I'r - Memorial University of Newfoundland

ange of Slatistica1 variat ion of the end members aodIor within their mixing arrays.
Consequently. only these plots aJlowed the relative cootnbWon ofprominc:nt primary and
secondary sourcesto bequantitatively estimated in the present stUdy.
Further, a comparison of the results of principa.I compooents analysis for both
molecular andisotopic composition enables the relative usefulness ofbotb data sets to be
quant ified. As it was shown in the previous discussion, the first two components in the
principal components anal ysis for molecular composition account for the alteration ofthe
PAH asse mblage by weathering processes. These two co mponents represent as much as
76.5% of total variance in samp les. Thus, only the third component in analysis for
molecular composition is responsible forthe actual relative contributionofdifferent
combust ion and petroleum sources. This component explains only 11.4% oftotal
variability. On the contrary, in isotopic composition. the first component ex plains the
relative contribution of the two primary sources. This component takes as much as
66,4% cf nxal variabil ity. A simple calculation brin gs one to conc lude that the isoIopic
data in this procedure was 5.8 times as useful as the molecular.
The above examples demonstralc that identification ofPAH isotopic co mposition
should be considered as a technique highJy suppl ementary to the conventional molecular
analysis. A similar conclusion was made by O 'Malley (1994), who studiedthe sources of
polycyclic aromatic hydrocarbons in two areasofeastern Canada.