STONY BROOK – Implementation of the Federal Clean Water Act has dramatically lowered the concentrations of several toxic metals in the Hudson River Estuary, although levels of dissolved mercury, silver and lead remain relatively high, and inorganic nutrients such as phosphate have not decreased significantly since the Act passed in 1972.
These are the results of a special sampling program undertaken by Dr. Sergio A. Sañudo-Wilhelmy of the Marine Sciences Research Center of the State University at Stony Brook and Dr. Gary Gill of the Laboratory for Oceanographic and Environmental Research of Texas A&M University. The work, funded by the Hudson River Foundation, will be published in the journal, Environmental Science and Technology.
Dr. Sañudo-Wilhelmy and Dr. Gill compared a suite of trace metals and phosphate concentrations in surface water samples collected along the Hudson River estuary between 1995 and 1997 with samples collected in the mid-1970s during the implementation of the Federal Clean Water Act.
Since 1972, the median concentrations of trace metals declined 36 per cent to 56 per cent for copper, 55 per cent to 89 per cent for cadmium, 53 per cent to 85 per cent for nickel and 53 per cent to 90 per cent for zinc.
While some nickel and copper previously deposited in the sediments at the bottom of the Hudson may periodically be stirred up and mixed with the surface waters,
Dr. Sañudo-Wilhelmy attributes the decreases in copper, cadmium, nickel and zinc to improvements in controlling discharges from municipal and industrial wastewater treatment plants.
This has been particularly true for the waters of the lower Hudson River in the New York-New Jersey metropolitan area, where most of the wastewater treatment plants are located. At the same time, however, phosphate and silver levels remain high. Silver, he says, is the best tracer of sewage, and the phosphates resemble sewage tracer silver. “This shows, he says, “that sewage treatment technology currently in use in the New York-New Jersey Metropolitan area does not remove phosphates.”
Some 50-miles upstream, the Hudson tells a different story. There, says Dr. Sañudo-Wilhelmy, “the river flows through a forested region and a less populated area than the densely settled, industrialized area surrounding the lower Hudson.” Yet, he found relatively high levels of lead and mercury.
Dr. Sañudo-Wilhelmy believes that atmospheric fall-out onto soils from mercury emissions and lead deposited in the soils before the elimination of leaded gasolines is washing into the Hudson. “It has recently been shown by other investigators,” he said, “that most of the atmospheric mercury measured in New York appears to originate in Ontario and Quebec and the Midwestern United States. This airborne mercury could be the ultimate source responsible for the levels of this toxic trace element observed in the water column of the Hudson.”
Contact: Judy Fischer at Marine Sciences, (516) 632-8678
