Articles | Volume 16, issue 10
Research article
25 May 2016
Research article |  | 25 May 2016

Bidirectional air–sea exchange and accumulation of POPs (PAHs, PCBs, OCPs and PBDEs) in the nocturnal marine boundary layer

Gerhard Lammel, Franz X. Meixner, Branislav Vrana, Christos I. Efstathiou, Jiři Kohoutek, Petr Kukučka, Marie D. Mulder, Petra Přibylová, Roman Prokeš, Tatsiana P. Rusina, Guo-Zheng Song, and Manolis Tsapakis

Abstract. As a consequence of long-range transported pollution, air–sea exchange can become a major source of persistent organic pollutants in remote marine environments. The vertical gradients in the air were quantified for 14 species, i.e. four parent polycyclic aromatic hydrocarbons (PAHs), three polychlorinated biphenyls (PCBs), three organochlorine pesticides (OCPs) and two polybrominated diphenylethers (PBDEs) in the gas-phase at a remote coastal site in the southern Aegean Sea in summer. Most vertical gradients were positive (Δc∕Δz > 0), indicating downward (net depositional) flux. Significant upward (net volatilisational) fluxes were found for three PAHs, mostly during daytime, and for two OCPs, mostly during night-time, as well as for one PCB and one PBDE during part of the measurements. While phenanthrene was deposited, fluoranthene (FLT) and pyrene (PYR) seem to undergo flux oscillation, hereby not following a day–night cycle. Box modelling confirms that volatilisation from the sea surface has significantly contributed to the night-time maxima of OCPs. Fluxes were quantified based on eddy covariance. Deposition fluxes ranged from −28.5 to +1.8 µg m−2 day−1 for PAHs and −3.4 to +0.9 µg m−2 day−1 for halogenated compounds. Dry particle deposition of FLT and PYR did not contribute significantly to the vertical flux.

Short summary
As a consequence of long-range transported pollution air–sea exchange can become a major source of anthropogenic organic pollutants. Fluxes were studied at a remote coastal site in the Mediterranean, based on gradient measurements in air, measurements in surface seawater and eddy covariance. Night-time maxima in air are explained by volatilisation from the sea surface. Fluctuation of the direction of air–sea exchange indicate that long-term observations are needed.
Final-revised paper