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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  19
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.
By "the toxic chemicals are being remobilised" (Line 3, Para. 6), the author means that the Pops
选项 A、are taking in the form of ice or water
B、are becoming more and more poisonous
C、are able to move easily and quickly in the water
D、are no longer trapped in the ice and cold water
答案D
解析 根据题干中的remobilised将本题出处首先定位到第6段第2句。该句提到，……在气候变暖和海洋冰面消退……的影响下，the toxic chemicals are being remobilised(被冻结的有毒化学物质正在复苏)。通过观察发现，这里提到的具体事例是为说明第5段提到的“北极地区的低温把具有挥发性的这些Pops冻结封存在冰层和冰冷的海水中…一全球变暖正在把这些Pops再次释放出来”，由此可知，第6段第2句说的是气候变暖使Pops被释放出来，即不再被困在冰层和冰冷的海水中了，故答案为[D]。
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