Environmental Pollution
Definition – causes, effects and control measures of: (a) Air pollution (b) Water pollution (c) Soil pollution (d) Marine pollution (e) Noise pollution (f) Thermal pollution (g) Nuclear hazards – soil waste management: causes, effects and control measures of municipal solid wastes – role of an individual in prevention of pollution – pollution case studies – disaster management: floods, earthquake, cyclone and landslides. Field study of local polluted site – Urban / Rural / Industrial /
Agricultural.
Pollution
Pollution is explained as any substance introduced into the environment that adversely affects the usefulness of resources.
Pollution can be in the form of solid, liquid or gaseous substance. Pollution causes damage to human, plant and animal life. The nature and concentration of pollutant determine the severity of effect of pollution.
Pollution is defined as the excess discharge of any substance into the environment which affects adversity quality of environment and causing damage to humans, plants and animals.
Types Pollutants
Ecologically, pollutants can be divided into three types
1. Degradable or non – persistent pollutants
2. Slowly degradable or persistent pollutants
3. Non – degradable pollutants.
Degradable or non – persistent pollutants
The pollutants that can be rapidly decomposed by natural processes is called degradable or nonpersistent pollutants.
Slowly degradable pollutants
Some pollutants remain in environment for longer time because they decompose very slowly by the natural processes.
Example: plastics, pesticides, etc. Non-degradable pollutants
Some pollutants can not be decomposed by natural processes are called nondegradable pollutants.
Example – Lead, mercury, nuclear wastes etc.
Classification of pollution
The pollutants that pollute the environment is divided into following types
1. Air pollution
2. Water pollution
3. Soil Pollution
4. Marine pollution
5. Noise pollution
6. Thermal pollution
7. Nuclear hazards
Air pollution
It is defined as the undesirable contamination of gas, smoke, dust, fume, mist, odour, or chemical particulates in the atmosphere which are injurious to human beings, plants and animals.
Causes of air pollution
1. Industrialization
2. Urbanization
3. Vehicles emission
4. Deforestation
5. Population
Types of air pollutants
Air pollutants can broadly classified into two types-
1. Primary pollutants
2. Secondary pollutants
Primary pollutants
Pollutants that are emitted directly from either natural events or from human activities are called primary pollutants. The natural events are dust storms; volcano etc and human activities can be emission from vehicles, industrial wastes. About 90% of global air pollution is constituted by five primary pollutants. These are
1. Carbon oxides (CO and CO2)
2. Nitrogen oxides
3. Sulphur oxides
4. Hydrocarbons
5. Particulate matter
Secondary pollutants
Primary pollutants when reacting with each other or from basic components of air; forms a new pollutants called secondary pollutant. For example – sulphuric acid, nitric acid, carbonic acid, etc.
Degradable pollutants
The pollutants that can be rapidly decomposed by natural processes is called degradable or nonpersistent pollutants. Example – domestic sewage, discarded vegetable etc.
2. Slowly degradable pollutants
Some pollutant remains in environment for longer time because they decompose very slowly by the natural processes.Example – Plastics, pesticides, etc,
3. Non – degradable pollutants
Some pollutants cannot be decomposed by natural processes are called non – degradable pollutants. Example – Lead, mercury, nuclear wasters etc.
Air pollution can broadly classified into two types-
1. Primary pollution
Pollutants that are emitted directly from either natural events or from human activities are called primary pollution. The natural events are dust storms, volcano etc and human activities can be emission from vehicles, industrial wastes .About 90% of global air pollution is constituted by five primary pollution.
These are i) Carbon oxides (CO and CO2) ii) Nitrogen oxides iii) Sulphur oxides iv) Hydrocarbons v) Particulate matter
2. Secondary pollution
Primary pollutants when reaction, with each other or from basic components of air; forms a new pollutants called secondary pollutant. For example sulphuric acid, carbonic. Etc.
Major Air pollutants
1. Carbon monoxide
It is a colourless, odourless, flammable gas, which is a product of incomplete combustion. If carbon were completely oxidized during burning, complete combustion to carbon dioxide would occur and carbon monoxide would not be a problem. It is important not to confuse carbon monoxide with carbon dioxide. Carbon monoxide (CO) is an incomplete combustion product and can be toxic even at low concentrations, whereas carbon dioxide (CO2) is a complete oxidation product.
