E N V IR O N ME NTAL C H E MIS T R Y

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CONTENT

● ENVIRONMENTAL POLLUTION ● AIR POLLUTION ● WATER POLLUTION ● SOIL POLLUTION ● NOISE POLLUTION

● RADIOACTIVE POLLUTIO ● THERMAL POLLUTION ● STRATEGIES TO ENVIRONMENTAL POLLUTION

ENVIRONMENTAL POLLUTION

Environmental pollution 1s the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings. A substance, which causes pollution, is known as pollutant. Pollutants can be solid, liquid or gaseous substances present in greater concentration than in natural abundance and are produced due to human activities or due to natural happenings. Environmental pollution is the unfavourable alteration of our surroundings, wholly or largely as a by-product of man's actions, through direct or indirect effects of the changes in the energy pattern, radiation levels, and chemical and physical constitution and abundance of organisms. Environmental pollution is a global problem and is common to both developed as well as developing countries, which attracts the attention of human beings for its severe long-term consequences.

The decline 1Il environmental quality as a consequence of pollution is evidenced by loss of vegetation, biological diversity, excessive amounts of harmful chemicals in the ambient atmosphere and in food grains, and growing risks of environmental accidents and threats to life support systems. Pollution is viewed from different angles by different people but is commonly agreed to be the outcome of urban-industrial and technological revolution and rapacious and speedy exploitation of natural resources, increased rate of exchange of matter and energy, and ever-increasing industrial wastes, urban effluents, and consumer goods.

Over the past couple of decades, various sources of pollution were identified that altered the composition of water, air, and soil of the environment. The substances that cause pollution are known as pollutants. A pollutant can be any chemical (toxic metal, radionuclides, organo phosphorus compounds, gases) or geochemical substance (dust, sediment), biological organism or product, or physical substance (heat, radiation, sound wave) that is released intentionally or inadvertently by man into the environment with actual or potential adverse, harmful, unpleasant, or inconvenient effects. Such undesirable effects may be direct (affecting man) or indirect, being mediated via resource organisms or climate change.

Depending on the nature of pollutants and also subsequent pollution of environmental components, the pollution may be categorized as follows:

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Air Pollution Water Pollution Soil/Land Pollution Noise Pollution Radioactive Pollution Thermal pollution

EFFECTS OF POLLUTION

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AIR POLLUTION .Air pollution is the presence of substances in the atmosphere that are harmful health of humans and other living beings, or cause damage to the climate or to materials. There are different types of air pollutants, such as gases (such as ammonia, carbon monoxide,sulfur dioxide, nitrous oxides, methane and chlorofluorocarbons), partic ulates (both organic and inorganic),and biological molecules.

Air pollution may cause diseases, allergies and even death to humans; it may also cause harm to other living organisms such as animals and food crops, and may damage the natural or environment. Both human activity and natural processes can generate air pollution. Air pollution is a significant risk factor for a number of pollutionrelateddiseases,including respiratory infections, heart disease, COPD, stroke and lung cancer. The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the cardiovascular system. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, and the individual's health status and genetics. Overall,air pollution causes the deaths of around 7 million people worldwide each year, and is the world's largest single environmental health risk various pollutioncontrol technologies and strategies are available to

GLOBAL WARMING AND GREENHOUSE EFFECT Climate change includes both the global warming driven by human em1ss1ons of greenhouse gases, and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century the rate of human impact on Earth's climate system and its global scale have been unprecedented. That human activity has caused climate change is not disputed by any scientific body of national or international standing. The largest driver has been the eID1ss10n of greenhouse gases, of which more than 90%are carbon dioxide (CO2)and methane. Fossil fuel burning for energy consumption is the main source of these emissions, with additional contributions , From agriculture, deforestation, and industrial processes. Temperature nse 1s accelerated or tempered by climate feedbacks, such as loss of sunlight-reflecting snow and ice cover, increased water vapour (a greenhouse gas itself), and changes to land and ocean carbon sinks.

Think it over If burning of fossil fuels, cutting down forest and trees add to greenhouse gases in the atmosphere we must find the ways to sethese just efficiently and judiciously. One of the simple things which we can do to reduce global warming is to minimize these of automobiles. Depending upon the situation,one can us icycle,public transport system.We should plant more trees to increase the green cover

ACID RAIN Acid rain" is a popular term referring to the deposition of a mixture from wet (rain, snow, sleet, fog, cloudwater, and dew) and dry (acidifying particles and gases)acidic components. Distilled water,once carbon dioxide is removed, has a neutral pH of 7. Liquids with a pH less than 7 are acidic, and those with a pH greater than 7 are alkaline. "Clean" or unpolluted rain has an acidic pH, but usually no lower than 5.7, because carbon dioxide and water in the air react together to form carbonic acid, a weak acid according to the following reaction: H20 (1)+ CO2 (g) = H2C03 (aq) Carbonic acid then can ionize in water forming low concentrations of carbonate and hydronium ions: H20 (1)+ H2C03 (aq)= HCQ3- (aq) + H3Q+(aq)

Unpolluted rain can also contain other chemicals which affect its pH (acidity level). A common example is nitric acid produced by electric discharge in the atmosphere such as lightning.

