Abstract
Abstract. Nitro-polycyclic aromatic hydrocarbons (NPAH) are ubiquitous in polluted air but little is known about their abundance in background air. NPAHs were studied at one marine and one continental background site, i.e. a coastal site in the southern Aegean Sea (summer 2012) and a site in the central Great Hungarian Plain (summer 2013), together with the parent compounds, PAHs. A Lagrangian particle dispersion model was used to track air mass history. Based on Lagrangian particle statistics, the urban influence on samples was quantified for the first time as a fractional dose to which the collected volume of air had been exposed. At the remote marine site, the 3–4-ring NPAH (sum of 11 targeted species) concentration was 23.7 pg m−3 while the concentration of 4-ring PAHs (6 species) was 426 pg m−3. The most abundant NPAHs were 2-nitrofluoranthene (2NFLT) and 3-nitrophenanthrene. Urban fractional doses in the range of < 0.002–5.4 % were calculated. At the continental site, the Σ11 3–4-ring NPAH and Σ6 4-ring PAH were 58 and 663 pg m−3, respectively, with 9-nitroanthracene and 2NFLT being the most concentrated amongst the targeted NPAHs. The NPAH levels observed in the marine background air are the lowest ever reported and remarkably lower, by more than 1 order of magnitude, than 1 decade before. Day–night variation of NPAHs at the continental site reflected shorter lifetime during the day, possibly because of photolysis of some NPAHs. The yields of formation of 2NFLT and 2-nitropyrene (2NPYR) in marine air seem to be close to the yields for OH-initiated photochemistry observed in laboratory experiments under high NOx conditions. Good agreement is found for the prediction of NPAH gas–particle partitioning using a multi-phase poly-parameter linear free-energy relationship. Sorption to soot is found to be less significant for gas–particle partitioning of NPAHs than for PAHs. The NPAH levels determined in the south-eastern outflow of Europe confirm intercontinental transport potential.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) may undergo chemical transformations in the gaseous and in the particulate phase (Finlayson-Pitts and Pitts, 2000; Keyte et al, 2013)
The Nitro-polycyclic aromatic hydrocarbons (NPAH) levels are distinctly lower at the marine than at the continental site, 11 3–4-ring NPAH = 22.5 and 58.5 pg m−3, respectively (Table 1)
Air mass history analysis suggests that the somewhat elevated concentration in the first sample collected at the marine site (Fig. 1a) is related to long-range transport influenced by passage over the urban areas of Izmir and Istanbul
Summary
Polycyclic aromatic hydrocarbons (PAHs) may undergo chemical transformations in the gaseous and in the particulate phase (Finlayson-Pitts and Pitts, 2000; Keyte et al, 2013). Secondary formation of NPAH from PAHs is thought to occur on short timescales (hours). 3- and 2-nitrofluoranthene (3-, 2NFLT) is indicative of primary and secondary sources, respectively These substances have been suggested as tracers for air pollution on the timescales of hours to days (Ciccioli et al, 1996; Finlayson-Pitts and Pitts 2000; Keyte et al, 2013), but their atmospheric lifetimes are still unknown. Eastern Mediterranean, clean summer 2012 Eastern Mediterranean, clean summer 2002 Ross Sea coast, Antarctica Himalayas, Nepal, 1991 Amazon rainforest, 1993 Rural northern Germany, 1991 Rural Denmark, winter–spring 1982 Semi-rural Denmark, all year 1998–1999 Remote Alps, 2002 Rural Alps, 2002 Rural Alpsd, winter 2002–2003 Rural Alpsd, summer 2003 Remote Alpse, winter 2002–2003 Remote Alpse, summer 2003 Rural southern France, 2004 – < 0.02c 29 < 0.03c
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
