Marine Pollution Causes Effects And Control Environmental Sciences Essay

The phrase heavy metals is used here as a general name for metals with densities in excess of 5 g/cm3. About 15 species are of practical concern. Heavy metals may be applied to soils deliberately to correct nutrient deficiencies or to kill pests. Very small amounts are needed to correct deficiencies, and these do not cause pollution. Repeated applications of inorganic pesticides containing heavy metals (for example, in sprays applied to fruit trees) may add amounts to soils large enough to be harmful. In contrast to organic pesticides, heavy metals do not disappear through decomposition but remain in soil indefinitely. Additional sources of soil contamination by heavy metals are industrial and traffic exhausts, flooding of land by contaminated waters, sewage sludge applied to land, and disposal of other refuse.

Heavy metals participate in several kinds of reactions in soils, and these affect their concentrations and solubility. The metal ions tend to be bonded to soil constituents through cation exchange; this may amount to substantial quantities even though concentrations in the soil solution are usually low. Some soil constituents seem to have specific affinities for heavy metal ions, resulting in their preferential adsorption over more abundant cations. The concentrations of heavy metals in the soil solution are also affected by equilibria with hydroxyl, carbonate, and phosphate ions. Precipitation of heavy metals by these anions can limit concentrations even though fairly large amounts are added to soil. On the other hand, some heavy metal ions are strongly chelated by organic substances of low molecular weight, thereby altering their adsorption behavior and permitting rather high concentrations in the soil solution. The actual concentration in a soil is thus a function of reactions of heavy metals with a variety of soil constituents.

Cadmium is considered as one of the most hazardous of the heavy metals because of its presumed effect on the development of vascular disease. Amounts of cadmium in soils are normally below 1 ppm, but values as high as 1700 ppm have been reported for surface samples collected near zinc-ore smelters. Cadmium is usually associated with zinc in nature, and the geochemical relationship between the two leads to their common occurrence with Zn/Cd ratios near 900. Cadmium is easily taken up by most plants. Some are quite sensitive to excess cadmium, and others are not.

(ii) Chromium (Cr)

This metal is a major component of the wastes of the plating industry. Cr is toxic for plant growth only at high concentrations. Chromium mobility within plants is extremely low. Soil pollution by chromium is seldom a problem because it is taken up by plants as chromate, a form that hardly occurs at prevailing pH values and redox potentials.

(iii) Cobalt (Co)

This can be highly toxic to plants. Most plant species cannot tolerate concentrations of cobalt exceeding 0.1 ppm. Usually cobalt contents of soil do not exceed 10 ppm. Preferential cobalt adsorption on soil constituents and fixation in clay mineral lattices might add to the problem.

(iv) Copper (Cu)

Copper is toxic to most plants at concentrations exceeding 0.1 ppm. Its concentration in drinking water for human consumption is considered safe when not exceeding 1.0 ppm. Concentrations above 20 ppm in feed and forage are toxic to sheep. Normal copper contents of soils are around 20 ppm. Mobility and displacement of copper in soils are low because of its strong bonding with organic matter and clay minerals.

(v) Lead (Pb)

This may accumulate in soils along roads from traffic exhausts and in the vicinities of lead-zinc smelters. Roadside concentrations as high as 2400 ppm have been reported. While (excessive) intake of lead by humans and animals is considered a serious health hazard, the primary pathway of such intakes is probably via surface contamination of crops and grasses (eaten by grazing animals) rather than via plant uptake. The mobility of lead in soil and plants tends to be low though in some cases considerable uptake by plants has been observed. Normal lead levels in plants range from 0.5-3 ppm. With respect to plant growth, lead toxicity levels appear to differ considerably for different plant species.

(vi) Mercury (Hg)

Extensive mercury poisoning was first reported at Minamata, Japan, in 1953. As a result of the strong interactions between mercury compounds and soil constituents, displacement of mercury in forms other than vapor is usually very low. Methylation of mercury, possibly occurring in nature under restricted conditions, constitutes one of the most serious hazards related to this element, because in this form mercury will accumulate easily in food chains. Because of this hazard, the use of alkylmercury fungicides for seed dressings has been banned in many countries.

(vii) Molybdenum (Mo)

This element is best known for its deficiency in certain soils. Under normal conditions molybdenum predominates in anionic form (molybdate), subject to adsorption by iron oxides and hydroxides much like phosphate. While normal molybdenum content in plants is around 0.1 ppm, toxicity symptoms have been observed at levels above 200-300 ppm (dry matter).

(viii) Nickel (Ni)

This element tends to be highly toxic to plants. As it is easily taken up by plants when present in soils, care must be exercised in disposal of waste containing nickel. Total nickel contents in soils range from 5-500 ppm, with 100 ppm as a rough mean value. The concentration in the soil solution is usually around 0.005-0.05 ppm, and contents in healthy plants do not exceed 1 ppm (dry matter).

(ix) Zinc (Zn)

The use of this element in galvanized iron is widespread. Zinc commonly occurs in soils at levels of 10-300 ppm, with 30-50 ppm as a rough average range. Sewage sludges may have very high zinc contents, and the possible accumulation of zinc in soil after disposal of such wastes deserves attention. In plants, zinc will become toxic at levels exceeding about 400 ppm (dry matter), where it probably interferes with the uptake of other essential elements. In soil, zinc appears to be rather mobile.

