Atmospheric particulate matter with diameter <2.5 um (PM2.5) was collected at Peking University (PKU) in Beijing, China before, during, and after the 2008 Olympics and analyzed for black carbon (BC), organic carbon (OC), lower molecular weight (MW<300) and MW302 Polycyclic Aromatic Hydrocarbons (PAHs), nitrated PAHs (NPAHs) and oxygenated PAHs (OPAHs). In addition, the direct and indirect acting mutagenicity of the PM2.5 and the potential for DNA damage to human lung cells were also measured. Significant reductions in BC (45%), OC (31%), MW< 300 PAH (26% – 73%), MW 302 PAH (22% – 77%), NPAH (15% – 68%) and OPAH (25% – 53%) concentrations were measured during the source control and Olympic Olympic period. However, the mutagenicity of the PM2.5 was significantly reduced only during the Olympic period. The PAH, NPAH, and OPAH composition of the PM2.5 was similar throughout the study, suggesting similar sources during the different periods. During the source control period, the parent PAH concentrations were correlated with NO, CO, and SO2 concentrations, indicating that these PAHs were associated with both local and regional emissions. However, the NPAH and OPAH concentrations were only correlated with the NO concentrations, indicating that the NPAH and OPAH were primarily associated with local emissions. The relatively high 2-nitrofluoranthene/1-nitropyrene ratio (25 – 46) and 2-nitrofluoranthene/2-nitropyrene ratio (3.4 – 4.8), suggested a predominance of photochemical formation of NPAHs through OH-radical-initiated reactions in the atmosphere. On average, the ΣNPAH and ΣOPAH concentrations were 8% of the parent PAH concentrations, while the direct-acting mutagenicity (due to the NPAH and OPAH) was 200% higher than the indirect-acting mutagenicity (due to the PAH). This suggests that NPAH and OPAH make up a significant portion of the overall mutagenicity of PM2.5 in Beijing.

Reactions of ambient particles collected from four sites within the Los Angeles, CA air basin and Beijing, China with a mixture of N2O5, NO2, and NO3 radicals were studied in an environmental chamber at ambient pressure and temperature. Exposures in the chamber system resulted in the degradation of particle-bound PAHs and formation of molecular weight (mw) 247 nitropyrenes (NPYs) and nitrofluoranthenes (NFLs), mw 273 nitrotriphenylenes (NTPs), nitrobenz[a]anthracenes (NBaAs), and nitrochrysene (NCHR), and mw 297 nitrobenzo[a]pyrene (NBaP). The distinct isomer distributions resulting from exposure of filter-adsorbed deuterated fluoranthene to N2O5/NO3/NO2 and that collected from the chamber gas-phase suggest that formation of NFLs in ambient particles did not occur by NO3 radical-initiated reaction, but from reaction of N2O5, presumably subsequent to its surface adsorption. Accordingly, isomers known to result from gas-phase radical-initiated reactions of parent PAHs, such as 2-NFL and 2- and 4-NPY, were not enhanced from the exposure of ambient particulate matter to N2O5/NO3/NO2. The reactivity of ambient particles toward nitration by N2O5/NO3/NO2, defined by relative 1-NPY formation, varied significantly, with the relative amounts of freshly emitted particles versus aged particles (particles that had undergone atmospheric chemical processing) affecting the reactivity of particle-bound PAHs toward heterogeneous nitration. Analyses of unexposed ambient samples suggested that, in nighttime samples where NO3 radical-initiated chemistry had occurred, heterogeneous formation of 1-NPY on ambient particles may have contributed to the ambient 1-NPY concentrations at downwind receptor sites. These results, together with observations that 2-NFL is consistently the dominant particle-bound nitro-PAH measured in ambient atmospheres, suggest that for PAHs that exist in both the gas- and particle-phase, the heterogeneous formation of particle-bound nitro-PAHs is a minor formation route compared to gas-phase formation.

The heterogeneous reactions of benzo[a]pyrene-d12 (BaP-d12), benzo[k]fluoranthene-d12 (BkF-d12), benzo[ghi]perylene-d12 (BghiP-d12), dibenzo[a,i]pyrene-d14 (DaiP-d14), and dibenzo[a,l]pyrene (DalP) with NO2, NO3/N2O5, and OH radicals were investigated at room temperature and atmospheric pressure in an indoor Teflon chamber and novel mono NO2-DaiP, and mono NO2-DalP products were identified. Quartz fiber filters (QFF) were used as a reaction surface and the filter extracts were analyzed by GC/MS for nitrated-PAHs (NPAHs) and tested in the Salmonella mutagenicity assay, using Salmonella typhimurium strain TA98 (with and without metabolic activation). In parallel to the laboratory experiments, a theoretical study was conducted to rationalize the formation of NPAH isomers based on the thermodynamic stability of OH-PAH intermediates, formed from OH-radical-initiated reactions. NO2 and NO3/N2O5 were effective oxidizing agents in transforming PAHs to NPAHs, with BaP-d12 being the most readily nitrated. Reaction of BaP-d12, BkF-d12 and BghiP-d12 with NO2 and NO3/N2O5 resulted in the formation of more than one mono-nitro isomer product, while the reaction of DaiP-d14 and DalP resulted in the formation of only one mono-nitro isomer product. The direct-acting mutagenicity increased the most after NO3/N2O5 exposure, particularly for BkF-d12 in which di-NO2-BkF-d10 isomers were measured. The deuterium isotope effect study suggested that substitution of deuterium for hydrogen lowered both the direct and indirect acting mutagenicity of NPAHs and may result in an underestimation of the mutagencity of the novel NPAHs identified in this study.

