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ENVIRONMENTAL CHEMISTRY BY AK DE PDF

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Environmental Chemistry By Ak De Pdf

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Feb 19, Looking for books on Environmental Chemistry? Check our section of free e- books and guides on Environmental Chemistry now! This page. Concept and scope of environmental chemistry – Segments of environment. REFERENCES: 1. A.K. De, Environmental Chemistry, 6th Edition, New Age. nov environmental chemistry lecture notes pdf environmental chemistry by ak de pdf introduction to environmental chemistry pdf fundamentals of.

They do not survive at moderate temperature, e. Man gets the infection through food chain cut fruits, salads, vegetables, contaminated drinking water, cold drink, etc. Uncooked food and vegetable can be disinfected by washing with iodine solution ppm or acetic acid 5—10 per cent or vinegar. From water, cysts can be removed by filtration and boiling. The cysts in milk can be killed by pasteurisation. The diagnosis is usually based on the detection of Entamoeba histolytica in the stools.

The antibody of the parasite can be easily detected by Immuno-fluorescence method. Prevention of Amoebiasis The disease can be prevented by i sanitary disposal of human excreta. Treatment The drugs usually prescribed by physicians are: Metronidazole — mg Flagyl to be taken one tablet thrice a day for 5—7 days.

Entrozyme mg —one tablet thrice a day for 7 days 3. Trinidazole 1—2 gm —one tablet for 3 days 4. Furamide mg —one tablet thrice a day for 10 days.

Fluorosis Fluoride in diet or drinking water above 1. The maximum tolerance level in human body is 1. The daily intake of F from food and drinking water is usually less than 1 ppm. Some parts of south India and South Africa have reported fluoride concentrations of 4 to 8 ppm.

In India, some 25 million people spread over districts in 15 states suffer from fluorosis. Fluoride does not concentrate in any tissue but only in the bones and teeth. Fluorosis affects bones, teeth, tissues and other organs of the body, leading to death after prolonged illness. It also leads to dental decoloration and deformation of bones causing knock knees, bow legs and stiffening of the joints, joint pains, back pain etc.

In endemic areas, large percentage of people suffer from gastrointestinal complaints, diarrhoea etc. The expectant and lactating mothers are vulnerable groups—there is high incidence of stillbirths and abortions. Provision of safe drinking water 1-ppm fluoride and creating awareness among people of the dangers of fluorosis are the urgent needs of the hour for prevention of fluorosis. The rate of depletion of resources is measured by two parameters—per capita mining and per capita consumption.

Per capita mining is calculated by dividing the amount of resource mined by the population. Per capita consumption is obtained by dividing the amount of resource actually processed by the population.

It is a better index of the standard of living of the population. Table 3. H2O 2. The world per capita mining figures indicate that five minerals are mined to the maximum extent—coal, petroleum iron ore, aluminium and phosphate rock.

However, the demand on resources is not equitably distributed over the entire population. This is reflected in the contrast between the per capita mining figures for the Asian and North American subcontinents. This disparity is further aggravated by the fact that USA, for example, imports substantial quantities of most of the resource so that its per capita consumption figure exceeds its per capita mining figure.

As far as metal resources are concerned, they may be grouped under two heads: Average reserve Av. Metals non-ferrous 0. Non-metal Resources The major non-metal resources include asbestos, carbonates, Cl2, granite, O2 , phosphate, potash, sand and gravel, Na compounds and H2O. Asbestos silicate minerals , the carbonates—principally those of Ca and Mg—sand and gravel, together with granite, constitue the common and most widely used building materials.

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As in the case of metals, the environmental aspects of many of these minerals are quite important. These relations are found as natural or biogeochemical cycles which involve continuous circulation of the essential elements and compounds required for life from environment to organisms and back to environment.

The natural cycles and ecosystems function in a balanced manner which stabilises biosphere and sustains the life processes on earth. About one-third of the solar energy absorbed by the earth is used to drive the hydrological cycle—massive evaporation of water from the oceans, cloud formation and rainfall which supplies our reserves with freshwater. The hydrological cycle At freezing temperature rainwater freezes into snow and forms hail in the presence of strong wind.

Water as rain, snow and hail is precipitated on land and water surfaces. On land surfaces water seeps into the soil and is stored as groundwater.

