Geochemistry and carbon isotopic ratio for assessment of PM10 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, δ¹³C 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 δ¹³C 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 not-exhaust traffic-related emissions.