2005年NPR美国国家公共电台三月-Studies Find High Mercury Levels in the W（在线收听） |
| Studies that will be released today show that fish, birds and mammals in New England have significant amounts of mercury in their bodies. The studies find the toxic metal in some unexpected habitats and they suggest that power plants in the Midwest are a major source of mercury for the Northeast. NPR's Richard Harris reports. Mercury pollution in the northeast should be getting better. In the past decade, mercury emissions from regional sources such as waste incinerators have been cut in half, but David Evers from the BioDiversity Research Institute in Gorham Maine says mercury levels in the environment remain stubbornly high. -There is enough mercury fallen on the landscape anywhere in the northeast to cause problems. It's just the right recipe needs to be there to create a problem. The new federally funded studies in the journal Ecotoxicology point out 9 hot spots where mercury contamination is a big problem. They range from southern Noverscoshed to northeast Massachusetts. In most of these places, the contamination isn't a surprise. Some of these areas are downwind of urban areas; others have environmental conditions such as acidic waters that promote mercury poisoning. But Evers also went to areas that are traditionally not thought of as trouble spots like dry mountaintops. He decided to look at big-nose thrush, an uncommon songbird that lives at high elevations. -There's a lot of people that ask me why you're doing this. There should be no mercury up there and my thought was why not, why not go to some of these habitats for these species that have high conservation concern and have a checklist to be able to say we don't have to worry about mercury in the species. But Evers now reports some unsettling news about these forest dwelling birds. -The big-nose thrush does have mercury levels in its body ,much higher than we would have predicted and so what we're finding is that mercury, in these mountaintops without staining water, is getting into these thrushes. These birds don't eat fish, which is the usual route of exposure for birds.Eric Miller from a private firm called the Ecosystem's Research Group in Norvichful Mount thinks he's tracked down the source. Mountaintop mercury apparently comes from dry particles of mercury in the air ,those settle on mountain vegetation. -We looked at mercury in leaves when they first emerge in the spring, say, deciduous leaves that are opening and emerging in the spring, and they have very low levels of mercury, and then a few weeks later, their level of mercury has increased and this continues throughout the growing season until a high level of mercury is present in these leaves at the end of the season. Insects eat the leaves and the big-nose thrushes eat the insects. Biologists are now trying to figure out whether these mercury levels are high enough to affect the health of these species. One thing is for sure, Miller says, the government computer models that are supposed to predict how mercury travels through the air, don't predict that dry particles of mercury would be a problem. And those mercury particles come from distant sources, often coal-burning power plants. Some of it blows halfway around the globe from China, but a lot comes from power plants in the Midwest. Miller documented these by studying mercury in rainfall. For example, at a monitoring station in Vermont,he found that 36 of the 38 most mercury-laden rainstorms started out as polluted clouds of air from elsewhere. -And the air moved first over the Midwest or first over the eastern urban corridor prior to arriving in Vermont and depositing the mercury with a rainfall there. The source of mercury is a huge political issue right now. Congress is planning to debate changes to the Clean Air Act which could well determine how quickly power plants scale back their mercury emissions. And the environmental protection agency is under a court order to announce a new mercury plan next week. Richard Harris, NPR News. |
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