Lq - 06 Man And The Environment

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Chapter 6 Structured Questions

Ch 6 Man and the environment [061001] The following diagram explains the greenhouse effect:

a

Name one major air pollutant that traps heat and warms the atmosphere. (1 mark)

b

What will be the effect on the overall air temperature?

c

Suggest one possible effect of this temperature change on the environment. (2 marks)

d

Other than industries and motor vehicles, suggest and explain another human activity which causes an increase in this air pollutant. (2 marks)

e

Industrial processes and motor vehicles produce air pollutants which may cause deaths of trees and marine organisms and also cause damage to manmade materials. What are these pollutants and how do they cause these environmental problems? (4 marks)

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(1 mark)

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-- ans -a

Carbon dioxide

1m

b

Overall increase in air temperature

1m

c

Ice in the polar regions may melt.

1m

The water level of the oceans will rise and the coastal area may sink below the sea

d

level.

1m

Deforestation causes the balance of carbon dioxide unable to maintain.

1m

Carbon dioxide produced from respiration of all organisms is more than that absorbed by plants for photosynthesis. Therefore, the level of carbon dioxide in the

e

atmosphere rises.

1m

Sulphur dioxide and nitrogen dioxide

1m

When these gases are dissolved in rain, acid rain results.

1m

Trees and marine organisms are killed because the rain makes soil and water acidic.

1m

Acid rain is corrosive and erodes metals, stones and other building materials.

1m

-- ans end --

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Chapter 6 Structured Questions

[061002] A river flows through an area of agricultural land where fertilizers are used frequently. a

Describe and explain how the use of fertilizers may affect the animals and plants living in the river. (4 marks)

b

Why do farmers use so much fertilizers? What are the alternatives to fertilizers? (3 marks)

c

Besides fertilizers, what chemicals are commonly used by farmers? What are the bad effects of them on humans and other animals? (3 marks)

-- ans -a

b

c

Fertilizers in soil contain phosphates and nitrates which are washed by rain to the river. 1m

Growth of algae is increased.

1m

Algae use up the dissolved oxygen in river at night.

1m

Aquatic organisms die of suffocation.

1m

Farmers practice monoculture. Continuous culture of the same crop uses up certain nutrients in the soil.

1m

Nutrients have to be added to sustain yield.

1m

Mixed cultivation / growing leguminous plants periodically (any 1)

1m

Pesticides are used to kill pests.

1m

Pesticides are toxic.

1m

Pesticides may accumulate along the food chains. If we consume contaminated food, our health is at risk.

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1m

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Chapter 6 Structured Questions

-- ans end --

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Chapter 6 Structured Questions

[061003] The diagram below shows a river polluted by the sewage discharged from both the town and the farm. upstream town sewage sewage

farm

fish downstream

a

Account for the sharp increase in bacterial population in the polluted water. (1 mark)

b

Explain how the sharp increase in bacterial population causes a decrease in the fish population downstream. (3 marks)

c

Explain why the discharged sewage may lead to algal blooms. Give four effects of algal blooms on the aquatic life in the river. (5 marks)

d Suggest one way to the government to help solve the problems. -- ans --

(1 mark)

a

Sewage discharged from the town and farm contains a lot of nutrients which can be used by bacteria for growth. 1m

b

A lot of oxygen in the river is used up by the bacteria for growth and decomposition

c

of organic matters.

1m

The fish die of suffocation.

1m

The bacteria also release toxins which poison the fish.

1m

The discharged sewage contains a lot of nutrients for the growth of algae.

1m

The large population of algae prevents sunlight from passing through the water. This reduces the photosynthetic rate of aquatic plants.  Oxford University Press 2005

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Chapter 6 Structured Questions

The large population of algae prevents diffusion of oxygen into the water. The fish die of suffocation.

1m

The algae block the gills of the fish. The fish die of suffocation.

1m

When the algae die, they are decomposed by the bacteria, which use up oxygen in the river. The fish die of suffocation. d

1m

Setting up of a sewage treatment plant to make the sewage less harmful before it is discharged.

