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  3. Polluted water is nothing new in the United States. We have lived through flaming rivers and caustic creaks that could take the

Polluted water is nothing new in the United States. We have lived through flaming rivers and caustic creaks that could take the

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问题     Polluted water is nothing new in the United States. We have lived through flaming rivers and caustic creaks that could take the hide off a hound. For decades, however, efforts to safeguard drinking water were hampered because no one had an accurate sense of the full range of contaminants in the water supply, nor of the geographic extent of the pollution. This year two separate research teams unveiled sophisticated new tools to find out exactly what chemical dangers are lurking in freshwater streams.
    "Research in Europe in the 1990s showed that pharmaceuticals were turning up in the water," says Dana Kolpin, leader of a U. S. Geological Survey Water Resources Division research ream that developed five new analytic methods for measuring water contaminants." Our big effort was to develop methods to measure very small amounts of organic chemicals. ’ The research team fanned out across 30 states nationwide and conducted two years of sampling from 139 streams. They were chosen, says Kolpin, on the basis of their location downstream from" intense urbanization and livestock production." In a study published in the March 15 Journal of Environmental Science & Technology, Kolpin and his colleagues reported they looked for 95 different contaminants, such as antibiotics, steroids, hormones, antioxidants, plasticizers, and various solvents. They found 82 of them. Nearly 80 percent of the streams showed one or more of the contaminants. The median stream contained seven. Even the good news--that the most frequently detected contaminants like fecal steroids, cholesterol, insect repellent, caffeine, disinfectant, fire retardant, and detergents were found in generally low concentrations--had to be qualified. Many of those compounds have no guidelines for safe amounts, and little is known about the effects of chronic exposure or the interactive effects of compounds that have been detected together.
    In a related Environmental Protection Agency study that is still in progress, a team of scientists at the Johns Hopkins Whiting School of Engineering is using gas chromatography and mass spectrometry to detect the presence of various anticonvulsants and anticancer drugs in drinking water. Led by Lynn Roberts and Ed Bouwer, the researchers track samples at sewage-treatment facilities in Massachusetts and Maryland to determine whether and in what quantities pharmaceuticals are getting through the waste-treatment plants and the extent to which they may be accumulating in coastal waters.
    The goal of both research teams is to provide a baseline of what organic compounds are in the water, in what quantities, and how they are getting there--key steps toward ensuring that the water we drink isn’t killing us.
Which of the following statements is true?
选项 A、Altogether 95 different contaminants have been found in streams.
B、Nearly 80 percent of the streams surveyed contains only the familiar contaminants.
C、The most frequently detected contaminants are usually in low concentrations.
D、The average number of contaminants in each stream surveyed is seven.
答案D
解析
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