Air Pollution in

Hong Kong
　

Chemistry Project the Written Report


  1. Introduction 3
  2. Sources of Air Pollution 3 - 7
    1. Vehicles 4 - 5
      1. Pollutants produced by vehicles 4
      2. Reasons why pollutants are produced 4
      3. Impacts of the pollutants from vehicles 4 - 5
      4. Method to eliminate pollutants 5
    2. Power Stations 6 - 7
      1. Pollutants produced by power stations 6
      2. Reasons why pollutants are produced 6
      3. Impacts of the pollutants from power stations 6
      4. Methods to eliminate pollutants 6 - 7
  3. Effects of Air Pollution 8 - 12
    1. Greenhouse Effect and Global Warming 8
    2. Photochemical Smog 9
    3. Ozone Depletion – CFCs 10 - 12
      1. The CFCs 10
      2. Ozone layer depletion 10 - 12
  4. Government 13 - 14
    1. Air Pollution Index 13
    2. International Protocol on Air Pollution 13 - 14
      1. The Montreal Protocol 13
      2. Framework Convention on Climate Change 13
      3. The Kyoto Protocol 14
    3. 1999 Policy Address 14
  5. News 15
    1. Indoor Air Quality 15
      1. Importance of IAQ 15
      2. Methods to improve indoor air quality 15
  6. Suggestions 16
    1. Students and Citizens 16
    2. Government 16
      1. Education Department 16
      2. Environmental Protection Department 16
    3. Environmental Associations 16
  7. Conclusion 17
  8. Reference 17
  9. Group Members 17
1. Introduction:

Air pollution is an all-time problem that Hong Kong faces after the development of commerce and industries. For the past decades, rapid growth in economy raises the living standard, together with the enormous increase in population, extremely heavy traffic and the building of skyscrapers besides streets, worsen the problem of air pollution in Hong Kong.

In this project, we would like to briefly introduce the sources and effects of the air pollution in Hong Kong, the policy of the HKSAR government, and measures and suggestions of the improvement of air quality.
 

2. Sources of Air Pollution:

Air pollution is caused by numbers of air pollutant. An air pollutant is a substance that is present in the atmosphere at a concentration sufficient to cause harm to humans, other animals, vegetation or materials.

Major air pollutants are carbon monoxide (一氧化碳), nitrogen oxides (氮氧化物), sulphur dioxide (二氧化硫), hydrocarbons (氫碳化合物), photochemical oxidants (光化氧化物) and particulates (微粒).

Pollutants of the air come from many sources, including factories, vehicles, power stations and etc. In our project, the focus would be put on the vehicles and power stations.

　
2.1 Vehicles

2.1.1 Pollutants produced by vehicles

Nitrogen oxides, carbon monoxide, hydrocarbon and lead bromide are the pollutants produced by running vehicles.

2.1.2 Reason why pollutants are produced

2.1.2.1 Nitrogen oxides

Petrol is injected into the cylinder of the car engine. After an electric spark is produced, the fuel in the engine ignites suddenly and intensely. The temperature there booms to about 2800oC and under this temperature, some nitrogen and oxygen in the cylinder combine to form nitrogen oxides. 2.1.2.2 Carbon monoxide and Hydrocarbons As the piston of the engine is pushed out of the cylinder, the combustion gases cool and expand in a very short period of time. This rapid change in temperature and pressure results in the incomplete combustion of the fuel. Normally the fuel will form carbon dioxide and water after complete combustion, but in incomplete combustion, carbon monoxide and hydrocarbons, which have not reacted, are formed as air pollutant. 2.1.2.3 Lead bromide In vehicles, incorrect timing of explosion in the engine causes knocking(爆震), this occurs especially in high-performance vehicles. Knocking increase the production of the previous mentioned air pollutants, carbon monoxide and hydrocarbons. To prevent knocking, anti-knocking compound is added to the fuel. One example of that is tetraethyllead(IV) (Pb(CH3CH2)4). When burned, this compound produces small particles of lead, which tend to combine with free radicals produced in the chain reaction of combustion. This slows down the reaction and makes the working of the engine smoother.