Acid rain is a by-product of a variety of human activities that emit the oxides of sulphur and nitrogen in the atmosphere.Burning of fossil fuels such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides. S02 and N02 after oxidation and reaction with water are major contributors to acid rain, because polluted air usually contains particulate matter that catalyse the oxidation 2S02+02+2H202= H2so4 4N02+02+2H20 = 4HN03 Acid rain is harmful for agriculture, trees and plants as it dissolves and washes away nutrients needed for their growth. It causes respiratory ailments in human beings and animals. When acid rain falls and flows and as ground water to reach rivers, lakes etc. It affects plants and animal life in aquatic ecosystem. It corrodes water pipes resulting in the leaching of heavy metals such as iron lead and copper into the drinking water. Acid rain damages buildings and other structures made of stone or metal. The Taj Mahal in India has been affected by acid rain

PHOTOCHEMICAL SMOG

Taj Mahal and Acid rain The air around the city of Agra, where the Taj Mahal is located, contains fairly high levels of sulphur and nitrogen oxides. It is mainly due to large number of industries and power plants around the area.use of poor quality of coal, kerosene and firewood as fuel or domestic purposes add up to this problem. The resulting acid rain reacts with marble, CaC03 of Taj Mahal (CaC03 H2S04 --+ CaS04 + H20 C02) causing damage to this wonderful monument that has attracted people from around he world. As a result, the monument is being slowly disfigured and the marble is getting discoloured an ustreless. The Government of India announced an action plan in early 1995 to prevent the disfiguring of this historical monument

When fossil fuels are burnt, a variety of pollutants are emitted into the earth's troposphere. Two of the pollutants that are emitted are hydrocarbons (unburned fuels) and nitric oxide (NO). When these pollutants build up to sufficiently high levels, a chain reaction occurs from their interaction with sunlight in which NO is converted into nitrogen dioxide (NO2). This NO2 in tum absorbs energy from sunlight and breaks up into nitric oxide and free oxygen atom. NO2(g) NO(g) + O(g) Oxygen atoms are very reactive and combine with the 02 in air to produce ozone. O(g) + 02 (g) + 03 (g) The ozone formed in the above reaction (ii) reacts rapidly with the NO(g) formed in the reaction (i) to regenerate N02. N02 is a brown gas and at sufficiently high levels can contribute to haze.

NO +03 N02+02

Ozone is a toxic gas and both N02 and 03 are strong oxidising agents and can react with the unburnt hydrocarbons in the polluted air to produce chemicals such as formaldehyde, acrolein and peroxyacetyl nitrate (PAN)

EFFECTS OF PHOTOCHEMICAL SMOG

Photochemical smog causes serious health problems. Both ozone and PAN act as powerful eye irritants. Ozone and nitric oxide irritate the nose and throat and their high concentration causes headache, chest pain, dryness of the throat, cough and difficulty in breathing. Photochemical smog leads to cracking of rubber and extensive damage to plant life. It also causes corrosion of metals, stones, building materials, rubber and painted

OZONE DEPLETION Depletion of ozone layer commonly known as ozone hole over the South Pole. In summer season, nitrogen dioxide and methane react with chlorine monoxide and chlorine atoms forming chlorine sinks, preventing much ozone depletion, whereas in winter, special type of clouds called polar stratospheric clouds are formed over Antarctica. These polar stratospheric clouds provide surface on which chlorine nitrate formed gets hydrolysed to form hypochlorous acid .Its also reacts with hydrogen chloride produced to give molecular chlorine. When sunlight returns to the Antarctica in the spring, the sun's warmth breaks up the clouds and HOCl and Cb are hydrolyzed by sunlight, and the chlorine radicals thus formed, initiate the chain reaction for ozone depletion.

EFFECTS OF DEPLETION OF OZONE LAYER UV radiations lead to ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplankton's, damage to fish productivity etc. It has also been reported that plant proteins get easily affected by UV radiations which leads to the harmful mutation of cells. It also increases evaporation of surface water through the stomata of the leaves and decreases the moisture content of the soil. Increase in UV radiations damage paints and fibres, causmg them to fade faster.

