Man's Effect on His Environment- Pollution



Man's Effect on the Environment- Pollution

M

an is the most successful mammal on Earth. With his apparent ‘intelligence’ he always try to ch_____ the environment in favour of his needs --more correctly his w____!. Advances in agriculture and medicine has brought about an explosion in human p_________, this together with human’s insatiable expectation for higher st_______ of living has depleted Earth’s most natural re_________ while dumping into the environment some of the most noxious p_______.

POLLUTION

A. Definition of pollution

Pollution is any undes_______ change in the physical, chemical and biological characteristics of our environment (air, water and land) and is mainly the result of man's activity.

B. Sources of pollution

[pic]

◆ the s_____-sighted / unsus____________ policy,

◆ the increase in human p__________ and the insatiable desire for a higher l______ st__________ .

C. Biodegradable vs Non-biodegradable pollutants

AIR POLLUTION

A. Types of air pollutants

1. Gas______ air pollutants

They include carbon monoxide, carbon dioxide, hydrogen sulphides, oxides of sulphur and nitrogen, ozone, hydrocarbons.

2. Part_________ air pollutants

|Smoke |Incomplete combustion may produce carbon particles and tarry hydrocarbons. These visible particulate substances |

| |constitute smoke. |

|Dust |Particles larger than that can be found in smoke. Thus it easily settles out from air |

|Heavy metal particles |Lead from exhaust gas of vehicles |

|Resp______ susp______ |RSP are those suspended particles in air that are less than 10 (m (micron) in diameter. |

|part_______ (RSP)* | |

Sources of air pollution in HK

According to the EPD report, around 20 % of the air pollutants are generated locally, the rest are attributed to the regional pollution of the Pan Pearl river delta.

List the 4 top local sources of air pollutants?

C) Controlling Air Pollution in HK (From the SAR Government / EPD)

|Sources |Problems |Measures taken by |

| | |the SAR government |

|Mobile Sources |Motor vehicle emissions account for |adopt tighter fuel and vehicle emission standards |

|(vehicles) |the bulk of the NOX in the air and |adopt cleaner alternatives (e.g. petrol) to diesel where practicable |

| |vehicles powered by diesel contribute|control emissions from remaining diesels with devices that trap pollutants |

| |most of the particulates to the air. |strengthen vehicle emission inspections and enforcement against smoky vehicles |

| | |promote better vehicle maintenance and eco-driving habits. Moving towards the |

| |Rapid growth in the no. of vehicles |greater use of electrified transport. |

| |in Hong Kong is expected to more than|Legislation against Idling engine |

| |off-set the reduction of NOX and | |

| |particulates gained by the new | |

| |vehicle emission standards. | |

|Stationary Sources |The bulk of the sulphur dioxide in |The Air Pollution Control Ordinance controls emissions from power plants, |

| |the air around us originates from the|industrial and commercial sources, construction activities and other sources |

| |burning of fuels by industry--from |A control on the sulphur content of industrial fuel introduced in 1990 reduced |

| |factory buildings. |sulphur dioxide to very low levels. |

|a. Power station |Power stations in Hong Kong are the |China Light & Power (CLP) and Hong Kong Electric have installed low-NOx burners, |

| |largest emitters of sulphur dioxide |electrostatic precipitators and flue-gas desulphurisation systems, which all help |

| |and nitrogen dioxide |to reduce air pollution. |

| | | |

| | |They have also addressed the problem at source by using low-sulphur coal. |

| | | |

| | |CLP opened Hong Kong's first natural gas power plant at Black Point in 1996, which |

| | |emits less pollution than a coal plant. |

| | | |

|b. Incinerators |The incinerator at Lai Chi Kok was closed in 1989 |

| |The incinerator at Kennedy Town was closed in March 1933. |

| |The Kwai Chung Incinerator was closed in 1996. |

| | |

|c. Construction activity |these contribute to air pollution |introduce regulations to require the construction industry to implement appropriate|

|and the open burning of |from particulates. |dust control measures and to restrict the open burning of refuse and waste material|

|refuse | |within densely populated areas. |

| | | |

|d. Regional air pollution |HK contributes between five and 20 per cent of regional air pollution, depending on the pollutant. |

|problem | |

| |Vehicles, industry and power plants in Hong Kong and the Pearl River Delta area all contribute to a regional air |

| |pollution problem, commonly seen as smog. The Hong Kong and Guangdong governments are working on a joint plan to reduce |

| |the total amount of emissions and stop air quality from further deteriorating. |

| | |

Air Pollution in HK (the press and the green groups)

|14區空氣監察 僅東區塔門合格 |

| |

| |

|　　本港空氣污染問題嚴重，去年更是10年來最差。上周三公布的審計報告揭露，環保署在全港設置14個空氣質素監察站，去年達法定指標的比率「插水式」下跌，由過去 |

|數年的六成多達標急跌至一成半，僅東區及塔門合格（見表），其餘各區污染物濃度均長期超標。 |

|　　根據環保署網頁資料，單是可吸入懸浮粒子的濃度，若超過全年法定標準，可引致呼吸系統疾病，肺功能衰退，部分粒子甚至可致癌。環保署並強調，隨着可吸入懸浮 |

|粒子濃度增加，也會提升病發和死亡率。 |

| |

| |

Effect of air pollution on human health

| Smog |[pic] |

| | |

|A s____ (smoke + fog) is formed when ex_____ fumes are trapped in a | |

|fog. | |

| | |

|The great London smog of 1952 started from December 4th and by December | |

|7th it became so dense that visibility was reduced to one metre. The | |

|smog allegedly killed 4,000 people in one week's time. | |

| | |

|Those killed were mainly elderly and new-born as well as those patients | |

|suffered from respiratory diseases, particularly bronchitis. | |

| | |

b) Temperature inversion

Occurs in cities is located with mountains at one side or both sides and sea nearby at the other, such as Shatin or Los Angeles.

Normally the air just over a city is w_____ than those above so that it rises and carries with it the air pollutants. Sometimes cool air from the nearby sea moves in under warm air; or cool air flows down the mountain sides into the city basin under warm air.

