Abstract
Abstract. Polycyclic aromatic hydrocarbon (PAH) concentration in air of the central and eastern Mediterranean in summer 2010 was 1.45 (0.30–3.25) ng m−3 (sum of 25 PAHs), with 8 (1–17)% in the particulate phase, almost exclusively associated with particles < 0.25 μm. The total deposition flux of particulate PAHs was 0.3–0.5 μ g m−2 yr−1. The diffusive air–sea exchange fluxes of fluoranthene and pyrene were mostly found net-depositional or close to phase equilibrium, while retene was net-volatilisational in a large sea region. Regional fire activity records in combination with box model simulations suggest that seasonal depositional input of retene from biomass burning into the surface waters during summer is followed by an annual reversal of air–sea exchange, while interannual variability is dominated by the variability of the fire season. One-third of primary retene sources to the sea region in the period 2005–2010 returned to the atmosphere as secondary emissions from surface seawaters. It is concluded that future negative emission trends or interannual variability of regional sources may trigger the sea to become a secondary PAH source through reversal of diffusive air–sea exchange. Capsule: In late summer the seawater surface in the Mediterranean has turned into a temporary secondary source of PAH, obviously related to biomass burning in the region.
Highlights
The marine atmospheric environment is a receptor for polycyclic aromatic hydrocarbons (PAHs) which are advected from combustion sources on land
PAH sampling on GFF and in polyurethane foam (PUF) can be subject to losses related to oxidation of sorbed PAH by ozone (Tsapakis and Stephanou, 2003)
The mean total 25 PAHs concentration is 1.45 ng m−3, and ranged from 0.30 to 3.25 ng m−3
Summary
The marine atmospheric environment is a receptor for polycyclic aromatic hydrocarbons (PAHs) which are advected from combustion sources on land (power plants, biomass burning, road transport, domestic heating). Upon deposition to surface water, PAHs partition between the aqueous and particulate (colloidal and sinking) phases and may bioaccumulate in marine food chains (Lipiatou and Saliot, 1991; Dachs et al, 1997; Tsapakis et al, 2003; Berrojalbiz et al, 2011). They were found enriched in the sea-surface microlayer relative to subsurface water (Lim et al, 2007; Guitart et al, 2010). This had been predicted by multicompartmental modelling for two–four-ring PAHs for polluted coastal waters and the open ocean (Greenfield and Davis, 2005; Lammel et al, 2009a) and was Published by Copernicus Publications on behalf of the European Geosciences Union
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