WATER POLLUTION Pollution of water originates from human activities. Through different paths, pollution reaches surface or ground water. Basily identified source or place of pollution is called as point source. e.g., municipal and industrial discharge pipes where pollutants enter the watersource. Non point sources of pollution arethose where a source of pollution cannot be easily identified, e.g., agricultural run-off (from farm, animals and crop-lands), acid rain, storm water drainage (from streets, parking lots and lawns), etc.

PATHOGEN : The most serious water pollutants are the disease causing agents called pathogens. Pathogens include bacteria and other organisms that enter water from domestic sewage and animal excreta. Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis which cause gastrointestinal diseases.

ORGANIC WASTES : The

other major water pollutant is organic matter such as leaves, grass, trash etc. They pollute water as a consequence of run off. Excessive phytoplankton growth within water is also a cause of water pollution.

These wastes are biodegradable. The large population of bacteria decomposes organic matter present in water. They consume oxygen dissolved in water. The amount of oxygen that water can hold in the solution is limited. In cold water, dissolved oxygen (DO) can reach a concentration up to 10 ppm (parts per million), whereas oxygen in air is about 200,000 ppm. That is why even a moderate amount of organic matter when decomposes in water can deplete the water of its dissolved oxygen. The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water, 1s called Biochemical Oxygen Demand (BOD). The amount of BOD in the water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically. Clean water would have BOD value of less than 5 ppm whereas highly polluted water could have a BOD value of 17 ppm or more.

CHEMICAL POLLUTANTS:

Water soluble inorganic chemicals that include heavy metals such as cadmium, mercury, nickel etc constitute an important class of pollutants. All these metals are dangerous to humans because our body cannot excrete them. Over the time, it crosses the tolerance limit. These metals then can damage kidneys, central nervous system, liver etc. This process 1n which nutrient enriched water bodies support a dense plant population, which kills animal life by depriving it of oxygen and results m subsequent loss of biodiversity is known as Eutrophication.

INTERNATIONAL STANDARD FOR DRINKING WATER Fluoride: For drinking purposes, water should be tested for fluoride 10n concentration. Its deficiency in drinking water is harmful to man and causes diseases such as tooth decay etc. Soluble fluoride is often added to drinking water to bring its concentration upto 1 ppm. Lead: Drinking water gets contaminated with lead when lead pipes are used for transportation of water. The prescribed upper limit concentration of lead in drinking water is about 50 ppb. Lead can damage kidney, liver, reproductive system etc.

Sulphate:Excessive sulphate (>500 ppm) in drinking water causes laxative effect, otherwise at moderate levels it 1s harmless. Nitrate: The maximum limit of nitrate in drinking water is 50 ppm. Excess nitrate in drinking water can cause disease such as methemoglobinemia ('blue baby' syndrome).

Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapours from the contaminants, or from secondary contamination of water supplies within and underlying the soil. Mappingof contaminated soil sites and the resulting clean-ups are time-consuming and expensive tasks

CAUSES PESTICIDE Pesticide are basically synthetic toxic chemicals with ecological repercussions. The repeated use of the same or similar pesticides give rise to pests that are resistant to that group of pesticides thus making the pesticides ineffective.

LAND POLLUTION Soil contamination or soil pollution as part of land degradation is caused by the presenceof xenobiotics (hum an-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste.Themost common chemicals involved are petroleum hydrocarbons, polynuclear aromatic hydrocarbons, solvents, pesticides, lead, and other heavy metals.

Therefore, as insect resistance of DDT increased, other organic toxins such as Aldrin and Dieldrin were introduced in the market by pesticide industry. Most of the organic toxins are water insoluble andnonbiodegradable. Over the time, the concentration of toxins in higher animals reach a level which causes senous metabolic and physiological disorders.

In response to high persistence of chlorinated organic toxins, a new series of less persistent or more bio-degradable products called organo phosphates and carbamateshave been introduced in the market.

The pesticide industry has shifted its attention to herbicides such as sodium chlorate (NaC103), sodium arsinite (Na3As03) and many others. Most herbicides are toxic to mammals but are not as persistent as organo chlorides.

These chemicals decompose in a few months. Like organochlorides, these too become concentrated in the food web. Some herbicides cause birth defects. Pesticides and herbicides represent only a very small portion of widespread chemical pollution.

INDUSTRIAL WASTE

Industrial solid wastes are also sorted out as biodegradable and non degradable wastes. Biodegradable wastes are generated by cotton mills, food processing units, paper mills, and textile factories. Non-biodegradable wastes are generated by thermal power plants which produce fly ash; integrated iron and steel plants which produce blast furnace slag and steel melting slag. Industries manufacturing aluminium, zinc and copper producemud and tailings. Fertilizer industries produce gypsum.