If there is no wind and the atmospheric pressure is high, a stable air column is established with the normal temperature grad____ reversed by having the cooler surface layers of air trapped under warmer upper layers. This process is known as temperature inversion. In these situations the upper layers of warm air prevent the vertical r___ and dis______ of pollutants.

|[pic] |

c) Photochemical smog

Temperature inversion traps pol______ at high concentration near the surface. Ex_____ gases from motor cars under intense sunlight and ___ light undergo photochemical reactions.

ultra-violet ray PAN + O3

nitrogen oxides + hydrocarbon

(motor car exhausts) (intense sunlight) (Peroxacyl nitrate) (ozone)

The P___ (peroxacyl nitrate) and o___ (O3) will cause severe e__-irritation, damage mucous membranes and kill plants.

d) Warmer climate (greenhouse effect)

There is evidence that the CO2 concentration (and other green_____ gases) is increasing in the atmosphere, thus more I___-red radiation from the earth is tr____, resulting in increase of air temperature. This effect is known as the 'Greenhouse Effect'.

It is estimated that the present carbon dioxide concentration of 0.033% will be increased up to 0.045% in the year 2050 and the average gl____ temperature is increased by about 3(C to 4(C. 'Greenhouse Effect' increase the instability of the global w_______ pattern.

|[pic] |[pic] |

2. Health hazards

a) Particulates are particles which act as l____ irritants that aggravate the resp_______ disease. (e.g. bronchitis and asthma). Asbestos dusts from factories may cause lung cancer (i.e. car___________).

Res_______ Sus_______Particles (RSP) are very small particles less than 10 millionths of a metres in diameter. They are easily inh___ and retained in the lungs. The major source of RSP in urban areas come from combustion sources such as ve____ emission, especially diesel vehicles. The second important source is SO2, which is subsequently converted into particulate sulphate in the atmosphere.

RSP is closely related with respiratory illness such as reduced l____ function, increased can___ risk, etc.

|Reference: *Health Effects of Total and Respirable Suspended Particulates |

|The health consequences of atmospheric suspended particulates depend on their ability to penetrate and deposit in the respiratory system. The |

|observed human health effects of RSP include: |

| |

|Slowing down the exchange of oxygen and carbon dioxide in the blood, causing shortness of breath. |

|Straining the heart, because it must work harder to compensate for oxygen loss. |

|The people most sensitive to these conditions include those with heart problems, or respiratory diseases like emphysema, bronchitis and asthma. |

| |

|The adverse health effects from particulate matter exposure are often not immediately noticed. Particulates can accumulate in the lungs after |

|repeated, long-term exposure causing respiratory distress and other health problems. The elderly and children are also very sensitive. |

b) The ac__ gases such as oxides of sulphur and nitrogen also aggravate the respiratory diseases of man. For example a bron_____ patient gets worse when the sulphur dioxide concentration is above 500 ug/m3.

c) The carbon monoxide emitted from motor cars has higher affinity than oxygen to combine irreversibly with hae________ to form the stable carboxyhaemoglobin, thus reducing the oxygen c________ cap______ of blood. CO concentration in air up to 1% is fatal.

d) Tetramethyl lead is added to petrol (in some countries) to promote the efficiency of the motor cars. The motor car exhausts contain lead in 'aerosol' form which may be breathed by the city dwellers, about 30(g daily. This amount can be eliminated in urine and faeces. However any excessive intake will be accumulated in the bones that will eventually damage the ner____ system.

3. Damages to plants

a) Smoke and dust in air will reduce the light i_______ that in turn will decrease the rate of photosynthesis.

b) Dust will block the st_______ of leaves and thus reduce photosynthesis.

c) S_________ dioxide in the atmosphere is harmful to veg_________. E.g. lichen :

|i) Sulphur dioxide diffuses through the stomata and dissolves on the moist |[pic] |

|mesophyll cells to form sulphurous a____ which disrupts photosynthesis and | |

|thus reduces crop yield. Plants have different degree of tolerance to sulphur| |

|dioxide. Lichen is very sensitive to polluted air. Lichen can be taken as an | |

|ind________ organism of clean air. | |

| | |

|ii) Sulphur dioxide dissolves in rain to form acid r____ which increases the | |

|acidity of soil. The acidic soil will reduce the b________ activities and | |

|render certain nutrients ins_______ (e.g. phosphorus) thus reduce the soil | |

|fertility. On the other hand, increase in acidity can cause too much | |

|aluminium to be dissolved in soil resulting in poisoning of plants. | |

[pic]

Q. With reference to the picture shown above, what is the effect of aluminium toxicity on the plant?

Reference Reading : Acid Rain

R_______ is a natural cleansing process of the atmosphere which scavenges various atmospheric gases and deposits them in ter_______ and aq_____ eco_________. The acidity or alkalinity of rainwater is quantified by its pH value. Because of the logarithmic nature of the scale, pH 4 is 10 times more acidic than pH 5, and 100 times more acidic than pH 6, and so on.

Many natural constituents of the atmosphere, including carbon dioxide, sulphates, nitrates, calcium, ammonia and sodium, all influence the pH of rainwater.

Different localities, however, have different compositions of these substances and as a result the reference pH value for rainwater (which can be regarded as the pH of natural ‘pure' rain) would be different from place to place.

For Hong Kong, clean rain is unlikely to fall below pH 6, so it is believed that rainfall pH values of less than 6 may be said to constitute 'acid rain'.

The most important effects of acid rain are those on biol_____ systems, man-made mat_____ and human h_____. Regarding the impact of acid rain on biological systems, the most well known effect of acid rain is on

aquatic ecosystems. Up to 1984, lakes in more than 13,000 km2 of south Norway were practically devoid of fish, and additionally, in 20,000 km2 of lakes the fish stocks were reduced. Furthermore, in aqueous systems with pH values less than 5, colloidal aluminium oxides are rendered soluble, liberating potentially toxic alum_______. indeed, extensive kills of adult fish in lakes are likely to be caused by a toxic combination of acidity and dissolved aluminium.