Sources of Carbon monoxide
Carbon monoxide is formed whenever a carbon material is burned e.g. automobile exhausts, cigarettes etc. In addition to motor vehicles, sources of carbon monoxide include burning coal, natural gas or biomass. Biomass combustion can be a significant source of exposure in rural areas or in underdeveloped countries where it is burned for cooking, heating and even light.
Atmospheric oxidation of methane gas and other hydrocarbons and even light. Atmospheric oxidation of methane gas and other hydrocarbons also produces carbon monoxide.
Effects of CO
Carbon monoxide accounts for more than 50% of air pollution nationwide and worldwide. It is a pervasive pollutant. Worldwide, hundreds of millions monoxide-related illness, which include headaches, dizziness and drowsiness. Reports show that about 11% heart failure caused by excess carbon monoxide.
In the normal situation, the iron atom in the blood protein haemoglobin, picks up oxygen from the lung and transports in to the body’s cells. There the haemoglobin releases oxygen and picks up the waste gas carbon dioxide, which it transports back to the lungs and releases. After releasing carbon dioxide, it picks up more oxygen. Carbon monoxide has 200 items greater affinity for the iron in haemoglobin than does oxygen and interrupts this cycle by displacing oxygen. The result is a lowered amount of oxygen reaching the heart which can lead to heart failure in sensitive people. Carbon monoxide also has other adverse effects in the body. For example, it interferes with the oxygen-carrying proteins in muscles.
When humans are exposed to CO, it forms carboxy haemoglobin at the expense of oxyhaemoglobin. Tissues are thus deprived of oxygen and asphyxiation occurs. If the victim continues to receive a high dosage of CO, then permanent brain damage and even death will result. Initial symptoms include dizziness, headache, nausea and faintness.
Chronic exposure at 25 mg m-3 of CO in air causes cardiovascular problems which can be particularly dangerous to a person who already suffers from such problems. The inhalation of 35 ppm for eight hours causes a loss in ability to learn and do complicated tasks, reduces awareness, decreases manual dexterity, and disturb sleep activity.
Measures to reduce carbon monoxide
About half of the motor vehicle carbon monoxide emissions in this country are produced by only
10% of the vehicles. Efforts are being made to find and remove these vehicles from road. Car can truck owners need to maintain their vehicles so that operate as cleanly as they were designed to operate. Other measures to control carbon monoxide emissions include facilities that burn fossil fuels or wood to maintain high burning efficiencies and prohibiting open burning trash and garbage.
2. Sulphur dioxide
Sulphur dioxide (SO2) is a Colourless gas with a sharp odour that accounts for about 18% of all air pollution.
Sources: Chemical industries, Metals meltings, Pulp and paper mills,Oil refineries
Effects of Sulphur dioxide
Sulphur dioxide reacts with moisture in eyes, lungs and mucous membranes to form strong irritating acid. It can trigger allergic reaction and asthama.
If moisture is present in the atmosphere, sulphur dioxides is converted into sulphuric acid or if conditions are dry, into sulphate particulates. The tiny- only 0.1 to 1 mm in diameter-sulphuric acid and sulphate particulates form aerosols. The aerosols contribute to the adverse healths effects of smog and haze and also play a serious role in haze. Sulphuric acid and sulphate are likewise directly involved in three serious global global change problems. Acidic deposition is one of those.
The stratospheric ozone depletion, where by sulphate particles in the stratosphere provide surfaces on which ozone-destroying reactions occur. A third major effect is the antiwarming influence they exert in global climate change.
3. Nitrogen dioxide Nitrogen dioxide is a reddish brown irritating gas. They account for about 6% of pollution.
Sources of nitrogen dioxide: Motor vehicle exhausts, Gasoline Volcanoes, Lightning
4. Lead
Lead a highly useful metal has been mined for thousands of years. And it has been known for thousands of years that lead is toxic to the nervous system. The level lead in modern human skeletons and teeth is at least a hundred-fold greater than the level found in pre-industrial age skeletons.
The combustion of alkyl lead additives in motor fuels accounts for major part of all lead emission into the atmosphere. An estimated 80-90 percent of lead in ambient air derives from the combustion of leaded petrol. The degree of pollution from this source differs from country to country depending on motor vehicle density and the efficiency of effort to reduce the lead content of petrol.
