativo; del instrumento ideológico a la valorización del patrimonio y, luego, a la narrativa cultural. El siglo xx nos muestra este dinamismo, sobre todo durante el franquismo, y nos revela que se puede hacer marketing territorial a partir de imágenes en apariencia banales y efímeras. Desviando la función inicial de la estampilla, reestructurando su lectura, podemos llegar a una nueva forma de observación y descubrir nuevos discursos. Así hacemos arqueología con este visual, comprendiendo la voluntad del poder, sus iniciativas en materia de comunicación y sus tendencias identitarias. España hace, a su manera, valorización turística con una imagen de marca, su marca patrimonial por excelencia: sus castillos.Palabras clave: Estampilla, sello, castillo, imagen de marca, marketing territorial, España, patrimonio. AbstractSpain is a country of castles. Spanish stamps reflect a collection of evolving images of this edifice. This iconography is both symbolic and figurative, going from ideological instrument to the promotion of its heritage, and to cultural narrative. The 20th century bears the testimony of this dynamic, notably during the Franco regime, and shows that territorial marketing can be done through apparently banal and ephemeral images. By diverting the original function of the stamp, by restructuring its message, one sees it in a new light and a new discourse is revealed. This visual archeology comes to mind while understanding the will of power, its communicative initiatives and identity trends. Spain in its own way promotes its tourism through this brand image, its heritage of excellence: its castles.

No abstract