Duluth-Superior Harbor Research Articles

Occurrence and Transport of Organic Microcontaminants in the Duluth-Superior Harbor

A large number of organic compounds were identified in sediments and suspended solids from St. Louis Bay in the Duluth harbor. Most of the organic compounds appeared to be naturally occurring plant decomposition products consisting of non-halogenated hydrocarbons, organic acids, aldehydes, ketones, amines, esters, alcohols, and phenols. However, the presence of polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAH) were confirmed by GC/MS methods. Particulate levels of PAH compounds such as fluorene, fluoranthene, and pyrene were found to lie in the 0.2 to 3 μg/g range. PCBs associated with suspended particles from St. Louis Bay and the Superior harbor were at concentrations of 0.2 to 0.9 μg/g and less than 0.1 μg/g, respectively. Measurements of PCBs in water from the St. Louis Bay showed an average value of 19 ng/L. Considering the concentration of PCBs in water and particulates in conjunction with average suspended solids levels, it was calculated that 81% of the PCBs were dissolved in water and 19% associated with suspended particles. It was estimated that suspended solid transport of PCBs and PAH to Lake Superior is less than 0.01% of airborne transport.

Transports in the Duluth-Superior Harbor

A hydrodynamic model and a water quality model for the Duluth-Superior harbor are developed and verified by using data on currents, water levels, and water quality parameters. The water quality model is subsequently used to simulate the transport of particulates resuspended by ship traffic and the dispersal of dissolved material spilled into the harbor at a major industrial site. Resuspension of bottom sediments by ship traffic is an important secondary source of harbor turbidity. Suspended solids in ship resuspension plumes range from 10 to 50 mg/L, five times the usual concentration of suspended solids in the harbor. An estimated 10 5 kg of material is resuspended per passage of a ship. The resuspended material is coarse and settles rapidly, thus only 0.1% of the material flows out directly into Lake Superior. Most of the material resuspended by ship traffic is redistributed to the low turbulence areas within the shipping channels. It was found that a spill of dissolved pollutant in the inner harbor would take from 8 to 21 days to reach Lake Superior at peak concentrations. The peak concentration of pollutant at the lake entries depends on seiche amplitude and ranges from 0.05 to 0.1% of the initial concentration at the spill site. At a 0.1% concentration level, the spill would extend over 30% of the harbor, and would remain in the harbor for 30 to 40 days.

Identification of Contaminants in Lake Superior Through Landsat I Data

Remote sensing signatures are developed for using Landsat data in identification of four types of particulate contaminants in Lake Superior. The criteria are based on the residual Landsat signal intensities and signal ratios. The signatures work well in differentiation of river runoff from high background turbidity due to erosion and resuspension. The threshold concentrations for identification of suspended solids in lakes range on the order of 1 mg/L for clear lakes such as Lake Superior and 5 mg/L for light absorbing water characteristic of the Duluth-Superior Harbor.

Discussion of “Woods on Duluth-Superior Harbor”

Discussion of “Woods on Duluth-Superior Harbor”

Notes on the use of alternating current in unloading coal

The receipts of coal in Duluth-Superior Harbor increased from 2,600,000 tons <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∗</sup> in 1900 to 8,300,000 tons in 1910. This coal comes principally from Pennsylvania and West Virginia and is brought by rail to Lake Erie ports where it is loaded into boats for transportation to Duluth and Superior. Of the receipts in 1910, two million tons was anthracite and the remainder bituminous coal. At Duluth-Superior Harbor the coal is unloaded from the boats and stored for future demand or loaded directly into cars for shipment to various points in Minnesota, North Dakota, South Dakota and Montana.

Notes on the Use of Alternating Current in Unloading Coal

The receipts of coal in Duluth-Superior Harbor increased from 2,600,000 tons ∗ in 1900 to 8,300,000 tons in 1910. This coal comes principally from Pennsylvania and West Virginia and is brought by rail to Lake Erie ports where it is loaded into boats for transportation to Duluth and Superior. Of the receipts in 1910, two million tons was anthracite and the remainder bituminous coal. At Duluth-Superior Harbor the coal is unloaded from the boats and stored for future demand or loaded directly into cars for shipment to various points in Minnesota, North Dakota, South Dakota and Montana.

Harbors: Harbors On Lake Superior, Particularly Duluth-Superior Harbor

Lake Superior is the greatest expanse- of fresh water on the globe. Its length, along the steamer track from Duluth, Minn., to Pt. Iroquois, Michigan, is 383 miles, and its greatest breadth is about 160 miles. Other dimensions and characteristics are as follows