Wastes and soil pollution

The large amount of waste produced every day in towns and cities and other human settlements end up in soil. The most common kinds of wastes can be classified into four types: agricultural, industrial, municipal, and nuclear (Table 5.13).

Table 5.13. Wastes and Soil Pollution

Sources

Effects

Agriculture

(i) accumulation of animal manures

(ii) excessive input of chemical fertilizers

(iii) illicit dumping of tainted crops on land

Mining and Quarrying

(i) using of explosives to blow up mines

(ii) using of machineries which emit toxic byproducts and leaks to the ground

Sewage sludge

Improper sanitation system causes sludge to leak at surrounding soil

Household

(i) improper waste disposal system causes waste accumulation

(ii) improper sanitation system

Dredged spoils

Method of dredging at fertile land causes soil infertility, leaving the soil more prone to external pollution

Demolition and construction

Nonbiodegradable rubbles or debris which undergo chemical reactions and increase soil toxicity

Industrial

Poisonous/toxic gases which are not filtered or neutralized

Control of Soil pollution

The following general methods of controlling soil pollution are in use.

Effluents should be properly treated before discharging them on to soil.

Solid wastes should be properly collected and disposed of by appropriate method.

From the wastes, recovery of useful products should be done.

Microbial degradation of biodegradable substances reduces soil pollution.

5.5 Marine Pollution: Causes, Effects and Control

The sea, which covers around 70 per cent of the earth’s surface, is home to millions of fish, crustaceans, mammals, microorganisms, and plants. It is a vital source of food for both animals and people. Thousands of birds rely on the sea for their daily food supplies. Fishermen throughout the world catch over 90 million tons of fish every year, and in many developing countries, fish is the principal source of protein.

People also depend on the sea for many of their medicines. Marine animals and plants contain many chemicals that can be used to cure human ailments: an estimated 500 sea species yield chemicals that could help treat cancer.

But the oceans now are in a very bad shape. People have treated the sea as a dumping ground for thousands of years, offloading rubbish, sewage, and more recently – industrial waste. Marine pollution frequently originates on land, entering the sea via rivers and pipelines. This means that coastal waters are dirtier than the open seas, with estuaries and harbours being especially badly affected. Additional pollution is actually created at sea by activities such as dredging, drilling for oil and minerals, and shipping.

Marine Pollution

For close to thirty years, most academics studying the phenomena of marine pollution have adhered to a definition developed by a UN body, the Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP), who define it as

“Introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazard to human health, hindrance to marine activities including fishing, impairment of quality for use of sea-water, and reduction of amenities.”

The definition has two important aspects:

First, it is action oriented. Marine pollution results from human activity. Thus, earthquakes or volcanic eruptions in the ocean floor and subsequent damage or change to the ocean ecosystems is not considered as pollution.

Second, the definition is amenable to measurement. Marine pollution is harmful, and its danger can be identified in a variety of ways. For example, it is easy to see the deleterious effects that oil spills have on the sea birds and mammals that happen to run into them. Scientists likewise can readily identify various toxic substances found in the marine environment, measure their quantities, and provide estimates of their potential danger for the health of both marine life and humans.

The important sources of marine pollution are shown in Fig. 5.4.

Toxics

Toxic waste is the most harmful form of pollution to marine creatures. Once a form of toxic waste affects an organism, it can be quickly passed along the food chain and might eventually end up in seafood, causing various problems. Toxic wastes arrive from the leakage of landfills, dumps, mines and farms. Sewage and industrial wastes introduce chemical pollutants like DDT. Farm chemicals (insecticides and herbicides) along with heavy metals (e.g. mercury and zinc) can have disastrous effect on marine life.

Mercury the most dangerous toxic element

Top priority is usually given to control the pollutant that poses a threat to human health, the most serious being mercury. Major sources of mercury include rivers, marine outfalls and direct dumping of chemical waste. Natural inputs like the weathering of mercury-bearing rocks, volcanic gases also contribute to mercury in the ocean. Dissolved mercury in the sea is adsorbed onto particulate matter and also forms stable complexes with organic compounds occurring in the sea. Inorganic mercury can be easily accumulated by living organisms.

Fig. 5.4. Sources of marine pollution.

A classic example of mercury poisoning happened in Minamata, a small Japanese coastal town dependent on fishing for a livelihood. In 1952, a nearby factory producing vinyl chloride and acetaldehyde using mercuric sulphate as a catalyst dumped its wastes in Minamata bay. Typically 300-1000 g of mercury is lost for each ton of acetaldehyde produced, 5% of which is in the form of methyl mercury. Mercuric chloride when used as a catalyst produces 1 g of methyl mercury per ton of product. Accumulated contamination was as high as 200 ppm mercury at the factory outfall.

The effects began with the death of a large number of fish in the early 1950s. This affected birds, cats, pigs, and humans. Birds lost coordination to fly. Cats were seen running in circles and foaming at the mouth. Local residents called these occurrences “the disease of the dancing cats”. Later, the disease was termed “Minamata Disease” when humans began to have symptoms of methyl mercury poisoning.

