Environmental Issues | Biology Notes for NEET/AIIMS/JIPMER

ENVIRONMENTAL ISSUES

INTRODUCTION

• Any change in physical, chemical and biological  characteristics of the environment which harm the human life is called pollution.
• Contamination is the presence of harmful organisms or their toxins that cause disease.
• Pollution is of two types: natural and man made.
• Natural pollution is caused by natural sources. E.g., Volcanic eruptions, emission of gas NOx, O3, UV rays, cosmic ray etc.
• Man made or anthropogenic pollution is caused by human activities. E.g., Burning of fuels, deforestation, pesticides, fertilizers, etc.
• Pollutant is any substance or chemical responsible for causing pollution.
• On the basis of form of their occurrence,  pollutants are divided into two categories –
• Primary pollutants  : These are present in the same form in which they are produced. e.g., carbon monoxide, DDT.
• Secondary pollutants : These are formed by reaction between the primary pollutants in the presence of sunlight, e.g., PAN, Ozone, HNO3, H2SO4 etc. Nitrogen oxides and hydrocarbons react photochemically to produce peroxyacetyl nitrates (PAN) and ozone.

The secondary pollutants may be more toxic than the primary one. The phenomenon is called synergism.

• On the basis of their degradation, pollutants are divided into two categories –
• Biodegradable pollutants : Pollutants which are decomposed or degraded by biological or microbial action,  e.g., domestic sewage, clothes, paper, etc.
• Non-biodegradable pollutants : Pollutants which are not decomposed or degraded by living organisms or micro-organisms.E.g., DDT, glass, plastics, aluminium cans, phenolic compounds,  pesticides, radioactive substances, heavy metals like mercury, lead, cadmium etc.
• On the basis of their existence in nature, pollutants are divided into two categories –
• Quantitative pollutants : These are naturally present in nature and are also added by man. These become pollutants only when their concentration reaches beyond a threshold value in the environment, e.g., CO2.
• Qualitative pollutants : These are not present in the nature but are added in nature only due to human activities, e.g., insecticides, fungicides, herbicides etc.
• On the basis of emission of pollutants, pollution is of following type -
• Point source : Pollution from a single point.  E.g., chimney, municipal sewer.
• Line source pollution : E.g., roads due to automobile exhausts.
• Area source pollution : E.g., mining areas, industrial areas.
• Diffuse source pollution : It is over a large area.  E.g., pesticides and fertilizers.
• On the basis of environmental study, pollution is of the following types –
• Air pollution
• Water pollution
• Soil pollution
• Noise pollution
• Radioactive pollution

AIR POLLUTION

• Air pollution is the occurrence or addition of foreign particles, gases or pollutants in the air which have an adverse effect on human beings, animals, vegetation etc.
• The two main categories of air pollutants are gases and particulates.
• The gaseous materials include various gases and vapours of  volatile substances or the compound with a boiling point below 200°C.
• Particulate matter consists of solid particles or liquid droplets (aerosols) small enough to remain suspended in air, e.g., soot, smoke, dust, asbestos, fibres, pesticides, some metals (including Hg, Pb, Cu and Fe) and also biological agents like tiny dust mites and flower pollen.
• Atmospheric particles having diameter > 10 µm, generally settle out in air less than a day, whereas particles with  diameters of 1µm or less can remain suspended in air for weeks.
• Suspended particulate matter in the lower atmosphere (troposphere) causes and aggravates human respiratory illness, like asthma, chronic bronchitis etc.

MAJOR AIR POLLUTANTS AND THEIR EFFECTS

CARBON MONOXIDE (CO)

Source : It is the main air pollutant (or most poisonous gas) released from the smoke of automobile.

Effect : Carbon monoxide is a highly toxic gas it combines with haemoglobin of the blood and blocks the transportation of oxygen. Thus, it impairs respiration and it causes death due to asphyxiation when inhaled in large amounts.

UNBURNT HYDROCARBONS (3,4 BENZOPYRINE, CH4, BENZENE)

Source : These are mainly released from automobiles and burning of fossil fuels (coal, petrol, diesel). Methane (CH4) is the most abundant hydrocarbon in atmosphere and its main source is marshy area and paddy field.

Effect : Hydrocarbons cause lung cancer.

NOTES 

Polynuclear aromatic hydrocarbons is an important hydrocarbons and it also causes lung cancer i.e. this is carcinogenic.