To prevent the accumulating of lead, 1,2-dibromoethane (CH2BrCH2Br) is also added. This results in the formation of lead bromide. This product is volatile and is exhausted by the car.

 2.1.3 Impacts of the pollutants from vehicles

2.1.3.1 Nitrogen oxides

They attack ozone layer and contributes to the formation of photochemical smog (光化煙霧). (Effects of photochemical smog will be discussed later.) And they are oxidized to nitrogen dioxide, which reacts with oxygen and water vapour to form nitric acid, one of the ingredients of acid rain. Acid rain can damage buildings and is also responsible for the deaths of large number of trees. 2.1.3.2 Carbon monoxide This is a colourless, odourless, tasteless and poisonous gas that combines with haemoglobin in the red blood cell to form a stable complex, carboxyhaemoglobin. Thus, the haemoglobin is not available to carry oxygen throughout the body. Even in relatively low level it causes death. 2.1.3.3 Hydrocarbons Hydrocarbons themselves cause little damage, but they react with oxygen, ozone and nitrogen oxides to form photochemical oxidants under sunlight, which are ingredients of photochemical smog. 2.1.3.4 Lead bromide It can be inhaled, while lead is a neurotoxin (神經毒素) which can cause damage to the brain and nervous system, particularly in young children. 2.1.4 Method to eliminate the pollutants

Installation of catalytic converter (觸媒轉化器) can reduce the emission of carbon monoxide, hydrocarbons and nitrogen oxides.

The catalytic converter is a device, with honeycomb-like structure inside, that is added to the exhaust pipe before the air pollutants are exhausted out from the vehicle. This special structure enhances the catalytic reaction by increasing the surface area for reaction. Besides, precious metals, platinum (鉑) and rhodium (銠) are coated onto the inner surfaces of the converter. When the exhaust gases pass through the converter, rhodium catalyses the reduction of nitrogen monoxide:

2NO (g) + 2CO (g) --> N2 (g) + 2CO2 (g)

                             Rb

While the platinum catalyses the oxidation of carbon monoxide and hydrocarbons.

2CO (g) + O2 (g) --> 2CO2 (g)

                          Pt

C7H16 (g) + 11O2 (g) --> 7CO2 (g) + H2O (g)

                                 Pt

2.2 Power Stations

2.2.1 Pollutants produced by power stations

Sulphur dioxide, fly ash and nitrogen oxides are the pollutants produced by power stations.

2.2.2 Reason why pollutants are produced

2.2.2.1 Sulphur dioxide

It is a major air pollutant. Sulphur dioxide is released during the combustion of coal which contains sulphur. 2.2.2.2 Fly ash Tonnes of fly ash is generated each day by coal-fire power plants in Hong Kong as coal always contains a proportion of ash which cannot be burnt. 2.2.2.3 Nitrogen oxides Under high temperature of combustion, it is produced in the similar way as mentioned in the part 2.1.2.1. Besides, the fossil fuels burnt may contain nitrogen compounds. In the combustion the nitrogen is oxidized and nitrogen oxides are formed. 2.2.3 Impacts of the pollutants from power stations

2.2.3.1 Sulphur dioxide

Sulphur dioxide is a colourless and toxic gas with acrid and sharp odour. It causes damage to respiratory system of animals and increase in asthma attacks (哮喘發作). It is mostly the sulphur dioxide causes acid rain. 2.2.3.2 Fly ash In the fly ash, there are mainly particulates. Very fine particulates are hazardous to human beings as they cannot be filtered by the cilia and mucus in the respiratory tract, but are drawn into the lungs, where they accumulate as well as constrict the respiratory passage and damage lung tissues, and cause respiratory illnesses. Some particulates are suspected to cause cancer. 2.2.3.3 Nitrogen oxides The effects of nitrogen oxides are mentioned in part 2.1.3.1. 2.2.4 Methods to eliminate the pollutants

