The Mega-City Environment

Mega-cities suffer from a catalog of environmental ills. A World Health Organization(WHO)/United Nations Environment Program(UNEP)study found that seven of the cities-Mexico City, Beijing, Cairo, Jakarta, Los Angeles, Sao Paulo and Moscow-had three or more pollutants that    1     the WHO health protection guidelines. All 20 of the cities studied by WHO/UNEP had at least one major pollutant that went beyond    2     health limits.

According to the World Resources Institute, “Millions of children living in the world’s largest cities, particularly in developing countries, are    3     to life-threatening air pollution two to eight times above the maximum based on WHO guidelines. Indeed, more than 80 percent of all deaths in developing countries    4     to air pollution-induced lung infections are among children under five.” In the big Asian mega-cities such as New Delhi, Beijing and Jakarta, approximately 20 to 30 percent of all respiratory diseases    5     from air pollution.

Almost all of the mega-cities face major fresh water challenges. Johannesburg, South Africa, is forced to draw water from highlands 370 miles away. In Bangkok, saltwater is invading aquifers(地下蓄水层). Mexico City has a serious    6     problem because of excessive groundwater withdrawal.

More than a billion people, 20 percent of the world’s population, live without regular    7     to clean running water. While poor people are forced to pay high fees for private water, many cities squander their resources through leakages and illegal    8    . “With the population of cities expected to increase to five billion by 2025,” says Klaus Toepfer, executive director of the UNEP, “the urban demand for water is set to increase rapidly. This means that any solution to the water crisis is closely linked to the governance of cities.“

Mega-city residents, crowded into unsanitary slums, are also subject to serious disease outbreaks. Lima, Peru(with population estimated at 9.4 million by 2015)suffered a cholera outbreak in the late 1990s partly because, as the New York Times reported, ”rural people new to Lima...live in houses without running water and use the outhouses(屋外厕所)that    9     the hillsides above.“

It’s worth looking at some of these    10     mega-cities in detail, because daily life there is likely to be the pattern for a majority of the world’s population. Most are already experiencing severe environmental problems that will only be worsened by rapid population increases.

The Inevitable Plastics Revolution

The Guardian once called plastic “Man’s worst invention”. One of the lesser-known uses of plastic is to reduce carbon emissions. For example, plastics make vehicles lighter thereby increasing their     1    ; it also increases the shelf life of foods, reducing food waste and the need to transport more. So plastics have an important role to play in creating a     2     future.

Currently that isn’t the case. Of the 24.5 million tons of plastic waste     3     in Europe each year, only 14 per cent is recycled. The rest is burned, buried or lost on land or at sea. Indeed, the European plastics industry emits 95 million tons of CO2 each year, about 3.7 per cent of total     4    . One-third of this comes from the burning of waste plastics.

That has to change, says Marc, one of the world’s leading chemicals and plastics manufacturers. “With a     5     population, we need to find a way to make better use of our resources.” In     6     with the recycling technology company, Mura Technology, it wants to     7     the plastics economy by dramatically increasing the amount of plastic that is recycled while also reducing carbon emissions. The approach will change the way we make plastic.

Today most plastic is made from petrochemicals, using processes     8     by fossil fuels. While a great deal is thrown away, a large proportion of plastics waste can be collected and sent to be     9     recycled. This involves washing, drying and grinding the material, then heating and     10     it into a new product. But at no stage is the chemical structure of the plastic changed. In order to reduce pollution, the plastics manufacturing sector needs technological innovation.

Boyan Slat has one huge goal. It’s a goal that could be good for people and animals all over the world.     1    , it looks like he’s going to meet his goal.

When he was 16. Dutch engineering student Slat was on vacation in Greece, and he started to think about all the rubbish that is pushed onto beaches by water. The oceans around the world are all of plastic—millions of tons of plastic.     2    , plastic doesn’t just disappear. It takes centuries to break down.

The present     3     of the oceans is bad and worrying, and Slat wanted to do something to change it. So he made it a personal goal to clean up the rubbish in the world’s oceans.

Slat started with an idea for an unusual machine to “catch” the plastic floating(漂浮)in the water using the     4     energy of the ocean. He left school in 2013 to begin work     5     his project The Ocean Cleanup. Soon, the project received a lot of attention.

A year later, Slat was named a “Champion of the Earth” by the United Nations for his valuable work.

Pollution is our great     1    . Pollution from     2     is a danger to our health, and may even     3     people. Factories sometimes pollute the rivers, and farmers cannot use the water for their crops. Pollution     4     over cities and villages, and that     5     even more danger. Cars use a lot of oil and cause pollution, too.

A Plastic Ocean a film to make you think. Think, and then act. We need to     1     on plastic. We've been     2     plastic in huge quantities since the 1940s. We live in a world full of plastic, and only a small part is     3     . What happens to all the rest? This is the question the film A Plastic Ocean answers. It is a documentary that looks at the impact that plastic waste has on the     4     .

The film begins as a journey to film the largest animal on the planet, the blue whale. But during the journey the filmmakers make the     5     discovery of a huge,     6     layer（层）of plastic floating in the middle of the Indian Ocean. This causes them to travel around the world to look at other areas that have been     7    . We see how marine species are being killed by all the plastic we are dumping in the ocean. The message about our use of plastic is     8     obvious.

But the film doesn't only present the     9     side. In the second half, the filmmakers look at what we can do to reverse the tide of plastic flowing around the world. They present short-term and long-term     10    . These include avoiding plastic containers and * single-use5 plastic products as much as possible.

Clean Air Act

The air in modern homes and offices is pretty clean,but not as clean as it might be.Often it contains small amounts of volatile(挥发性的）,poisonous,organic compounds.Long-term    1     to these is a bad thing,so clearing them out of the air people breathe is widely accepted as     2    

Finding an effective way to do so has proved difficult.But Stuart Strand, Long Zhang and Ryan Routsong, of the University of Washington,in Seattle,think they have succeeded,As they report in Environmental Science and Technology, their method involves     3     a gene from a rabbit into a popular indoor plant nicknamed Devil's vine—a type of ivy hat is so called because it is    4     difficult to kill.

The idea of     5     plants to de- pollute   the atmosphere inside buildings has been around for decades-but has met with only qualified success. One experiment involving unmodified spider plants,for example,showed that they are indeed     6     of removing formaldhyde (甲醛) from the air.The     7     is that to make much of a difference in a space as large as a house would require turning most of the rooms into spider-plant forests.

Dr Strand, Dr Zhang and Mr Routsong thus sought something suitably transgenic ( 转 基 因 的),but that does not flower indoors. The plant they settled on was Devil's vine,     8     because of its toughness.With the help of a bacterium,they were able to ferry the rabbit version of the gene into the plant's chromosomes(染色 体),and thus to,engineer a type of Devil's vine able to produce an air-cleaning substance. To test the     9     of their idea, the researchers put their modified ivy to work inside greenhouses filled with air containing high levels of harmful substances.The plants performed well,reducing the harmful substances in air to     10    .