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Scientists in Israel have discovered a new way to test for water pollution by "listening" to what the plants growing in water have to say．By shining a laser beam(激光束) on the tiny pieces of algae(海藻) floating in the water, the researchers said they hear sound waves that tell them the type and amount of pollution in the water．
"It is a red light, telling us that something is beginning to go wrong with the quality of water," said Zvy Dubinsky, an aquatic biologist at Israel's Bar Ilan University．"Algae is the first thing to be affected by a change in water quality．"
As water sources deteriorate worldwide, the testing of algae could be used to monitor water quality faster, more cheaply and more accurately than techniques now in use, Dubinsky said．The secret is to measure the rate of photosynthesis(光合作用) in the algae, meaning the plant's ability to transform light into energy．During photosynthesis, plants also release oxygen into the air．
Dubinsky's technique is easy to perform because of the over-abundance of algae in the planet's water．Most of the oxygen in the atmosphere comes from algae．A prototype tester shoots a laser beam at water samples to stimulate photosynthesis in the algae．But not all of the laser's heat is used．
Depending on the condition of the algae and the rate of photosynthesis, some of the heat is shot back into the water, creating sound waves, Dubinsky said．With a special underwater microphone, researchers are able to analyze the strength of the sound waves and determine the health of the algae and the condition of the surrounding water．
"Algae suffering from lead poisoning, like waste discharged from battery and paint manufacturing plants, will produce a different sound than those suffering from lack of iron or exposure to other toxins," said researcher Yulia Pinchasov．
72．To study water quality, scientists choose algae mainly because ．
A．algae is most easily affected by pollution
B．most oxygen is produced by algae
C．the amount of algae is decreasing
D．algae is a kind of plant floating in the water
73．When Dubinsky studied water quality, he mainly focused on ．
A．the amount of laser used by algae
B．the rate of photosynthesis in the algae
C．the condition of the algae
D．the heat of laser used by algae
74．After the study, scientists proved that ．
A．the increase in population is caused by lack of water
B．global warming causes water resources to reduce worldwide
C．algae can show the type and amount of pollution in the water
D．algae is dying out in the ocean around the world
75．What would be the most suitable title for the passage?
A．Water pollution is reduced with the growth of algae
B．Pollution makes it hard for plants to make photosynthesis
C．Water pollution affects the growth of marine plants
D．Scientists listen to plants to find pollution
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Scientists in Israel have discovered a new way to test for water pollution by “listening” to what the plants growing in water have to say.
By shining a laser beam (激光束) on the tiny pieces of algae floating in the water，the researchers said they hear sound waves that tell them the type and amount of contamination (致污物) in the water.
“It is a red light，telling us that something is beginning to go wrong with the quality of water，” said Zvy Dubinsky，an aquatic biologist at Israel’s Bar Ilan University.“Algae is the first thing to be affected by a change in water quality.”“The secret，” he said，“is to measure the rate of photosynthesis (光合作用) in the algae，meaning the plant’s ability to transform light into energy.” During photosynthesis，plants also release oxygen into the air.
Dubinsky’s technique is easy to perform because of the over?abundance of algae in the planet’s water.Most of the oxygen in the atmosphere comes from algae.A prototype tester that occupies about one square meter of a laboratory desktop，shoots a laser beam at water samples to stimulate photosynthesis in the algae.But not all of the laser’s heat is used.Depending on the condition of the algae and the rate of photosynthesis，some of the heat is shot back into the water，creating sound waves，Dubinsky said.With a special underwater microphone，researchers are able to analyze the strength of the sound waves and determine the health of the algae and the condition of the surrounding water.
“Algae suffering from lead poisoning，like waste discharged from battery and paint manufacturing plants，will produce a different sound than those suffering from lack of iron or exposure to other toxins，” said researcher Yulia Pinchasov.She said that testing algae photosynthesis can determine water quality more accurately and easily than labor?intensive methods now used like chemical and radioactive carbon testing.
1.The underlined word “algae” in Paragraph 2 probably refers to a kind of________.
A．instrument? B．plant
C．wood? D．pollutant
2.Why is the algae tested?
A．Because it floats on the water.
B．Because it can have photosynthesis.
C．Because it is the first to be polluted.
D．Because it can produce different sounds.
3.We can infer from the passage that________.
A．algae can produce a loud sound when polluted
B．algae can die easily from pollution
C．photosynthesis of the algae can only be caused by sunlight
D．photosynthesis of the algae is related to water quality
4.What would be the best title for the passage?
