Connecting the oxidation of soot to its redox cycling abilities

Abstract

Although it is known that soot particles are emitted in large quantities to the atmosphere, our understanding of their environmental effects is limited by our knowledge of how their composition is subsequently altered through atmospheric processing. Here we present an on-line mass spectrometric study of the changing chemical composition of hydrocarbon soot particles as they are oxidized by gas-phase ozone, and we show that the surface-mediated loss rates of adsorbed polycyclic aromatic hydrocarbons in soot are directly connected to a significant increase in the particle redox cycling abilities. With redox cycling implicated as an oxidative stress mechanism that arises after inhalation of atmospheric particles, this work draws a quantitative connection between the detailed heterogeneous chemistry occurring on atmospheric particles and a potential toxic mechanism attributable to that aerosol.

Relationship between chemical composition and oxidative potential of secondary organic aerosol from polycyclic aromatic hydrocarbons

“…Generally, DTT t of NSOA filter under O 3 exposure was higher than that of N 2 exposure. The study of Antiñolo et al (2015) also showed an increased redox activity of soot accompanied by an increased amount of oxygenated derivatives (quinone) under heterogeneous oxidation. However, the enhanced oxidative capacity from heterogeneous ozonolysis appeared to decrease with longer exposure to O 3 (Fig.…”

“…Specific molecular characteristics of these high MW OP contributors are currently unknown, and understanding them will be the subject of future research. It is very likely that the oligomers also contain redox-active quinone functional groups, such as those formed on the surface of oxidized soot (Antiñolo et al, 2015), and are therefore important for OP.…”

“…Tuet et al (2017b) studied the DTT activity of chamber-generated SOA from both biogenic and anthropogenic volatile organic compounds under various conditions, showing that naphthalene SOA (NSOA) has the highest OP. Previous work (Antiñolo et al, 2015;Bolton et al, 2000;Charrier and Anastasio, 2012;Cho et al, 2005;Jiang et al, 2017;Tuet et al, 2017b) indicated that polycyclic aromatic hydrocarbons (PAHs) are unreactive towards DTT while their oxidation products, such as quinones, can be highly redox-active. Quinones can be directly emitted from traffic or formed from secondary oxidation (Cho et al, 2004;McWhinney et al, 2013), and are able to consume antioxidants in a catalytic cycle ( Fig.…”

“…ROS include a variety of oxidants such as superoxide (O q − 2 ), hydroxyl radical ( q OH), and hydrogen peroxide (HOOH), which could either be introduced into human body directly from inhaled PM or generated by targeted cells (Nel et al, 1998;Pöschl and Shiraiwa, 2015;Rhee, 2006;Verma et al, 2015b). The generation of ROS during multiphase in-teractions between air pollutants and the human respiratory tract is closely related to the chemical composition, since the combination of various pollutants may influence chemical reactivity as well as bioavailability of PM while having synergistic or nonlinear influences on its OP (Antiñolo et al, 2015;Charrier et al, 2015;Fang et al, 2015;Shiraiwa et al, 2012;Xiong et al, 2017).…”

“…OP is exhibited as the capacity of inhaled PM to induce oxidative stress, the redox imbalance generated through consumption of antioxidants and production of reactive oxygen species (ROS) (Antiñolo et al, 2015;Shen et al, 2011;Shiraiwa et al, 2012). ROS include a variety of oxidants such as superoxide (O q − 2 ), hydroxyl radical ( q OH), and hydrogen peroxide (HOOH), which could either be introduced into human body directly from inhaled PM or generated by targeted cells (Nel et al, 1998;Pöschl and Shiraiwa, 2015;Rhee, 2006;Verma et al, 2015b).…”