Assessment of atmospheric pollution by oxygenated and nitrated derivatives of polycyclic aromatic hydrocarbons in two regions of the Czech Republic

In this study, a method for monitoring 16 representatives of nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) and six oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) in airborne particulate matter (PM) was developed and validated. Soxhlet extraction, followed by solid phase extraction (SPE) on silica, was used to isolate the target compounds. Instrumental analysis was performed by gas chromatography coupled with (tandem) mass spectrometry (GC-MS(/MS)) operated in electron impact (EI) and negative ion chemical ionization (NICI) modes. GC-EI-MS/MS was selected for further experiments due to its higher selectivity of measurement and ability to measure derivatives simultaneously with 20 commonly analyzed PAHs (EU + US EPA priority list). This is the first study documenting the simultaneous analysis of OPAHs, NPAHs, and parent PAHs in a single run. This analysis strategy was successfully validated at two concentration levels of artificial contamination, i.e., 0.8 and 4 ng per filter, with recoveries in the 70–104% range and less than 23% repeatability. The newly developed method was used for the analysis of 45 air samples from two cities in the Czech Republic, namely Ceske Budejovice and Most (a place with heavy industry), and two sampling seasons (February vs. May 2017). Five representatives were found in all samples from the oxy-PAH group, with 9,10-anthraquinone (9,10-ANTQ) being the most abundant (0.010–2.49 ng m−3 air). Three major nitro-PAHs, namely 9-nitroanthracene (9-nANT), 2-nitrofluoranthene (2-nFA), and 1-nitropyrene (1-nPYR), were found in 89%, 96%, and 33% of the samples, respectively, found in concentration ranges of <0.60–902, <0.60–276, and <0.60–117 pg m−3 air. Slightly higher levels of oxy- and nitro-PAHs were found in Ceske Budejovice compared to Most, but the difference was not statistically significant (p-value >0.05). A statistically significant difference was observed between February and May, where the concentrations in February were up to 20 and 50 times higher for individual oxy- and nitro-PAHs, respectively, in both regions. The diagnostic ratio 2-nFA/1-nPYR >5 showed that indirect emissions were the primary nitro-PAH source in Most of nitro-PAHs in Most and in both sampling campaigns. In Ceske Budejovice, the opposite trend was observed in winter, i.e. 2-nFA/1-nPYR <5, indicating direct emissions as the main source. In summary, direct emissions of OPAHs and NPAHs originate from fossil (transportation-related) and solid fuel (heating-related) combustion. In contrast, indirect emissions are related to atmospheric reactions of PAHs with OH radicals (spring, winter) and NO3 radicals (winter). The total TEQB[a]P was higher in winter than spring, with higher inhalation cancer risk.