Hazardous wastes such as inflammables, composite explosives or highly reactive substances are produced by industries dealing in metals, chemicals, drugs, pharmaceuticals, dyes, pesticides, rubber goods etc. The disposal of non-degradable industrial solid wastes, if not done by a proper and suitable method, may cause serious threat to the environment.

High noise levels can contribute to cardiovascular effects in humans and an increased incidence of coronary artery disease. In animals, noise can increase the risk of death by altering predator or prey detection and avoidance' interfere with reproduction and navigation,

and contribute to permanent hearing loss. A substantial amount of the noise that humans produce occurs in the ocean. Up until recently, most research on noise impacts has been focused on marine mammals, and to a lesser degree, fish.

NOISE POLLUTION Noise pollution, also known as environmental noise or sound pollution, is the propagation of noise with ranging impacts on the activity of human or animal life, most of them harmful to a degree. The source of outdoor noise worldwide is mainly caused by machines, transport, and propagation systems. Poor urban planning may give rise to noise disintegration or pollution . ' side-by-side industrial and residential buildings can result in noise pollution m the residential areas.

the energy of the radiation being emitted, the type of radiation, and the proximity of the contamination to organs of the body. It is important to be clear that the contamination gives rise to the radiation hazard, and the terms "radiation" and "contamination" are not interchangeable.

The sources of radioactive pollution can be classified into two groups: natural and man made. Following an atmospheric nuclear weapon discharge or a nuclear reactor containment breach, the air, soil, people, plants,

RADIOACTIVE POLLUTION Radioactive contamination, also calledradiological contmination, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids or gases (including thehuman body), where their presence is unintended or undesirable from the International Atomic Energy Agency (IAEA) definition). Such contamination presents a hazard because of the radioactive decay of the contaminants, which produces such harmful effectsas 1on1z1ng radiation (namely a, p,and y rays) and free neutrons. The degree of hazard 1s determined by the concentration of the

become contaminated by nuclear fuel and fission products. A spilled vial of radioactivematerial like u ranyl nitrate may contaminate the floor and any rags used to wipe up the spill. Cases of widespread radioactive contamination include the BikiniAtoll, the RockyFlats Plant in Colorado, the Fukushima Daiichi nuclear disaster, the Chernobyl disaster, and the area around the Mayak facility in Russia.

THERMAL POLLUTION

Thermal pollution, sometimes called "thermal enrichment," 1s the degradation of water quality by any process that changes ambient water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature,

the sudden change 1n temperature decreases, oxygen supply and affects ecosystem compositi on. Fish and other organisms adapted to particular temperature range can be killed by an abrupt change in water temperature (either a rapid increase or decrease) known as "thermal shock."

STRATEGIES TO CONTROL ENVIRONMENTAL POLLUTION Waste Management Solid waste is not the only waste, which you see in your household garbage box. Besides household discards, there are medical, agricultural, industrial and mining wastes. The improper disposal of wastes is one of the maJor causes of environmental degradation. 'Swachh Bharat Abhiyan' or 'Clean India Mission' launched by the Government of India Two programmes are being implemented under the broad umbrella of the Swachh Bharat Abhiyan.

These are Swachh Bharat Mission-Urban (SBM-U) and Swachh Bharat Mission Gramin (SBM-G). The SBM-U primarily aims at making Urban India free from open defecation and achieving 100% scientific management of solid waste in the country. The SBM-G targets to bring about an improvement in the general quality of life in rural areas by promoting cleanliness and hygiene, and eliminating open defecation.

It is accelerating its efforts to achieve the goal of universal sanitation coverage by 2 October, 2019, which is the birth anniversary of Mahatma Gandhi.(, WASTE MANAGEMENT Collection and Disposal Domestic wastes are collected in small bins, which are then transferred to community bins by private or municipal workers. From these community bins, these are collected and carried to the disposable site. At the site, garbage is sorted out and separated into biodegradable and non biodegradable materials.

Non-biodegradable materials such as plastic, glass, metal scraps etc. are sent for recycling. Biodegradable wastes are deposited in landfills and are converted into compost. The waste if not collected in garbage bins, finds its way into the sewers. Some of it is eaten by cattle. Non biodegradable wastes like polythene bag, metal scraps,etc. choke the sewers and .cause 1nconven1ence.Polythene bags, if swallowed by animals can cost their lives also. As a normal practice, therefore, all domestic wastes should be properly collected and disposed. The poor management causes health problems leading to epidemics due to contamination of ground water.