1m

-- ans end --

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Chapter 6 Structured Questions

[061004] The diagram below shows the various components of a sewage treatment plant. untreated sewage

settling tank

aeration pond

air

effluent digester

filter

a

What is the function of the settling tank?

(1 mark)

b

Why is air bubbled into the aeration pond?

c

What is the function of the digester? Give the names and uses of two substances produced in the digester. (4 marks)

d

Even though the sewage has passed through several stages in the treatment process, the effluent may still cause algal blooms because of its high content of a certain substance. What is it? (1 mark)

(4 marks)

-- ans -a

To let the solid part of the sewage / sludge settle down to the bottom.

1m

b

To stir up the sewage.

1m

To make the bacteria and fungi active

1m

in decomposing organic substances in the sewage

1m

into harmless inorganic compounds.

1m

Anaerobic bacteria carry out fermentation of the sludge in the digester.

1m

c

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As fuel to power the sewage treatment plant. Sludge

d

1m 0.5m

As plant fertilizers in farming.

1m

Mineral

1m

-- ans end --

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Chapter 6 Structured Questions

[061005] Foam rubber is widely used in packaging and making disposable lunch boxes. However, it causes a great environmental problem because it is nonbiodegradable. a

Suggest how the industry owners, restaurant owners and the government reduce the problem caused by foam rubber wastes. (You may consider the 4R principle -- Reduce, Reuse, Replace and Recycle.) (6 marks)

b

Suggest two ways of conserving the environment as a consumer and explain. (4 marks)

-- ans -a

Industry owners:

avoid non-essential packaging use biodegradable materials for packaging use recycled foam rubber Restaurant owners: use disposable products made of biodegradable materials allow and encourage customers to bring their own containers Government: educate the public in the problems caused by foam rubber wastes encourage the industrial sectors to use biodegradable materials by providing subsidies (any 6) b

1m x 6

BYOB (Bring your own bag) -- cut down plastic wastes

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Chapter 6 Structured Questions

Do not buy commodities with too much packaging -- cut down solid wastes Buy electric appliances with high energy efficiency -- reduce pollution caused by power plants indirectly Buy recycled products -- cut down solid wastes, save resources Each correct answer with explanation

2m x 2

-- ans end --

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Chapter 6 Structured Questions

concentration / density

[061101] The graph below shows the concentrations of dissolved oxygen and phosphate, as well as the densities of organisms A and B in a river. The negative value of distance means the upstream and positive value means the downstream from a farm. The concentrations or densities are not in scale.

-500

12 10 dissolved oxygen phosphate organism A organism B

8 6 4 2 0 0

500

1000

1500

distance from the farm (m) a

i

Organism A is a micro-organism. Give one example of it.

(1 mark)

ii

Give one example of organism B.

(1 mark)

b

Explain why the phosphate concentration in the river increased suddenly near the farm. (2 marks)

c

Explain why the dissolved oxygen concentration decreased significantly with the increase in phosphate concentration. (2 marks)

d

Give two reasons for the drop in the density of organism B.

(2 marks)

-- ans -a

i

Microscopic algae

1m

ii

Fish, crab or other free-living freshwater animals

1m

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b

c

Chapter 6 Structured Questions

Farmers used excessive fertilizers that contained phosphate.

1m

Rain washed the fertilizers to the river.

1m

Algae grew rapidly with rich phosphate supply.

1m

Respiration and decomposition of the algae consumed a lot of dissolved oxygen. 1m d

Depletion of oxygen / suffocation.

1m

Killed by the toxins released from the algae.

1m

-- ans end --

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Chapter 6 Structured Questions

[061102] Answer the questions below with reference to the following news about red tide.

