The Contamination of Groundwater

Groundwater has been traditionally considered to be a pure form of water. Because of its filtration through soil and its long residence time underground, it contains much less natural organic matter and many fewer disease-causing microorganisms than water from lakes or rivers, although the latter point may be a misconception, according to recent evidence. Some groundwater is naturally too salty or too acidic for either drinking or irrigation purposes and may contain too much sodium, sulfide, or iron for many uses.

Humans have been concerned about the pollution of surface water in rivers and lakes for a long time. Indeed, a recent survey indicated that stream water in both agricultural and urban areas of the United States contains pesticide concentrations that exceed human-health benchmark standards. In contrast, the contamination by chemicals of groundwater was not recognized as a serious environmental problem until the 1980s, notwithstanding the fact that it had been occurring for half a century. To a large extent, groundwater contamination was neglected because it was not immediately visible—it was "out of sight, out of mind"—even though groundwater is a major source of drinking water. We were ignorant of the long-range consequences of our waste disposal practices. Ironically, surface water can be cleaned up relatively easily and quickly, whereas groundwater pollution is a much harder, much more expensive, long-range problem to solve.

Because we are now aware of the consequences—including high remediation costs—of the uncontrolled disposal of organic chemical wastes, most large corporations in developed countries have become much more responsible in their disposal of chemicals. Unfortunately, the collective discharges from smaller sources, including many municipalities, small industries, and farms, have not yet been controlled in like manner. Similarly, the huge number of septic tanks that exist are collectively a major source of nitrate, bacteria, viruses, detergents, and household cleaners to groundwater.

Continue reading here: Nitrate Contamination of Groundwater

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