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 C18H12Cl12. 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 anti-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 (N =
11, median =150 pg/L) compared to those in water from the other four tributaries (N = 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. Anti-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.