Oxidative potential of size-resolved PM related to water-soluble components and total and bioaccessible mass fractions of PAH derivatives

Abstract

Size-resolved samples (<0.49, 0.49？0.95, 0.95？1.5, 1.5？3.0, 3.0？7.2 and > 7.2 μm) of atmospheric particulate matter (PM) were collected at an urban Mediterranean and a rural central European site and analyzed for the mass fraction of water-soluble organic carbon (WSOC), humic-like substances (HULIS) and water-soluble elements. In addition, the total mass fractions of several polycyclic aromatic hydrocarbon (PAH) derivatives i.e., nitrated-PAHs (NPAHs), oxygenated-PAHs (OPAHs), chlorinated-PAHs (ClPAHs), and brominated PAHs (BrPAHs), as well as the bioaccessible fraction (extracted with simulated epithelial lining fluid) of OPAHs and NPAHs were analyzed in the same PM samples. The oxidative potential (OP) of PM was determined using the dithiothreitol (DTT) assay. Total concentrations of PM, WSOC, most water-soluble elements and ∑16NPAHs were higher at the urban site, whereas those of ∑20BrPAHs, Cr, As, as well as of the mass-normalized and the air volume-normalized OP (OPmDTT, OPVDTT) were higher at the rural site. OPAHs’ bioaccessibility ranged 0.7 %？25 % and NPAHs’ from 4.2 % to 100 %. Multiple linear regression analysis (MLR) indicated OPmDTT to be mostly driven by Cu, Fe, and 11H-benzo(a)fluoren-11-one at the urban site, and by water-soluble Co and 2-methyl-1,4-naphthoquinone at the rural site. The OP of the PM collected from the two sites in this study could have been influenced by redox active constituents not determined in this study in addition to possible differences in the photochemical age of their secondary organic aerosol content.