In addition to lowering of pH of some soils, acid rain accelerates the le______ of calcium and magnesium, which are important nutrients. Similarly, acidification mobilises heavy metals such as cadmium, nickel, lead and aluminium. These minerals can affect the plants themselves or, when they eventually enter aquatic systems, they can affect aquatic organisms.

The potential effects of acid rain on agricultural c_____ are also noteworthy. At low pH values, the number of species of crops that can be cultivated decreases, and this is especially true for important staple crops such as corn and wheat.

Acid rain also adversely affects the microbial activities of the soil, so that many ecological processes such as de____________ of organic matter and the turnover of nu______ such as nitrogen, are inhibited by the acidification of the soil.

As acidic rainwater is equivalent to a mild acid, it has corrosive effects. Stone, marble and even concrete, may be affected in this way. Acid rain also promotes corrosion of metallic materials, affecting structural steel, motor vehicles, electronic equipments, etc. In addition, increased soil acidity may lead to higher corrosion rates of buried materials such as pipelines and power cables.

Acid rain is not likely to have direct effects on human health. However, the acidification of reservoirs, wells and catchment areas can result in the release of both lead and copper in plumbing systems. Health effects from long term exposure to such dissolved metals may be expected. Indirect effects of acid rain may occur in the human food chain by the consumption of fish from acidified lakes and ponds where heavy metal accumulation has resulted, or the consumption of leafy vegetables that have been exposed to excessive rain dosages of leached heavy metals.

Most studies show that emissions of sulphur dioxide and oxides of nitrogen are the major precursors of acid rain. While these 2 pollutants can be produced naturally (e.g. from volcanoes), most of these gases are

present in the atmosphere as a result of man-made emissions, mainly the burning of fossil fuels.

Depending upon meteorological conditions, pollutants may either disperse locally or be transported for hundreds, or even thousands of kilometers away from their points of origin before deposition as acid rain.

WATER POLLUTION

Water pollution is the addition of undesirable matter into water that deteriorates the quality of water and makes it unsuitable for man's uses in respect to drinking, washing, irrigation, industry and recreation or to support aquatic life.

A. Sources of water pollution

• D__________ wastes include human sewage, refuse and detergents.

• A__________ wastes include manure of poultry and pigs, pesticides and excessive fertilizers.

• I___________ wastes include organic matter, detergents, poisonous chemicals, hot water, oil and suspended particles.

• Excessive silt from erosion of the watersheds caused by improper control of soil e_______ during agricultural practice, overgrazing, mining and timbering.

B. Different types of water pollution

1. Organic waste pollution

2. Inorganic nutrient pollution

(a) detergents (b) excess fertilizers - eutrophication

3. Chemical pollution

(a) pesticides (b) industrial chemical wastes

4. Thermal pollution

5. Oil pollution

6. Silt pollution

ORGANIC WASTE POLLUTION

The human se____, refuse, agr_______ wastes like man___ of chicken and pigs and certain industrial wastes from slaughter houses, tanneries, dairies, breweries, paper mill and textile factories contain large amount of or_____ matter. These wastes are discharged, either treated or untreated, into rivers or the sea.

A. Measurement / Indication of the organic pollution

1. Biochemical oxygen demand (BOD)

The biochemical oxygen demand and (BOD) is defined as the amount of dissolved oxygen (in mg per litre) absorbed by the micro-organisms to de_______ the organic matter present in a sample of water kept at 20'C for 5 days. The higher the BOD (i.e. higher oxygen demand) the higher is the degree of organic pollution.

2. Indicator organisms

Unpolluted stream has a characteristic fa_____ and fl___. Once the water is polluted, the structure of the com______ will also change.

The water polluted with organic matter has lo____ oxygen content so that the more sensitive organisms disappear, whereas the detritus feeder, particularly if they can tol____ the low oxygen level, grow prosperously.

Therefore various organisms, known as in______ organisms or index species,, can be used to indicate the relative degree of pollution. They can be divided into several groups according to the degree of pollution. In extreme cases of pollution all living organisms die except ba______ and se____ fungi.

|Some insects larvae are indicators of ‘clean’ water--little |[pic] |

|organic load. For examples, the m__fly and st___fly nymphs | |

| | |

| | |

|E. Coli is an indicator organism for aquatic pollution. | |

| | |

|It is a non-pathogenic bacterium living in the intestine and| |

|is discharged with fa____. | |

| | |

|Pathogenic bacteria are usually associated with E. Coli in | |

|intestine but they are difficult to detect. However E. Coli| |

|can live longer outside the body and can easily be detected | |

|and counted by a simple technique. | |

| | |

|Therefore the coliform count measures the degree of faecal | |

|pollution and indicates the relative amount of the | |

|pathogenic bacteria. | |

B. Organic pollution in Hong Kong

1. Stream pollution

Agri_______ wastes mainly in form of manure of p__, and pou____ add a daily BOD load of about 44,000 kg into the streams in New Territories. They contribute about 85% of the total polluting load while the dom___ sewage contributes about 11% and the ind______ effluents about 4%:

a) The agricultural wastes seriously pollute the L___ Chuen Ho near Tai Po.

b) The rich organic matter from tanneries pollutes River Indus (Ng T___ Ho) at Sheung Shui.

2. Marine pollution

It is estimated that every day about 1 million cubic metres of sewage are produced in HK and about 25 % of these are discharged, untreated, into the Victoria Harbour (2002 EPD report). Hong Kong still depends on ocean dil____ and cur_____ to clear these organic pollutants.

a) Effect of reclamation

But reclamation of land crests some shelt____ bays such as Kowloon Bay and Kwai Chung Container Station where the dil____ and removal of sewage by currents is greatly hindered. As a result f____-smelling water are found there.

b) Polluted beaches

Faecal pollution of Hong Kong is so heavy that even some of the most popular beaches on the Hong Kong Islands are seriously polluted. The safety limit of coliform bacteria for swimming set by the World Health Organization (WHO) in 1967 is 1,000/100 ml.

c) Sheltered bays

i) Tolo Harhour (Tai Po Hoi)

Tolo Harbour is an inlet where the effect of cur____ to remove sewage is rather low. The coliform counts of as high as 92,000 had been found in this harbour. This value exceeds the standards set for swimming (1,000 coliform/100 ml) by 92 times, and for cultivated seafood such as clam (50 coliforms /100 ml) by 1,840 times. The presence of both path______ organisms and to___ substances in water form potential risk to public health.

ii) Deep Bay (Hau Hoi Wan)

Deep Bay at the Northwest of New Territories is a m__ flat where many fil___-feeding organisms are found. The discharge of human sewage, agricultural wastes and industrial wastes from San Tin, Yuen Long into D___ Bay causes pollution. The mussels, clams and oy_____ accumulate the faecal bacteria and certain heavy m____ from water and thus become contaminated and way lead to shell___ food poisoning.