The mining and smeltering of lead ores create pollution problems in some areas. Children up to 6 years of age are a population at increased risk for lead exposure as well as for adverse health effects as children have behaviour lead exposure as well as adverse health effects as children have behaviour characteristics which increase the risk of lead exposure, the blood-brain barrier is not yet fully developed in young children and hematological and neurological effects of lead occur at lower threshold in children than in adults.
5.Particulate Matter
Particular matter is defined as single particles or aggregates of particles with diameters greather than 2x10-10 m. some particulate matter is natural i.e. rain, snow, fog, hail and mist, while others are often the result of human processes, e.g. smoke, soot and fumes. Some natural particulates are affected by human actions such as fog and wind-blown soils. smoke and soot are the products of incomplete combustions of coal, petrol and diesel fuels in furnaces, domestic heating systems and vehicle engines.
Aerosols are mixture of minute solid or liquid particles suspended in air that from a haze or spoil visibility.
The main problem to humans caused by atmosperic particulate matter is how far it is able to penetrate the resporatory system. particles in the size range 30x10-6 to 100x10-6 m lodge in the nasal cavity, larynre and trachea. range 30x10-6 to 100x10-6 m lodge in the nasal cavity, larynre and trachea. some examples of particles of this size are pollen, fungal spores, cement dust and coal dust. particles less than 15x10-6 m find their way into the bronchus and bronchioles e.g. tabacco, smoke and fumes. particles of 4x10-6 m and less can enter alveoli where gaseous exchange take place between the bloodtream and air e.g. asbestos dust, glass and viruses.
Particulate matter comes from two major sources. First, those emissions that come directly from sources such as coal combustion, wind-blown dust and quarrying. these are called primary particulates. Other particulars can be formed from chemical reactions between pollutant gases such as sulphur dioxide, the oxides of nitrogen and ammonia such reactions lead to the formation of solid sulpahte and nitrations. Organic aerosols may also be formed by the oxidation of volatile organic compounds. These particulates are termed as secondary particulates are termed as secondary particulates.
Emissions of particles smaller than 10µm in diameter (PM10) are controlled to meet an EPA standard of 150 micrograms per cubic meter (µg/m3) of air. Although many cities barely meet this standard – studies have shown associations between very fine particulates and increased respiratory problems and premature death rates at levels only one third of the standard. In the near future, particulates of diameters 2.5µm and less may be regulated.
Techniques to reduce air pollution i) Reducing air pollutants from industry
Industry, in its broadest sense is a major contributor to air pollution. However, the management of these sources of pollution has not always been undertaken in the most efficient manner. The following two points should be considered in management strategy.
A holistic view of pollutant emissions must be taken. Thus strategies to reduce air pollution must not lead, for example, to greater water pollution.
The whole process operation must be examined. Pollutants may actually represent losses of valuable material (e.g. solvents), and measures to prevent their loss may actually save money.
Changing the nature of the fuel
Where pollutant emissions are due to the type of fuel being used for combustion modifying the fuel can have significant effects on emissions.
Changing process conditions to reduce pollutant production
Some pollutants are produced during the process itself. Examples include the production of nitrogen oxides during combustion, or dioxins during incineration. Alternations to the way that processes are operated can significantly reduce the creation of these pollutants.
Clearing the flue gases
If it not possible to prevent the production of pollutants, then it is likely to be necessary to prevent their release into the environment by cleaning the exhaust gases.
Reducing ammonia emissions from agriculture
The most important source of ammonia emissions from agriculture is that from livestock waste. The ammonia may be emitted at any stage, from the production of the waste through to its storage and use on the load.
Reducing nitrogen intake animals
Careful assessment of the protein requirements of livestock is an important means of reducing the amount of nitrogen excreted. By matching live weight food requirements to nitrogen excreted. By matching live weight food requirements to nitrogen input, it is generally possible to reduce nitrogen intake by about 5 percent.
Animal housing
Intensive animal housing can producing important point sources of ammonia emissions. A build –up animal waste in moist conditions is ideal for pollution production. However, a wide range of techniques are now available for its waste. Attempts to remove the waste through scraping have only a small effect on ammonia emissions.
