VOA慢速英语-SCIENCE IN THE NEWS - 'Dead Zones' Expand in Coastal

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty¹.

VOICE TWO:

And I'm Faith Lapidus. This week, we will tell about two studies. Both involve the world's oceans. One study examined the health of coastal² waters for fish and other sea life. The other study examined the quality of air in coastal cities.

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VOICE ONE:
　
A device is used to measure the amount of oxygen in the Pacific Ocean off the coast of Oregon in a 2006 photo

A recent study has raised serious questions about the health of the world's coastal waters. Coastal waters are important feeding grounds for fish and other sea life. But the waters of many coastal areas are being starved of oxygen. The result is that increasingly large areas of ocean are becoming "dead zones" with almost no sea life.

Robert Diaz was the lead writer of the study. He says historically good fishing areas are becoming dead zones. Mister Diaz is a professor at the Virginia Institute of Marine³ Science at the College of William and Mary. He worked with Rutger Rosenberg of the University of Gothenburg in Sweden. Their study appeared last month in Science, a publication of the American Association for the Advancement⁴ of Science.

VOICE TWO:

The scientists found that an increasing amount of chemical nutrients⁵ have been entering coastal waters. The nutrients are mainly nitrogen and phosphorus. They come from crop fertilizers and wastewater that pollute streams and rivers, which flow to the sea.

Nitrogen can also come from the atmosphere. Agriculture, the burning of fossil fuels and natural processes can produce nitrogen compounds. For example, nitrous oxide⁶ is a gas linked to climate change. Nitrogen then enters the ocean through rainfall and other atmospheric⁷ processes. Mister Diaz says one fourth of the nitrogen affecting coastal areas comes from the atmosphere.

VOICE ONE:

The nutrients cause an explosion in populations of phytoplankton, small organisms that use light to make food. Phytoplankton create oxygen on their own. But as they die, they sink to bottom waters where bacteria break down the organisms.

The bacteria use up oxygen in the water. This creates areas at the bottom of coastal waters that have little or no dissolved oxygen. Fish, crabs⁹ and other sea life cannot live in water that lacks oxygen. They must either move to more oxygenated waters or die.

VOICE TWO:

Sometimes the oxygen level in the water drops so quickly that it kills all sea life. Professor Diaz tells VOA this happened near the coast of New York in nineteen seventy-six. The damage to the coastal fishing industry was estimated at five hundred million dollars.

The study shows that the problem of oxygen-poor water or hypoxia is growing every year. Professor Diaz began studying dead zones in the nineteen eighties. He has found that the number of dead zones around the world has doubled every ten years since the nineteen sixties.

The study found more than four hundred dead zones around the world. They affect more than two hundred forty-five thousand square kilometers of ocean.

VOICE ONE:

Dead zones are generally seasonal¹⁰. They increase in size during the warm summer months when there is more light for phytoplankton and algae¹¹. But after becoming dead zones, it is very difficult for coastal waters to regain¹² good levels of oxygen. Some areas, such as parts of the Baltic Sea, have become permanent dead zones.

The Gulf¹³ of Mexico has a huge dead zone extending from the mouth of the Mississippi River. It has doubled in size in the past twenty years to about twenty-two thousand square kilometers. Hypoxic waters in the Gulf threaten an important shrimp¹⁴ and crab⁸ fishing industry.

Close to Washington, D.C., up to forty percent of the bottom waters of the Chesapeake Bay become a dead zone in the summer.

VOICE TWO:

The world's largest dead zone is in the Baltic Sea. Professor Diaz says about half of the Baltic dead zone contains no oxygen. This creates another problem. Different bacteria live in water that completely lacks dissolved oxygen. They are known as anaerobic¹⁵ bacteria because they do not need oxygen to live. Some of these bacteria produce poisonous hydrogen sulfide gas.

Professors Diaz and Rosenberg say no other environmental problem facing coastal waters has changed so much over such a short period of time. They say the only way to reduce dead zones is to keep fertilizers on the land and out of the sea. They say it is important that scientists and farmers work together to find ways to reach this goal.

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VOICE ONE:

You are listening to SCIENCE IN THE NEWS, a program in VOA Special English. With Faith Lapidus, I'm Bob Doughty in Washington.

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Coastal cities are often considered good places to live. When many people think of such cities, they think of healthful, fresh air from the sea. But scientists at the University of California at San Diego found that this idea can be far from correct.