Reference Reading : Environmental consideration of coastal reclamation

With a population of over 6 million concentrated in an area of a little over 1000 km2, crowded Hong Kong is heavily dependent on its port facilities to sustain its entrepreneurial trade. Nearly 30,000 oc___ going ships enter and leave Hong Kong each year plus almost 200,000 Ch___ trade vessels.

The steep terrain which encircles Victoria Harbour has necessitated extensive reclamation of land from the sea since the establishment of the British settlement in 1841. This has been to provide port and wharf facilities but also to accommodate the growing city population. Even before this date, however, the previously scanty population of farmers and fishermen had resorted to coastal wetland reclamation to extend locally limited areas of usable land for the construction of paddy fields and shrimp and fish ponds.

Reclamation has thus come naturally to Hong Kong people as a way to increase the available area of low-ly____ land.

Of late, land has been reclaimed to allow for urban exp_____ due to the absence of a coastal plain. Although reclamation has enlarged Hong Kong's land area by less than 2%, over 25% of the land in the urban areas has been won from the sea. Early reclamation schemes were concentrated on the two sides of Vict____ Harbour. New cities beyond the harbour area notably at Tuen Mun and Shatin have been built on sites which required extensive hill terracing and landfill. Over 4 km2 of land has been reclaimed for these two schemes alone. With the growth of the population, the area of land reclaimed from the sea has undergone an exponential rise. Reclaimed land has provided sites for a variety of com______, ind______ and res_______ buildings and has in addition, provided much of the space required for tran_____, wharves and docks, the Kowloon-Canton Railway terminus, roads, including the Harbour Tunnel approaches, and Kai Tak Airport Armed forces' establishments, public buildings and public open spaces too have found sites on reclaimed land.

The demand for and shortage of building land around the harbour is reflected in high pro_____ values, the most valuable land being in reclaimed sections of the central business district. Large profits have been made from land even when it was won at great exp_____ from the sea.

Environmental impacts of reclamation

By making room for expanding urban areas at the expense of the foresh____ and sea b___, reclamation harms the marine environment in many ways. Formerly confined to shores around Victoria Harbour, even remote coastal areas of Hong Kong are now threatened by reclamation. in recent years development has begun to spread to Lantau and Lamma Islands. The beautiful remote Sai Kung Peninsula and the islands and inlets to the south are popular among walkers, picnickers, amateur sailors and skin divers and the beaches are among the most attractive in Hong Kong. Yet even these remote and economically unpromising areas have reclamation projects underway and planned when completed, the new shores will be both visually unattractive and difficult if not possible to access.

Reclamation alters the config_______ of the coastline and reduces the ar__ and vol_____ of water in an inlet, modifying ti____ ranges, cur_____ and w_____. These changes have serious effects on coastal eco____, changing forever the existing fabric of life.

Faster currents and bigger waves may cause erosion while reduced currents may cause sil____ in a harbour. The problem of pol______ is greatly aggravated by the reduction of water volume and area in sea inlets, as for example Tolo Harbour. Where the reclaimed land provides sites for industrial townships or intensive farming, additional sources of pollution result.

The destruction of tidal mangr____, mar____ and mud____ which are an important natural source of oxygen replenishment may further exaggerate pollution problems. The ecological consequences of these combined factors can be disastrous and may turn a once ecologically rich body of water into a marine desert. T____ Harbour in the New Territories is seriously threatened in this way from the combined effects of: volume loss with the completion of Pl_____ C___ Reservoir in 1969; land reclamation for Shatin, Tai Po and now Ma On Shan; rapidly expanding agricultural practices around streams draining into it and a dramatically expanded urban population in the new cities.

It is unfortunate that the most easily reclaimed coastal areas are those with the richest inter_____ flora and fauna. Reclamation can only be successful on shores sheltered heavy wave action. Thus, shallow sand and mudflats sea gra____, mang_____ are the first to reclaimed and such areas are in Hong Kong increasingly r___. Such shallow sheltered waters formerly yielded abundant f___ catches but also play an essential role in the life c____ of many marine species. Coastal wetlands are sources of nut____ for fish, provide their br_____ ground, and offer protection to their young. In the long run, continued coastal reclamation may be counter-productive in Hong Kong. There is a growing world-wide concern for coastal wetlands, threatened by development as a result of reclamation.

Coastal reclamation has, no doubt, contributed to Hong Kong's success in the provision of valuable low-lying land. Such areas of artificial land have an extremely high com______ value. Conversely, winning such narrow coastal strips of land from the sea and coastal wetlands can consequences that affect far more extensive areas than those immediately involved in the reclamation process. Unbridled reclamation could destroy virtually all of Hong Kong’s coastal wet____, replacing them with a steep wall of featureless granite blocks and concrete. People are already excluded from large areas of Hong Kong’s shoreline because of the steepness of the reclamation. As reclamation proceeds, so more people will be unable to access and instead of the shore being a part of their lives, it will be of no value, except to the industrial occupier. Land will have been obtained, but at what cost, and to whom?

