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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 (北极的) 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 the lead sources. The dominant lead ratio found in Greenland snow matched that found ingasoline from the United States.

In a study published in the journal Ambio, scientists found that 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 respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.

The study published in the journal Nature indicates that

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

B.lead deposits in arctic snow on the increase.

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

D.the U.S. is the major source of lead pollution in arctic snow.

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更多“Lead deposits, which acc…”相关的问题
第1题
Which of the following may lead to family quarrels according to the passage?A.Unawareness
Which of the following may lead to family quarrels according to the passage?
A.Unawareness of energy cycles.
B.Familiar monologues.
C.A change in a family member's energy cycle.
D.Attempts to control the energy cycle of other family members.
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第2题
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A、refers to

B、comes to

C、happens to

D、responds to

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第3题
Which of the following sentences is not hedged?()
A.TV violence appears to lead to real violence of young people.
B. This proves that TV violence causes juvenile delinquency.
C. Implications of these findings may be that it would be sensible to cut down on the portrayal of violence inTV programmes aimed at young people.
D. There might be a link between TV violence and real violence.

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第4题
According to the second paragraph, which of the following statements is not true?A.Jack We
According to the second paragraph, which of the following statements is not true?
A.Jack Welch believed large companies would be successful in the long run.
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第5题
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Nowadays, people are very busy. Often, both parents work outside the home. Children are expected to take on more responsibility at home to help their parents. They also have sporting and leisure activities as well as school expectations.
The busyness also adds another factor: the need to use cars to get from one place to another quickly.
Today, society places a lot of emphasis on technology. Computers, DVDs, CDs, television, PlayStations and Xboxes have become major leisure activities, rather than traditional more active pursuits. This has led to a more sedentary lifestyle.
The media provide entertainment and information. (79)Unfortunately, they also promote fast food which fits easily into busy lifestyles. It is much more convenient at times to buy a quick takeaway rather than prepare a meal. The media constantly bombard(轰炸) their audience with "perfect" body images, the need to buy the most fashionable clothes, the most up-to-date computer games, the best places to visit and the best things to do.
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Perhaps the important factor influencing healthy lifestyles is motivation, or the desire to be healthy. Any person who wants to be healthy will find a way to be healthy—if he/she is motivated enough!
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A.benefits of a healthy life style
B.demands of daily life
C.factors affecting a healthy lifestyle
D.a positive approach to healthy living
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第6题
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Sea resources are () declining in many parts of the world and the problem cannot be (). It is only () care and planning in this generation () the food () of the sea can continue () future generations.
1、A) on B) in C) at D) by
2、A) exhaustible B) inexhaustible C) vast D) uncountable
3、A) fact B) event C) evidence D) trend
4、A) that B) those C) which D) what
5、A) Furthermore B) Regardless of C) Fortunately D) In addition to
6、A) by the way B) under way C) in some ways D) to such an extent
7、A) many B) as C) much D) such
8、A) apply B) utilize C) organize D) depend on
9、A) for B) at C) in D) on
10、A) affects B) results C) effects D) significance
11、A) get B) breed C) consume D) devise
12、A) provide B) meet C) supply D) present
13、A) refer B) represent C) recognize D) reveal
11、A) by B) for C) in D) with
15、A) rapidly B) almost C) frequently D) effectively
16、A) considered B) adapted C) ignored D) acquired
17、A) with B) under C) in D) by
18、A) in which B) by which C) in this way D) that
19、A) deposits B) supplies C) components D) blocks
20、A) with B) by C) for D) on

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第7题
SmokingSince 1939, numerous studies have been conducted to determine whether smoking is a
Smoking
Since 1939, numerous studies have been conducted to determine whether smoking is a health hazard. The trend of the evidence has been consistent and indicates that there is a serious health risk. Research teams have conducted studies that show beyond all reasonable doubt that tobacco smoking is associated with a shortened life expectancy.
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A.Right
B.Wrong
C.Not mentioned
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第8题
What are the several steps of savings deposits?
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第9题
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According to the article, what contributes to the population increase?
A.Birth explosion.
B.Birth Control.
C.Technological innovations.
D.Death Control.
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第10题
根据下列材料,请回答下列各题: Passage One Questions 56 to 60 are based on the following passage. Living in a time when an ever-increasing number of news providers push a constant stream of headlines at us every day, people cannot say they do not feel overwhelmed. But what of its the ways we choose to read the news that make us feel overwhelmed? An interesting new study conducted by Avery Holton and Iris Chyi from the University of Texas looks at the factors that contribute to the concept of information overload. They surveyed more than 750 adults on their digital consumption habits and perceptions of information overload. What the findings suggest, Holton said, is that the news platforms a person is using can play a bigger role in making him feel overwhelmed than the sheer number of news sources being consumed. So even if you read The Huffington Post and The New York Times in a day, you may not feel as drowned with news ff you read on your phone instead of on your desktop. The more contained, or even constrained, aplat form. feels, the more it can contribute to people feeling less overwhelmed, Holton said. That may also explain why people have feelings of being overwhelmed by Facebook, which like reading on the web, can be a bottomless hole of stories, videos, and endless links. But it doesnt explain why people in the survey had different feelings towards Twitter, which can also be a stream of links. One possible explanation is whether you define yourself" as a news fan. The survey asked people to report. how much they enjoyed keeping up with the new——people who said they did had less of a perception of information overload. If youre the type of person who wants to follow news during the day, its likely you have an established routine and a set of sites you check regularly. You also may not need as much context around the news. All of that would make Twitter a good source for you. Conversely, if youre more passive about following the news, you might need to make more , of an effort to find the right sources or find background or contextual information, which could lead to feelings of being overloaded, Holton said. "Knowing what youre looking for can decrease overload or perceptions of overload. So can constant engagement," he said. The new study conducted by Avery Holton and Iris Chyi
A.examines how news providers take advantage of headlines
B.studies what can lead to the concept of information overload
C.discusses solutions for people who feel overwhelmed
D.reviews different attitudes to the digital consumption

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第11题
Culture is activity of thought, and receptiveness to beauty and humane feeling,【1】of information have nothing to do with it. A merely well-informed man is the most useless【2】on God's earth. What we should【3】at producing is men who【4】both culture and expert knowledge in some special direction. Their expert knowledge will give them the ground to start【5】, and their culture will lead them as【6】as philosophy and as high as【7】. We have to remember that the valuable【8】development is self-development, and that it【9】takes place between the ages of sixteen and thirty. As to training, the most important part is given by mothers before the age of twelve.
In training a child to activity of thought, above all things we must【10】of what I will call "inert ideas" —that is to say, ideas that are merely【11】into the mind without being【12】, or tested, or thrown into fresh combinations. In the history of educaton. the most【13】phenomenon is that schools of learning, which at one epoch are alive with a craze for genius, in a【14】generation exhibit merely pedantry and routine. The reason is that they are overladen with inert ideas. Except at【15】intervals of intellectual motivation, education in the past has been radically【16】with inert ideas. That is the reason why【17】clever women, who have seen much of the world, are in middle life so much the most cultured part of the community. They have been saved from this horrible【18】of inert ideas. Every intellectual revolution which has ever stirred humanity【19】greatness has been a【20】protest against inert ideas.
(1)
A.Chips
B.Scraps
C.Fractions
D.Plates

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