Other Toxic Materials

Toxic materials are substances derived from industrial, agricultural, household cleaning, gardening and automotive products. They do not always kill wildlife, but they can threaten inland and coastal waters. Examples of toxic materials include:

Dioxins come from bleaching paper, incineration of solid wastes containing PVC and other materials, and the process of making herbicides. Dioxins and related compounds degrade slowly and are toxic to marine life. They cause genetic chromosomal aberrations in marine life and are suspected of causing cancer in humans.

PCBs are used in the making electrical equipments and hydraulic fluids. Developmental problems in children and reproductive problems in some other animals have been linked to PCBs. Slowly degrading PCBs accumulate as they pass along the ocean food web.

PAHs come from oil spills, road runoff, and burning wood and coal.

Marine life and people suffer ill effects from PAHs. PAHs cause genetic and chromosomal problems in fish and most marine organisms.

Sewage and fertilizers

The discharge of sewage can cause public health problems either from contact with polluted waters or from consumption of contaminated fish or shellfish. The discharge of untreated sewage effluents also produces long-term adverse impacts on the ecology of critical coastal ecosystems in localized areas due to the contribution of nutrients and other pollutants. Pollution due to inadequate sewage disposal causes nutrient enrichment around population centers, and high nutrient levels and even eutrophication near treatment facilities and sewage outfalls.

Around the world, untreated sewage flows into coastal waters, carrying organic waste and nutrients that can lead to oxygen depletion, as well as disease-causing bacteria and parasites that require closing beaches and shellfish beds. The inadequate number of sewage treatment plants in operation, combined with poor operating conditions of available treatment plants, and the disposal practices of discharging mostly untreated wastewater are likely to have an adverse effect on the ocean.

Oil

The sites most vulnerable for accidents are areas where tankers and barges move through restricted channels and in the vicinity of ports. In spite of regulations established, tankers and barges do not always use port facilities for the disposal of bilge and tank washing and wastes, and a significant amount of oil, which exceeds that from accidental oil spills, is discharged into the coastal areas.

The impact of oil pollution on the ecology of coastal and marine ecosystems is particularly destructive following massive oil spills caused by maritime accidents. However, gas exchange between the water and the atmosphere is decreased by oil remaining on the surface of the water, with the possible result of oxygen depletion in enclosed bays where surface wave action is minimal. Coral death results from smothering when submerged oil directly adheres to coral surfaces and oil slicks affect sea birds and other marine animals. In addition, tar accumulation on beaches reduces tourism potential of coastal areas.

Mining and Dredging

Mining affects the marine ecosystem and the habitat. Mining can erode beaches, degrade water quality, and spoil coastal habitats. Mining coral to process for lime can remove the habitat of local marine species and weakens coastal storm defense. Mined or dredged areas take a very long time to recover. Because of this, strict regulations govern the dredging of the ocean floor

Synthetic Organic Chemicals

Many different synthetic organic chemicals enter the ocean and become incorporated into organisms. Ingestion of small amounts can cause illness or death. Halogenated hydrocarbons are a class of synthetic hydrocarbon compounds that contain chlorine, bromine, or iodine are used in pesticides, flame retardants, industrial solvents, and cleaning fluids. The level of synthetic organic chemicals in seawater is usually very low, but some organisms can concentrate these toxic substances in their flesh at higher levels in the food chain. That is an example of biological amplification.

Marine debris

More garbage such as plastic bags, rope, helium balloons, and stray fishing gear, build up in the oceans every year. Synthetic materials stay in the environment for years, killing or injuring ocean species, like whales and turtles, which mistake litter for food or get entangled in it. Ghost fishing by lost nets not only kills innocent ocean creatures but also reduces fishers’ catches.

Plastic is not biodegradable and therefore affects the oceans for long periods of time. Sea turtles mistake plastic bags for jellyfish and die from internal blockages. Seals and sea lions starve after being muzzled by six-pack rings or entangled by nets.

Effects of Marine Pollution on Living Marine Resources

Tens of thousands of chemicals are used to meet society’s technological and economic needs. Marine pollution is not only attributed to oil and chemical spills, but much of the debris and toxic substances affecting marine animals, in actual fact, originate on land. Pesticides, plastic bags, balloons, cigarette butts, motor oil, fishing line, find their way into local waterways either though direct dumping, through storm drains (whatever is left on streets, parking lots, can be washed into storm drains which lead directly to local waters), or through sanitary sewers, affecting living marine resources.

The time taken by a few common types of litter to biodegrade is given in Table 5.14.

Two basic ways by which chemical contaminants can affect living marine resources are:

By directly affecting the exposed organism’s own health and survival, and

By contaminating those resources that other species, including humans, may consume.

Researchers have been studying this dual impact of contaminants using a variety of marine organisms ranging from bottom-dwelling invertebrates and fish to species such as salmon and marine mammals. These biological effects include:

Diseases such as liver lesions in bottom fish,

Decreased reproductive success in bottom fish,

Impaired immune competence in anadromous fish, and

Growth impairment in invertebrates.

Marine pollution can have serious economic impact on coastal activities and on those who exploit the resources of the sea. In most cases such damage is caused primarily by the physical properties of these pollutants creating nuisance and hazardous conditions.

