华盛顿地下天然气管道发现 5893 多处泄露More than 5,893 leaks from aging natural gas pipelines have been found under the streets of Washington, D.C. by a research team from Duke University and Boston University. A dozen of the leaks could have posed explosion risks, the researchers said. Some manholes had methane concentrations as high as 500,000 parts per million of natural gas -- about 10 times greater than the threshold（门槛） at which explosions can occur. Four months after phoning in the leaks to city authorities, the research team returned and found that nine were still emitting dangerous levels of methane. "Finding the leaks a second time, four months after we first reported them, was really surprising," said Robert B. Jackson, a professor of environmental sciences at Duke who led the study. The researchers published their findings this week in the peer-reviewed journal Environmental Science & Technology "Repairing these leaks will improve air quality, increase consumer health and safety, and save money," Jackson said. "Pipeline safety has been improving over the last two decades. Now is the time to make it even better." Nationally, natural gas pipeline failures cause an average of 17 fatalities, 68 injuries, and $133 million in property damage annually, according to the U.S. Pipeline and Hazardous Materials Safety Administration. In addition to the explosion hazard, natural gas leaks also pose another threat: Methane, the primary ingredient of natural gas, is a powerful greenhouse gas that also can catalyze ozone formation. Pipeline leaks are the largest human-caused source of methane in the United States and contribute to $3 billion of lost and unaccounted for natural gas each year. Jackson's ...
