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Mercury as a Global Pollutant
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11195 |
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Section : |
NATURAL SCIENCE
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| Issue
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10 / 1993 |
3,238 Words |
| Author
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William F. Fitzgerald
William F. Fitzgerald is professor of marine sciences at the University of Connecticut, Groton, Connecticut. |
Mercury is an important industrial element that is liquid at room temperature, heavy, bright, and toxic. Common images of mercury poisoning include the Mad Hatter's behavior in Alice in Wonderland and the scraggly, tremor-afflicted scrawl of those working in mercury mines in Italy and Spain. Researchers and public health officials see their worst nightmares fulfilled, however, in W. Eugene Smith's poignant photograph of a helpless teenager, Tomoko Uemura, being bathed by her mother. Tomoko was born mentally handicapped and irreversibly deformed because Mrs. Uemura, while pregnant, ate seafood that had been contaminated by methylmercury discharged from a local chemical factory in Japan.
Mercury and its compounds are commonly found in products such as fluorescent lamps, thermometers, thermostats, batteries, and dental amalgams. In addition, mercury is used in the production of fungicides, pharmaceuticals, paints, and the industrially essential chemicals chlorine and caustic soda. Geochemical studies reveal that mercury travels freely around the globe through the air, from which it is deposited on both land and water. The amount of mercury entering the atmosphere from anthropogenic, or human-related, sources--mainly coal combustion, smelting, and waste incineration--considerably exceeds that from natural sources such as volcanoes, forest fires, and the surface of the ocean. The annual amounts of mercury released from human activities ranges between 3,600 and 4,500 tons, or about 50-75 percent of the total amount from all sources. However, the real figures for the anthropogenic contribution may be even higher, because recent research shows that gaseous elemental mercury escaping from the surface of water bodies includes a pollution-derived component.
Nearly undetectable in air and water
The amounts of mercury in air and water are so extraordinarily minute that even the use of highly sophisticated equipment cannot guarantee accurate measurements. In addition to ultrasensitive equipment, researchers must also employ an ultraclean, rigorously careful investigative approach. Unfortunately, before 1985 the need for such care in data sampling and handling was not well appreciated, so much of the pre-1985 mercury research and environmental assessments were inaccurate. Today there is a heightened awareness of the need not only for accurate and comprehensive measurements of mercury in nature, but also for ultra trace-metal-clean sampling and analytical protocols.
Recent improvements in analytical equipment, in combination with trace-metal-free
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