By Peg Van Patten, Connecticut Sea Grant

Once they get past gazing at the periodic chart in chemistry class, most people give little thought to the properties of metals or their origins. When found in large ore deposits, metals can make so many valuable products: Just look around you to appreciate an assortment of coins, jewelry, autos, batteries, electronic components, tools, machinery, and utensils made of metals and metal alloys. But incineration, mining, smelting, plating and other industrial processes produce metalliferous waste products that can pollute the air, soil, and water.

Surprisingly, the making of cement or the burning of wood can release quantities of metals such as cadmium, copper, nickel, lead, and zinc to the atmosphere. These metals can become serious environmental and health concerns even when widely dispersed. Heavy metals, such as lead, silver, and cadmium, are very toxic to aquatic and estuarine organisms even in minuscule amounts. They tend to be absorbed onto or into particles that clump together and sink in the water, accumulating in benthic sediments before being released into the water column over time, particularly when sediments are disturbed.

Areas of the Northeast have been showing the effects of metal contamination for a long time.

" Narragansett Bay has probably been subjected to metal pollution longer than any other estuary on the western side of the Atlantic," says Scott W. Nixon, University of Rhode Island Graduate School of Oceanography oceanography professor and Rhode Island Sea Grant director. "Metal pollution in any significant extent is a by-product of the Industrial Revolution, and the New England textile industry had its beginnings with the introduction of Samuel Slater's factory system in the textile mills on the Blackstone River." The cotton mill established there in 1790 was the first in America to use water-powered machinery for spinning cotton. Shortly thereafter, water-powered woolen mills sprang up along the Connecticut River in Connecticut and Massachusetts. By the mid-1800s, textile mills accounted for about one-quarter of all industrial employment in the region.

Zinc, cadmium, and other metals were used as mordants in the dyeing process to color the fabrics. Mercury and arsenic were also ingredients of pesticides sometimes used to prevent insect damage to wool and cotton. "Mad Hatter's disease," made popular by a character in Alice in Wonderland, referred to mercury poisoning, which sometimes afflicted workers in felt-processing factories. But the biggest use of metals by far was the production of the machinery to run the industrial factories. Tin, iron, copper, and pewter were used for tools as well as machinery. They were also used in producing arms. One of several Connecticut arms factories supplying weapons to the Union army during the Civil War produced 1,000 rifles per day. Some metals escaped into the air, soil, and water during these processes, and some were deposited in basins or buried as a means of waste disposal.

The demand for metals only increased following the Civil War, with the burgeoning of technology and the proliferation of large factories. The adverse effects of metals increased accordingly. While the bulk of metals emitted to the atmosphere had previously been deposited on fields and forests, increased paving of roads, sidewalks, and roofs meant more metals and other pollutants washed into streams and rivers in storm runoff. Those pollutants quickly found their way into bays and estuaries.

"Ironically, Narragansett Bay now contains far more gold and silver than it did when European explorers first came searching for precious metals," says Nixon. The Bay is downstream from a huge jewelry manufacturing center that operated in Providence around 1900. In a 1995 report, "Metal Inputs to Narragansett Bay: A History and Assessment of Recent Conditions," Nixon documents historical inputs of metals in Narragansett Bay and its associated rivers and provides recent data on current metal fluxes.

The good news, Nixon points out, is that anthropogenic inputs of metals, such as copper, chromium, and lead, to Narragansett Bay are now lower than input directly from the coastal ocean, due to legislation for environmental regulations and changes in the economic base. This reduction in pollutants is probably true for most estuaries in the Northeast, for the same reasons. However, there is still the problem of metal deposits lingering in the sediments.

Aquatic algae can take up metal ions in the water and store them in their tissues. Once ingested by an animal, or absorbed through its skin or gills, metals can be concentrated as they progress from smaller to larger organisms within the food web. The effects on organisms will be very different, depending on factors such as the particular organism, its feeding mode, the current stage of its life cycle, the season, the type of metal and its chemical form, and how it is transported and ingested or absorbed. For example, studies indicate that lead behaves like calcium in fish bodies, concentrating in bones and fins, while mercury accumulates in the oily tissue and liver. Still other studies suggest that salmonid eggs don't hatch in waters polluted with certain heavy metals.