2.2.4.1 Methods to eliminate sulphur dioxide

The sulphur content in the fuel of power stations is limited to 0.5% - 1.0% by weight since 1990. Besides, the installation of flue gas desulphurization (FGD) system (煙氣脫硫系統). This system utilizes the “wet limestone-gypsum(石灰-石膏) scrubbing process” which can remove up to 90% of the sulphur dioxide emitted. Lastly, a technique called pulverized fluidized bed combustion (PFBC) which burn coal in a bed of limestone can remove sulphur by 80%. At the same time, it cuts the emission of nitrogen oxides, too. 2.2.4.2 Methods to eliminate fly ash In Hong Kong, power stations are equipped with electrostatic precipitators (靜電沉積器). Flue gas from the boiler is passed through a chamber where particulates become charged. The charged particulates get attracted onto a collecting electrode, where the particles are deposited and removed. This keeps the flue gas emitted by the chimney clean. 2.2.4.3 Methods to eliminate Nitrogen Oxides Nitrogen dioxide is one of the major pollutants in the air. Power plants in Hong Kong are equipped with low nitrogen oxide burner. It cuts the back emission of nitrogen oxides from existing boilers. In the burner, the flame temperature is controlled to the combustion zone and the availability of oxygen is reduced. Half of the emission of nitrogen oxides is reduced in this way. 3. Effects of Air Pollution:

3.1 Greenhouse Effect and Global Warming

The mean temperature of our planet is fixed by a steady state balance between the energy received from the sun and equal quantity of heat energy radiated back into space by the earth. If disturbances in either incoming or outgoing energy upset this balance, the average temperature of the earth's climate could upset food production, create deserts, raise the level of oceans or start a new ice age. One mechanism for regulating the earth's temperature is the greenhouse effect (溫室效應).

The sun emits radiation in a band of wavelengths from ultraviolet to infrared (UV to IR, 200nm to 3000nm) with a maximum in the visible spectrum at 500nm. This radiation passes through the atmosphere of the earth with very little absorption. When the radiation reaches the earth, it warms the ground or sea. The warm surface of the earth radiation cannot travel freely through air. Infrared radiation is absorbed by water vapour, carbon dioxide, ozone and other gases in the lower atmosphere, warming up the lower layers of the atmosphere, which radiate some heat back to the ground and some out into space. The warming effect of carbon dioxide and water vapour has been named the greenhouse effect. The effect is compared with the glass of a greenhouse, which lets sunlight enter and prevents infrared radiation from leaving.

Actually, in addition to reflecting infrared radiation, real greenhouses trap heat mainly by preventing warm air from escaping by convection. There is more water in the atmosphere than carbon dioxide, so most of the greenhouse heating of the earth's surface is due to water vapour. However, there is a gap in the absorption by water, which is partly plugged by carbon dioxide.

Increasing the concentration of carbon dioxide in the atmosphere increases the amount of the infrared radiation absorbed and increases the warming effect of the lower atmosphere. A concentration could be reached at which the carbon dioxide would capture all of the radiation at the correct wavelengths for absorption by carbon dioxide; after this concentration is reached any further increase cannot lead to a further rise in temperature. It follows that there is no danger of a runaway effect that might result in desert conditions over all the earth.

The greenhouse effect is a natural phenomenon. Without it, the earth would be uninhabitable. It is what keeps us from being a frozen planet. If gases such as carbon dioxide did not trap the sun's energy, the earth's mean temperature would be about -20°C, rather than its current 15°C.

3.2 Photochemical Smog

Hydrocarbons enter the atmosphere from natural sources, such as the decomposition of dead plant material, and from man-made sources. The atmospheric hydrocarbons that come form human activity account for only 15% of the total, but their effect on humans is great because they are released mostly in urban air. The outstanding emitter of hydrocarbons is the petrol engine. Incineration of rubbish is another sources. By themselves hydrocarbons cause little damage, but in the presence of light, photochemical oxidants (oxidizing agents produced by photochemical reactions) are formed. These oxidizing agents react with many of the unsaturated hydrocarbons in the air. Ultimately, all atmospheric hydrocarbons are oxidized to carbon dioxide and water, but some of the intermediate oxidation products are irritating and toxic.

