Chemical Spills
Chemical spills are any accidental releases of synthetic chemicals that pose a risk to the environment.
Spills occur at any of the steps between the production of a chemical and its use. A railroad tank car may spring a leak; a pipe in a manufacturing plant may break; or an underground storage tank may corrode allowing its contents to escape into groundwater. These spills are often classified into four general categories: the release of a substance into a body of water; the release of a liquid on land; the release of a solid on land; and the release of a gas into the atmosphere. The purpose of this method of classification is to provide the basis for a systematic approach to the control of any type of chemical spill.
Some of the most famous chemical spills in history illustrate these general categories. For example, seven cars of a train carrying the pesticide metam sodium fell off the tracks near Dunsmuir, California, in August 1991, breaking open and releasing the chemicals into the Sacramento River. Plant and aquatic life for 43 mi (70 km) downriver died as a result of the accident. The pesticide eventually formed a band 225 ft (70 m) wide across Lake Shasta before it could be contained.
In 1983, the Environmental Protection Agency (EPA) purchased the whole town of Times Beach, Missouri, and relocated more than 2,200 residents because the land was so badly contaminated with highly toxic dioxins. The concentration of these compounds, a by-product of the production of herbicides, was more than a thousand times the maximum recommended level.
In December 1984, a cloud of poisonous gas escaped from a Union Carbide chemical plant in Bhopal, India. The plant produced the pesticide Sevin from a number of chemicals, many of which were toxic. The gas that accidentally escaped probably contained a highly toxic mixture of phosgene, methyl isocyanate (MIC), chlorine, carbon monoxide, and hydrogen cyanide, as well as other hazardous gases. The cloud spread over an area of more than 15 mi2 (40 km2), exposing more than 200,000 people to its dangers.
Chemists have now developed a sophisticated approach to the treatment of chemical spills, which involves one or more of five major steps: containment, physical treatment, chemical treatment, biological treatment, and disposal or destruction. Soil sealants, which can be used to prevent a liquid from sinking into the ground, are an example of containment. One of the most common methods of physical treatment is activated charcoal, because it has the ability to adsorb toxic substances on its surface, thus removing them from the environment. Chemical treatment is possible because many hazardous materials in a spill can be treated by adding some other chemical that will neutralize them, and biological treatment usually involves microorganisms that will attack and degrade a toxic chemical. Open burning, deep-well injection, and burial in a landfill are all methods of ultimate disposal.
Resources
Books
Unterberg, W., et al. How to Respond to Hazardous Chemical Spills. Park Ridge, N.J.: Noyes Data Corporation, 1988.
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