Atmospheric particulate matter (PM) is an heterogeneous and dynamic mixture of particles with different origins, and its harmful effects are more strongly linked to its size and chemical composition than to its mass. The capability of some chemical compounds, present in airborne particulate matter, to generate reactive oxygen species (ROS) is known as “oxidative potential” (OP), and it represents a usefull indicator of PM toxicity. The high production of ROS causes oxidative damages to cells that ultimately can lead to different chronic diseases. Although numerous studies were performed in the las years, however the biologiclal mechanisms of toxicity and its relation with the chemical and physical properies of particulate matter are still largely unknown and futher research is need. In this work was investigated the oxidative potentialof the water-soluble fraction of PM 2.5 and PM 10 , collected at an urban background site in Southern Italy. The analysis of the OP were performed using the dithiothreitol (DTT) assay, a surrogate for cellular antioxidants, which analyses the rate of DTT depletion catalysed by chemical species present in the PM. Organic and Elemental carbon content was determined on all the collected samples in order to study the correlation between carbonaceous fractions and oxidative potential as well as to quantify the contribution of the combustion sources. DTT activity normalised by sampled air volume (OP V ) and normalised by collected aerosol mass (OP M ) were investigated. Results showed a seasonal trend in PM concentrations, in both size fractions, with larger concentrations during the cold seasons compared to the warm seasons. The same trend was also observed in carbonaceous faraction. OP V showed a similar trend with values larger in PM 10 compared to PM 2.5 as well as greater OP V values was observed in high carbon content samples. OP M was instead larger for PM 2.5 than PM 10 . Also, OP V was well correlated both with mass concentration of PM and carbonaceous fractions, while no significant correlation has been observed with OP M .
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