A key step in the formation of photochemical oxidation is the photochemical decomposition of the nitrogen and nitrogen dioxide:

NO2  -->  NO + O

Oxygen atoms are extremely reactive. Many react with dioxygenn to form ozone.

O + O2  -->  O3

The photochemical oxidants, atomic oxygen, ozone and peroxides, attack alkenes in a large number of complex reactions. Research workers have outlined a scheme that found out 81 different reactions that may occur in the photochemical oxidation of propene. Among the varied products of the photochemical oxidation of alkenes are the irritating, lachrymatory (催淚) compounds, methanal, propenal, and notorious ‘peroxyacetyl nitrate’ (PAN)

PAN is both toxic and irritating. At concentrations, it causes eye irritation. Plants are very senstive: a fraction of 1 ppm causes damage to vegetation.

As chemical reactions continue in the atmosphere, more ozone is produced and ozone levels soar. Small molecules combine to form larger molecules and eventually tiny particles. These particles and brown colour of nitrogen dioxide give the air a dirty, ‘smoggy’ appearance. Eventually, the intermeduate oxidation products are converted into carbon dioxide and water. Until that happens, they are irritating and toxic to the population. This type of pollution is called photochemical smog.
　

3.3 Ozone Depletion – CFCs

3.3.1 The CFCs

3.3.1.1 Properties of CFCs

The chlorofluorocarbons (CFCs) (氯氟碳化合物) are organic chemicals that are non-flammable, non-toxic, odourless and very unreactive. They have relatively low boiling temperature so that they are good solvents. 3.3.1.2 Uses of CFCs CFCs are widely used in aerosol sprays like hair spray, perfumes, deodorants and domestic insecticide spray. You can also find CFCs in household products such as window-cleaning liquids, polishes, waxes and etc. Besides, CFCs are used in refrigerators and air-conditioners as a refrigerant fluid. Originally, sulphur dioxide and ammonia were being used as refrigerant fluids, but CFCs are much safer to use as they are non-toxic and non-corrosive.

In the manufacturing of thermal foam insulation for building and production of plastic cup and food packaging, CFCs are used as blowing agents.

 3.3.2 Ozone layer depletion

3.3.2.1 The ozone

Ozone (臭氧) is a pale blue gas with pungent smell. In small concentration, it is harmless. Yet is the concentration rises above 100 ppm, it will cause respiratory problems and headaches.

In the lower part of the atmosphere, ozone is formed be the reaction between nitrogen oxides and hydrocarbons in sunlight, and from air by electric sparks which occur in car engines or electrical appliances such as photocopiers or during lightning.

 3.3.2.2 Functions of ozone layer In the stratosphere, zone is formed from atmospheric oxygen by absorption of ultra-violent radiation.

O2     -->     O + O

        UV-light

O + O2  -->  O3

When ozone absorbs UV-lights of wavelength 215 – 295 nm, it under-goes photodissociation (光分解作用) and splits up again:

O3  -->   O + O2

This reaction is responsible for the vital screening effect if ozone. In the stratosphere (平流層), ozone is constantly created and destroyed.

The thin layer of ozone can filter out 99% of the dangerous UV-light from the sun. Thus it can protect the oxygen gas in the lower atmosphere from being dissociated and keep those harmful rays from penetrating to the Earth’s surface.

 3.3.2.3 Causes of ozone depletion As said before, CFCs are very stable and will not break down even for a long time. After they are produced, they move freely and may slowly diffuse to the upper atmosphere. At there, UV-lights of the right frequency photolyses the CFCs, breaks the relatively weaker C – Cl bond in CFCs and causes the forming of Cl• radicals and chlorine oxide radicals (ClO•). These species convert the ozone in the stratosphere into dioxygen.

O3 (g) + Cl•(g)----> O2 (g) + ClO•(g)

ClO• radicals then react with free oxygen radicals:

ClO•(g) + O•(g)----> Cl•(g) + O2 (g)

These two reactions form a chain. The Cl• radicals are being regenerated, and acts as a catalyst in converting O3 and O• into O2. So, one Cl• radical can catalyse the breaking down of about one million O3 molecules.

