Geochemistry and carbon isotopic ratio for assessment of PM 10 composition, source and seasonal trends in urban environment

Investigating the nature of PM10 is crucial to differentiate sources and their relative contributions. In this study we compared the levels, and the chemical and mineralogical properties of PM10 particles sampled in different seasons at monitoring stations representative of urban background, urban traffic and suburban traffic areas of Naples city. The aims were to relate the PM10 load and characteristics to the location of the monitoring stations, to investigate the different sources contributing to PM10 and to highlight PM10 seasonal variability. Bulk analyses of chemical species in the PM10 fraction included total carbon and nitrogen, d13C and other 20 elements. Both natural and anthropogenic sources were found to contribute to the exceedances of the EU PM10 limit values. The natural contribution was mainly related to marine aerosols and soil dust, as highlighted by X-ray diffractometry and SEM-EDS microscopy. The percentage of total carbon suggested a higher contribution of biogenic components to PM10 in spring. However, this result was not supported by the d13C values which were seasonally homogeneous and not sufficient to extract single emission sources. No significant differences, in terms of PM10 load and chemistry, were observed between monitoring stations with different locations, suggesting a homogeneous distribution of PM10 on the studied area in all seasons. The anthropogenic contribution to PM10 seemed to dominate in all sites and seasons with vehicular traffic acting as a main source mostly by generation of non-exhaust emissions Our findings reinforce the need to focus more on the analysis of PM10 in terms of quality than of load, to reconsider the criteria for the classification and the spatial distribution of the monitoring stations within urban and suburban areas, with a special attention to the background location, and to emphasize all the policies promoting sustainable mobility and reduction of both exhaust and notexhaust traffic-related emissions.