INORGANIC NUTRIENTS POLLUTION

1. Eutrophication

The growth of. aquatic plants is usually limited by the low concentrations of ph_____ and n_____ in water. The high phosphate content of detergents supports excessive growth of algae (algal bloom). This nutritional enrich________ of water that promotes the growth of aquatic plants is called eutrophication.

a) Rich growth of blue-green algae

Initially the high phosphate content supports the rapid growth of both blue-green algae and green algae. Eventually the former outgrows the latter because the growth of green algae will be limited by the nitrate content in water while the b___-g_____ algae/bacteria can f__ atmospheric n______.

b) Thick mat of floating plants and oxygen depletion

Eutrophication encourages the growth of fl______ plants which will reduce the pen________ of light to the submerged plants. In addition the thick mat of floating plants on a cloudy day or at night will compete with fish for dis_____ oxygen. The depletion of the oxygen content may kill the fish as well as the submerged plants and the de___________ of the dead remains further deplete the oxygen content of water. This thick mat of floating plants such as water hyacinths may also interfere with navi______.

3. Disease

In addition the increasing nitrate content of water in reservoirs, in the order of 8 or 9 ppm nitrates, can cause an______ in babies. This disease is caused by a modified form of normal oxyhaemoglobin so that the oxygen carrying capacity of red blood cells is reduced and breathing becomes very difficult.

Reference Reading : Red tides

|From time to time areas of sea around Hong Kong (and particularly in T____ |[pic] |

|Harbour) take on a pink colour. This is the result of a red tide. Such | |

|tides have been documented in virtually all parts of the world, and they | |

|are brought about by dense aggregations of a single or several species of | |

|uni_______ al___which are mainly diatoms and dinoflagellates. | |

| | |

|On a world scale, much attention has focussed on red tides because they can| |

|result in mass dea_____ of fish and invertebrates and also in human | |

|po______ as a result of consuming infected s_______ (the most common type | |

|is called paralytic shellfish poisoning or PSP). The econ____ losses and | |

|health haz_____ resulting from red tides have led to the development in | |

|many countries of extensive surveillance and management programmes. | |

In Hong Kong, red tides were first noted in 1957, but, since then the number of incidents recorded has grown substantially. The location and frequency of such occurrences up to 1983 are illustrated. To Update this information for Tolo Harbour, the years 1984, 1985 and 1986 there have been 15, 16 and 17 incidents reported.

So far, eighteen species of algae have been identified as the causative agents of red tides in Hong Kong, and 15 of these are dinoflagellates. The most common species are Noctiluca scintillans, Gymnodinium spp. and Prorocentrum spp. (the last two being tox__ producing forms). An analysis of the seasonal variation in frequency of red tides between 1975 and 1984 shows that they occur more frequently in sp___(Mar and Apr).

It is believed that the drain____ of large quantities of organic matter into Hong Kong's co_____ waters (i.e. the pollution load) provides the potential for the exponential growth of these dinoflagellates, and that the increasing t__________ and l intensity in spring, coupled with very little verticle mixing in the water column and lower surface sal_____ at this time "trigger" the outbreak of red tides.

Among the red tide organisms, the t____ producing species can result in the death of fish and marine invertebrates. Their toxins can also acc_______ in shellfish and consumption of the intoxicated shellfish by humans may lead to various forms of "s_______ p_________" such as paralytic shellfish poisoning (PSP), neurotoxic shellfish Poisoning (NSP) and diarrhetic shellfish poisoning DSP). Red tides in general lead to deox__________ of seawater and this can also lead to fish kills by hypoxia or simply by g__ clogging.

So far the major effects of toxic red tides in Hong Kong have been in terms of fish kills in the maric______ industry. Between 1980 and 1984, 11 such kills were attributed to red tides, resulting in a total loss of 86 tonnes of fish valued at HK$4.2 million. There is no evidence of any impact on the shellfish industry of Hong Kong. However, since the major threat of toxic red tides in relation to shellfish is to the consumer rather than the shellfish, the Agriculture, Fisheries and Con_________ Department has been carrying out toxicity tests on red tides. They have concluded that the potential risk of toxin accumulation in shellfish cannot be overlooked, although no cases of shellfish poisoning have yet been documented in Hong Kong. Thus, at present, the management strategy adopted in Hong Kong has.been developed with special reference to mariculture.

Red tides can also cause minor irr______ to the eyes, skin and respiratory system of swimmers. Again, there is no documented evidence of such occurrences in Hong Kong, but this is hardly surprising since such minor ailments are seldom reported and never recorded. Also, fish and invertebrates killed by red tides may be washed ashore and decay to produce unpleasant od_____ and an unpleasant vis___ impact. This decreases the general amenity value of the beach for some time. In Hong Kong only one such incident has been recorded, in 1980, when the south-western shores of T___ H______ were affected for several days.

CHEMICAL POLLUTION

Chemical pollution is caused by pest______ or ind_______ chemical wastes discharged into water.

A. Pesticides

Pesticides are poi______ chemicals deliberately sprayed to kill a particular organism (e.g. h____icides, f____icides and i_____icides). Their application in agriculture and horticulture may cause pollution because they may poison man or other non-tar___ organisms.

Since DDT is soluble in f__ but insoluble in water or in blood, it will be accumulated in fa___ tissues and will not be ex_____ out of the animal. Thus DDT concentration slowly builds up inside the body. Thus DDT is con___________ progressively as it moves up the f____ c_____.

B. Industrial wastes

Some industries discharge harmful chemical wastes into the rivers that eventually reach the sea. These wastes include acids as well as heavy metal salts like l___, mer_____ and cad____. These heavy metal salts can be concentrated along the food chains.

THERMAL POLLUTION

Water may be withdrawn from the river or the sea to c___ some industrial process such as that in a p____ station. There is a power station in Lamma Island and another in Ap Lei Chau in Hong Kong. The hot effluent from the power station will raise the water temperature.

1. High temperature will raise the m________ rate and oxygen consumption of the aquatic organisms. It causes some fish like salmon and trout die or migrate to other places. They are replaced by other fish that normally inhabit warmer waters. The ship worm Teredo which causes timber damage is said to flourish. Thus thermal pollution causes change in the aquatic community.

2. Theoretically high temperature will decrease the oxygen sol______ in water and the resulting deoxygenation may seriously affect the aquatic organisms. In practice the hot water is returned from the power station in greatly agitated form that has been supersaturated with oxygen.

OiL POLLUTION

Oil is a very obvious pollutant of the seas. It is caused by wreck of oil tankers, cleaning of the tanks and seeping from shipping and shipyards.

