Lead deposits, which accumulated in soil and snow during the 1960's and 70's, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation world-wide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasoline and thus enabled scientists to differentiate the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the North-eastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990.
The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
1. The study published in the journal. Nature indicates that（ ）.
2. Lead accumulation worldwide decreased significantly after the use of unleaded gas in the US（ ）.
3. How did scientists discover the source of lead pollution in Greenland?
4. The authors of the Ambio study have found that（ ）.
5. It can be inferred, from the last paragraph that scientists（ ）.
问题1选项
A.the Clean Air Act has not produced the desired results
B.lead deposits in arctic snow are on the increase
C.lead will stay in soil and snow longer than expected
D.the US is the major source of lead pollution in arctic snow
问题2选项
A.was discouraged
B.was enforced by law
C.was prohibited by law
D.was introduced
问题3选项
A.By analyzing the data published in journals like Nature and Ambio.
B.By observing the lead accumulations in different parts of the arctic area.
C.By studying the chemical elements of soil and snow in Northeastern America.
D.By comparing the chemical compositions of leaded gasoline used in various countries.
问题4选项
A.forests get rid of lead pollution faster than expected
B.lead accumulations in forests are more difficult to deal with
C.lead deposits are widely distributed in the forests of the US
D.the upper layers of soil in forests are easily polluted by lead emissions
问题5选项
A.are puzzled by the mystery of forest pollution
B.feel relieved by the use of unleaded gasoline
C.still consider lead pollution, a problem
D.lack sufficient means to combat lead pollution
第1题:D
第2题:B
第3题:D
第4题:A
第5题:C
细节事实题。由题干定位到第二段"A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland." 最近发表在《自然》（Nature）杂志上的一项研究表明，美国通过空气传播的含铅气体排放是导致格陵兰雪中铅含量高的主要原因。可知该研究表明美国是到导致北极雪中铅污染的主要来源。D项正确。B项与“A study by Dr. Boutron published in 1991 showed that lead levels in arctic snow were declining.”不符。AC两项内容与该研究无关。答案D。
细节事实题。根据题干定位到第一段“In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation world-wide has decreased significantly.” 在《清洁空气法》强制要求美国使用无铅气体的二十年里，全世界的铅积累量已显著下降。可知对美国使用无铅气体是法律的强制要求。B项正确。
判断推理题。根据题干定位到文中第三段“In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasoline and thus enabled scientists to differentiate the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.” “在他的新研究中，布隆博士发现美国使用的含铅汽油中不同形式的铅的比例与欧洲、亚洲和加拿大的汽油不同，因此科学家能够区分铅的来源。在格陵兰雪中发现的主要铅含量与在美国汽油中发现的铅含量相当。”由此可知科学家通过将美国含铅汽油中的化学成分与其他国家的对比，找到了格林兰雪中铅的来源。D项正确。
细节事实题。由题干定位到倒数第二段“The forest environment processed and redistributed the lead faster than the scientists had expected. 森林环境处理和重新分配铅的速度比科学家预期的要快。”可知A项正确。
判断推理题。由最后一段“Scientists say both studies demonstrate that certain parts of the ecosystem respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute. 科学家们说，这两项研究都表明，生态系统的某些部分对大气污染的减少做出了迅速反应，但这些发现不应被用作污染的许可证。”可知虽然大气污染减少后，生态系统也作出了相应快速积极的反应，但是科学家仍然认为不能抱有侥幸心理，应该仍然控制污染。故C项正确。
