I'r - Memorial University of Newfoundland

Intens ity o(degradation (the South lone): Most stations oftbe South Zone indicate
that processes ofweathering can strongly impact on PAH in sediments at these sites (Fig.
5.2.3 ). The intensive degradation is demonstrated by a shift ofthese statiOIlJl from the
prominent end members andtheir mixing curves towards predominance of5- over 4-ring
co mpounds (Fig. 4.2.2. 4.2.3). The low values exhibited by these stations on PC 1 for
molecular composition (Fig. 4.2.5a) are also indicative ofpreferential removal oflower
mole cular weight compounds from sediments and therefore. increased intensity of
decomposition. Two major mechanisms seem to be involved in regulating these
processes : presence ofoil in sediments and sedimentation rates. These two mechanisms
seem to detennine the position ofstations on the respective axis (Fig. 4.2.5a). Stations
with relatively low sedimentation rate s andcharacterized by importance ofpetrolewn
de mons trate the highest intensityofweathering (e.g ., St. 953). Since most sites in this
zone meet at least one ofthe conditions. these processes seem to be generally important
(Fig. 5.2.3).
A single station within this zone (973) exh ibits slow rates ofPAH decomposition
(Fig. 5.2.3). Here, 4-ring compounds seem to dominate over 5-ring PAH (Fig. 4.2.5a).
Th is station also plots very close to the mixing curves for molecular composition
indi catin g little PAH contri bution from sources other than those under consideration (Fig.
4 .2.2.4.2.3 ). The processe s of weathering, at this site, can possibly be masked by
cont inuous fresh suppl y of PAH from the closely located co mm unity (Monroe; Fig.
5.1.1). Thi s supply can be pro vided through direct releases ofsewage and atmospheric
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