A. Effects of oil pollution

1. The spilled oil covering the seashores kills seaweed, molluscs and crustaceans.

2. The spilled oil also kills sea b____ because of the following reasons:

a) The sea birds cannot fly when their feathers become soaked with oil.

b) When the sea birds clean their feathers, they ingest sufficient oil to poison themselves.

c) The oil interferes with the insulation provided by the feathers so that the sea birds easily die of cold or pneumonia.

3. The oil contaminates beaches and thus spoils a valuable rec_________ resource.

SILT POLLUTION

|A. Turbid water |Excessive silt in water increases tur______ and thus reduces light penetration. As a result the photosynthesis|

| |of the aquatic plants is reduced with a consequent reduction in oxygen production. |

|B. Damage bottom dwellers |The settlement of the silts may bury the bottom dw______ organisms. |

|C. Affect uses by man |The turbid water becomes less suitable to man for dr______ purpose or rec________ amenity. |

|D. Eutrophication |The excessive silt resulted from soil erosion introduces large amount of nitrates and phosphates into water |

| |that may promote e____________ and algal bloom. |

|E. Change drainage pattern |The p____ management of soil resulted from improper practices in agriculture and timbering in several |

| |provinces in China silted up the water courses that led to fl______ in early 1982. |

CONTROL OF WATER POLLUTION

A. Sewage treatment plant

Domestic sewage is purified in a sewage treatment plant before it is discharged into rivers or seas to reduce water pollution and the hazard on health. Sewage is treated to different stages and by different processes.

1. Primary treatment

During this treatment the solid matter and suspended particles are removed.

a) Screening

Sewage passes through a sieve (grid) which scr____ out bulky solid matter such as bottles, paper, sticks and stones.

b) Removing grit

The 'filtered' sewage flows along a grit chamber to allow heavy particles se____ out at the bottom as grit which is then removed away by worm conveyor.

c) Sedimentation (settling)

The suspension flows from the grit chamber into the sedimentation tank (settling chamber) where the large particles of or_____ matter se____ down at the bottom as primary sludge within 10 hours. Some fats and wood will float on the surface. These scum are skimmed off and may be treated further with sludge in a sl_____ digestion chamber (fermentation tank). The supernatant liquid is, called eff_____. This primary treatment can reduce the BOD of the sewage by about 40 percent.

|[pic] |

2. Secondary treatment

During this treatment the organic matter in effluent is oxi_____ to harmless forms. There are two methods of effluent treatment.

Percolating filter (Trickling filter)

i) The effluent is sprayed by a sprinkler (which may be fitted on a slowly-rotating arm) onto a 2 metre deep fil___ bed (tank). This 'filter' is composed of gravel of 4 to 6 cm in diameter. These gr_____ expose a large s______ area to the a__ for oxidation, and support rapid growth of a_______ bacteria, fungi, protozoa and other m_____-organisms.

ii) The saprophytic microbes use the organic matter in the effluent as f___ and thus purify the sewage. Up to this stage the BOD of the sewage has been reduced by as much as 90 percent.

iii) The ciliated prot_____, nematode worms, Annelid w____, insect and fly lar___ also live in the filter. They feed on micro-________ particularly bacteria. This prevents the filter bed from becoming blocked by the over-growth of the micro-organisms. In reality, the com_______ of organisms that strive in the filter bed make up an ecosy_______ that is the heart of the functioning of the secondary treatment.

iv) The percolate is passed to a humus tank for sett_____. The effluent is chlor_____ and ready for discharged.

Activated sludge

i) The effluent introduced into the ae_______ tank is aerated by either violent mec_______ stirring or by the bubbling of comp_____ air through the fluid. This treatment greatly encourages the growth of b________ and p_________in a thin layer of sludge which con_____ much of the organic matter of the sewage.

ii) The sewage is passed into a set_______ tank where micro-organisms and large particles settle down as sludge. The effluent is chlorinated and discharged into river. A portion of sludge is inoc______ into the aeration tank to encourage a rapid growth of the desirable micro-organisms. The bulk of the sludge is removed to the s______ digestion chamber (fermentation tank).

|[pic] |

Sludge digestion chamber (fermentation tank)

i) The sludge in this chamber undergoes an________ decomposition that produces carbon dioxide and methane. M_______ can be used as fuel for power generation or for heat.

ii) The remains of sludge can be dried and used as soil cond______. It improves water-retaining capacity and supplies certain minerals such as nitrates and phosphates. But it may contain pathogens or some toxic industrial wastes. Often it is dumped at sea, or used as land___.

3. Tertiary treatment

i) This involves further chemical and biological treatment which renders the sewage effluent fit for drinking. However, this is very expensive and is only carried out when absolutely necessary. Hong Kong only have a few number of secondary treatment plants.

ii) Lagoons and ponds -- This treatment is used in the Mediterranean and tropics. A series of exposed lagoon lakes is constructed with sewage entering at one end and coming out at the other and.

Photosynthetic algae or plants remove the fertilizing elements, mainly ph______ and ni_____ to reduce the danger of eutrophication. While bacteria grow on the muddy substrate reduces the BOD further.

iii) Effluents are disin_____ chemically before discharged.

B. Legislation

✓ Leg_______ should be raised to impose heavy punishing f___ on those discharge untreated agricultural and industrial wastes into rivers or sea.

✓ The permitted level of toxic substance in industrial effluents should be more st____.

✓ Legislation is effective only to the extent that it is enf______.

✓ Citizens are held financially responsible (p_______ p___ principle) for part of the sewage treatment costs; companies are charged against the pollution caused by their activities.

LAND POLLUTION

Land pollution is the addition of undesirable matter to the land that damage the ter_______ organisms, reduce the uses of the land by man for agri_______, res_______, rec_______ or other purposes, or increase the risk of h______ hazards to man

1. Large quantity of domestic refuse

The daily production of solid waste in HK is about 9,500 tonnes of which about 60% is domestic refuse and the remaining 40% is industrial waste.

Waste collected in the major urban centres of population are delivered to the ref___ tr_____ st_____ where the waste will be compacted and containerised in purpose built containers for onward transportation to the remote landfills.

