Newark Bay Study - Passaic River Public Digital Library

1-28
Longitudinal, vertical and lateral profiles for TCDD and OCDD in Newark Bay sediments
are presented in Figures 1-10, 1-11 and 1-12. The concentrations of TCDD in surface sediments are
about 0.4 ng/g near the mouth of the Passaic River, then decrease within the Bay to an average
concentration of 0.01 ng/g (Figure 1-10). In the Kill van Kull, TCDD levels drop by one order of
magnitude relative to Newark Bay. Peak levels in the surface sediments occur within one mile of
Newark Bay. Unlike the Passaic River where the peak concentrations occur at depth, vertical
profiles generally show a consistent trend of decreasing TCDD levels in deeper sediments (Figure 1-
11). It is noteworthy that most cores were analyzed for TCDD to a depth of 6 ft below the surface;
the analysis for layers between 6 ft and 14 ft was only performed on a limited number of cores.
The data also show some spatial variation in TCDD concentration in the lateral direction.
For example, a comparison of TCDD levels in surface sediment collected east and west of the midchannel
(refer to Figure 1-12) reveals some differences in concentrations (open vs. closed circles);
those differences are however less pronounced than what is observed for total PCBs (tPCBs). The
data also show significant differences within a cluster of samples collected from the same reach and
river mile (open circles). In addition, there is no clear pattern to the lateral distribution of TCDD
levels – concentrations appear to vary independently of proximity to the shoreline.
One interesting aspect of the TCDD distribution in Newark Bay is the decrease in the ratio
of 2,3,7,8-TCDD to total TCDD in surface sediments south of the lower Passaic River (Figure 1-
13). The ratio varies from about 0.64 in Newark Bay, to about 0.36 in Kill van Kull, with average
values of about 0.58 and 0.48, respectively. Although slightly lower, the ratio in northern Newark
Bay is comparable to 0.71 as calculated by Chaky (2003). The dominance of the 2,3,7,8-TCDD in
the lower Passaic River and Newark Bay suggests that the ratio may be used as a tracer to fingerprint
dioxin contamination in the study area. The use of the ratio should however be subject to further
scrutiny by, for example, testing it on other dioxin congeners, before it becomes a reliable
fingerprinting tool.
OCDD is also widely distributed throughout Newark Bay (Figure 1-14). The highest levels
in the surface sediment are also found near the mouth of the Passaic River, where peak
concentrations reach 7.3 ng/g (compared to 22.6 ng/g in the lower Passaic River proper). Figure 1-
14 also shows a decrease in OCDD concentrations from the mouth of the lower Passaic River
through the first couple of miles to the south in Newark Bay. It is, however, interesting to note that
OCDD levels in surface sediments increase again between RM2.5 and RM5.5 in the Bay suggesting
the presence of other potential sources of OCDD in Newark Bay proper. Unlike TCDD, the
concentration in deep sediments has a tendency to increase in particular between RM2.5 and RM5.5.
For example, between 2 and 4 ft below the surface sediment, OCDD levels remain comparable to
those found in the surface sediments and in some cases even exceed them. In addition, levels of
OCDD reach a maximum concentration of 6.2 ng/g in sediment buried between 2 and 4 ft,
compared to only 2 ng/g in the surface sediment at the same location. Depth profiles at selected