Single-particle characterization of polycyclic aromatic hydrocarbons in background air in northern Europe

Abstract

Abstract. We investigated the distribution of polycyclic aromatic hydrocarbons (PAHs) on individual ambient aerosol particles at the Swedish western coast in a pristine environment for 10 d in October 2019. The measurements were carried out using new technology with single-particle mass spectrometry (SPMS) that reveals both the inorganic particle composition as well as the particle-bound PAHs (Schade et al., 2019). More than 290 000 particles were characterized; 4412 of them reveal PAH signatures. Most of the PAH-containing particles were internal mixtures of carbonaceous material, secondary nitrate and metals from distant sources in central and eastern Europe. We characterize the aerosol with respect to the inorganic composition, comparable to conventional SPMS, before we discuss the distribution of PAHs within this particle ensemble. Vice versa, we analyze the single-particle PAH spectra for characteristic patterns and discuss the inorganic composition, origin and atmospheric processing of the respective particles. The study period comprised different meteorological situations: clean air conditions with winds from the North Sea/Kattegat and little terrestrial air pollution, long-range transport from eastern Europe and southern Sweden, and transport of aerosols from central Europe over the sea. For all meteorological conditions, PAHs were detected in particles whose inorganic content indicates traffic emissions, such as combinations of soot, iron and calcium as well as in particles with biomass-burning signatures. However, there were variations in their amounts, dependent on the geographic origin. Because of strong mixing, rapid degradation and speciation limits, e.g., for PAHs of the same nominal mass, the application of diagnostic ratios for source apportionment is limited under the conditions of our study. Nevertheless, the combination with the inorganic content and meteorological data provides unique insights into the particles' origin, aging and mixing state. We exemplarily show how the observation of PAH profiles and inorganic secondary components on a single-particle level can open a new door to investigate aerosol aging processes. To our best knowledge, we herewith present the first comprehensive study on the single-particle distribution of PAHs in ambient air as well as the first set of combined data on PAHs and inorganic composition on a single-particle level.

Compositional and seasonal differences of gas and particle phase polycyclic aromatic hydrocarbons (PAHs) over the southern Baltic Sea coast

“…Much higher levels of PAHs, as compared with results from this study, were www.nature.com/scientificreports/ observed in the Middle East, especially in Giza, Egypt 41 . On the contrary, a recent ship-borne AQABA project 22 reported distinct regional patterns in PAHs trends, showing substantially lower concentrations of parent PAHs in the gas and particle phases over the Mediterranean Sea, the Red Sea, the Arabian Sea, the Gulf of Oman, and the Arabian Gulf than those determined over coastal Chinese regions 42 and the Baltic Sea 43 . Specifically, the mean concentration of Σ 26 PAHs in the coastal marine atmosphere of southern Europe was 2.99 ± 3.35 ng m −3 , with the highest values registered in the Mediterranean Sea (mean 4.40 ng m −3 ) and the lowest in the Arabian Sea (mean 0.59 ng m −3 ).…”

Detection of ship emissions from distillate fuel operation via single-particle profiling of polycyclic aromatic hydrocarbons

“…To demonstrate the field applicability of our PAH-marker approach, we re-analyze subsets of the data from a field study at the Swedish coast in autumn 2019, see Passig et al 50 for details. Briefly, we used the same SPMS system and the same configuration as in the laboratory but with additional particle concentration (see the “Methods” section above) to account for the general clean air conditions with less than 10 μg m −3 PM2.5.…”

“…The field experiments shown here were part of a measurement campaign at the Swedish West coast. 50 The clean air conditions there required aerosol preconcentration (Model 4240, MSP corp., USA) 52 and drying (Model MD-700-12S-1, Perma Pure LLC, U.S.). Wind data were acquired from the local station Nidingen, 8 km south of the sampling site.…”

“…With regard to the different ionization processes, LDI and REMPI mass spectra were separately normalized and independently clustered using a vigilance factor of 0.8, a learning rate of 0.05, and 20 iterations. 50 In order to identify the main particle classes, we applied a regrouping algorithm, where clusters from the initial clustering are merged in a second ART-2a run. 51 The results were regularly cross-checked against those of manual merging.…”

Real-Time Investigation of Primary Ship Engine Emissions by Vacuum Resonance-Enhanced Multiphoton Ionization High-Resolution Orbitrap Mass Spectrometry

“…Nonetheless, due to the high complexity and challenging molecular profile of ship emissions, it is necessary to use various systems that allow us to comprehensively understand the organic matrix. In this regard, state-of-the-art instrumentation like the aerosol mass spectrometer (AMS), , extractive electrospray ionization (EESI), or aerosol time-of-flight (ToF) − mass spectrometer have shown tremendous potential. Nevertheless, these advanced approaches are targeting the particle phase of the aerosol.…”