The natural water level or water table exists below the ground. Groundwater does not remain static but moves in various directions. It moves up and reaches soil surface where it is drawn by plant roots. Another important groundwater resource is the aquifers. These exist above the impermeable rock strata—water percolates through porous rocks and forms these underground lakes or reservoirs. From the latter water can be pumped by digging tube wells and extracted by sinking wells.

When there is good rainfall, all the rainwater on land do not percolate into the soil. Surface water run-off flows into streams, rivers, seas, lakes and reservoirs. Normal evaporation from the oceans exceeds precipitation by 10 per cent. This excess 10 per cent moves as water vapour over land surface and balances the hydrological cycle. Plants absorb groundwater by root pressure and transpirational pull but give off excess water through leaves by the process of transpiration.

Thus, water vapour level in the atmosphere is balanced and at the same time ensures conduction of water and dissolved mineral salts throughout the plants. Thus, the hydrologic cycle consists of a balanced continuous process of evaporation, transpiration, precipitation, surface run-off and groundwater movements. There is continuous exchange of nitrogen within the ecosystems operating the nitrogen cycle.

Proteins produced by plants and animals in their metabolic processes are organic compounds of nitrogen. The major load of nitrogenous organic residue in soil originates from death and decay of plants and excreta of animals. Plants absorb nitrates from soil which re-enter the nitrogen cycle. Some soil micro-organisms break down soil nitrate into nitrogen by denitrification process while others transform nitrogen into soluble nitrogen compounds see Fig.

The nitrogen cycle 2. The atmosphere is the minor reservoir of carbon dioxide while the oceans are the major reservoir, containing as much as 50 times more as that of air where it is stored as bicarbonate mineral deposit on the ocean floor. The latter regulates the carbon dioxide level in the atmosphere. The cycle operates in the form of carbon dioxide exchanging among the atmosphere, biosphere and the oceans Fig. The Carbon dioxide balance sheet per year is given: This can be reduced by 50 per cent if we can stop deforestation Fig.

The atmosphere contains billion tonnes of carbon dioxide; biosphere, vegetation and soil about billion tonnes and the oceans about 1,36, billion tonnes of carbon dioxide. Phosphate minerals exist in soluble and insoluble forms in rocks and soil. Plants absorb inorganic phosphate salts from soil and change them into organic phosphate. Animals obtain their phosphate by eating plants. After death and decay, plants and animals return phosphates to the soil.

Bulk of the phosphate in soil is fixed or absorbed on soil particles but part of it is leached out into waterbodies. The natural phosphate cycle is affected by pollution, mainly from agricultural run-off containing superphosphate and also from domestic sewage.

Phosphate pollution of rivers and lakes is the cause of algal bloom eutrophication which reduces dissolved oxygen in water and disrupts the food chain. The phosphate cycles on land and in water are shown in Figs.

The phosphate cycle in water 2. Some sulphur bacteria act as the media for exchanges of sulphur within the ecosystems. The sulphur cycle Fig. The sulphur oxidation process is shown in the upper half of the cycle.

The lower section shows the conversion of sulphate into plant and cellular proteins and the decay of dead plant and animal material by bacterial action. In polluted waters under anaerobic conditions hydrogen sulphide is produced by bacteria giving deposits of iron sulphide.

In unpolluted waters under aerobic conditions the sulphur bacteria transform sulphides into sulphates for further production of proteins. The sulphur cycle B. In , Volta invented the battery, the first source of electric current. Electricity generation using heat of steam marked the begin- ning of thermal power production in the middle of 19th cen- tury. The demands on energy are increasing with progress in human civilization.

The quality of life or standard of living is linked with the quantum of energy consumption. But generally much of the energy about 60 per cent is wasted. Maximum wastage is observed in power plants and vehicles. The conventional energy resources are fossil fuel coal, petroleum and diesel , wood, natural gas, hydroelectricity and nuclear energy. The energy, as consumed by man, is: This is times more than the total global energy consumption from all fuels. The stock of coal is likely to last several centuries.

The natural defect of coal is that it is a dirty fuel to burn. On combustion, it emits sulphur dioxide which is an offensive gas, forms sulphuric acid in air and causes acid rain in far- away places. Thus, it poses environmental hazards see acid rain in previous chapter. Excavation of coal from mines is followed by soil subsidence depression which endangers the residential areas above the coal mines.

