Determination of the ¹³C ¹²c ratios of individual PAH from environmental samples: can PAH sources be apportioned?

Compound-specific carbon isotope analysis was performed on polycyclic aromatic hydrocarbons (PAH) isolated from environmental samples. Analysis of δ ¹³C of individual PAH standards, including isomeric parental PAH, can be accomplished with a precision of 0.2-0.3%. In environmental samples, the precision and accuracy of similar δ ¹³C determinations are matrix-dependent, due to limitations imposed by coelution and the presence of an unresolved complex mixture (UCM). For samples of varying UCM the maximum deviations from the mean values ranged from 0.1 to 0.4% for well separated compounds and from 0.3 to 1.1% for high-molecular weight coeluting isomers. Allowing for these analytical limitations, isotopic characterization was performed for parental PAH compounds in primary and secondary sources and estuarine sediment materials. The potential of this technique for source apportionment of PAH was demonstrated using sediments from St John's Harbour and Conception Bay (Newfoundland). Additional experiments were conducted to evaluate whether the isotopic integrity of PAH was maintained after vaporization, photolytic decomposition and microbial degradation. To date, our results indicate that no significant isotopic fractionation accompanies these types of weathering reactions for the investigated 2-, 3-, 4- and 5-ring parental PAH.