Nitro-polycyclic aromatic hydrocarbons – gas-particle partitioning, mass size distribution, and formation along transport in marine and continental background air
Gerhard Lammel1,2, Marie D. Mulder1, Pourya Shahpoury2, Petr Kukučka1, Hana Lišková1, Petra Přybilová1, Roman Prokeš1, and Gerhard Wotawa31Masaryk University, Research Centre for Toxic Compounds in the Environment, Brno, Czech Republic 2Max Planck Institute for Chemistry, Multiphase Chemistry Department, Mainz, Germany 3Zentralanstalt fuer Meteorologie und Geodynamik, Wien, Austria
Received: 21 Dec 2016 – Accepted for review: 25 Jan 2017 – Discussion started: 30 Jan 2017
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 to.
At the remote marine site, the 3–4 ring nitro-PAH (sum of 11 targeted species, with 2-nitrofluoranthene (2NFLT) and 3-nitrophenanthrene being the most abundant) concentration was 23.7 pg m−3 while the concentration of 4-ring PAHs (6 species) was 426 pg m−3. Urban fractional doses in the range < 0.002–5.4 % were received. At the continental site, the ∑11 3–4rNPAH and ∑6 4rPAH were 58 and 663 pg m−3, respectively, with 9-nitroanthracene and 2NFLT being highest concentrated amongst the targeted NPAHs. The NPAH levels observed in the marine background are the lowest ever reported and remarkably lower, by more than one order of magnitude, than one 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 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 prediction of NPAH gas-particle partitioning using a multi-phase poly-parameter linear free energy relationship. Sorption to soot is found less significant for gas-particle partitioning of NPAHs than for PAHs.
The NPAH levels determined in the southeastern outflow of Europe confirm intercontinental transport potential.
Lammel, G., Mulder, M. D., Shahpoury, P., Kukučka, P., Lišková, H., Přybilová, P., Prokeš, R., and Wotawa, G.: Nitro-polycyclic aromatic hydrocarbons – gas-particle partitioning, mass size distribution, and formation along transport in marine and continental background air, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1145, in review, 2017.