Moreover, flyash arising from combustion of coal is a nuisance as solid waste which brings about environmental problems. Also being a solid, coal is less convenient to handle than petroleum or natural gas. In order to overcome these problems, the developed countries use less polluting forms of coal by transforming it into gaseous, liquid or low sulphur, low-ash solid fuel.

In a typical case, high-grade ash-free coal is produced as solvent- refined coal SRC by suspending pulverized coal in a solvent and treating with 2 per cent of its weight of hydrogen at a pressure of pounds per sq. Energy 47 The product is a semi-solid, m.

This compares well with the best-grade anthracite coal. This heat is utilised to produce steam at high temperature and pressure.

The latter is then used to run a steam turbine which is linked with the generator producing electricity. Thermal power stations are operated on the above principle by combustion of coal in a furnace. They are the sources of severe air pollution. The reactants CO and H2 are obtained from coal, oxygen and steam: USA is the largest consumer of petroleum in the world about 80 per cent of total energy consumption in USA.

The Industrial Revolution was initially fuelled by coal but later on preference was given to oil and gas which provide cleaner fuels and easy transportation. Energy consumption patterns in USA 2.

In Venezuela, South America, 10, mega-watts of hydroelectricity is produced which is equivalent to the production of electricity from 10 thermal power plants. But at present, only 16 per cent or 6, megawatts of hydroelectricity is generated. For generation of electricity from hydel project, it is nec- essary to utilise energy produced from the descent of water from higher to lower level. In practice, a water reservoir is constructed by means of dam in a river for storage of water.

Subsequently the stored water is released from upper level into a water-driven turbine placed at a lower level Fig. The hydel projects of Maithon, Panchyet and Jaldhaka are typical examples. Hydroelectricity from hydel project The merits of hydroelectricity are: But there are several environmental issues—flora and fauna in the region are disturbed due to construction of dam; local people become refugees as they are uprooted from their houses; the capacity of the reservoir gets reduced due to siltation; occurrence of floods in the area when surplus water has to be discharged in monsoon season.

Hydroelectric dams are costly and take a long time for construction. Nuclear power plants do not emit polluting gases such as carbon dioxide, sulphur dioxide, like thermal power plants.

But they have some severe drawbacks, viz. The radioactive wastes remain lethal deadly for thousands of years and for this no foolproof disposal method has been devised. That is why big nuclear power projects have not succeeded in the long run. In India, the production target was fixed at 10, megawatts by AD, but the actual production is much less in the nuclear power stations at Tarapur, Rajasthan and Chennai. Nuclear power plants cannot match thermal power plants at present but in future, its unlimited resources will allow it to dominate the energy scenario when other energy resources are exhausted.

Heavy large atoms like Uranium and Plutonium split up into smaller atoms when bombarded by neutrons nuclear particles with mass 1 and charge 0. This splitting or fission liberates vast amounts of energy, which through conventional techniques is converted into electricity. Thus nuclear power is generated. It has been calculated that 1 kg of Uranium on a complete fission by slow neutrons releases energy equal to 1.

This means energy-wise, 1 lb. The major important products are wood, paper, cellophane, rayon, plywood, plastic, particle board, turpentine, methanol, etc. Ideally, as in USA forests cover 38 per cent. It is interesting to compare between India and USA in respect of deforestation. According to an estimate, an American destroys as much forest for his needs for paper as an Indian for his domestic fuel. The value of a year-old tree has been estimated as about more than Rs 20 lakhs—the various functions of a year-old tree are roughly evaluated as follows: Trees—sources of many important products Thus the tree, with its year services as above, costs about Rs.

The public should be made aware of the value of a tree and its services to man and environment during its life time.

In India, 76 per cent of population lives in villages— almost all of them use wood as fuel for cooking. This is the main reason for extensive deforestation in rural areas: Deforestation helps increase in greenhouse gas, carbon dioxide concentration.

Hence for the welfare of the country as a whole, it is essential to minimise deforestation by adopting alternative resources of afforestation on a large scale to meet the needs of domestic fuel. For production of one unit of energy, mineral oil, coal and wood, on burning, produces respectively 35 per cent, 75 per cent and 80—90 per cent more carbon dioxide than natural gas. Hence, natural gas is the obvious choice as a cleaner fuel. Its reserves, however, are limited and can continue to feed only for the next 70—80 years.