Table 5.14. Degradation time of materials

Materials

Time to degrade

Materials

Time to degrade

Tin cans

50 years

Wool

1 year

Painted wood

13 years

Plastic rings

400+ years

Newspaper

6 weeks

Plastic bottles

450 years

Paper towels

2 – 4 weeks

Aluminium cans

200 years

Disposable diapers

450 years

Monofilament line

600 years

Polystyrene foam

Indefinite

Cardboard

2 months

Impact on coastal activities

Contamination of coastal amenity areas is a common feature of many spills leading to public disquiet and interference with recreational activities such as bathing, boating, angling and diving. Hotel and restaurant owners and others who gain their livelihood from the tourist trade can also be affected.

Oil and chemical spills can adversely affect industries that rely on a clean supply of seawater for their normal operations. If substantial quantities of floating or sub-surface pollutants are drawn through intakes, contamination of the condenser tubes may result, requiring a reduction in output or total shutdown.

Simply, the effects of marine pollution are caused by either the physical nature of the pollutants themselves (physical contamination and smothering) or by their chemical components (toxic effects and accumulation leading to tainting). Marine life may also be affected by clean-up operations or indirectly through physical damage to the habitats in which plants and animals live.

The main threat posed to living resources by the persistent residues of spilled oils and water-in-oil emulsions (“mousse”) is one of physical smothering. The animals and plants most at risk are those that could come into contact with a contaminated sea surface:

Marine mammals and reptiles.

Birds that feed by diving or form flocks on the sea.

Marine life on shorelines and

Animals and plants in Mari culture facilities.

Subsequently the inability of individual marine organisms to reproduce, grow, feed or perform other functions can be caused by prolonged exposure to pollutants, if not eventual death. Sedentary animals in shallow waters such as oysters, mussels and clams that routinely filter large volumes of seawater to extract food are especially likely to accumulate oil components and harmful chemicals, poisoning consumers.

In addition to that, birds, whales and other marine creatures often mistake cigarette butts (which find their way into the waters) for food. The butts contain small plastic pieces that can interfere with the digestion of food, casing marine life to starve. Monofilament fishing line can be lethal to seals, sea lions, fish and other animals. Many marine species, including seals, herring, gulls, sharks, and shellfish have died or suffered injuries from plastic bags, nets and monofilament fishing lines.

Impacts on specific marine habitats

The impact that marine pollution can have on selected marine habitats are given below. Within each habitat a wide range of environmental conditions prevail and often there is no clear division between one habitat and another.

In coastal areas some marine mammals and reptiles, such as turtles, may be particularly vulnerable to adverse effects from contamination because of their need to surface to breathe and to leave the water to breed. The impact of oil on shorelines may be particularly great where large areas of rocks, sand and mud are uncovered at low tide. The amenity value of beaches and rocky shores may require the use of rapid, effective clean-up techniques, which may not be compatible with the plants and animals.

In tropical regions, mangrove trees have complex breathing roots above the surface of the organically rich and oxygen-depleted mud in which they live. Oil may block the openings of the air breathing roots of mangroves or interfere with the trees’ salt balance, causing leaves to drop and the tress to die. Fresh oil entering nearby animal burrows can damage the root systems and the effect may persist for some time inhibiting decolonization by mangrove seedlings.

Living corals grow on the calcified remains of dead coral colonies that form overhangs, crevices and other irregularities inhabited by a rich variety of fish and other animals. If the living coral is destroyed the reef itself may be subject to wave erosion.

Birds which congregate in large numbers on the sea or shorelines to breed, feed or molt are particularly vulnerable to oil pollution. Although oil ingested by birds during preening may be lethal, the most common cause of death is from drowning, starvation and loss of body heat when their body surfaces are coated with oil.

Impact on fisheries and Mariculture

The pollutants in the waters, especially in the case of oil spills can also damage boats and gears used for catching or cultivating marine species. Floating equipment and fixed traps extending above the sea surface are more likely to become contaminated by floating oil whereas submerged nets, pots, lines and bottom trawls are usually well protected, provided they are not lifted through an oily sea surface.

An oil or chemical spill can also cause loss of market confidence since the public may be unwilling to purchase marine products from the region irrespective of whether the seafood is actually tainted. Bans on the fishing and harvesting of marine products may be imposed following a spill, both to maintain market confidence and to protect fishing gear and catches from contamination.

5.6 Noise Pollution

Noise usually means unwanted sound of appreciable intensity which goes on for a length of time (seconds to hours) that irritates people. The noise may emanate from factories, offices and market place, roads (traffic-related), running and shuttling of trains, landing and take-offs of aircrafts at airports, use of loudspeakers in meetings, rallies, celebrations, etc. When the quality and the intensity of the noise is practically constant (varying less than ±5 dBA) over an appreciable time (seconds or longer), it is often called “steady-state” noise. The first reaction to any form of unwanted sound is annoyance, followed by irritation, restlessness and extreme reaction. Since noise travels through air, all forms of noise are considered as polluting air and noise is considered as an air pollutant.

Sound is defined as a pressure variation that the human ear can detect. Just like dominoes, a wave motion is set off when an element sets the nearest particle of air into motion. This motion gradually spreads to adjacent air particles further away from the source. Depending on the medium, sound propagates at different speeds. In air, sound propagates at a speed of approximately 340 m/s. In liquids and solids, the propagation velocity is greater, 1500 m/s in water and 5000 m/s in steel.

