Source apportionment of the redox activity of urban quasi-ultrafine particles (PM0.49) in Thessaloniki following the increased biomass burning due to the economic crisis in Greece.

The source apportionment of the redox activity of quasi-ultrafine particles (PM0.49), measured by the cell-free dithiothreitol (DTT) assay, was attempted at two urban sites (urban traffic, UT and urban background, UB) in Thessaloniki, northern Greece, following the increased biomass burning due to the economic crisis. Both, the per-mass and per-volume DTT redox activities of PM0.49 particles were found to be substantially higher at the UB site in the cold season underscoring the increase in PM toxicity with the shift from traditional oil burning to biomass burning for residential heating. Two different approaches were employed to link the measured redox activity of PM0.49 with specific sources: (a) Principal Component Analysis of the chemical components of PM0.49 followed by Multilinear Regression of the measured redox activity on factor tracers (PCA-MLR), and (b) Robotic Chemical Mass Balance receptor modeling of the ambient PM0.49 mass followed by Multilinear Regression of the redox activity on the estimable source contributions (RCMB-MLR). Both approaches indicated that the major contributors to the measured redox activity of PM0.49 were vehicular traffic at the urban traffic site and residential wood burning at the urban background site.