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Oxidative potential (OP) of particulate matter (PM) − defined as the capacity of PM to oxidize target molecules generating reactive oxygen species (ROS) − has been proposed as a more health relevant metric than PM mass. In this study two cell-free methods were used to assess the OP of PM filters collected at an urban site and to evaluate correlation with PM mass and PM composition. Among the different assays existing, two inexpensive and user-friendly methods were used both based on spectrophotometric measurements of depletion rate of target reagents oxidized by redox-active species present in PM. One assay measures the consumption of dithiothreitol (OP DTT ) and the other the ascorbate (OP AA ). Although both assays respond to the same redox-active species, i.e., quinones and transition metals, no correlations were found between OP DTT and OP AA responses to compounds standard solutions as well as to ambient samples. When expressed in relation to air volume, OP DTT m −3 strongly correlates with PM 2.5 mass whereas no correlation was found for OP AA m −3 with PM 2.5. When expressed on mass basis, both OP DTT μg −1 and OP AA μg −1 show a strong dependence on the sample composition, with higher OP for summer samples. OP DTT m −3 were highly correlated with the determined metals (Cu, Zn, Cr, Fe, Ni, Mn) whereas OP AA m −3 showed only moderate correlation with Cu and Mn. Thus, the two assays could potentially provide complementary information on oxidative potential characteristic of PM. Consequently, the combination of the two approaches can strengthen each other in giving insight into the contribution of chemical composition to oxidative properties of PM, which can subsequently be used to study health effects. [ABSTRACT FROM AUTHOR]

• Caffeic Acid adsorption onto ZSM-5 depends on pH. • Caffeic Acid is incorporated into the zeolite framework. • The hydroxyl group of caffeic acid interacts with the framework oxygen atoms. • Competitive adsorption on ZSM-5 follows the order Toluene > Caffeic Acid. Wastewaters and polluted natural water can contain a large variety of organic substances deriving from both natural and anthropogenic sources. Hydrophobic zeolites have great potential for the removal of different organic substances and among them aromatic, chlorinated, and oxygenated compounds. In this work the influence of caffeic acid - an allelochemical representing low molecular weight natural organic matter - on the adsorption of toluene in aqueous matrix has been investigated. To accomplish this task, the adsorption of caffeic acid on ZSM-5 has been studied. Differently from toluene, whose adsorption is not significantly influenced by pH, the uptake of caffeic acid onto zeolite strongly depends on pH, the maximum saturation capacity (46 mg g−1) was obtained at pH 4, corresponding to the nonionized form of caffeic acids. Additionally, caffeic acid interacts with zeolite framework and water molecule as suggested from the shift in the apparent dissociation constant evaluated from adsorption data and confirmed by structural investigation. Competitive adsorption of binary mixture of toluene and caffeic acid in a wide concentration range shows that ZSM-5 is a selective adsorbent for Toluene, and when caffeic acid is present at high concentration (100 mg L−1) the adsorbed quantity of toluene from solution is reduced of less than 15 %. [ABSTRACT FROM AUTHOR]