Enrichment of organic pollutants in the sea surface microlayer (SML) at Terra Nova Bay, Antarctica: influence of SML on superficial snow composition

Abstract

Concentrations of dissolved and particle-associated n-alkanes, phthalates and polycyclic aromatic hydrocarbons (PAHs) were measured in sea surface microlayer (SML) and sub-surface water (SSL) samples collected in the coastal area of Terra Nova Bay, Antarctica, during the Austral spring 1998/1999. SML concentrations of the selected organic compounds were higher than SSL values and the enrichment factors were greater in the particulate phase than in the dissolved phase. During the same campaign, ''fresh'' snow samples, collected at different altitudes (from sea level up to 2670 m) near the coast on Mt Melbourne, immediately after a snowy event, were analysed in order to provide more information on air/sea exchange processes. The same classes of organic compounds found in sea water were also present in ''fresh'' snow samples. The surfactant fluorescent organic matter (SFOM), adsorbed on the microdrop aerosol surface, could be considered the main constituent of the enrichment and the carrier at higher altitudes of organic compounds. In fact, hydrocarbons (n-alkanes and PAHs), which are not surfactants like phthalates, could interact with SFOM and follow the same fate.

n-Alkanes, PAHs and surfactants in the sea surface microlayer and sea water samples of the Gerlache Inlet sea (Antarctica)

“…Currently, the screen [11], the rotating drum [12], the glass plate [13], and Teflon plate methods are the most widely used [4]. The Multi-Use Microlayer Sampler (MUMS) [5][6][7][14][15][16] was used to collect SML and SSW samples simultaneously. This device consists of a radio controlled floating structure which can collect SML and SSW at the same time.…”

“…The analytical procedure used for sea water samples is described in details elsewhere [5,14]. Briefly, particulate and dissolved fractions were separated by filtration through glass fibre filters (Whatman GF/F, 0.45 µm nominal pore size) using an all glass vacuum holder.…”

“…n-Alkanes analysis were conducted using a Varian 4290 gas chromatograph- [5,14]. All concentrations were given in terms of water volume.…”

“…All extracts were cleaned-up by using Silica gel 60 HR (Merck) column (0.6 × 10 cm), as described elsewhere [5,14]. n-Alkanes analysis were conducted using a Varian 4290 gas chromatograph- [5,14].…”

“…The SML thus represents both a sink and a source for hydrophobic organic compounds, as well as a very important driver enhancing air-water exchanges via volatilisation or bubble bursting associated with breaking waves, mechanical tearing and spilling over of wave crests. Various studies have focused their attention on levels of organic and inorganic pollutants in the atmosphere, sea water, ice, snow, sediments and biota in remote areas to monitor distribution and exchange processes, but, to our knowledge, few measurements [5][6][7] have been made to study contamination of the SML in remote areas, such as Antarctica.…”