Compared to the static air pressure (105 Pa), the audible sound pressure variations are very small ranging from about 20 µPa (20 Ã- 10-6 Pa) to 100 Pa. The sound pressure level of 20 µPa corresponds to the average person’s threshold of hearing. A sound pressure of approximately 100 Pa is so loud that it causes pain and is therefore called the threshold of pain. The ratio between these two extremes is more than a million to one.

Sound pressure level alone is not a reliable indicator of loudness. The frequency or pitch of a sound also has a substantial effect on how humans will respond. While the intensity (energy per unit area) of the sound is a purely physical quantity, the loudness or human response depends on the characteristics of the human ear.

A direct application of linear scales (in Pa) to the measurement of sound pressure leads to large and unwieldy numbers. Therefore, the acoustic parameters are conveniently expressed as a logarithmic ratio of the measured value to a reference value. This logarithmic ratio is called a decibel or dB. Using dB, the large numbers are converted into a manageable scale from 0 dB at the threshold of hearing (20 µPa) to 130 dB at the threshold of pain (~100 Pa). Some examples of common noise and their decibel levels are given in Table 5.16.

The decibel scale is open-ended. 0 dB or dBA should not be construed as the absence of sound. Instead, it is the generally accepted threshold of best human hearing. Sound pressure levels in negative decibel ranges are inaudible to humans. On the other extreme, the decibel scale can go much higher. For example, gun shots, explosions, and rocket engines can reach 140 dBA or higher at close range. Noise levels approaching 140 dBA are nearing the threshold of pain. Higher levels can inflict physical damage on such things as structural members of air and spacecraft and related parts.

Table 5.16. Equivalent sound levels in decibels normally occurring inside various places

Place

Leq (decibels)

Small Store (1-5 persons)

Large Store (more than 5 persons)

Small Office (1-2 desks)

Medium Office (3-10 desks)

Large Office (more than 10 desks)

Miscellaneous Business

Residence

Typical movement of people – no TV or radio

Speech at 10 feet, normal voice

TV listening at 10 feet, no other activity

Stereo music

40-45

55-60

50-70

How is noise measured?

Basically, there are two different instruments to measure noise exposures: the sound level meter and the dosimeter. A sound level meter is a device that measures the intensity of sound at a given moment. Since sound level meters provide a measure of sound intensity at only one point in time, it is generally necessary to take a number of measurements at different times during the day to estimate noise exposure over a workday. This measurement method is generally referred to as area noise monitoring.

A dosimeter is like a sound level meter except that it stores sound level measurements and integrates these measurements over time, providing an average noise exposure reading for a given period of time such as an 8-hour workday. The dosimeter measures noise levels in those locations in which a person works or spends long intervals of time. Such procedures are generally referred to as personal noise monitoring.

Human hearing is limited not only to the range of audible frequencies, but also in the way it perceives the sound pressure level in that range. In general, the healthy human ear is most sensitive to sounds between 1,000 Hz – 5000 Hz, and perceives both higher and lower frequency sounds of the same magnitude with less intensity. In order to approximate the frequency response of the human ear, a series of sound pressure level adjustments is usually applied to the sound measured by a sound level meter. The adjustments, or weighting network, are frequency dependent.

The A-scale approximates the frequency response of the average young ear when listening to most ordinary everyday sounds. When people make relative judgments of the loudness or annoyance of a sound, their judgments correlate well with the A-scale sound levels of those sounds. There are other weighting networks that have been devised to address high noise levels or other special problems (B-scale, C-scale, D-scale etc.) but these scales are rarely, if ever, used in conjunction with highway traffic noise. Noise levels are generated in the A-scale as dBA. In environmental noise studies, A-weighted sound pressure levels are commonly referred to as noise levels.

Sources of noise

Various sources of noise (Table 5.17) are industry, road traffic, rail traffic, air traffic, construction and public works, indoor sources (air conditioners, air coolers, radio, television and other home appliances), etc. In Indian conditions, indiscriminate use of public address system and diesel generator (DG) sets, has given a new dimension to the noise pollution problem.

Noise in Industrial Areas. Mechanized industry creates serious noise problems, subjecting a significant fraction of the working population to potentially harmful sound pressure levels of noise. It is responsible for high noise emissions indoors as well as outdoors of plants. The characteristics of industrial noise vary considerably, depending on specific equipments and their working life.

Noise in Residential Areas. In residential areas, noise may stem from mechanical devices (e.g., heat pumps and ventilation systems, traffic) as well as voices, music and other kinds of noises generated by neighbors (e.g., lawn mowers, parties, and other social activities). Due to low-frequency characteristics, noise from ventilation systems in residential buildings may cause considerable concern even at low and moderate sound pressure levels.

Table 5.17. Noise from various sources

Source

Sound level in dB

Effects

Rocket launching

180

Danger

Gun shot

140

Danger Level (threshold of pain)

Jet engine

130

Cause damage, 3.5 min/day

Car horn

120

Cause damage, 7.5 min/day

Night club

110

Cause damage, 30 min/day

Lawn mower

105

Cause damage, 1 h/day

Trucks/scream

Cause damage, 8 h/day

Alarm Clock

Annoying

Transportation Noise

Road traffic. The noise of road vehicles is mainly generated from the engine and from frictional contact between the vehicle and the ground and air. In general, road contact noise exceeds engine noise at speeds higher than 60 km/h. The sound pressure level from traffic can be predicted from the traffic flow rate, the speed of the vehicles, the proportion of heavy vehicles, and the nature of the road surface. Special problems can arise in areas where the traffic movements involve a change in engine speed and power, such as at traffic lights, hills, and intersecting roads.