2. Methods of solid waste disposal

a) Sanitary landfill

• Sanitary landfill involves covering the solid wastes with a layer of s___ every day. This method is less eye-sore and is more satisfactory than the former method. It has several drawbacks:

• It is more expensive.

• It still can pollute gr______ water.

• Covering a natural habitat with refuse is ecologically dest________.

• Such sanitary landfill has limited life____; and in H.K., we cannot spare many suitable sites for such purpose.

• The met_____ gas resulting from the anaerobic decomposition in the depths of the fill may seep into buildings and pose an explosion hazard. Thus the filled land is of limited uses.

• One such filled land in Tap Shek Kok is used as the construction site of the new power station of China Electric Company Limited. Another one in Tsuen Wan is planned to build a million-dollars outdoor recreational complex.

c) Incineration (ALL closed by 1996)

Incineration involves burning solid wastes, thus reducing their bu__ before final disposal. There is an incinerator plant in Kennedy Town on Hong Kong Island. It can handle 750 tons of refuse and burn them down to about 100 tons of ash which is removed and dumped on reclamation sites. The ash is alkaline and contains boron at level highly toxic to most plants.

i) The incinerator has several drawbacks:

• a__ pollution: by producing both particulate and nitrogen oxide. This pollution can be reduced by equipping the incinerator with efficient air pollution control apparatus

• expensive.

ii) The incinerator has several advantages:

• It reduces the v______ of the wastes by 80 % therefore much less area is required for final disposal.It can handle a m______ of garbage and rubbish without prior separation which is a process far too costly.

• It eliminates the h______ hazards associated with dumping.

• When the ash is carried along the conveyor belt, electro-magnets are used to remove ferrous metals. It is an example of solid waste rec______.

The heat produced in the process is used to drive an electricity generator. This provides p____ for the incinerator and helps to offset running costs.

Q. What are your recommendations to the local waste problem?

• Improve infrastructure to facilitate source separation and recycling of domestic waste

• Implement product responsibility schemes to reduce waste ASAP

• Appropriate economic instruments and charges to encourage waste reduction/recycling ASAP

• Develop a more stable and healthy local waste recycling industry (Eco-park and long term policy)

• Adopt appropriate waste treatment methods (vol. reduction) –Decision is needed ASAP

|焚化爐勢重現香港 成本較堆填高數倍2010年前不徵垃圾費 |[pic] |

|明報 減廢系列之一 | |

| | |

|1997年起關閉的焚化爐，勢將「捲土重來」。 | |

|堆填區10 年內爆滿 | |

|消息指出，堆填區10年後爆滿，處理垃圾問題迫在眉睫，政府希望 | |

|一籃子措施能盡快上馬。 | |

|但有關文件不會觸及最具爭議的焚化爐選址及垃圾費水平問題。 | |

|現時香港有3個堆填區，每日接收9280噸都市固體廢物(年約340萬噸| |

|)，當中有7000多噸來自家居、2200多噸來自工商業，政府預計6至1| |

|0年內堆填區會飽和，垃圾處置屆時將無以為繼。消息人士指《路向 | |

|大綱》會策略性地闡述香港到2014年的處理垃圾方案，政府先會集中| |

|「減廢」工作。家居方面，會推動全港屋苑做源頭分類；工商方面 | |

|，研究立法強制生產者回收產品及提供回收途徑；同時會在屯門環 | |

|保園引進多種回收工業，讓本地廢物循環再造。 | |

|香港目前家居廢物回收率僅14%，工商廢物回收率則有四成，政府計| |

|劃在未來10年將整體都市固體廢物回收量提升至50%，餘下約五成，| |

|即平均每日4600噸難以回收或缺乏回收價值的廢物，傾向透過焚化 | |

|爐燒毁。 | |

|消息人士謂，政府曾考慮其他處理方式，包括堆肥及再闢堆填區， | |

|但前者會產生惡臭，難以大規模實行，後者亦非長遠之策，因此焚 | |

|化是最終、最可行的大型處理垃圾方法。 | |

|不過焚化營運成本高昂，據政府早前提交立法會的文件顯示，不同 | |

|焚化技術焚燒一噸垃圾的營運成本近500元，比堆填區棄置的125元 | |

|高出3倍；若使用最先進的氣化技術，以逾攝氏1000度熱解氣化廢物| |

|，每噸營運成本高達近800元。 | |

|消息透露，在「污者自付」原則下，政府有必要透過徵收垃圾費支 | |

|付龐大的焚化開支。政府在5年內，即2010年前，也不會徵收垃圾費| |

|，直至焚化爐落實運作。 | |

|選址三條件：遠離東面 人口少 交通便利 | |

|■遠離香港東面，因本港多吹東風，易將焚化爐排放物吹到各區； | |

|■要在 人口密度低地區，減少社區影響； | |

|■要水陸交通便利，方便運輸。 | |

|地球之友助理總幹事劉祉鋒認同這三大原則，估計最大機會的選址 | |

|是在新界西區的沿海地區，如屯門及天水圍。 | |

|焚化爐在70至80年代是香港主要處理垃圾設施，至90年代因空氣污 | |

|染及排放致癌物問題，香港5個焚化爐陸續關閉。消息人士強調，現| |

|今焚化爐技術已經大躍進，排放出來的氣體潔淨得像清新空氣，有 | |

|信心不會污染本港環境。 | |

NOISE POLLUTION

Noise is a very loud and unpleasant sound. It is regarded as a pollutant because it is irr_______, causes m______ stress and may even lead to temporary or permanent d________.

A. Measurement of noise

The l_________ (intensity) of sound is measured by scientists in units called decibels (dB) which are based on the intensity just audible to the human ears. For example 80 dB means l08 times the intensity just audible to human ear. Noise can be measured by a sound-level meter.

B. Effects of noise pollution

1. Brief exposure to extremely loud sound at the painful level above 120 dB can rupture ear______ and cause immediate deafness.

2. Continuous exposure to very loud sound within the range of 80 dB to 100 dB will eventually lead to partial or complete deafness.

