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Lead Pollution

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 worldwide 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 （北極的） 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 gasolines and thus enabled scientists to differentiate （區(qū)分）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（人類環(huán)境雜志），scientists found that lead levels in soil in the Northeastern 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（生態(tài)系統(tǒng)）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

A.the US is the major source of lead pollution in arctic snow.

B.the Clean Air Act has not produced the desired results.

C.lead will stay in soil and snow longer than expected.

D.lead deposits in arctic snow are on the increase.

正確答案：A

解析：問題問的是：自然雜志上刊登的研究表明什么？第二段開頭提到自然雜志上刊登的研究表明從產自美國通過空氣傳播的含鉛氣體排放是導致格陵蘭雪地中鉛濃度高的主要原因。而格陵蘭就是位于北極圈內。因此A正確，美國是北極雪中鉛污染的主要來源。

2.Lead accumulation worldwide decreased significantly after the use of unleaded gas in the US

A.was discouraged.

B.was prohibited by law.

C.was enforced by law.

D.was introduced.

正確答案：C

解析：美國法律強制使用無鉛汽油后，世界范圍的鉛金屬積累量明顯減少了。第一段最后一句話支持這一說法，注意，文中的“mandated”與C選項中的“enforced”意思相同，都是“強制”的意思。

3.How did scientists discover the source of lead pollution in Greenland

A.By analyzing the data published in journals like Nature and Ambio.

B.By comparing the chemical compositions of leaded gasoline used in various countries.

C.By observing the lead accumulations in different parts of the arctic area.

D.By studying the chemical elements of soil and snow in Northeastern America.

正確答案：B

解析：問題問的是：科學家是怎樣發(fā)現(xiàn)格陵蘭的鉛污染來源的？第三段提到科學家發(fā)現(xiàn)美國汽油中的各種鉛金屬比重不同于歐洲，亞洲和加拿大的。通過比較這些鉛比的不同判斷出格陵蘭雪中鉛污染主要來自美國。因此B正確。

4.The authors of the Ambio study have found that

A.forests get rid of lead pollution faster than expected.

B.lead deposits are widely distributed in the forests of the US.

C.lead accumulations in forests are more difficult to deal with.

D.the upper layers of soil in forests are easily polluted by lead emissions.

正確答案：A

解析：問題問的是：人類環(huán)境雜志研究的作者發(fā)現(xiàn)了什么？倒數(shù)第二段結尾提到森林環(huán)境處理鉛的速度之快超出科學家們的預期。因此A正確。

5.It can be inferred from the last paragraph that scientists

A.feel relieved by the use of unleaded gasoline.

B.are puzzled by the mystery of forest pollution.

C.lack sufficient means to combat lead pollution.

D.still consider lead pollution a problem.

正確答案：D

解析：問題問的是：通過最后一段能推測出什么？最后一段提到了兩項研究說明了某些生態(tài)系統(tǒng)對大氣污染的減少給出了快速的回應，但是這并不能作為進一步的污染行為的許可證。因此D正確，科學家們仍然認為鉛污染是個問題。