A．Scientists Listen to Plants to Find Water Pollution
B．A Prototype Tester Is Used to Determine Water Pollution
C．The Importance of Photosynthesis of the Algae
D．The Problem of Chemical and Radioactive Carbon Testing
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Laser(激光)is short for Light Amplification by Stimulated Emission of Radiation．Laser light is different from daylight or electric lights．Industry put lasers to work almost immediately after they were invented in nineteen sixty． 1 ．
The first medical operation using a laser took place the year following its invention．Doctors Charles Campbell and Charles Koester used a laser to remove a tumor from a patient's eye at Columbia-Presbyterian Hospital in New York City． 2 ．
Lasers have made measurement an exact science．Astronomers have used lasers to measure the moon's distance from Earth． 3 ．For example, drawing a perfectly level straight line on a construction site is easy using a laser．
4 ．And the jewelry industry uses lasers to write on the surface of the world's hardest substance, diamonds．
Lasers are found in many products used almost everywhere．Over one hundred years ago, writers imagined that beams of light could be powerful weapons．Today, lasers guide missiles and bombs．American defense companies are working on giant laser guns recognizable to science fiction fans everywhere． 5 ．
Scientific American magazine says huge lasers turn only about twenty to thirty percent of the energy they use into a laser beam．The rest is lost as heat．
That has not stopped scientists from working to perfect powerful lasers that, one day, may be able to shoot missiles out of the sky．
A．But weapons were not the first to use it on the list．
B．All lasers have several things in common．
C．Mappers and builders use laser technology every day．
D．But there are technological difficulties．
E．Lasers have also changed the way we communicate．
F．Manufacturers have used lasers for years to cut and join metal parts．
G．Since then, doctors have used lasers to cut and remove tissue safely with little risk of infections．
Most people know precious gemstones (宝石) by their appearances. An emerald flashes deep green, a ruby seems to hold a red fire inside, and a diamond shines like a star. It’s more difficult to tell where the gem was mined, since a diamond from Australia or Arkansas may appear the same to one from the Democratic Republic of the Congo. However, recently, a team of scientists has found a way to identify a gemstone’s origin.
Beneath the surface of a gemstone, on the tiny level of atoms and molecules（分子）, lie clues (线索) to its origin. At this year’s meeting of the Geological Society of America in Minneapolis, Catherine McManus reported on a technique that uses lasers (激光) to clarify these clues and identify a stone’s homeland. McManus directs scientific research at Materialytics, in Killeen, Texas. The company is developing the technique. “With enough data, we could identify which country, which mining place, even the individual mine a gemstone comes from,” McManus told Science News.
Some gemstones, including many diamonds, come from war-torn countries. Sales of those “blood minerals” may encourage violent civil wars where innocent people are injured or killed. In an effort to reduce the trade in blood minerals, the U.S. government passed law in July 2010 that requires companies that sell gemstones to determine the origins of their stones.
To figure out where gemstones come from, McManus and her team focus a powerful laser on a small sample of the gemstone. The technique is called laser-induced breakdown spectroscopy. Just as heat can turn ice into water or water into steam, energy from the laser changes the state of matter of the stone. The laser changes a miniscule part of the gemstone into plasma, a gas state of matter in which tiny particles（微粒）called electrons separate from atoms.
The plasma, which is superhot, produces a light pattern. (The science of analyzing this kind of light pattern is called spectroscopy.) Different elements（元素）produce different patterns, but McManus and her team say that gemstones from the same area produce similar patterns. Materialytics has already collected patterns from thousands of gemstones, including more than 200 from diamonds. They can compare the light pattern from an unknown gemstone to patterns they do know and look for a match. The light pattern acts like a signature, telling the researchers the origin of the gemstone.
In a small test, the laser technique correctly identified the origins of 95 out of every 100 diamonds. For gemstones like emeralds and rubies, the technique proved successful for 98 out of every 100 stones. The scientists need to collect and analyze more samples, including those from war-torn countries, before the tool is ready for commercial use.
Scientists like Barbara Dutrow, a mineralogist from Louisiana State University in Baton Rouge, find the technique exciting. “This is a basic new tool that could provide a better fingerprint of a material from a particular locality,” she told Science News.
1.We learn from Paragraph 1 that __________________.
A. an emerald and a ruby are names of diamonds.
B. it’s not difficult to tell where the gem was mined.
C. appearances help to identify the origin of gemstones.?
D. diamonds from different places may appear the same.
2.Why did the U.S. government pass law that requires companies selling gemstones to determine the origins of their stones?
A. To look for more gemstones.?????????????
B. To encourage violent civil wars.
C. To reduce the trade in blood minerals.??????
D. To develop the economy.
3.Which of the following facts most probably helps McManus and her team in identifying the origin of stones?
A. Heat can turn ice into water or water into steam.
B. Gemstones from the same area produce similar light patterns.
C. Laser can changes a miniscule part of the gemstone into plasma.
D. Materialytics has already collected patterns from thousands of gemstones.
4.From the last two paragraphs, what can be inferred about the laser technique?
A. It is ready for commercial use.
B. People can use the new tool to find more gemstones.
C. It can significantly reduce the gemstones trade in blood minerals.
D. It will bring about a revolutionary change in identifying the origin of minerals.
5.The author wrote this passage mainly to ________.
A. tell us how to identify the origin of diamonds.
B. introduce a laser technique in identifying a stone’s origin
C. prove identifying the origin of gemstones are difficult
D. attract our attention to reducing trade in blood minerals
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