In this way, CFCs effectively deplete the ozone layer.

 3.3.2.4 Effects of ozone depletion As the concentration of ozone decreased, the ozone layer became thinner and thinner, and gradually a ‘hole’ on it was developed. This ‘hole’ decreases the absorption of UV-light, so more UV-light reaches the Earth’s surface and this increases the incidence of skin cancer. There was report predicted that 10% reduction in ozone would result in a 20% increase in being suffered of skin cancer.

It also affects the climate. As ozone can warm the atmosphere, depletion of it lowers the atmosphere’s temperature. Besides, as CFCs have a strong ability, about 10,000 times stronger than CO2’s, of absorbing infrared radiation given off by the Earth. Thus emission of CFCs increases the ability of atmosphere to absorb infrared radiation, so it contributes to the greenhouse effect.

 3.3.2.5 Worldwide control of ozone depletion In 1995, 150 government signed an agreement to phase out the use of CFCs by 2020. Yet many developing countries have not signed that yet because they think it is unfair that they should be asked to help solving a problem which the rich nations have created. 3.3.2.6 Possible alternatives of CFCs There are at least two kinds of alternatives of CFCs. They are the hydrohalocarbons and the perfluorocarbons.

Examples of hydrohalocarbons include HCFCs and HFCs. They can be used as refrigerant as they do not contain Cl atom, so they will not release damaging Cl• radicals into the atmosphere. Besides, their molecules include C-H bond(s) which are relatively reactive. That means the compound will break down in the atmosphere more quickly than CFCs, so they will not persist at there for so long.

Perfluorocarbons including CF4 and C2F6. These completely fluorinated alkanes do not react with hydroxyl radicals or ozone, thus they are not involved in ozone depletion or photochemical smog formation.
　

 4. Government:

4.1 Air Pollution Index

The Air Pollution Index (API) (空氣污染指數) is a simple way of describing air pollution levels to provide timely information about air pollution to the public and to enhance awareness. Since June 1995, the Environmental Protection Department (EPD) (環境保護署) has been reporting the API and making a forecast for the following day. In Hong Kong the API converts air pollution data from several types of pollutants into a value ranging from 0 to 500. Similar systems are widely used in many other places such as the United States, Singapore, Malaysia, Taiwan and the Philippines.

The API forecast serves as an alert to the public before the onset of serious air pollution episodes. It helps the general public, especially susceptible groups such as those with heart or respiratory illnesses, to consider taking precautionary measures when necessary.

4.2 International Protocol on Air Pollution

4.2.1 The Montreal Protocol

Many European and American countries banned using spray which contains CFCs in 1978. In September of 1987, 40 countries signed The Montreal Protocol (蒙特利爾公約). Under the protocol, the countries must decrease the production of 5 kinds of CFCs to the 50% of 1986 in 1998.

China, India and also Hong Kong had joined the reduction of CFCs. In June of 1989, Hong Kong legislated the law to ban the production, import and export of CFCs.

4.2.2 Framework Convention on Climate Change

In 1992, Framework Convention on Climate Change (氣候變化框架公約) was used to solve the problems caused by greenhouse gases. The protocol required the organizations to update and disclosure the information about the sources of greenhouse gases as well as to setup and enforce laws to slow down the climate change and other possible effects

To the developed countries, it limits the emission of greenhouse gases. The target is reducing the emission of greenhouse gases to 1990’s level in 2000. Subsidization is also provided to developing countries, so that the countries can follow the protocol.

4.2.3 The Kyoto Protocol

The Kyoto Protocol (京都條約) is about the measure after 2000. In 2010, the industrial countries will reduce the emission of greenhouse gases. From 2008 to 2012, the emission of greenhouses will be minimize to 95% of 1990’s level.
　