Rail traffic. Railway noise depends primarily on the speed of the train but variations are present depending upon the type of engine, wagons, and rails. Impact noises can be generated in stations and marshaling-yards because of shunting operations. The introduction of high-speed trains has created special noise problems. At speeds greater than 250 km/h, the proportion of high frequency sound energy increases and the sound can be perceived as similar to that of over flying jet aircraft.

Air traffic. The introduction of the early turbojet transport aircraft led to a surge of community reactions against commercial and military airports. More research has been devoted to aircraft noise than to any other environmental noise problem. The main mechanism of noise generation in the early turbojet aircraft was the turbulence created by the jet exhaust mixing with the surrounding air. This noise source has been significantly reduced in modern high bypass ratio turbo-fan engines that surround the high velocity jet exhaust with lower velocity airflow generated by the fan. The fan itself can be a significant noise source, particularly during landing and taxiing operations. Fan noise can be controlled to a certain extent by providing acoustic absorption in the fan cowling.

There is some concern over the possible use of advanced multi-bladed turbo-prop engines in the future, as these engines can produce relatively high levels of tonal noise. Aircraft takeoffs are known to produce intense noise including vibration and rattle but also landings cause noise annoyance especially when reverse thrust is applied. In general, larger and heavier aircrafts produce more noise than lighter aircrafts. The smaller aircraft types as used for private business, flying training and leisure purposes can cause particular noise problems near to general aviation airports.

Sonic booms. The sonic boom is a shock wave system in air generated by an aircraft, when it flies at a speed slightly greater than the local speed of sound. The shock wave extends from an aircraft throughout supersonic flight in a roughly conical shape. At a given point, the passage of the shock wave causes an initial sudden rise in atmospheric pressure followed by a gradual fall to below the normal pressure and then a sudden rise back to normal. These pressure fluctuations, when recorded, appear in their typical form as so-called N-waves. When they occur with a separation greater than about 100 ms, the sonic boom has a characteristic double sound. High intensity sonic booms can damage property. Lower intensity sonic booms can cause a startle response in people as well as animals. The startle response is a secondary effect due to the sudden and unexpected exposure. The sonic boom can be heard as a very loud and boomy sound. An aircraft in supersonic flight trails a sonic boom that can be heard up to 50 km on either side of its ground track depending upon the flight altitude and the size of the aircraft.

Construction Noise, Public Works Noise. Building construction and earth works are activities that can cause considerable noise emissions. A variety of sounds is present from cranes, cement mixers, welding, hammering, boring, and other work processes. Construction equipment is often poorly silenced and maintained and building operations are sometimes carried out without considering the environmental noise consequence. Street services such as garbage disposal and street cleaning can cause considerable disturbance if carried out at sensitive times of day.

In certain instances, military activities may be an important noise source such as noise produced by heavy vehicles (tanks), helicopters, and small and large firearms. Noise from military airfields may present particular problems compared to civil airports, for example, if used for training interrupted landings and takeoffs.

Building Services Noise. Building service noise can affect people both inside and outside the building. Ventilation and air conditioning plants and ducts, heat pumps, plumbing systems, and lifts, for example, can compromise the internal acoustic environment and upset nearby residents.

Domestic Noise. Noise from neighbors is often one of the main causes of noise complaints. These complaints are largely due to the inconsiderate or thoughtless use of powered domestic appliances (vacuum cleaners, washing machines, lawn mowers, etc.), systems for music reproduction, TV sets, or hobby activities. Substantial societal problems, more infrequent but nonetheless important, are caused by disturbing noise emanating from neighbors and their social activities.

Noise from Leisure Activities. The possibilities of using powered machines in leisure activities are increasing all the time. For example, car racing, off-road vehicles, motorboats, water skiing, snowmobiles, bursting of fire-crackers, etc., can all contribute significantly to loud sound pressure levels in previously quiet areas. Shooting activities not only have considerable potential for disturbing nearby residents, but can also damage the hearing of those taking part.

Effects of noise

Temporary hearing loss (or noise-induced threshold shift, NITTS), lasting from a few seconds to several days or weeks can result from brief exposure to high sound levels or from day-long exposure to more moderate levels of continuous noise. Regular (day-by-day) exposure to such levels over a long period (days to years) can result in damage to the inner ear, associated with a sensorineural hearing loss (NIPTS) which is permanent and, so far as is presently known, incurable. It can only be prevented by protecting the ear from excessive noise exposure. NIPTS is usually preceded by, and may be accompanied by, a NITTS attributable to fatigue of the hearing organ. The typical pattern seen in the audiogram is a maximum loss in the range 4000 to 6000 Hz, with a somewhat smaller loss (initially) at the higher test frequencies.

Although noise is a significant environmental problem, it is often difficult to quantify associated costs. Four categories of impact from transport noise have been identified:

Productivity losses due to poor concentration, communication difficulties or fatigue due to insufficient rest

Health care costs to rectify loss of sleep, hearing problems or stress

Lowered property values

Loss of psychological well-being.

