As a result of pollution, Lake Erie, on the borders of the USA and Canada, is now without any living things. Pollutions in water are not simply a matter of “poisons” killing large numbers of fish overnight. Very often the effects of pollution are not noticed for many months or years because the first organisms to be affected are either plants or plankton. But these organisms are the food of fish and birds and other creatures. When this food disappears, the fish and birds die in this way a whole food chain can be wiped out, and it is not until dead fish and water birds are seen at the river’s edge or on the sea shore that people realize what is happening. Where do the substances which pollute the water come from? There are two main sources – sewage and industrial waste. As more detergent is used in the home, so more of it is finally put into our rivers, lakes and seas. Detergents harm water birds dissolving the natural substance which keep their feather waterproof. Sewage itself, if it is not properly treated, makes the water dirty and prevents all forms of life in rivers and the sea from receiving the oxygen they need. Industrial waste is even more harmful since there are many high poisonous things in it, such as copper and lead. So, if we want to stop this pollution, the answer is simple, sewage and industrial waste must be made clean before flowing into the water. It may already be too late to save some rivers and lakes, but others can still be saved if the correct action is taken at once.

Pollution in water is noticed .............

Câu hỏi liên quan

• What is the main idea of this passage?

• According to paragraph 4, which of the following is the most fascinating to booklovers?

• The word "Here" in line 9 refers to……………

ZUNIA12

• Psychological reasons for wearing garments include _______.

• In what year did Melville’s book about his experiences as a cabin boy appear?

• The word “principle” in paragraph 3 is closest in meaning to ........

• According to the passage, why did colonial printers avoid major publishing projects?

• It can be inferred from the passage that the courtship of great horned owls ................

• What will happen when an object is dropped into the water?

• What is the main idea of the passage?

• According to the passage, which type of memory is the shortest?

• What should a diver do when ascending?

• When did the the Pilgrims make a difficult trip to across the ocean from England?

• Who is intended to benefit from the advice given in the article?

• What is the main topic of the passage?

• According to the passage, which of the following is the mother owl's job?

• Which of the following is a kind of petal?

• The topic of this passage is______________.

• When did Tolkien begin to create this trilogy?

• The word “imprisonment” in paragraph 2 is closet in meaning to _________.