At present, in India the exploitable reserve of natural gas is about billion cubic metres. This is an enormous and model energy resource, which is clean, pollution-free and inexpensive. It requires to be converted into other forms of energy by suitable techniques—it can meet our energy demands forever. The solar energy, incident on earth in one week, is equivalent to the energy from the entire coal reserve of the world.

Again the solar energy available on earth for 45 minutes is enough to meet our energy demand for one year. However, the major problem is that sunlight is diffused widespread in nature and difficult to be stored and utilized. At present, solar energy is ten times more expensive than thermal power. But with advanced technology, it will be cheaper and will hold the key to meet our energy demands in future.

Sunlight may be directly converted into electricity through photovoltaic cell. The latter is a device for conversion of light energy into electrical energy. The efficiency of conversion of light into electricity is only 18 per cent and it is expensive at current prices. We can use solar energy in two ways: Use of the former permits one to boil water or dry foodgrains. Accordingly, several gadgets have been produced such as solar cooker for cooking , solar dryer for drying grains , solar water heater for heating water , solar distillation for water purification , etc.

Recently there have been extensive use of these solar equipments in rural and semi-urban areas. By using the second method, i. Since these solar cells are made of silicon, these are called silicon cells. The advantages of solar photovoltaics are that they can replace systems which use diesel and they are free from chemical and noise pollutions. They could be installed in remote areas in forests and deserts where installation of electric cables are cost-prohibitive.

Solar power, with government subsidy Department of Non-conventional Energy Source DNES , Government of India is being used in remote rural areas in West Bengal in the forms of solar lanterns, solar streetlights and solar pumps for irrigation. Solar powered small pumps are being used in Delhi, Haryana and Himachal Pradesh.

It is desirable to use solar cookers in villages on a large scale so that extensive deforestation can be prevented. About 1 tonne of wood per head per year can be saved by this process. Figure 4. In these countries, 20—25 per cent of fuel is consumed for providing hot water to houses and buildings.

An average house with roof area about sq. Light is absorbed in a plate, with the generation of positive and negative charges, which are collected at the electrodes on either side. The silicon solar cell, developed for space programmes, consists of a sandwich of n-type and p-type silicon semi- conductors e. The silicon cell produces electricity but is quite expensive since very high-grade crystalline silicon is required for the cell. Solar cell for electricity generation 2. Besides being an important domestic energy source, it offers an environmentally-clean technology.

There is a vast reserve of biogas in Indian villages. It is estimated that million tonnes of animal dung per year is available from million cattle population. On an average 10 kg of wet dung is available per animal per day, which at 66 per cent collection efficiency, can yield 22, million cubic meters of biogas through biogas plants. Besides, biogas slurries can produce million tonnes of organic manure per year which can be a good substitute for chemical fertilisers for agriculture.

The composition of the biogas is: The proportion of methane and carbon dioxide varies considerably as does the calorific value. India, with its climatic diversity, has areas which are quite windy.

According to the Indian Meteorological Department, average annual wind velocity is 6. Such velocities are available for 6—7 months in a year. There are some limitations for setting up wind power mills or windmills.

They require locations where the wind velocity is at least 6. In Denmark and Holland, there are rows of windmills in extensive areas and these generate 50 megawatts of electricity.

A standard windmill produces 55 kilowatts of electricity daily. Windmills spread over extensive areas on seashore or very high site present a beautiful scenery. Windmills prevent earthquakes where continuous wind flow causes soil erosion. The technology for harnessing wind energy has become commercial in some developed countries but in India it is still in the preliminary stage.

The Department of Non- conventional Energy Sources, Government of India has installed several wind pumps with pumping capacity of 20 litres. A windmill with a capacity to pump litres of water per hour at a pumping head of 19 metres has been installed. Prospective sites are in Gujarat and Orissa on the seacoast. Italy is the pioneer in this field.

During the oil crisis period in , England developed the technology for harnessing geothermal energy. If in many areas wells are dug about 5-km. With advanced technology, it may be possible to generate electricity from geothermal energy in India and other developed countries. Agricultural wastes are mainly crop residues. They are dried and used as fuel. Straw, jute sticks and other crop residues are burnt by villagers for cooking and partial boiling of paddy. In certain industries, the waste materials can be utilised as a source of energy.