The World Health Organization (WHO) suggests that noise can affect human health and well-being in a number of ways, including

Annoyance reaction,

Sleep disturbance,

Interference with communication,

Performance effects,

Effects on social behaviour and

Hearing loss.

Noise can cause annoyance and frustration as a result of interference, interruption and distraction. Research into the effects of noise on human health indicates a variety of health effects. People experiencing high noise levels (especially around airports or along road/rail corridors) differ from those with less noise exposure in terms of: increased number of headaches, greater susceptibility to minor accidents, increased reliance on sedatives and sleeping pills, increased mental hospital admission rates. Exposure to noise is also associated with a range of possible physical effects including: colds, changes in blood pressure, other cardiovascular changes, increased general medical practice attendance, problems with the digestive system and general fatigue.

There is fairly consistent evidence that prolonged exposure to noise levels at or above 80 dB can cause deafness. The amount of deafness depends upon the degree of exposure. It is reported that high noise levels can contribute to cardiovascular effects and exposure to moderately high levels during a single eight hour period causes a statistical rise in blood pressure of five to ten points and an increase in stress and vasoconstriction leading to the increased blood pressure noted above as well as to increased incidence of coronary artery disease.

Noise can have a detrimental effect on animals by causing stress, increasing risk of mortality by changing the delicate balance in predator/prey detection and avoidance, and by interfering with their use of sounds in communication especially in relation to reproduction and in navigation. Acoustic overexposure can lead to temporary or permanent loss of hearing. An impact of noise on animal life is the reduction of usable habitat that noisy areas may cause, which in the case of endangered species may be part of the path to extinction. One of the best known cases of damage caused by noise pollution is the death of certain species of beach whales, brought on by the loud sound of military sonar.

Noise also makes species communicate louder, which is called Lombard vocal response. Scientists and researchers have conducted experiments that show whales’ song length is longer when submarine-detectors are on. If creatures don’t “speak” loud enough, their voice will be masked by anthropogenic sounds. These unheard voices might be warnings, finding of prey, or preparations of net-bubbling. When one species begins speaking louder, it will mask other species’ voice, causing the whole ecosystem to eventually speak louder.

European Robins living in urban environments are more likely to sing at night in places with high levels of noise pollution during the day, suggesting that they sing at night because it is quieter, and their message can propagate through the environment more clearly.

Zebra finches become less faithful to their partners when exposed to traffic noise. This could alter a population’s evolutionary trajectory by selecting traits, sapping resources normally devoted to other activities and thus lead to profound genetic and evolutionary consequences

Control of Noise Pollution

Generally the determination of land use zoning includes the separation of activities, which are incompatible due to noise levels. For example, heavy industrial area will be separated from residential areas by light industrial, recreational facilitates and/or retail activities. However, changing land uses over many decades and earlier inappropriate zoning controls have resulted in unacceptable noise levels for some areas and uses.

Responsibility for noise control

No single government authority has the responsibility or capacity to be able to minimize all forms of noise pollution. The Police and local administration are generally responsible for neighbourhood noise issues and have authority to issue noise abatement directions to control noise from premises. Local administration has an essential role in minimizing the effects of excessive noise, particularly in their local residential areas, from smaller factories, non-scheduled premises and public places. Consideration of the implications of environmental noise at the planning stage can often avoid or minimize the need for supplementary noise controls.

However, in some instances, noise reduction or mitigation measures are essential, for example:

Controls on noise levels generated from a source (e.g. vehicle/machine design, driver/operator behaviour)

Controls on noise transmission (e.g. through the use of noise barriers)

Measures to reduce the level of sound reaching a receiver (e.g. soundproofing sensitive or affected buildings).

The railway sector has, in recent years, recorded an increase in the identification and reporting of noise problems by the community. There is a range of initiatives to address this issue, including:

Retrofitting existing locomotives to reduce noise emitted

Upgrading existing track to continuously welded rail which removes rail joints – a significant source of noise and vibration

Designing new bridges to reduce noise and retrofitting of existing bridges with noise attenuation devises

Deploying quieter rolling stock in noise sensitive areas

Use of electric locomotives at night time wherever possible in the Sydney metropolitan area

Altering the holding pattern of trains to avoid them being held at signals for extended periods in built up areas.

Ministry of Environment and Forests, Government of India has notified the Noise Pollution (Regulation and Control) Rules, 2000 by its notification dated 14 February 2000 in exercise of the powers conferred by the Environment (Protection) Act, 1986 and the Environment (Protection) Rules, 1986. The preamble to the Rules said that

Whereas the increasing ambient noise levels in public places from various sources, inter-alia, industrial activity, construction activity, generator sets, loud speakers, public address systems, music systems, vehicular horns and other mechanical devices have deleterious effects on human health and the psychological well being of the people, it is considered necessary to regulate and control noise producing and generating sources with the objective of maintaining the ambient air quality standards in respect of noise.

The above Rules have given authority to the State governments for categorizing the areas into industrial, commercial, residential or silence areas/zones for the purpose of implementation of noise standards for different areas, and for taking measures for abatement of noise including noise emanating from vehicular movements and ensuring that the existing noise levels do not exceed the ambient air quality standards specified under these rules.

