Detection of nitro-substituted polycyclic aromatic hydrocarbons in the antarctic airborne particulate

Nitro-PAH have been determined in the Antarctic air particulate for the first time. This achievement was made possible by the use of an extremely sensitive and specific analytical procedure, which allowed us to investigate the composition of size-fractionated airborne particulates, collected in the Terra Nova Bay area (Antarctica) during two-days high-volume sampling periods. Eleven air-particulate samples and three blanks were extracted and analyzed by gas chromatography - electron capture negative ion - tandem mass spectrometry. The high specificity of the procedure relies on both the ionization method and the fixed setting of the second mass-analyzer, selectively filtering the NO(2)(-) ions (m/z 46). Only the most volatile nitro-PAHs (nitro-and dinitronaphtalenes) were detected in the Antarctic air particulate, unlike in temperate areas. Single nitro-PAH concentrations varied in the 1-200 fg/m(3) range. Principal component analysis allowed to cluster the blanks, clearly distinguishing them from the samples, and to classify the samples, as a function of their composition. Nitro-PAH distribution proved to depend on the sampling day but not on the particle size-fraction within the same sampling period. For two air particulate samples the analytical data proved to be biased by sea-triggering the sampling device. The origin of Antarctic nitro-PAHs remains uncertain: while the abundance ratio of the two nitro-naphtalene isomers supports the hypothesis of local direct emission, the high abundance of dinitro- with respect to mononitro-derivatives suggests that an efficient gas-phase nitration may take place on a substrate possibly transported from other continents.