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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

admin2012-02-29  51
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 is said about the warming in the Arctic?
选项 A、Human activities have sped it up.
B、It may change the food chains.
C、It is affected by the release of the Pops.
D、It happened earlier than other regions.
答案B
解析 根据题干中的warming in the Arctic将本题出处定位到末段。该段提到，这些被冻结的持久性有机污染物的发展情况取决于北极地区变暖的速度……持久性有机污染物会累积在脂肪中，因此最终会集中在食物链中……北极地区的食物链本身可能会被气候变化改变。由此可知，北极地区的气候变暖会影Ⅱ向持久性有机污染物在食物链中的集中，从而可能会改变食物链，故答案为[B]。文中提到该地区变暖的速度远远快于低纬度地区，但是未提及是Human activities加速该地区变暖的，故排除[A]。北极地区气候变暖使Pops被释放出来，而不是Pops的释放影响气候变暖，[C]颠倒二者之间的因果关系，故排除。该地区变暖的速度快于低纬度地区并不能说明该地区的气候变暖比其他地区早，故排除[D]。
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