Contamination of Antarctic snow by polycyclic aromatic hydrocarbons dominated by combustion sources in the polar region

Firn samples attributed to the period between 2002 and 2005 were collected from a snow pit on the Ekstrom Shelf Ice in the Weddell Sea (70 degrees 43.8'S, 8 degrees 25.1'W). Low-volume meltwater samples (5 mL) were extracted by solid-phase microextraction (SPME) and analysed for polycyclic aromatic hydrocarbons (PAHs) by gas chromatography-mass spectrometry. The recovery of the analytical method for the 4-6 ring PAHs was low. PAH concentrations in snow were found within the range of 26-197 ng L-1. The most prevailing substances were determined to be naphthalene, 1- and 2-methylnaphthalene, acenaphthylene, acenaphthene and phenanthrene, with naphthalene accounting for an overall mean of 82% of total PAH. Potential emission sources of PAHs in snow were studied using back-trajectory statistics and available emission data of combustion sources in and around Antarctica. The distance to the sources (ships and research stations) in this region was found to control the snow PAH concentrations. There was no indication for intercontinental transport or marine sources.