Food processing, jute, sugar, paper and textile industries are the major industries where the waste materials can be utilised for the production of heat and electricity. Various processes have been developed for effective use of bagasse, jute, cotton and paper industries for energy production. Some latex-containing plants like Euphorbias and oil palms are rich in hydrocarbons and can yield an oil- like substance under high temperature and pressure.

This oily material can be burnt in diesel engines directly or may be refined to form gasoline. This gas is generated directly by electrolysis of water H2O , as shown in Fig. Electricity is passed between electrodes immersed in a conducting aqueous solution. H2 is generated at the cathode and O2 at the anode. Here H2 is oxidised at the cathodes, where electrons are produced, and passed through the circuit to the anode, where O2 is reduced.

The overall efficiency of this conversion and reconversion is quite lower to various energy barriers connected with the electrode processes. A lot of current electrochemical researches are centered on lowering these energy barriers. H2 transport by pipeline is more efficient and less expensive than electrical transmission over large urban centres. These considerations have given rise to the concept of the hydrogen economy Fig. It can be consumed directly for electrical generation and heating, and can be used to synthesize liquid fuels by chemistry similar to that described for coal gasification.

Local power stations Industrial fuels and reducing gas Synthetic chemicals and Large electric power liquid fuel and water electrolysis plant Underground H2 Domestic fuel transport pipeline Fig. The Hydrogen economy 2. This can be used as a fuel in existing internal combustion engine, with little or no adjustment.

Individually, methanol or ethanol itself can be used as fuel instead of gasoline in a suitable designed internally combustion engine. Methanol is produced by the destructive distillation of wood, or from synthesised gas manufactured from coal or natural gas Sec.

Because of its photosynthetic origin, alcohol is a renewable resource. The manufacture of alcohol can be carried out by fermentation of sugar resulting from the hydrolysis of cellulose in wood wastes and crop wastes.

Fermentation of these waste products provides an excellent opportunity for recycling. This country possesses few fossil-fuel resources, but it provides optimum conditions for the growth of large quantities of biomass from the fermentation of sugarcane. In Brazil, a new abundant source of fermentable biomass is Cassava or manioc, a root crop growing in large quantities throughout the country.

Questions 1. Name the major natural resources. Give examples of a renewable and b non- renewable resources. What is the significance of forest resources? Explain the imortance of biodiversity and its conser- vation. What are the sources of water? Name also the sources of freshwater.

Express their quantities in term of percentage of water resources. Name the important water quality perameters. Mention their tolerance limits as per USPH standards.

What are water-borne diseases? Give an account of environmental factors for the outbreak of cholera. How can it be prevented? Write a note on fluorosis. What are the major minerals mined to the maximum extent? How do you classify metals? Name some base metals and also precious metals. Write notes on: Name conventional and non-conventional sources of energy. Compare their effects on environment. What are the products of combustion of coal? Discuss their damaging effect on environment.

Starting from coal, how would you manufacture material? Comment on: We have degraded lands, destroyed forests at suicidal rates, thrown tonnes of toxic waste into rivers indiscriminately and poured toxic chemicals into the seas. Furthermore, we discharged green-house gases into the atmosphere leading to climatic changes.

The net result is: We shall discuss water pollution, land pollution, noise pollution and air pollution in this and the next chapters. It is a historical fact that faecal human excreta or stool pollution of drinking water caused water-borne diseases, which wiped out entire populations of cities. In the developing countries like India, everyday some 25, people die of water-borne diseases, e.

In India about 2 lakhs out of 6 lakh villages have no access to safe drinking water—women have to walk 1—14 km daily for collecting water for drinking and cooking.

In urban areas, 40 per cent people are without access to safe water. The major sources of water pollution are domestic sewage from urban and rural areas, agricultural run-off wash water and industrial waste which are directly or indirectly discharged into waterbodies. Organic pollutants 2. Inorganic pollutants 3. Sediments 4. Radioactive materials 5. Thermal pollutants Organic Pollutants These include domestic sewage, pesticides, synthetic organic compounds, plant nutrients from agricultural run- off , oil, wastes from food-processing plants, paper mills and tanneries, etc.