The effects of metal pollutants in water don't stop with the organism, of course. They impact the species, the community, and the ecosystem as a whole. For example, in some rivers associated with past mining activities, in England and Wales, ecologists found fewer species of invertebrates than expected. Certain species apparently disappear completely when an aquatic system is polluted with metals. As ecologists know, when a species disappears, the entire ecosystem is affected through the food web and nutrient cycling interactions.

Probably the most well-known case of human toxicity to metals was the outbreak of Minimata disease in Japan in the 1950s. Methyl mercury discharged into the bay from a chemical plant caused the deaths of 649 people and the illness of 1,385 more. This toxic form of mercury causes severe human birth defects and attacks the central nervous system, brain, kidneys, and liver. Victims had eaten large amounts of mercury-contaminated fish and shellfish.

"The groups at risk from mercury or other metal poisoning are mostly pregnant women, very young children, and those with weakened immune systems," says Nancy Balcom, Connecticut Sea Grant marine extension educator. "Most people don’t eat enough seafood to worry about the minuscule amounts of metals or PCBs their bodies may be exposed to, and the health benefits of seafood are substantial." People who eat large quantities of seafood—more than one seafood meal per day—should be concerned, however, and anglers should make sure they are not fishing in contaminated waters. In general, Balcom adds, people should heed the state-issued health advisories on mercury contamination in large predatory fish such as tuna and swordfish.

It isn't always easy to point the finger at a "hot spot" of contamination; identifying less obvious sources can get complicated, particularly when there is a "soup" of contaminants. Sources of heavy metal pollution include rivers, sewage treatment plants, tidal exchange, urban runoff, combined sewer outflows, and deposition from the atmosphere. Effective pollution mitigation requires an understanding of the sources and quantities of heavy metal inputs. While the problem has been evident for a long time, the scientific community has only recently acquired the technological capability to detect, measure, and analyze metals in extremely small amounts under ultra-clean conditions. Northeast Sea Grant scientists who have been busy developing and improving techniques to analyze metal contamination are also trying to identify sources of contamination, transport mechanisms, and the sinks, or fate, of these metals.

Gaboury Benoit, Yale School of Forestry and Environmental Studies environmental chemistry associate professor, is conducting a Connecticut Sea Grant research project to identify the sources and quantities of heavy metal pollution. He is looking at the mass balance of heavy metals in New Haven harbor, connecting the Quinnipiac River and Long Island Sound. Benoit is examining the ratios of metals, how they occur, and possible sources using ultra-clean sampling, handling, and analysis techniques. This allows him to measure trace metal concentrations in parts per trillion. Such a concentration would be roughly equivalent to a droplet in an Olympic-size swimming pool, yet even an amount this small could be toxic in some situations.

Benoit is finding clear trace metal trends in different portions of the river, with much higher concentrations in the industrialized zones. He is also finding a variety of sources, local concentration trends, and heavy metal pathways in the river. Some metals, such as lead, occur everywhere without much variation, because of the diffuse nature of the sources. (When lead was a common ingredient of the gasoline used in automobiles, it dispersed all over the globe via the atmosphere.) Other metals, such as cadmium, tend to occur in peaks near a source. Benoit found large silver deposits near the former site of a silver plating industry in Meriden, and a metal sludge lagoon in Southington. He found an unusually high cobalt concentration in Jordan Cove that probably originated 20 years ago and may be related to a nearby nuclear power plant. His experiments show that storms, currents, tidal influence, and changes in effluent volume all influence the dispersion of heavy metal contaminants.

"The most important result of the investigation is the development of a heavy metal 'budget' for the river, which can serve as an important management tool." says Benoit. For instance, his studies show that the metal sources to Long Island Sound are mainly riverine, and that large storms and snowmelt contribute half of the heavy metal input to the river, about 25 percent of which is removed by marshes. Hence, costly efforts to remove heavy metals from sewage effluent (tertiary wastewater treatment) would not have much effect on heavy metal levels.

