Source apportionment of the oxidative potential of fine ambient particulate matter (PM_2.5) in Athens, Greece

The main objective of this study was chemical characterization and source apportionment of the oxidative potential of ambient PM_2.5 samples collected in an urban background area in Athens, Greece. Ambient PM_2.5 samples were collected during the summer (June-September) of 2017 and winter (February-March) of 2018 at a residential, urban background site in the outlying neighborhood of the Demokritos National Laboratory in Athens, Greece. The collected PM samples were analyzed for their chemical constituents including metals and trace elements, water-soluble organic carbon (WSOC), elemental and organic carbon (EC/OC), and marker of biomass burning (i.e., levoglucosan). In addition, the DCFH in vitro assay was performed to determine the oxidative potential of the PM_2.5 samples. We performed a series of statistical analyses, including Spearman rank-order correlation analysis, principal component analysis (PCA), and multi linear regression (MLR) to determine the most significant species (as source tracers) contributing to the oxidative potential of PM_2.5. Our findings revealed that the intrinsic (per PM mass) and extrinsic (per m³ of air volume) oxidative potentials of the collected ambient PM_2.5 samples were significantly higher than those measured in many urban areas around the world. The results of the MLR analyses indicated that the major pollution sources contributing to the oxidative potential of ambient PM_2.5 were vehicular emissions (characterized by EC) (44%), followed by secondary organic aerosol (SOA) formation (characterized by WSOC) (16%), and biomass burning (characterized by levoglucosan) (9%). The oxidative potential of the collected ambient PM_2.5 samples was also higher in summer compared to the winter, mainly due to higher concentrations of EC and WSOC during this season. Results from this study corroborate the impact of traffic and SOA on the oxidative potential of ambient PM_2.5 in greater Athens area, and can be helpful in adopting appropriate public health policies regarding detrimental outcomes of exposure to PM_2.5.