These reduce dissolved oxygen D. Dissolved oxygen D. Decrease in D. Sewage and agricultural run-off provide plant nutrients in water giving rise to the biological process known as eutrophication. Large input of fertiliser and nutrients from these sources leads to enormous growth of aquatic weeds which gradually cover the entire waterbody algal bloom. This disturbs the normal uses of water as the waterbody loses its D. The production of synthetic organic chemicals more than 60 million tonnes each year since multiplied more than 10 times since These include fuels, plastic fibres, solvents, detergents, paints, food additive, pharmaceuticals, etc.

Their presence in water gives objectionable and offensive tastes, odour and colours to fish and aquatic plants. Oil pollution of the seas has increased over the years, due to increased traffic of oil tankers in the seas causing oil spill and also due to oil losses during off-shore drilling.

Oil pollution reduces light transmission through surface water and hence reduces photosynthesis by marine plants, decreases D. Pesticides have been largely used for killing pests and insects harmful for crops and thereby boosting the crop production. At present, there are more than 10, different pesticides in use. They include insecticides for killing insects , e. It has been found that pesticide residues contaminate crops and then enter the food chain of birds, mammals and human beings.

The persistent pesticide, viz. Thus, the average level of DDT in human tissues is found to be 5—10 ppm, maximum being among the Indians 25 ppm compared to the Americans 8 ppm. Inorganic Pollutants This group consists of inorganic salts, mineral acids, metals, trace elements, detergents, etc. Acid mine drainage: Coal mines, particularly those which have been abandoned, discharge acid sulphuric acid and also ferric hydroxide into local streams through seepage.

The acid on entering the waterbody destroys its aquatic life plants, fish, etc. Sediments Soil erosion, as a matter of natural process, generates sediments in water. Solid loadings in natural water are about times as large as the solid loading from sewage discharge. Soil erosion is enhanced 5—10 times due to agricultural and times due to construction activities. Bottom sediments in aquatic bodies streams, lakes, estuaries, oceans are important reservoirs of inorganic and organic matter, particularly trace metals, e.

Radioactive Materials Radioactive pollution is caused by mining and processing of radioactive ores to produce radioactive substances, use of radioactive materials in nuclear power plants, use of radioactive isotopes in medical, industrial and research institutes and nuclear tests. The discharge of radioactive wastes into water and sewer systems is likely to create problems in future. This has a harmful effect on the aquatic life in the waterbody whose D.

An important case is that of Arsenic As contamination of groundwater. This arises from excessive pumping of groundwater by shallow tube wells for irrigation in some West Bengal districts along the Hooghly river course and also in Bangladesh along the Padma river course. In this process, air oxygen is injected into groundwater bed which leaches the overlying mineral, iron pyrites iron, arsenic, sulphide , oxidises it and releases arsenic into groundwater.

More than one million people in six districts of West Bengal drink arsenic-contaminated groundwater from tube wells in the region. Among them, 20 lakh people suffer from various diseases related to arsenic poisoning like loss of hair, brittle nails, bronchitis, gangrene, etc. Several hundred deaths have also been reported.

Similar calamity has threatened the lives of Bangladesh in the districts along the Padma river course. Environmental Pollution 69 The Ganga originates from the Himalayan glacier and flows along a stretch of some km before joining the Bay of Bengal.

The Ganga basin is fertile and home of about 40 per cent of population million people of the country. But in recent years it is ranked as the most-polluted river of India and a killer in the highly- polluted areas.

2 ak de environmental chemistry 6 rd edn new age

The Ganga basin carries water from 25 per cent of land. Ganga is the source of drinking water in the region and irrigation water for agriculture—she also supplies fish to the local markets and water to industries on both sides of the river. The Ganga basin provides maximum population density—many class I population , and above , class II pop.

Both domestic and industrial sewages join the Ganga river without any treatment and thus causes terrible pollution. Hooghly river in West Bengal near Kolkata presents the worst polluted zone. There are more than industries on both sides of the km stretch river belt—there are about outlets of untreated sewage to the river Hooghly. The entire sq. Besides huge quantities of soil from soil erosion due to extensive deforestation are washed by rain water into the river causing siltation.

This reduces the flow of water in the Bhagirathi- Hooghly river with the result that ultimately the river will be choked and dead. Though the latter has less load on waterbody, it contains toxic matter inorganic and organic which are more hazardous.

