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

Nitro-PAH have been determined in the Antarctic air particulate for the fir st time. This achievement was made possible by the use of an extremely sens itive and specific analytical procedure, which allowed us to investigate th e composition of size-fractionated airborne particulates, collected in the Terra Nova Bay area (Antarctica) during two-days high-volume sampling perio ds. Eleven air-particulate samples and three blanks were extracted and anal yzed by gas chromatography - electron capture negative ion - tandem mass sp ectrometry. The high specificity of the procedure relies on both the ioniza tion method and the fixed setting of the second mass-analyzer, selectively filtering the NO2- ions (m/z 46). Only the most volatile nitro-PAHs (nitro- and dinitronaphtalenes) were detected in the Antarctic air particulate, unl ike 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 depen d on the sampling day but not on the particle size-fraction within the same sampling period. For two air particulate samples the analytical data prove d to be biased by sea-triggering the sampling device. The origin of Antarctic nitro-PAHs remains uncertain: while the abundance r atio of the two nitro-naphtalene isomers supports the hypothesis of local d irect emission, the high abundance of dinitro- with respect to mononitro-de rivatives suggests that an efficient gas-phase nitration may take place on a substrate possibly transported from other continents.