A report on the subject recently was published in Proceedings¹⁶ of the National Academy of Sciences. University of California Professor Mark Thiemens led the research team. His team's report blames ships that release dirty smoke by burning low-cost, high-sulfur¹⁷ fuel. The report says both ships at sea and those using their engines in port to produce electricity are to blame.

VOICE TWO:

The researchers worked at the Scripps Institution of Oceanography in La Jolla, California. They directly measured smoke released from the smokestack of a ship. They also tested air at the end of the Scripps Pier¹⁸. The area is just north of San Diego, which is both a major city and port. The Scripps Pier is also close to waters with heavy shipping¹⁹ traffic and the city of Los Angeles. Los Angeles has the third largest port in the world.

Primary sulfate is produced when a ship burns fuel called bunker oil. Bunker oil contains a large amount of sulfur. Most sulfur released by ships burning bunker oil is a gaseous²⁰ pollutant²¹ -- sulfur dioxide. After a time, sulfur dioxide becomes sulfate in the atmosphere. The researchers say this primary sulfate may be only a small part of what ships produce.

VOICE ONE:

The researchers found that ship smoke could cause up to forty-four percent of the sulfate particulates²² found in coastal California's atmosphere. They say the levels rose to nearly fifty percent on days when ships burning high sulfur fuel in the nearby ports were a major influence.

Professor Thiemens said no one had really expected that ships would be responsible for so many particulates. He said the extremely small particles are especially threatening. They measure only one and one half microns in size. A micron is one millionth of a meter.

The researchers say the particulates can travel long distances because they stay in the atmosphere longer than other pollutants²³. Professor Thiemens noted²⁴ that the air of Los Angeles influenced air quality in San Diego. That distance is almost one hundred eighty kilometers.

VOICE TWO:

Primary sulfur particulates also can threaten human health. When people breathe, the particulates stay in their lungs. Other scientists have said that up to sixty thousand people around the world die each year from dirty ship smoke.

Gerardo Dominguez was a lead writer of the report. He developed a chemical test that showed differences between ship smoke and gases from trucks, cars and other causes. The researchers also used another test that let them identify sulfur molecules²⁵ in the atmosphere. Professor Thiemens had developed that method earlier.

VOICE ONE:

Other pollutants from ships include nitrogen oxide and carbon dioxides. Earlier this year, a United Nations report said gases from ships produce more than one billion tons of carbon dioxide every year. Ships are not governed under the Kyoto Protocol²⁶, the agreement that establishes limits for gases linked to climate change. But international rules requiring ship fuels that burn cleanly are to become effective in twenty fifteen.

The state of California has already approved new fuel requirements. They are to begin next July. All tankers²⁷, supply and passenger ships will have to use cleaner-burning fuels within forty kilometers of the coast.

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VOICE TWO:

This SCIENCE IN THE NEWS program was written by Mario Ritter and Jerilyn Watson. Our producer was Brianna Blake. I'm Faith Lapidus.

VOICE ONE:

And I'm Bob Doughty. Read and listen to our programs at voaspecialenglish.com. Join us again at this time next week for more news about science in Special English on the Voice of America.

 

1 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。

2 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

3 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

4 advancement   

n.前进，促进，提升

参考例句：

• His new contribution to the advancement of physiology was well appreciated.他对生理学发展的新贡献获得高度赞赏。
• The aim of a university should be the advancement of learning.大学的目标应是促进学术。

5 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

6 oxide   

n.氧化物

参考例句：

• Oxide is usually seen in our daily life.在我们的日常生活中氧化物很常见。
• How can you get rid of this oxide coating?你们该怎样除去这些氧化皮？

7 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

8 crab   

n.螃蟹，偏航，脾气乖戾的人，酸苹果；vi.捕蟹，偏航，发牢骚；vt.使偏航，发脾气

参考例句：

• I can't remember when I last had crab.我不记得上次吃蟹是什么时候了。
• The skin on my face felt as hard as a crab's back.我脸上的皮仿佛僵硬了，就象螃蟹的壳似的。

9 crabs   

n.蟹( crab的名词复数 )；阴虱寄生病；蟹肉v.捕蟹( crab的第三人称单数 )

参考例句：

• As we walked along the seashore we saw lots of tiny crabs. 我们在海岸上散步时看到很多小蟹。 来自《简明英汉词典》
• The fish and crabs scavenge for decaying tissue. 鱼和蟹搜寻腐烂的组织为食。 来自《简明英汉词典》