3. Continuous exposure to loud sound within the range of 50 dB to 80 dB may affect the physio______ and psycho_______ processes of the body. The changes include increased secretion of adrenal hormones and gastric juice, increase in blood p_______ and rate of heart beat. Prolonged effect may lead to irritation, headache and mental st______.

C. Sources of noise pollution in Hong Kong

1. Traffic Noise

The traffic den____ in Hong Kong is very high because there are over 220,000 registered vehicles on this tiny place. The t___ buildings embracing the streets reflect sounds that aggravate the noise pollution. The heavy traffic in a road junction in Central was measured to have an average level of 80 dB.

2. Industrial Noise

Machines in f______ produce an average noise at 85 dB. Most noise comes from textile, garment and leathering industries.

3. Construction noise

Noise is produced by the con_______ machines like loaders, concrete mixers, excavators, compressors, pile drivers and pneumatic drills. They produce an average noise at 80 dB except the last two produce noise at about 90 dB.

D. Control of noise pollution in Hong Kong

1. Control of traffic noise

a) Reducing the number of registered ve____ by heavy tax will not only reduce the serious problem of traffic congestion but also help to reduce the noise produced in streets. If the increase in the number of vehicles is not restricted, in ten years' time the number will rise up to 400,000 vehicles.

b) By legislation vehicles should be ins______regularly to ban the noisy vehicles to run in streets.

c) Rows of bu___ growing along the sides of the roads can reduce noise by about 8 decibels.

2. More efficient noise suppressers should be designed for both motor vehicles, industrial and construction machines to minimize the noise level. Workers operating noisy machines should be supplied with ear pl___ to protect their ears.

3. Legislation governs the ti___ when the activities producing loud noise are prohibited.

a) Piling and other loud construction noise are prohibited between 11 pan. and 6 am. on normal days.

b) Aircraft stop taking off and landing between midnight and 6:30 am. The majority of taking off and landing use the route over the sea that helps to reduce the effect of noise pollution over the citizens in Kowloon. The permanent solution was to remove the airport to the new site in Chek Lap Kok at the north of Lantau Island.

e) Prosecution should be enforced on those producing loud noise after 11 p.m.

|Sources of noise |Noise intensity |Subjective impression | |

| |(decibels) | | |

| | | |[pic] |

|Jet aircraft taking off(15 m) |140 | | |

|Hydraulic press (1m) |130 |Painfully loud | |

|Loud rock band |120 | | |

|Thunder |110 |Uncomfortably loud | |

|Some factory machines |100 | | |

|Traffic in enclosed streets |90 |Very loud | |

|Lawn-mower at 17 m |80 | | |

|Traffic on open roads, vacuum cleaner |70 |Loud | |

|Average traffic, average talking |60 | | |

|Air-conditioner at 4 m, average home |50 | | |

|Quiet radio |40 |Quiet | |

|Quiet home |30 | | |

|Whispering |20 |Very quiet | |

| | | | |

| | | | |

|Sound -proof room 0 | |Silent | |

RADIATION POLLUTION

A. Sources of radiation

1. The rock and soil of the en_________ contain certain radioactive elements like uranium, thorium and potassium-40. They emit certain amount of natural radiation.

2. The f__ -out from nuclear bomb tests or accident at a n______ power station adds radiation to our environment.

B. Effects of radioactive pollution

Strontium-90 is a very common radioactive fall-out. It has a half life of 28 years and is metabolized similarly to ca______ so that it is easily absorbed by plants and is concentrated along the foodchain. Thus when we eat these contaminated plants and animals, we will also accumulate this radioactive waste inside our body.

1. Carcinogenic (cancer-causing)

Bone ma_____ are very sensitive to very low dose of radiation which may cause leuk_____ (blood cancer. Radiation may cause cancerous growth of the tissues in other organs of the body like the skin, mouth and lungs.

2. Genetic damage

When the radioactive wastes are accumulated in the sex organs, they may speed up the m_______ rate inside the g____ cells. These may lead to genetic ab___________ in future generations.

B. Fire and Deforestation

1. Planned fire

Only destroys certain vegetation but saves the fire-re______ plants. After such surface fire, the a__ produced fertilize the land.

2. Disastrous “crown fire”

Crown fire destroys most veget_______ as well as the slow moving animals.

3. The undesirable effects of fire:

a) Great temperature fluctuation

The burnt soil gives a black surface which is a good absorber of solar energy. Without any plant cover the soil rapidly gains heat and loses heat i.e. great temperature fluctuation

| b) Water loss |[pic] |

|i) Humus is an important component of soil to | |

|hold water. Burnt humus means more water loss by| |

|evaporation. | |

| | |

|ii) The resulting higher soil temperature | |

|further increases the loss of water by | |

|evaporation. | |

| | |

|iii) Without any plant cover the soft surface | |

|further dries up by wind. | |

| | |

|c) Less organic food | |

|Due to loss of humus. Less food is available to | |

|the soil animals. | |

| | |

|d) Risk of nutrient loss | |

|The resulting ash and decay of the dead plants | |

|rapidly increases the concentration of several | |

|elements such as potassium, calcium, magnesium| |

|and phosphorus. These support growth of new | |

|plants but could be readily washed away by | |

|rainfall -leaching. | |

| | |

End

-----------------------

How does pollution circulate in the Pearl River Delta?

Pollution Circulation Pattern in the Pearl River Delta

The pollution rises from everywhere, then it moves toward the cooler air over the Pearl River Estuary, then it falls and spreads out. This is why the Western NT and the Tung Chung area are especially polluted. (HKUST)

[pic]

dom______

agr__________

in________

Se_____ and ref____

pest______

W____-killer

Chemical fer________

• gas emi______,

• radio______ waste,

• toxic ch______

Biodegradable pollutants

Non-biodegradable pollutants

or_____ substances that can be decomposed by natural processes (e.g. putrefaction by bacteria) into harmless substances. e.g. farm waste, manure, sewage

cannot be de_________ by natural decomposers. Some of them have their toxicity persisted indefinitely.

could be accumulated along food chains --- bio-mag__________.

inorganic substances such as mer____, lead

cadmium

organic compounds like D___ that are degraded slowly

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download