Fish farmers on alert over spread of red tide

The fears of fish farmers grew after two more new blooms of red tide were discovered off Hong Kong Island. Red tide is an algal bloom that turns the colour of seawater to pink or reddish brown. Despite the government's Red Tide Interdepartmental Working Group has confirmed the species of the algae is non-toxic, fish farmers are worried that their fish would be killed. The algae outbreak has also raised the concerns about the pollution level in Victoria Harbour.

a

Give three ways of how the algae may kill the fish in fish farms even they are non-toxic. (3 marks)

b

Suggest two measures to the fish farmers to avoid their fish being killed by the red tide. (2 marks)

c

How may the occurrence of red tide be related to the pollution level in the harbour? (2 marks)

-- ans -a

The algae may use up the dissolved oxygen in the water during the night, hence the fish die of suffocation. The algae may block the gills of fish, hence the fish die of suffocation. The algae may reduce sunlight penetration into the water and therefore the photosynthetic rate of aquatic organisms is lowered. This decreases the amount of dissolved oxygen in the water and hence the fish die of suffocation.

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Chapter 6 Structured Questions

The algae may prevent oxygen from dissolving into the water, hence the fish die of suffocation. When the algae die, the dissolved oxygen in the water may be depleted during the decomposition of the algae by bacteria, hence the fish die of suffocation. (any 3) b

1m x 3

Pumping oxygen into the water at night to increase the dissolved oxygen content. Stop feeding the fish to reduce the oxygen requirement of the fish as well as the ecosystem. Enclose the fish cages with plastic sheets to separate the fish from the red tide. (any 2)

c

1m x 2

The red tide may be caused by the availability of nutrients such as nitrogen, potassium and phosphorus.

1m

These nutrients are commonly found in domestic sewage.

1m

-- ans end --

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Chapter 6 Structured Questions

temperature (oC)

[061103] Plant refuse is left in an uncovered container undisturbed. The change in temperature of the refuse is recorded in the graph below.

80 60 40 20 0 0

2

4

6

8

10

12

14

time (day) a

Explain the change in temperature during the first two days.

(3 marks)

b

Suggest one possible use of the plant refuse after two weeks.

(1 mark)

c

Suggest two methods to speed up the above process. Explain your answer. (4 marks)

-- ans -a

Bacteria and fungi decompose the plant refuse,

1m

releasing heat energy.

1m

The temperature therefore rises.

1m

b

Used as fertilizers.

1m

c

Turn the refuse everyday with a plough or punch holes into it with a fork so that the decomposers can get enough oxygen to carry out decomposition. Add some water to the dry refuse

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Chapter 6 Structured Questions

to favour the the growth of decomposers.

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Chapter 6 Structured Questions

Cover the refuse with a layer of soil to keep the refuse warm because decomposers work best at higher temperature. (any 2 methods and correct explanations)

2m x 2

-- ans end --

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Chapter 6 Structured Questions

[061104] The graph below shows the amount of greenhouse gases emitted in Hong Kong from 1990 to 2002. [Source of information: Environmental Protection Department] 45000

9

total amount of greenhouse gases (x 10 g)

40000 35000 30000 25000 20000 15000 10000 5000 0 1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

year

a

Give two examples of greenhouse gases.

(2 marks)

b

How do greenhouse gases lead to greenhouse effect?

(3 marks)

c

Suggest one reason to account for the decrease in the emission of greenhouse gases from a peak in the early 1900s throughout the mid- and late-1990s. (1 mark)

d

Give one example of what the government did to reduce the emission of greenhouse gases. (1 mark)

-- ans -a

Carbon dioxide, nitrous dioxide, methane, sulphur hexafluoride, chloro-fluoro

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2002

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Chapter 6 Structured Questions

carbons / CFCs (any 2) b

c

1m x 2

Greenhouse gases act as a shield around the Earth

1m

to trap the heat reflected from the ground.

1m

This raises the atmospheric temperature.

1m

Part of the electricity has been supplied from the Guangdong Daya Bay Nuclear Power Station since its operation. Therefore, less coal has been used in electricity generation in Hong Kong. Migration of local factories to the mainland.

d

(any 1)

1m

The introduction of liquefied petroleum gas (LPG) taxis.

1m

-- ans end --

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