For poultry units, droppings should be dried rapidly. Deep litter systems alone do not really reduce emissions. However, a reduction of up to one –third can be achieved by regular mixing of deep litter. For poultry kept in battery cages, droppings can be collected on conveyor – belt systems. If these droppings are rapidly removed to contained storage, a reduction in emissions of up to 60 percent can be achieved.
Animal waste storage
It is generally not possible to use animal waste as it is produced. The waste is produced continually through out the year, but spreadin is limited, for example, to periods between cropping. Storage of waste is therefore required. Some waste storage does occur within animal housing, but much is separate. It is possible to achieve a reduction of between 70 and 90 percent in ammonia amissions by simply covering the waste.
Waste spreading
The spreading of waste is the cause of about one-half of the ammonia emissions from agriculture. Spreading does also sometimes cause a public nuisance due to the odour produced in the spreading operation. However, contrary to public perception, the actual spraying of waste over land contributed to less than 1 percent of the ammonia emitted. Most of the emissions take place within the first twenty – four hours, as the waste lies on the land surface.
Managing pollution from motor vehicles
The problem of traffic pollution is a particulary difficult issue. Traffic volume is increasing rapidly in almost every country in the world, and strategies to manage the resulting pollution are desperately needed. There are a number of tyoesof management that can be adopted
:
1) Changing the type of fuel used to one that produces less pollution.
2) Removing inefficient and grossly polluting vehicles.
3) Adopting measures to clean the exhaust gases.
4) Attempting to manage the pollution once it has been produced.
5) Adopting measures to manage the use of motor vehicles.
Some of these measures are best adopted at national or international levels, others are open to local management. a) Managing fuel type
The best-known example of this has been the adoption of unleaded petrol. Lead is added toincfease the octane level and there are two ways to produce the same effect in unleaded fuel.
The first is to improve the octane level of the petrol with a substitute for the lead, such as tertiary butyl ether (TBE). Many countries have adopted strategies to reduce the lead in petrol. Its use is completely banned in the US, Canada, Austria, Sweden and some other countries.
Options are also open for zero emission vehicles. In essence this means electric vehicles and the term ‘zero emission’ is only partially true. Thus while the vehicles themselves do not produce emissions. The degree towhich alternative fuels can be adopted relies heavily on consumer responses. For example, consumers need to be sure that supplies are available. This is a big problem for gas, electricity and biofuels in many countries where outlets may be limited. b) Removing gross polluters While many estimates can e given of emission from different types of motor vehicles and fuel type, is evident that older vehicles and those which are incorrectly maintained contribute a disproportionate amount to aerial pollution. c) Cleaning exhaust gases
Catalysts do not deal with the problem of particulate emissions. Most transport particulate are produced form diesel vehicles. It is possible to fit a simple particulate trap in the exhaust. d) Traffic management
One alternative to prevention and management of traffic emissions is to reduce the need for or the use of motor vehicles. Two issues can be considered: vehicle speed and vehicle use.
The quantity of pollutants emitted per kilometer driven varies with the speed of the vehicle. Figure shows hour emission vary for non-catalytic petrol cars. For example, when care travel much faster than 70 km/h, nitrogen oxide emissions being to increase. Thus the efficient enforcement of speed limits on motorways would help to reduce pollutant emissions. Fig. 3.1.1 also demonstrates the problem of emissions at very low speeds. Thus as congestion inn towns and cities increases and traffic shown down, emissions are increasinging much faster than the actual growth in vehicle numbers. This requires a management response to reduce vehicle use and to keep moving those vehicles that are used.
Turbidity or cloudiness. This can stunt the growth of aquatic plants by limiting the amount of sunlight reaching them.
Water Pollution
Any physical, biological or chemical change in water quality that adversely affects living organisms or makes water unsuitable for certain use is referred as Water pollution.
When the quality or composition of water changes by means it becomes unsuitable for any purpose and is said to be polluted.
Water pollution Sources
Water pollutants are categorized as point source pollution and non-point source pollution.
1. Point source pollution
Point source pollution is defined as any single identifiable source of pollution from which pollutants are discharged.
Example: Industrial discharge, factory smoke stack, municipal sewage etc. Point source pollution sources are discrete and identifiable and hence easy to monitor and regulate.