4.3 1999 Policy Address

The Policy Address included 17 paragraphs about air pollution. Here is the summary of the measures:
 
 
Vehicles Number Measures
Taxi
18 000
 Will not import diesel taxi since year 2000, LPG taxi
Mini-bus
6 000
 LPG mini-bus
Mini-diesel car
70 000
 Particles collector (微粒收集器)
Medium and Heavy diesel car
4 000
 Catalytic converter
Bus
12 000
 Catalytic converter

The LPG will be the main fuel of vehicles in future. It is a more “clean” fuel since carbon dioxide and water will be released only after the complete combustion. Of course, we agree this new measure. However, there are some problems that government should notice. First of all, is the sufficiency of LPG station. Secondly, the training of technician in garage is also very important. As a result, they can convert the diesel engine to LPG engine and to repair the LPG cars. Besides, giving finical subsidization to diesel car owner can encourage them to use LPG.

Although LPG buses were not introduced, all the new buses are using environmental friendly engine. You may notice the backside of the new buses.

In the Policy Address, public transport system will be promoted to reduce the using of diesel fuel. Pedestrians' area will be established.
　

5. News:

5.1 Indoor Air Quality

The indoor air quality (IAQ) (室內空氣質素) also important since most citizens spend most time inside home, office, or other indoor environment. The good indoor air quality depends on the actions of everyone in the building, a partnership and close coordination between property management and occupants is the best way to maintain a healthy and pleasant indoor environment.

5.1.1 Importance of IAQ

On the average, we spend more than 70% of our time at homes, in offices and other indoor environment. Polluted indoor environment may give you headache, itchy eyes, respiratory difficulties, skin irritation, nausea and fatigue.

5.1.2 Methods to improve indoor air quality

Controlling indoor air quality involves integrating three main strategies. They include to

1) Manage the sources of pollutants by:

Removing them from the building (adopt a no-smoking policy)

Isolating them from people (relocate photocopiers away from general working area)

Controlling the timing of their use (re-schedule pest control work outside normal office hours) 2) Dilute pollutants and remove then from the building through ventilation.

3) Use filtration to remove the air pollutants
　

6. Suggestions:

6.1 Students and Citizens

When you have complaints, suggestions about the pollution in Hong Kong, you can write a letter or an email to environmental associations or environmental Protection Department. Also, we can have an “environmental friendly” lifestyle. For example, using public transport system in stead of taking a taxi. If you have time, you may take part in the activities held by environmental associations.

6.2 Government

6.2.1 Education Department

Environmental studies should be included in Primary and Secondary syllabus in order to increase the awareness and knowledge of environmental. The education is one of the important solutions to solve the environmental problem because they are the owners of future.

6.2.2 Environmental Protection Department

Environmental Protection Department should cooperate with Transport Department in order to check the emission of exhaust gas from cars. If the pollutants emitted were over the standard, the car owner should be to impose a fine.

Also, EPD should sensor the government policy that may involve pollution. It should estimate the result and cost. If necessary, suggest the best way to government in order to minimize the damage to environment.

Finally, EPD should also cooperate with scientist and other countries’ government and environmental department. This can make us keep in touch with the world of the newest technology to reduce pollution and the most update condition of pollution.

6.3 Environmental Associations

Environmental Associations also have the responsibility to monitor the government and giving comments or suggestions. They also hold many activities about environmental protection to educate citizens through seminars, games, camping or field trips.

Environmental Associations have the function that express your opinions to government.
　

7.Conclusion:

The air pollution problem should not be ignored anymore. Everyone in the world has the responsibility to maintain the air in good quality. Air pollution is not a regional problem. Governments should cooperate together to keep the world clean, not only the air. At this moment, we should not only care about the profits in economies. We should be responsible to our offspring that providing the healthy and clean earth for them. This conforms to sustainable development.

　
8. Reference:

　
9. Group Members:

7C (4) Terence Kwong, Kei Man 鄺杞文

7C (11) Rock Tse, Fei Lung 謝輝龍

7C (14) Kelvin Wong, Ting Ho 黃霆浩

7C (15) John Wu, Ying Kit 胡英傑
 

Finished Date: 16 December1999