Oxidative potential in PM field samples
In this work were selected three most important oxidative potential (OP) assays reported in the literature: the dithiothreitol (DTT), the acid ascorbic (AA) and the 2′,7′-dichlorofluorescin (DCFH) assays. These assays were applied to different field samples in order to identify the relations between OP values and chemical and dimensional characteristics of particles. The analysis of the soluble and insoluble fractions of dusts deriving from specific emission sources evidenced a very different behavior of the three assays. Furthermore, the study showed that the insoluble fraction is able to generate OP values similar or even higher than the soluble (and bio-accessible) fraction. The application of the three OP assay to PM2.5, PM10 and size-segregated samples (10-stage impactor) collected in the cities of Ferrara and Rome allowed us to confirm the non-inter-changeability of the three methods and the importance of combining the different assays, in order to successfully predict the overall capacity of PM of causing oxidative stress. Furthermore, the relations between chemical composition and OP results were studied by the application of multivariate statistical computations to the experimental data set.