0.24 Issues and options  (Page 6/6)

Best management practices

Best management practices are techniques and methods designed to minimize environmental impacts. In agriculture, these practices include growing native crops or those suited to local conditions, rotating crops, minimizing soil tilling, and reducing pesticide use. With proper care, soils can remain fertile and healthy for many years.

Environmental remediation

For many thousands of years, ever since they built the first campfire, human activity has generated air, water, and soil pollution. For most of human history, however, these contaminants had relatively little environmental impact. But over the last few centuries, pollution levels skyrocketed as a result of population growth and the Industrial Revolution. As a result, regulations have been enacted to control emissions. Even where these are effective in curbing current pollution sources, high levels of contamination may exist from past activity. And new contamination can occur through industrial accidents or other inadvertent releases of toxic substances. Danger to human health from both historic and modern contamination requires that cleanup measures be implemented. This is the purpose of environmental remediation.

Contamination sources

Just under 300 million tons of hazardous wastes are produced each year in the United States. Although the safe disposal of wastes is mandated, accidental releases do occur, and sometimes regulations are ignored. Some of the most widespread or dangerous pollutants that require remediation come from mining, fuel spills and leaks, and radioactive materials.

Heavy metals (copper, lead, mercury, and zinc) can leach into soil and water from mine tunnels, tailings, and spoil piles. Acid mine drainage is caused by reaction of mine wastes, such as sulfides, with rainfall or groundwater to produce acids, like sulfuric acid. The Environmental Protection Agency estimates that 40% of the watersheds in the western United States are contaminated by mine run-off.

Organic contamination can result from discharge of solvents to groundwater systems, natural gas or fuel spills, and above-ground and underground storage tank leakage.

Radioactive contamination of soils, water, and air can result from mining activity, processing of radioactive ores, and improper disposal of laboratory waste and spent fuel rods used at nuclear power plants. The best-known example of radioactive contamination is the Chernobyl disaster. In 1986, workers at a Russian nuclear power plant ignored safety procedures during a reactor test, and the fuel rods superheated the cooling water to cause an explosion that killed 30 people and released a huge cloud of radioactive steam. Although more than 100,000 people were evacuated from around the plant, a dramatic increase in cancer rates among the population has occurred. As the steam cloud dispersed into the atmosphere, increases in radioactivity were measured over much of the northern hemisphere.

Remediation efforts

Many communities are struggling to find the funds and technological expertise needed to clean up polluted areas. Some settings, such as brownfields, can be reclaimed fairly easily. Other areas, because of their size or the extreme toxicity of their contaminants, require very expensive, complex, and long-term remediation. Many of these have been designated as Superfund sites.

Brownfields are abandoned industrial or commercial facilities or blighted urban areas that need to be cleansed of contamination before they can be redeveloped.

Superfund sites are areas with the most toxic contamination in the United States. The contamination may not only make the site itself too dangerous to inhabit, but often leaks toxic levels of pollutants into the surrounding soil, water, or air. An example of a Superfund site is Love Canal in Niagara Falls, New York. The canal was a chemical waste dump for many years, then in the 1950’s was covered with soil and sold to the city. Over time, many homes and a school were built over the former dump. In the 1970’s, heavy rains raised the water table and carried contaminants back to the surface. Residents noticed foul smells, and gardens and trees turned black and died. Soon after, rates of birth defects, cancer, and other illnesses began to rise sharply. In 1977, the State of New York and the federal government began remediation work. Buildings were removed, and all residents were bought out and relocated, contaminated deposits and soils were excavated, and remaining soils and groundwater were treated and sealed off to prevent further spread of the contamination. Remediation activities have now been completed at this site.

Remediation methods

The type of pollution and the medium affected (air, water, or soil) determine remediation methods. Methods include incineration, absorption onto carbon, ion exchange, chemical precipitation, isolation, or bioremediation. Bioremediation is the use of plants, bacteria, or fungus to “digest” the contaminant to a non-toxic or less toxic form. All of these methods tend to be expensive and time-consuming.

Remediation is aimed at neutralization, containment, and/or removal of the contaminant. The goal is to prevent the spread of the pollution, or to reduce it to levels that will not appreciably risk human health. Many times, it is physically impossible or financially unfeasible to completely clear all contamination. Often, experts and the public disagree on how clean is clean enough.