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  3. The warming of the Arctic is releasing a new wave of banned toxic chemicals that had been trapped in the ice and cold water, sci

The warming of the Arctic is releasing a new wave of banned toxic chemicals that had been trapped in the ice and cold water, sci

admin2012-05-17  16
问题     The warming of the Arctic is releasing a new wave of banned toxic chemicals that had been trapped in the ice and cold water, scientists have discovered.
    The researchers warn that the amount of the poisons stored in the polar region is unknown and their release could "undermine global efforts to reduce environmental and human exposure to them."
    The chemicals leaking out as temperatures rise include DDT, lindane, chlordane, PCBs and HCBs. All of these persistent organic pollutants (Pops) are banned under the 2004 Stockholm Convention.
    Pops can cause cancers and birth defects and take a very long time to degrade (降解), meaning they can be transported for long distances and accumulate over time.
    Over past decades, the low temperatures in the Arctic trapped volatile (易挥发的) Pops in ice and cold water. But scientists in Canada and Norway have now discovered that global warming is freeing the Pops once again.
    They examined measurements of Pops in the air between 1993 and 2009 at the Zeppelin research station in Svalbaard and Alert weather station in northern Canada. After allowing for the decline in global emissions of Pops, the team showed that the toxic chemicals are being remobilised by rising temperatures and the retreat of the sea ice, which exposes more water to the Sun. For example, air concentrations of PCBs and HCBs have shown a rising trend from about 2004 onwards.
    Hayley Hung, a member of Environment Canada and of the team, said its work provided the first evidence of the releasing of Pops in the Arctic. "But this is the beginning of a story," she said. "The next step is to find out how much is in the Arctic, how much will leak out and how quickly." With the exception of lindane, there was little existing knowledge of the scale of the Pops stored in high latitude (纬度) regions.
    The fate of the frozen Pops depends on the speed of warming in the Arctic — it is currently heating up much more quickly than lower latitudes — as well as how the chemicals interact with snow and rain. Pops accumulate in fats and are therefore concentrated up the food chain, but Hung cautions that food chains themselves in the Arctic may be altered by climate change.
What do we learn about Pops from the passage?
选项 A、They pose a threat to marine life and humans.
B、They are substances that are easily degraded.
C、They can be found only in the polar region.
D、They will decrease in number if moving in the air.
答案A
解析 根据题干中的Pops将本题出处定位到第4段。该段提到，Pops(持久性有机污染物)会导致癌症和出生缺陷，而且降解需要非常长的时间……这些物质可以被运输到很远的地方，且时间一长会越积越多。根据Pops的危害可推断出，这些很难降解且会累积的Pops会对海生生物和人类造成威胁，故答案为[A]。[B]中的easily degraded与文中提到的take a very long time to degrade矛盾，故排除。文中提到这些物质可以被运输到很远的地方，也就是说，在其他地方也能找到这些物质，且根据常识也可知这些物质在其他地方也存在，故排除[C]。文中提到这些物质会随时间积累下来，也就是说在移动过程中会越积越多，[D]与之矛盾，故排除。
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