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  3. Many people consider the wider use of biofuels a promising way of reducing the amount of surplus carbon dioxide (CO2n) being pum

Many people consider the wider use of biofuels a promising way of reducing the amount of surplus carbon dioxide (CO2n) being pum

admin2011-02-25  54
问题     Many people consider the wider use of biofuels a promising way of reducing the amount of surplus carbon dioxide (CO2n) being pumped into the air by the world’s mechanized transport. The theory is that plants such as sugar cane, maize (corn, to Americans), oilseed rape and wheat take up CO2 during their growth, so burning fuels made from them should have no net effect on the amount of that gas in the atmosphere.
    Theory, though, does not always translate into practice, and just as governments have committed themselves to the greater use of biofuels, questions are being raised about how green this form of energy really is. The latest comes from the International Council for Science (ICSU) based in Paris.
    The ICSU report concludes that, so far, the production of biofuels has aggravated rather than ameliorated global warming. In particular, it supports some controversial findings published in 2007 by Paul Crutzen of the Max Planck Institute for Chemistry in Germany. Dr. Crutzen concluded that most analyses had underestimated the importance to global warming of a gas called nitrous oxide (N2nO). The amount of this gas released by farming biofuel crops such as maize and rape probably negates by itself any advantage offered by reduced emissions of CO2n.
    Although N2nO is not common in the Earth’s atmosphere, it is a more potent greenhouse gas than CO2n and it hangs around longer. The result is that, over the course of a century, its ability to warm the planet is almost 300 times that of an equivalent mass of CO2n.
    N2nO is made by bacteria that live in soil and water and, these days, their raw material is often the nitrogen-rich fertiliser that modern farming requires. Since the 1960s the amount of fertiliser used by farmers has increased sixfold, and not all of that extra nitrogen ends up in their crops. Maize, in particular, is described by experts in the field as a “nitrogen-leaky” plant because it has shallow roots and takes up nitrogen for only a few months of the year. This would make maize (which is one of the main sources of biofuel) a particularly bad contributor to global N2nO emissions.
    But it is not just biofuels that are to blame. The ICSU report suggests N2nO emissions in general are probably more important than had been realised. Previous studies, including those by the International Panel on Climate Change (IPCC), a United Nations-appointed body of experts, may have miscalculated their significance — and according to Adrian Williams of Cranfield University, in Britain, even the IPCC’s approach suggests that the global-warming potential of most of Britain’s annual crops is dominated by N2nO emissions.
Scientists realize that maize
选项 A、contributes little to global N2nO emissions.
B、absorbs nitrogen very efficiently in crops.
C、is largely responsible for the surplus N2nO.
D、may experience a bad harvest for bacteria.
答案C
解析 事实细节题。由题干关键词scientists， maize将信息定位于倒数第二段后两句。由该处可知，玉米是一种“漏氨”的作物，它是N2nO排放的一大罪魁祸首。故 [C]正确。[A]与[C]相反，故错误；[B]也与原文中“漏氨”的说法矛盾，故错误；[D]“可能因为细菌而歉收”，原文未提及。
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