Modeling the Formation, Degradation, and Spatiotemporal Distribution of 2-Nitrofluoranthene and 2-Nitropyrene in the Global Atmosphere.

Jake Wilson,Ulrich Pöschl,Thomas Berkemeier,Benjamin A. Musa Bandowe,Cornelius Zetzsch,Mega Octaviani,Marco Wietzoreck,Gerhard Lammel

doi:10.1021/acs.est.0c04319

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are common atmospheric pollutants and known to cause adverse health effects. Nitrated PAHs (NPAHs) are formed in combustion activities and by nitration of PAHs in the atmosphere and may be equally or more toxic, but their spatial and temporal distribution in the atmosphere is not well characterized. Using the global EMAC model with atmospheric chemistry and surface compartments coupled, we investigate the formation, abundance, and fate of two secondarily formed NPAHs, 2-nitrofluoranthene (2-NFLT) and 2-nitropyrene (2-NPYR). The default reactivity scenario, the model with the simplest interpretation of parameters from the literature, tends to overestimate both absolute concentrations and NPAH/PAH ratios at observational sites. Sensitivity scenarios indicate that NO2-dependent NPAH formation leads to better agreement between measured and predicted NPAH concentrations and that photodegradation is the most important loss process of 2-NFLT and 2-NPYR. The highest concentrations of 2-NFLT and 2-NPYR are found in regions with strong PAH emissions, but because of continued secondary formation from the PAH precursors, these two NPAHs are predicted to be spread across the globe.

Highlights

Nitrated polycyclic aromatic hydrocarbons (PAHs) (NPAHs) are a group of PAH derivatives substantially contributing to the toxicity of polluted air.[7,11−17] Many NPAHs are emitted together with PAHs from primary combustion sources; for example, 9-nitroanthracene, 3-nitrofluoranthene, and 1-nitropyrene are produced and emitted upon diesel combustion.[18−20] Other NPAHs are produced in the atmosphere by chemical transformation of PAHs
Alongside the results using the simplest interpretation of literature input parameters, we present results from sensitivity scenarios to explore two uncertainties related to the chemical formation and loss of NPAHs in the atmosphere: the concentration of NO2 and the rate of photodegradation
The constant scaling factor is applied for all aerosols, despite the fact that particulate matter (PM) composition and color strongly influence the photochemical degradation process.[70,72−75] Photolysis with different efficiencies might be expected in aged, long-range transported aerosols and in natural aerosols

Summary

INTRODUCTION

Human exposure to polluted air is associated with severe health effects: asthma, chronic obstructive pulmonary disease, lung cancer, cardiovascular diseases, and mortality.[1−4] Polluted air contains a complex mixture of organic and inorganic chemical species including polycyclic aromatic hydrocarbons (PAHs) and their photochemical degradation products, which exhibit mutagenicity and other hazardous properties.[5−10]. This has been documented for the mutagenicity of fluoranthene (FLT), pyrene (PYR), chrysene, and their nitrated derivatives[5,7,9,32,33] and for the developmental toxicity of phenanthrene, anthracene, PYR, and their nitrated derivatives.[17] The spatial and temporal distributions of 2NFLT and 2-NPYR, have not yet been characterized For these compounds, there is a lack of long-term air monitoring, and monitoring data are available only for few geographic locations.[16] As 2-NFLT and 2-NPYR are not directly emitted and their photochemical formation in air does not occur instantaneously, their distributions cannot be assumed to be identical to those of the parent PAHs. Because of long-range transport, both products[34−37] and their precursors[38,39] can be found in remote areas away from the source.[34,37,40]. We discuss the predicted spatial distributions of 2-NFLT and 2-NPYR column densities and near-surface concentrations

METHODS

RESULTS AND DISCUSSION

■ ACKNOWLEDGMENTS

■ REFERENCES