Such biological decomposition is carried out under aerobic conditions, i. In the first stage, solid wastes are removed from water by screening—any scum suspended matter is removed and the sludge muddy solid or sediment allowed to settle at the bottom. The residual liquid is exposed to biological oxidation of soluble organic materials through a bed of microbes in activated sludge.

Then the solids are removed after sedimentation. Finally the liquid effluent is subjected to chlorination for destroying pathogenic micro- organisms. Now this effluent is fairly clean and suitable for domestic use. The water treatment plants, in general, are simpler than sewage treatment plants.

They operate in three steps— i Aeration to settle suspended matter. The purified water is then supplied by munici- palities through pipes for domestic uses.

Liquid waste is partly absorbed by soil, partly seeps into underground water and the rest joins waterbodies in the locality. It is solid waste which, when dumped into land, accumulates on it and causes pollution. With progress in industrialisation, the noise level has been rising continuously. In the 19th century the development of the steam engines, petrol engines and machines in factories resulted in increas- ingly noisy environment. In the 20th century this was fur- ther accelerated by introduction of diesel engine, jet engines, turboprop, high-tech machineries, construction site machin- eries and automobile traffic.

Noise has been recognised as one of the dimensions of pollution which brings about deg- radation of the environment and creates health and commu- nication hazards. Sound waves travel through the medium from the source to the recipient or listener. The rate of the oscillation of the medium is known as the frequency of the sound, the unit being hertz Hz or cycles per second.

Botkin and Keller. Willey India. Environment and pollution Law Manual; S. Mohanty, Universal Law Publisher Ltd. New Delhi Elements of Ecology. Smith and Smith. Fundamentals of Ecology.

Das and Das.

Tata McGraw-Hill, India. Environment and Ecology. Pandey and Misra. Ane Books Private Limited. Russell et. Mohan P. Himalaya Publishing House. Reklefs and Miller. Begon Townsend and Harper. Willey and co. Instant Notes on Ecology. Viva Publishing. Biological Science. Green, Stout, Taylor and Soper. Tata McGraw-Hill. Instant Notes in Animal Biology. Viva Publications.

Life Science. Remote sensing of urban environment; B. Sokhi, S. Rashid, Manak publication pvt Ltd. Remote sensing and image interpretation, 3rd edition, Lilles and R. Environmental Geology; Edward A.

Keller Prentice Hall, New Jersey Biotechnological methods of pollution control, S. Abbasi, E. Ramsani, Universities Press Bioremediation; Baker, H.

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Bioremediation principles; Eweis, J. Microbiology; Pelczar, M. Environmental Statistics and data analysis,; Ott, W, R. Physical Chemistry; P. Rakshit, Sarat Book House, Calcutta Physical Chemistry; K.

This note covers the following topics: NA Pages. This note explains the following topics: Thermodynamics, Chemical Equilibrium, Photochemistry, Photolysis rate, frequency, Chemical lifetime , Heterogenous Reactions, Chemistry of the upper atmosphere, Chemistry of the stratosphere, Ozone Hole, Tropospheric chemistry, Tropospheric chemistry. This note addresses the challenges of defining a relationship between exposure to environmental chemicals and human disease.

Topics covered include epidemiological approaches to understanding disease causation, biostatistical methods, evaluation of human exposure to chemicals, and their internal distribution, metabolism, reactions with cellular components, and biological effects, and qualitative and quantitative health risk assessment methods used in the U.

Author s: James Sherley, Dr. Laura Green and Prof. Steven Tannenbaum. This note provides a detailed overview of the chemical transformations that control the abundances of key trace species in the Earth's atmosphere. Environmental chemistry is a range of concepts from chemistry and various environmental sciences.

Topics covered includes: The overall goal of this book is to gain an understanding of the fundamental chemical processes that are central to a range of important environmental problems and to utilize this knowledge in making critical evaluations of these problems.

This book explains the fundamental chemical processes that are central to a range of important environmental problems and to utilize this knowledge in making critical evaluations of these problems.The Ganga basin carries water from 25 per cent of land. Millions of workers suffer from progressive hearing damage and become prone to accidents under their working conditions.

It is a historical fact that faecal human excreta or stool pollution of drinking water caused water-borne diseases, which wiped out entire populations of cities. The prevention and control of a disease depends on the knowledge of environment. Balaram Pani. Tetracycline and co-trimoxazole should be administered as antibiotic.

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