Sediments from the Magothy River contain arsenic and those from the Severn contain copper, zinc and nickel. In the upper reaches of the Chester River, there are banned pesticides, Dieldrin and DDT, and in the Potomac River, polychlorinated biphenyls (PCBs).
Those rivers, isolated from the heavy manufacturing assumed to cause such pollution, are among 10 areas of concern noted in a Chesapeake Bay Program report on tidal rivers released yesterday.
Nine of those areas -- the Middle, Back, Magothy, Severn, Chester and the upper and middle segments of the Patuxent and Potomac rivers -- are in Maryland. The tenth is the James River near the mouth of the bay in Virginia.
Although the rivers are safe, the chemicals are an "early warning sign" that they are "not completely healthy," according to Kelly Eisenman, toxics coordinator for the bay program.
The report, which examines 31 rivers, is "a tool" that "helps us target where to get some more data" and where to focus pollution control efforts, she said.
The study acknowledges the three long-standing toxic hot spots among Chesapeake Bay's tributaries -- Baltimore Harbor, the Anacostia River in Washington and the Elizabeth River in Virginia.
In a new step, it focuses on such rivers as the Middle and Back, north of Baltimore, and the James in southern Virginia, which are showing early signs of toxic pollution, and such others as the Sassafras on the Eastern Shore, which has very low or no toxicity.
"We've always known about the toxic hot spots," Eisenman said. "What we haven't known is how these other areas are doing. There's a lot of data out there, but no one ever took all that data and put it together."
The data show that even rivers that seem to be removed from the worst sources of pollution aren't safe from heavy metals.
Eisenman said the metals may not be from industries at all, but from "nonpoint" sources -- those that don't originate from a specific point, such as a factory or a sewer plant, but from air pollution and even the weathering of rocks.
Lina Vlavianos, a member of the Severn River Commission and an environmental activist in Anne Arundel County, said she is "not surprised" that scientists found copper in river sediments, because the metal is in the water discharged from Nevamar, a plastics manufacturer near the head of the river, but she is puzzled by the other metals.
"The Severn?" she asked. "What industry do we have that is discharging? This is disturbing."
Eisenman said that in the past, bay scientists and regulators have concentrated on the impact of factories and power plants, but now they must turn to studying nonpoint sources of pollution.
"Copper from the brake pads on your car could be deposited on the roads and wash off when it rains," she said.
"We have found urban runoff to be a substantial source of metals in the bay. Household products that wash down the drains and off lawns contain metals. Boat paints designed to keep off barnacles have metals; any number of things," Eisenman said.
The study also shows that:
Water taken from the Middle River in the spring and fall of 1998 had "adverse effects" on bay organisms in laboratory tests, and that water from two spots in the river ranked fourth and eighth highest for toxicity among samples taken from 46 stations in 16 rivers along the bay.
Scientists did not have enough information -- or had inconclusive information -- on 20 other rivers, including the Bush and Gunpowder rivers in Baltimore and Harford counties.
The Army's Aberdeen Proving Ground, which borders the Bush and Gunpowder, is preparing reports on those rivers, and the bay program is waiting for that report, Eisenman said.
Scientists from the program will "focus on" the rivers with insufficient or inconclusive data this summer and next, she said.