These rules further stipulate that all development authorities, local bodies and other concerned authorities while planning developmental activity or carrying out functions relating to town and country planning shall take into consideration all aspects of noise pollution as a parameter of quality of life to avoid noise menace and to achieve the objective of maintaining the ambient air quality standards in respect of noise. An area comprising not less than 100 meters around hospitals, educational institutions and courts may be declared as silence area/zone for the purpose of these rules.

These Rules impose the following restrictions on the use of loud speakers/public address systems:

A loudspeaker or a public address system shall not be used except after obtaining written permission from the authority.

A loudspeaker or a public address system shall not be used at night (between 10.00 p.m. to 6.00 a.m.) except in closed premises for communication within, e.g. auditoria, conference rooms, community halls and banquet halls.

The Rules have specified the Ambient Air Quality Standards in respect of Noise as given in Table 5.18.

Table 5.18. Ambient Air Quality Standards in respect of Noise

Area Code

Category of Area/Zone

Limits in dB(A) Leq

Day Time

Night Time

(A)

Industrial area

(B)

Commercial area

(C)

Residential area

(D)

Silence Zone

In the above, Day time means from 6.00 a.m. to 10.00 p.m. and Night time from 10.00 p.m. to 6.00 a.m. The Silence zone is defined as an area comprising not less than 100 meters around hospitals, educational institutions and courts. The silence zones are zones, which are declared as such by the competent authority. Mixed categories of areas may be declared as one of the four above-mentioned categories by the competent authority.

5.7 Thermal Pollution: Cause, Effects and Control

Thermal pollution is a temperature change in natural water bodies caused by human influence. The main cause of thermal pollution is the use of water as a coolant, especially in power plants. Water used as a coolant is returned to the natural environment at a higher temperature. Increases in water temperature can impact on aquatic organisms by (a) decreasing oxygen supply, (b) killing fish juveniles that are vulnerable to small increases in temperature, and (c) affecting ecosystem composition.

Nature and Origin of the Pollutant

Thermal pollution is usually associated with increases of water temperatures in a stream, lake, or ocean due to the discharge of heated water from industrial processes, such as the generation of electricity. Increases in ambient water temperature also occur in streams where shading vegetation along the banks is removed or where sediments have made the water more turbid. Both of these effects allow more energy from the sun to be absorbed by the water and thereby increase its temperature. There are also situations in which the effects of colder-than-normal water temperatures may be observed. For example, the discharge of cold bottom water from deep-water reservoirs behind large dams has changed the downstream biological communities in systems such as the Colorado River in the USA.

The major sources of thermal pollution are electric power plants and industrial factories. In most electric power plants, heat is produced when coal, oil, or natural gas is burned or nuclear fuels undergo fission to release huge amounts of energy. This heat turns water to steam, which in turn spins turbines to produce electricity. After doing its work, the spent steam must be cooled and condensed back into water. To condense the steam, cool water is brought into the plant and circulated next to the hot steam. In this process, the water used for cooling warms by 5 to 10 degrees Celsius, after which it may be dumped back into the lake, river, or ocean from which it came. This raises the water temperature. Similarly, factories contribute to thermal pollution when they dump water used to cool their machinery.

The second type of thermal pollution is much more widespread. Streams and small lakes are naturally kept cool by trees and other tall plants that block sunlight. People often remove this shading vegetation in order to harvest the wood in the trees, to make room for crops, or to construct buildings, roads, and other structures. Left unshaded, the water warms by as much as 10 degrees Celsius. In a similar manner, grazing sheep and cattle can strip streamsides of low vegetation, including young trees. Even the removal of vegetation far away from a stream or lake can contribute to thermal pollution by speeding up the erosion of soil into the water, making it muddy. Muddy water absorbs more energy from the sun than clear water does, resulting in further heating. Finally, water running off of artificial surfaces, such as streets, parking lots, and roofs, is warmer than water running off vegetated land and, thus, contributes to thermal pollution.

Effects of Thermal Pollution

All plant and animal species that live in water are adapted to temperatures within a certain range. When water in an area warms more than they can tolerate, species that cannot move, such as rooted plants and shellfish, will die. Species that can move, such as fish, will leave the area in search of cooler conditions, and they will die if they can not find them. Typically, other species, often less desirable, will move into the area to fill the vacancy.

In general, cold waters are better habitat for plants and animals than warm ones because cold waters contain more dissolved oxygen. Many freshwater fish species that are valued for sport and food, especially trout and salmon, do poorly in warm water. Some organisms do thrive in warm water, often with undesirable effects. Algae and other plants grow more rapidly in warm water than in cold, but they also die more rapidly; the bacteria that decompose their dead tissue use up oxygen, further reducing the amount available for animals. The dead and decaying algae make the water look, taste, and smell unpleasant.

Even when the water temperature changes by one or two degrees, this may have a tremendous influence on the aquatic community leading to threats to biodiversity. Increase in temperature affects the activities of the enzymes changing the rate at which various metabolic activities proceed in aquatic animals. This in turn increases food consumption resulting in food shortage and ultimately a decline in the population of the species. In such cases, the species may migrate to a more favourable environment. Since climate change is responsible for warming up of the oceans, it has been observed that the species which live in colder water are migrating towards the North to avoid the increase in temperature.

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