I'r - Memorial University of Newfoundland

the three previous ly identified zones (Fig. 5.1.1) generally possess similar molecular and
isotopic compositions ofcompounds. the relative coorribulioo ofvarious soum:s 10 the
PAH assemblage and the degree ofweatbering at differcnr: sites might vary significantly
within a single zooc.
5.1.2.1 The City Zorre
It was previously shown that although the major cities arc included into a single
cluster on the spatial distribution scheme (Fig. 5.1.1), certain within-cluster variations
may occur. These variations can be attributed to somewhat different sources participating
in the formation ofthc PAH assemblage and diffcrcnt degreeofdecompositioD. The
tarter is demonstrated by the incorporation ofstations representing the signal ofmajor
cities into three different clusters (Fig. 5.23).
{)etroit (StQtion 970: Thesignal at Detroit seems10 be largely formed from
combustion sources but with non-negligible cootribution from pctroIeum-rdatcd sources
(Fig. 5.2.3). This is indicated by a shift of this site towards the petroleum range 00 PC I
for isotopic composition (Fig. 4.2.19a). The isomer natios also demonstrate that although
generally in the combustion range , station 971 can be significantly affected by pctrolewn­
related sources (FaIPy; Fig. 4.2.1). In the principal components analysis for molecular
composition. this station was also found closer to the petroleum end member than the
other major cities (Fig. 4.2.5c). Finally, quantification ofthc relative contribution of
these two sources utilizing mixin g curves for oDe values showed that app roximately 20­
30C'/o of PAH here can originate from petroleum sources (Fig. 4.2.8-4.2.17). However. the
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