Size-segregated particulate matter oxidative potential near a ferromanganese plant: Associations with soluble and insoluble elements and their sources

The oxidative potential (OP) of particulate matter (PM) is considered a better health metric of PM exposure than mass concentration since its value is highly dependent on PM composition. OP assays have shown different sensitivities to PM components and particle sizes. In this work, an urban-industrial mixed site with high levels of airborne Mn and Fe, due to the proximity of a ferromanganese alloy plant, was chosen to study the association between PM elements and three OP assays (ascorbic acid (AA), dithiothreitol (DTT), and 2,7-dichlorofluorescein (DCFH)) in size segregated PM samples (PM 10-2.5 and PM 2.5 ). Urban samples from a nearby area were also collected. The concentration of 39 elements in both the soluble (in a phosphate buffer aqueous solution) and insoluble fractions of PM 10-2.5 and PM 2.5 was determined by ICP-MS. Soluble elements were then associated with OP and local sources using Principal Component Analysis (PCA). Four sources of soluble elements have been identified in the urban-industrial site. The main factor was attributed to road traffic; although Cu and Fe, two active transition metals in OP assays, were associated to this factor, their low solubility, mainly in the coarse fraction, has led to low factor loadings of OP; the second factor was attributed to a ferromanganese plant, since it presented the highest factor loadings for soluble Mn in both PM 10-2.5 and PM 2.5 ; it was the main factor associated with OP-DTT and OP-DCFH values, mainly in the coarse fraction. Crustal material and sea salt aerosol were also identified as sources. • PM OP assays (OP-DTT, OP-AA, and OP-DCFH) were assessed near a ferromanganese plant • The Mn industrial source showed the highest factor loadings of PM OP (DTT and DCFH). • Factor loadings of OP in the crustal material factor were close to zero • The contribution of traffic emissions to OP was low due to the low solubility of Cu and Fe • OP-AA was poorly associated with the studied elements