2 research outputs found
Identification of Marbon in the Indiana Harbor and Ship Canal
Marbon
is isomeric with Dechlorane Plus (DP). Both are produced
by the Diels–Alder condensation of hexachlorocyclopentadiene
with cyclic dienes, and both have elemental compositions of C<sub>18</sub>H<sub>12</sub>Cl<sub>12</sub>. Dechlorane Plus is commonly
found in the environment throughout the world, but Marbon has, so
far, only been detected at low levels in one sediment core collected
near the mouth of the Niagara River in Lake Ontario. Here we report
on the concentrations of Marbon and <i>anti</i>-DP in 59
water samples from five Lake Michigan tributaries [the Grand, Kalamazoo,
St. Joseph, and Lower Fox Rivers, and the Indiana Harbor and Ship
Canal (IHSC)], 10 surface sediment samples from the IHSC, and 2 surface
sediment samples from the Chicago Sanitary and Ship Canal. Three Marbon
diastereomers were detected in the water and sediment samples from
the IHSC, which is far from the location of its previous detection
in Lake Ontario. The sum of the concentrations of the three Marbons
was greater in the water from the IHSC (<i>N</i> = 11, median
=150 pg/L) compared to those in water from the other four tributaries
(<i>N</i> = 11–13, medians =0.9–2.0 pg/L).
Marbon concentrations in sediment samples from the IHSC were up to
450 ng/g dry weight. <i>Anti</i>-DP was also measured for
comparison. Its concentrations were not significantly different among
the water samples, but its sediment concentrations in the IHSC were
significantly correlated with those of Marbon. The source of Marbon
contamination in the IHSC is not clear
Updated Polychlorinated Biphenyl Mass Budget for Lake Michigan
This
study revisits and updates the Lake Michigan Mass Balance
Project (LMMBP) for polychlorinated biphenyls (PCBs) that was conducted
in 1994–1995. This work uses recent concentrations of PCBs
in tributary and open lake water, air, and sediment to calculate an
updated mass budget. Five of the 11 LMMBP tributaries were revisited
in 2015. In these five tributaries, the geometric mean concentrations
of ∑PCBs (sum of 85 congeners) ranged from 1.52 to 22.4 ng
L<sup>–1</sup>. The highest concentrations of PCBs were generally
found in the Lower Fox River and in the Indiana Harbor and Ship Canal.
The input flows of ∑PCBs from wet deposition, dry deposition,
tributary loading, and air to water exchange, and the output flows
due to sediment burial, volatilization from water to air, and transport
to Lake Huron and through the Chicago Diversion were calculated, as
well as flows related to the internal processes of settling, resuspension,
and sediment–water diffusion. The net transfer of ∑PCBs
is 1240 ± 531 kg yr<sup>–1</sup> out of the lake. This
net transfer is 46% lower than that estimated in 1994–1995.
PCB concentrations in most matrices in the lake are decreasing, which
drove the decline of all the individual input and output flows. Atmospheric
deposition has become negligible, while volatilization from the water
surface is still a major route of loss, releasing PCBs from the lake
into the air. Large masses of PCBs remain in the water column and
surface sediments and are likely to contribute to the future efflux
of PCBs from the lake to the air