Contamination of Green Bay water with lead and cadmium by a 37-m long, 2-m draft research vessel

During late April 1989, Green Bay, Lake Michigan water was sampled for dissolved concentrations of lead and cadmium. Samples used to document horizontal contamination of the water by a research vessel were collected using a rubber boat rowed 2, 50, 100, and 200 m upwind of the anchored mother ship. Samples used to document vertical contamination of the water column by the research vessel were collected from the vessel at water depths of 0.2, 2, 5, 10, and 20 m. Both lead and cadmium blanks were < 0.5 ng/l and below their limits of detection at the 95% level of confidence of 3.5 and 0.98 ng/l, respectively. Concentrations of lead in the horizontal direction varied between 3.5 ng/1 at 200 m from the ship and 7.7 ng/1 at 2 m from the ship. Cadmium concentrations varied from 2.8 ng/l at 2 m from the ship to 1.5 ng/1 at 200 m from the ship. Lead concentrations in the vertical direction varied between 8.4 ngll at a depth of 0.2 m and 3.3 ng/l at 5 m. Cadmium concentrations ranged between 4.5 ng/l at 2 m and 2.2 ng/1 at 20 m. The vertical studies were inconclusive and appeared to be influenced by resuspension of bottom sediments. Uncontaminated samples can be collected as close as 100 m to the research vessel.