Reactive oxygen species associated with water-soluble PM<sub>2.5</sub> in the southeastern United States: spatiotemporal trends and source apportionment

Abstract

Abstract. We assess the potential of the water-soluble fraction of atmospheric fine aerosols in the southeastern United States to generate reactive oxygen species (ROS) and identify major ROS-associated emission sources. ROS-generation potential of particles was quantified by the dithiothreitol (DTT) assay and involved analysis of fine particulate matter (PM) extracted from high-volume quartz filters (23 h integrated samples) collected at various sites in different environmental settings in the southeast, including three urban-Atlanta sites, in addition to a rural site. Paired sampling was conducted with one fixed site in Atlanta (Jefferson Street), representative of the urban environment, with the others rotating among different sites, for ~250 days between June 2012 and September 2013 (N=483). A simple linear regression between the DTT activity and aerosol chemical components revealed strong associations between PM ROS-generation potential and secondary organic aerosol (WSOC – water-soluble organic carbon) in summer, and biomass burning markers in winter. Redox-active metals were also somewhat correlated with the DTT activity, but mostly at urban and roadside sites. Positive matrix factorization (PMF) was applied to apportion the relative contribution of various sources to the ROS-generation potential of water-soluble PM2.5 in urban Atlanta. PMF showed that vehicular emissions contribute uniformly throughout the year (12–25%), while secondary oxidation processes dominated the DTT activity in summer (46%) and biomass burning in winter (47%). Road dust was significant only during drier periods (~12% in summer and fall). Source apportionment by chemical mass balance (CMB) was reasonably consistent with PMF, but with higher contribution from vehicular emissions (32%). Given the spatially large data set of PM sampled over an extended period, the study reconciles the results from previous work that showed only region- or season-specific aerosol components or sources contributing to PM ROS activity, possibly due to smaller sample sizes. The ubiquitous nature of the major sources of PM-associated ROS suggests widespread population exposures to aerosol components that have the ability to catalyze the production of oxidants in vivo.

In vitro Evaluation of Oxidative Stress Caused by Fine Particles (PM2.5) Exhausted from Heavy-Duty Vehicles Using Diesel/Biodiesel Blends under Real World Conditions

“…So far, we have not found reported DTT loss rate values for diesel/biodiesel exhausted particles. However, as it can be observed from Table 5, other studies used similar particle 24 and the reported results from Verma et al, 35 and McWhinney et al 50 (also see Figure 3). We can also conclude oxidative potential of particles emitted from the burning of diesel/biodiesel blends is comparable to fossil diesel-emitted particles.…”

“…24,25 For instance, some transition metals (such as Fe and Cu) and organic species (e.g. polycyclic aromatic compounds and quinones or quinone-like compounds) as well as humic-like substances (HULIS), black and brown carbon (BC and BrC) within PM are known to increase the production of ROS either in vitro or in vivo, especially if they are present in fine and ultrafine size range, [4][5][6]24,[30][31][32][33][34][35] since they are able to go more profoundly in the respiratory system. Meanwhile, considering diesel/biodiesel blends exhausts are substantially composed by ever small size PM, such as nanoparticles and/or ultrafine particles rich in semi-volatile organic compounds and trace metals, 1,7,16 it is likely ROS may be contributing to the adverse health effects caused by DEP or even BEP.…”

On the Redox Activity of Urban Aerosol Particles: Implications for Size Distribution and Relationships with Organic Aerosol Components

“…Higher wintertime DTT activity has been frequently reported [9,24,26,27,36,53], on the contrary, other studies found higher activity in summer as compared to winter [31,44,47].…”

“…DTT activity is impacted by both local emissions associated by individual site characteristics and regional sources [36]. Some field studies carried out at different locations, with different contributing sources, found higher DTT activity at continuous traffic and underground sites [43], and/or near freeways [24].…”

An apportionment method for the Oxydative Potential to the atmospheric PM sources: application to a one-year study in Chamonix, France

“…Previous studies (Bates et al, 2015;Fang et al, 2016;Verma et al, 2014) also highlighted the importance of this source to explain the OP AA and DTT. We may explain such high intrinsic OP by the presence of metals in this source -notably the copper (Charrier et al, 2015).…”