The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO3/N2O5, OH radicals, and O3 were studied in a laboratory photochemical chamber. Ambient PM2.5 and PM10 samples were collected from Beijing, China and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O3 and OH and NO3 radicals. Changes in the masses of 23 PAHs and 20 NPAHs, as well as the direct and indirect-acting mutagenicity of the PM (determined using the Salmonella mutagenicity assay with TA98 strain), were measured prior to and after exposure to NO3/N2O5, OH radicals, and O3. In general, O3 exposure resulted in the highest relative degradation of PM-bound PAHs with more than four rings (benzo[a]pyrene was degraded equally well by O3 and NO3/N2O5). However, NPAHs were most effectively formed during the Beijing PM exposure to NO3/N2O5. In ambient air 2-nitrofluoranthene (2-NF) is formed from gas-phase NO3 radical- and OH radical-initiated reactions of fluoranthene, and 2-nitropyrene (2-NP) is formed from gas-phase OH radical-initiated reaction of pyrene. There was no formation of 2-NF or 2-NP in any of the heterogeneous exposures, suggesting that gas-phase formation of NPAHs did not play an important role during chamber exposures. Exposure of Beijing PM to NO3/N2O5 resulted in an increase in direct-acting mutagenic activity which was associated with the formation of mutagenic NPAHs. No NPAH formation was observed in any of the exposures of the Riverside PM. This was likely due to the accumulation of atmospheric degradation products from gas-phase reactions of volatile species onto the surface of PM collected in Riverside prior to exposure in the chamber, thus decreasing the availability of PAHs for reaction.

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This air synthesis review presents the current state of knowledge on the sources, fates, and effects for polycyclic aromatic compounds (PACs) and related chemicals released to air in the oil sands region (OSR) in Alberta, Canada. Through the implementation of the Joint Canada–Alberta Oil Sands Monitoring Program in 2012 a vast amount of new information on PACs has been acquired through directed monitoring and research projects and reported to the scientific community and public. This new knowledge addresses questions related to cumulative effects and informs the sustainable management of the oil sands resource while helping to identify gaps in understanding and priorities for future work. As a result of this air synthesis review on PACs, the following topics have been identified as new science priorities: (i) improving emissions reporting to better account for fugitive mining emissions of PACs that includes a broader range of PACs beyond the conventional polycyclic aromatic hydrocarbons (PAHs) including, inter alia, alkylated-PAHs (alk-PAHs), dibenzothiophene (DBT), alk-DBTs, nitro-PAHs, oxy-PAHs including quinones and thia- and aza-arenes; (ii) improving information on the ambient concentrations, long-range transport, and atmospheric deposition of these broader classes of PACs and their release (with co-contaminants) from different types of mining activities; (iii) further optimizing electricity-free and cost-effective approaches for assessing PAC deposition (e.g., snow sampling, lichens, passive ambient sampling) spatially across the OSR and downwind regions; (iv) designing projects that integrate monitoring efforts with source attribution models and ecosystem health studies to improve understanding of sources, receptors, and effects; (v) further optimizing natural deposition archives (e.g., sediment, peat, tree rings) and advanced forensic techniques (e.g., isotope analysis, marker compounds) to provide better understanding of sources of PACs in the OSR over space and time; (vi) conducting process research to improve model capabilities for simulating atmospheric chemistry of PACs and assessing exposure to wildlife and humans; and (vii) developing tools and integrated strategies for assessing cumulative risk to wildlife and humans by accounting for the toxicity of the mixture of chemicals in air rather than on a single compound basis.

No abstract

Extracts of passive air samples collected from 15 passive sampling network sites across the Athabasca Oil Sands region were used to explore the application of in vitro assays for mutagenicity (Salmonella mutation assays) and cytotoxicity (lactate dehydrogenase assay) to assess the toxicity of the air mixture. The air monitoring of polycyclic aromatic compounds (PACs) and PAC transformation products, including nitrated polycyclic aromatic hydrocarbons (NPAHs) and oxygenated polycyclic aromatic hydrocarbons (OPAHs) was then linked to the potential toxicity of air. The PACs in air during April to May 2014 were elevated near mining activities and declined with distance from the source region, whereas NPAHs and OPAHs exhibited a more variable spatial distribution with the highest levels in Fort McMurray. Overall, the air samples exhibited a weak mutagenicity. The highest indirect-acting mutagenicity was observed for sites closest to mining activities; however, the indirect-acting mutagenicity did not decline sharply with distance from mining areas. Indirect-acting mutagenicity was strongly correlated with levels of total PACs, benzo(a)pyrene equivalent mass, and OPAHs. Most of the samples exhibited cytotoxic potential, but the magnitude of the response was variable across the sample region and did not correlate with levels of target analytes. This indicates that PACs and PAC derivatives were not a major contributor to the cytotoxicity observed in the air samples.