In another ongoing project, Benoit and coinvestigator Xuhui Lee, Yale School of Forestry and Environmental Studies biometeorology associate professor, are developing a mobile micrometeorological system that can measure changes in mercury between the air and the surfaces of salt marshes in Connecticut. The researchers hope that their system, currently set up in Branford, Conn., will help explain how metals such as mercury move between the air and water. They will also examine environmental parameters that may influence the flux in mercury, thus contributing to the overall understanding of chemical cycling in and around Long Island Sound.

While Benoit and Lee look in the water and air, another Sea Grant researcher, Johan Varekamp, is examining soggy soil for metal contaminants. Varekamp, Wesleyan University earth and environmental sciences professor, analyzes sediment cores from Connecticut marshes along Long Island Sound for copper, zinc, lead, molybdenum, silver, and other elements. He finds Connecticut River sediments to be relatively high in zinc, with lead concentrations showing variations chronologically tied to human activity, such as colonial hunting, automobile use, and the environmental legislation of the 1970s.

Henri Gaudette, University of New Hampshire Institute for the Study of Earth, Ocean and Space (EOS) geochemistry professor, is carrying out a project sponsored by Maine-New Hampshire Sea Grant to identify the sources of metal contamination in the Gulf of Maine coastal zone. Gaudette has developed techniques of isotopic analysis and is applying them to detect signatures, or "fingerprints" of uranium and lead found in sediments, biota, and precipitation. By looking at differences in these isotopic signatures, he can classify metal contamination as either point (identifiable, localized source) or nonpoint (dispersed sources), and then evaluate the contribution and effects of each. Gaudette believes that the results will provide important tools for making management decisions as well as a basis for future remedial actions.

One of Gaudette's test sites is the Cape Rosier-Blue Hill areas of coastal Maine. This region is considered a point source because two mines are known to have operated there. A second group of sites, in the Great Bay estuary and lower Piscataqua River, is known to be contaminated from past industrial activity. However, specific sources and "hot spots" need to be identified and evaluated. Because Gaudette and his students have been examining Great Bay sediment cores for iron, copper, lead, zinc, cadmium, and chromium for more than 20 years, there is now an established database for the area.

Such a database does not exist for other sites, such as Booth Bay in the Gulf of Maine. Specific sources for metal contamination there are undetermined, but the investigators hope to discern whether the site may be considered "nonpoint".

"Our data thus far suggest that the inner Booth Bay Harbor is heavily impacted by metals and that the impacts become more pronounced as one progresses from the open Gulf of Maine to the inner harbor," Gaudette explains. "This suggests a local source." Gaudette is now applying his isotopic techniques to analysis of the metal contamination in Booth Bay and will compare these results to those at other sites.

Both Gaudette and Benoit note the trend of heavier concentration of metal contaminants in the sediments of harbors compared to their surroundings. Benoit suggests this fact indicates that harbors may serve an important function as collection sites or filters of heavy metals, protecting estuaries and bays. This function would be thwarted if harbor sediments were dumped in surrounding estuaries, as often happens.

In Boston's Inner Harbor, dredging to accommodate the navigation of large vessels is just beginning. Because dredge spoils in industrialized locations are often heavily contaminated with metals and organic hydrocarbons, they must be disposed of in a way that will not remobilize contaminants into the water. According to Judith Pederson, MIT Sea Grant coastal processes manager, the program’s latest Marine Center project brings together researchers from MIT, University of Massachusetts-Boston, and the Harvard School of Public Health in a study of Boston Harbor—a case study to test the effectiveness of capping dredge spoils. Capping is just what the word implies, placing the material on the seafloor and covering it with an impervious material so that materials can move vertically under the cap but can't escape to surrounding waters. The research team is testing different capping methods and materials in collaboration with the U.S. Army Corps of Engineers and harbor managers.

As technology continues to improve, we can expect more and better analytic methods to fill the scientific sleuths' toolboxes. With these tools, we can better understand the effects of both people and nature on the nation's estuaries, and we can devise better methods to contain contaminated materials. The 21st century promises new hope in identifying contaminants from source to sink, understanding how materials move and how they affect organisms at various life stages, and how containment and remediation efforts can best be carried out.