10 seasonal   

adj.季节的，季节性的

参考例句：

• The town relies on the seasonal tourist industry for jobs.这个城镇依靠季节性旅游业提供就业机会。
• The hors d'oeuvre is seasonal vegetables.餐前小吃是应时蔬菜。

11 algae   

n.水藻，海藻

参考例句：

• Most algae live in water.多数藻类生长在水中。
• Algae grow and spread quickly in the lake.湖中水藻滋蔓。

12 regain   

vt.重新获得，收复，恢复

参考例句：

• He is making a bid to regain his World No.1 ranking.他正为重登世界排名第一位而努力。
• The government is desperate to regain credibility with the public.政府急于重新获取公众的信任。

13 gulf   

n.海湾；深渊，鸿沟；分歧，隔阂

参考例句：

• The gulf between the two leaders cannot be bridged.两位领导人之间的鸿沟难以跨越。
• There is a gulf between the two cities.这两座城市间有个海湾。

14 shrimp   

n.虾，小虾；矮小的人

参考例句：

• When the shrimp farm is built it will block the stream.一旦养虾场建起来，将会截断这条河流。
• When it comes to seafood,I like shrimp the best.说到海鲜，我最喜欢虾。

15 anaerobic   

adj.厌氧的

参考例句：

• Anaerobic respiration occurs only in particularly active tissues such as muscles during severe exercise. 厌氧呼吸只有在处于剧烈运动状态的肌肉等特别活跃的组织中才会发生。
• Infection,especially anaerobic infection, is much more apt to occur.感染，特别是厌氧感染很容易发生。

16 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

17 sulfur   

n.硫，硫磺（=sulphur）

参考例句：

• Sulfur emissions from steel mills become acid rain.炼钢厂排放出的硫形成了酸雨。
• Burning may produce sulfur oxides.燃烧可能会产生硫氧化物。

18 pier   

n.码头；桥墩，桥柱；[建]窗间壁，支柱

参考例句：

• The pier of the bridge has been so badly damaged that experts worry it is unable to bear weight.这座桥的桥桩破损厉害，专家担心它已不能负重。
• The ship was making towards the pier.船正驶向码头。

19 shipping   

n.船运（发货，运输，乘船）

参考例句：

• We struck a bargain with an American shipping firm.我们和一家美国船运公司谈成了一笔生意。
• There's a shipping charge of ￡5 added to the price.价格之外另加五英镑运输费。

20 gaseous   

adj.气体的，气态的

参考例句：

• Air whether in the gaseous or liquid state is a fluid.空气，无论是气态的或是液态的，都是一种流体。
• Freon exists both in liquid and gaseous states.氟利昂有液态和气态两种形态。

21 pollutant   

n.污染物质，散布污染物质者

参考例句：

• Coal itself is a heavy pollutant.煤本身就是一种严重的污染物。
• Carbon dioxide may not be a typical air pollutant.二氧化碳可能不是一种典型的污染物。

22 particulates   

n.微粒，粒子( particulate的名词复数 )

参考例句：

• Techniques for controlling particulates include filtering, washing, centrifugal separation, and electrostatic precipitation. 控制颗粒污染物的技术包括过滤、洗涤、离心分离、静电沉降。 来自英汉非文学 - 环境法 - 环境法
• Only micronic particulates penetrate to the depth of the lung. 只有微细粒子穿透到肺深部。 来自辞典例句

23 pollutants   

污染物质（尤指工业废物）( pollutant的名词复数 )

参考例句：

• Pollutants are constantly being released into the atmosphere. 污染物质正在不断地被排放到大气中去。
• The 1987 Amendments limit 301(g) discharges to a few well-studied nonconventional pollutants. 1987年的修正案把第301条（g）的普通排放限制施加在一些认真研究过的几种非常规污染物上。 来自英汉非文学 - 环境法 - 环境法

24 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

25 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

26 protocol   

n.议定书，草约，会谈记录，外交礼节

参考例句：

• We must observe the correct protocol.我们必须遵守应有的礼仪。
• The statesmen signed a protocol.那些政治家签了议定书。

27 tankers   

运送大量液体或气体的轮船[卡车]( tanker的名词复数 )； 油轮； 罐车； 油槽车

参考例句：

• They should stop offloading waste from oil tankers into the sea. 他们应当停止从油轮上往海里倾倒废弃物。
• The harbour admits large tankers and freighters. 这个港口容得下巨型油船和货轮。