Polycyclic aromatic hydrocarbons (PAHs) and their alkylated, nitrated and oxygenated derivatives in the atmosphere over the Mediterranean and Middle East seas

Abstract

Abstract. Polycyclic aromatic hydrocarbons (PAHs) and their alkylated (RPAHs), nitrated (NPAHs) and oxygenated (OPAHs) derivatives are air pollutants. Many of these substances are long-lived, can undergo long-range atmospheric transport and adversely affect human health upon exposure. However, the occurrence and fate of these air pollutants have hardly been studied in the marine atmosphere. In this study, we report the atmospheric concentrations over the Mediterranean Sea, the Red Sea, the Arabian Sea, the Gulf of Oman and the Arabian Gulf, determined during the AQABA (Air Quality and Climate Change in the Arabian Basin) project, a comprehensive ship-borne campaign in summer 2017. The average concentrations of ∑26PAHs, ∑19RPAHs, ∑11OPAHs and ∑17NPAHs, in the gas and particulate phases, were 2.99 ± 3.35 ng m−3, 0.83 ± 0.87 ng m−3, 0.24 ± 0.25 ng m−3 and 4.34 ± 7.37 pg m−3, respectively. The Arabian Sea region was the cleanest for all substance classes, with concentrations among the lowest ever reported. Over the Mediterranean Sea, we found the highest average burden of ∑26PAHs and ∑11OPAHs, while the ∑17NPAHs were most abundant over the Arabian Gulf (known also as the Persian Gulf). 1,4-Naphthoquinone (1,4-O2NAP) followed by 9-fluorenone and 9,10-anthraquinone were the most abundant studied OPAHs in most samples. The NPAH composition pattern varied significantly across the regions, with 2-nitronaphthalene (2-NNAP) being the most abundant NPAH. According to source apportionment investigations, the main sources of PAH derivatives in the region were ship exhaust emissions, residual oil combustion and continental pollution. All OPAHs and NPAHs except 2-nitrofluoranthene (2-NFLT), which were frequently detected during the campaign, showed elevated concentrations in fresh shipping emissions. In contrast, 2-NFLT and 2-nitropyrene (2-NPYR) were highly abundant in aged shipping emissions due to secondary formation. Apart from 2-NFLT and 2-NPYR, benz(a)anthracene-7,12-dione and 2-NNAP also had significant photochemical sources. Another finding was that the highest concentrations of PAHs, OPAHs and NPAHs were found in the sub-micrometre fraction of particulate matter (PM1).

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

“…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 ). Moreover, this study 22 also found that Phe was the most abundant parent PAH, followed by Flu, Ace, Flt, and Pyr, with mean contributions of 24%, 10%, 6%, and 5%, respectively.…”

“…A pronounced contribution of Phe to the total PAHs can be found in summer and is displayed in Fig. 3 C. It should be noted that previous studies have found a relatively high contribution of 3-ring compounds to the total PAHs in the coastal regions and offshore 22 , 44 – 46 . As shown in Fig.…”

“…Much higher levels of PAHs, as compared with results from this study, were 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 ).…”

“…Over southern Europe (i.e. Mediterranean Sea, Black Sea, North Sea, Arabian Sea) 21 , 22 , only a few studies examined the contribution of shipping-related PAH inputs. So far, PAH-oriented studies in Poland have been limited to PM 10 and PM 2.5 fractions and urban regions i.e.…”

Characterization of nitrated polycyclic aromatic hydrocarbons in secondary organic aerosol derived from photooxidation of naphthalene in the presence of NO2

“…Nitrated polycyclic aromatic hydrocarbons (NPAHs) generated by the substitution of one or more hydrogen atoms in the aromatic ring of polycyclic aromatic hydrocarbons (PAHs) with nitro group (-NO 2 ) are a common type of organic nitrogen compounds in aerosol particles (Bandowe and Meusel 2017; Lammel et al 2020;Wietzoreck et al 2022). Apart from the primary emission sources such as incomplete combustion of coal, petroleum and biomass (Zhao et al 2017;Nežiková et al 2021;Zhang et al 2021), NPAHs can also be generated through the oxidation of PAHs by OH or NO 3 radical in the atmosphere.…”