Newark Bay Study - Passaic River Public Digital Library

1-14
Bottom sediments were also characterized in detail as part of this early sampling program
(~100 surface sediment samples). The results indicated that the surface sediments of the northern
region of Newark Bay are primarily composed of particulate material having a grain size that is
representative of silt. The lower Hackensack River sediments have a somewhat coarser texture than
the lower Passaic River and northern Newark Bay sediments. The sediment composition becomes
coarser in texture in the direction of South Newark Bay, a trend that likely reflects the more intense
long-term dredging activity and relatively high current speeds in that area, particularly in the Kill van
Kull. Surficial bottom sediment concentrations were also measured, with a focus on levels of total
organic carbon (TOC) and 8 metals: Hg, Cd, Pb, As, Cu, Zn, Cr and Ni. The concentrations of
these constituents will be discussed in a later section of this report.
Suszkowski used the 1976 monthly monitoring data, supplemented by additional sources of
information on velocity profiles at the 4 Newark Bay boundaries, to develop a detailed inorganic
solids balance for the system. The approach was to evaluate the surface and bottom layer flows at
each of the four points of entry to the Bay (discussed above), and to then assign the observed
average TSS concentration to each of these. (It is of interest to note that the boundary at the Passaic
River had a distinctly different TSS profile than the other locations, with the surface layer TSS being
consistently higher than the bottom layer TSS concentration.) The product of the flow and TSS
concentration in the surface and bottom layers yields an estimate of the mass flux rate, and the
difference between the surface and bottom layer fluxes represents an estimate of the net flux across
each Newark Bay boundary. Additional internal sources of solids, including TSS inputs from
wastewater treatment plants, urban runoff and phytoplankton production were also quantified.
Finally, a net solids balance for the entire Bay was obtained by evaluating the sum of all of these
inputs.
The results of Suszkowski’s solids balance analysis are summarized on Figure 1-3. It is
evident from these results that the Passaic River, Kill van Kull and Arthur Kill were all net sources
of TSS to Newark Bay, while the Hackensack River was a net sink of solids at the time of this
investigation. This latter finding was recently confirmed by simulations performed with the Newark
Bay model by Pence (2004). The simulations involved the initialization of a particle concentration
of 1 mg/L in the Passaic River, on a monthly basis, and then tracking the movement over these
particles over the course of an annual cycle. The particles tended to move from the Passaic River,
into Newark Bay, and then left Newark Bay by transport into the Hackensack River, or by transport
out of the system in the surface layers of the Arthur Kill and Kill van Kull. The difference in
transport regimes for the Hackensack and Passaic Rivers is partly explained by the relatively low
freshwater flow in the Hackensack River, as this facilitates the upstream transport of solids from the
Bay. Additionally, during high flow events there is relatively little upstream storage in the Passaic
River, so peak flow rates propagate through the system with relatively little attenuation. This differs
from the situation in the Hackensack River, where upstream reservoir storage will absorb many of