ETHYLENE

Effect : Falling of leaves without particular reason, falling of flowering bud before time.

NITROGEN OXIDE (NO, NO2) 

Source : Burning (combustion) of fossil fuel in automobiles. It forms about 10% of pollutants.

Effect : These nitrogen oxides form photochemical smog in the atmosphere and release ozone. Nitrogen oxide is also responsible for acid rain.  Entry of nitrogen oxides and ozone in humans causes respiratory problems such as emphysema, bronchitis, swelling of lung and lung cancer etc.

SULPHUR OXIDE (SO2, SO3) 

Source : These are most harmful gaseous pollutants, the main source of sulphur oxides are coal burning, smelters, oil refineries. It forms about 18% of total air pollutants.

Effect : Lichens and mosses do not grow in SO2 polluted areas. Lichens and mosses are indicator of SO2 pollution. Oxides of sulphur produce acid rain and smog in the atmosphere.

Smoke : SO2, SO3, NO2, NO, CO, CO2

CONTROL OF AIR POLLUTION

CONTROL OF PARTICULATE MATTER

Two devices are used to remove particulate air pollutants – Arresters and Scrubbers

• Arresters are used to separate particulate matter from contaminated air. Arresters are of different types 
• Cyclonic separators and trajectory : These are commonly used to separate out particular matters from industrial emissions with minimum moisture content. These separators work on the principle of dust separation by centrifugal force.
• Electrostatic precipitator : It is the most efficient device to remove fine particulate pollutants. Electrostatic precipitation devices work on the principle of electrical charging of dust particles and collecting it on a differently charged platform.

Fig. : Electrostatic precipitator

• Scrubbers are used to clean air for both dust and gases. Wet and dry are the two types of scrubbers that are used for dust  separation.

CONTROL OF GASEOUS POLLUTANTS

Combustion, absorption and adsorption techniques are used to control gaseous pollutants.

• Combustion : In the combustion process, oxidisable gaseous pollutants are completely burnt at a high temperature. Petrochemicals, fertilizers, paints and varnish industries use combustion control of gaseous pollutants.
• Absorption : In this technique, gaseous pollutants are absorbed in suitable absorbent materials.
• Adsorption : This technique is applied to control toxic gases, vapours and inflammable compounds that could not be efficiently removed or transferred by a aforesaid technique. Such air pollutants are adsorbed on large solid surfaces.
• Some other methods are : 
• Engines should not be kept started when vehicles are in rest condition.
• Barium compound mixed with petrol reduces the smoke.
• It is also very essential to check the quality of gases released from the factories.
• Industries should not be established at one place.
• The smoke should be released into the atmosphere after filtration and purification (by cyclone collector or electrostatic precipitators).
• To separate particles larger than 50µm, gravity settling tanks or porous filters are being used.

EFFECT OF AIR POLLUTANTS

Air pollutants are involved in causing four major environmental effects : Smog, acid rain, greenhouse effect (global warming), and ozone layer depletion.

SMOG

• It is produced by the combination of smoke and fog. 
• It causes silvering/glazing and necrosis in plants, allergies and asthma/bronchitis in human.
• Smog is of two types 
• Classical or London smog or Sulphurous smog – It occurs at low temperature and contains H2S, SO2, smoke and dust particles. In it, secondary pollutants are absent.

It was first observed in winter months at  London in 1905. It is formed due to domestic and industrial  combustion of coal.

• Photochemical smog or Los Angeles smog : It was first observed in the mid day at Los Angles in 1943. The cause of this smog was thought to be due to combustion of petroleum in automobiles.

Photochemical smog occurs at high temperature over cities and towns. It is formed by the reaction of  two air pollutants - nitrogen oxides (mainly NO2) and  hydrocarbons (HC) that react with one another in the presence of UV radiations of sunlight to produce ozone (O3) and PAN (peroxy acetyl nitrate) which constitute the photochemical smog.

Nitrogen oxides + Hydrocarbons PAN + Ozone 

Ozone and PAN are commonly referred to as oxidants. Breathing ozone affects the respiratory and nervous system, resulting in headache, respiratory distress and exhaustion. It also causes irritation in eyes and asthma. Ozone is known to destroy crops of potato, Alfalfa and spinach to the extent of 50%. It also damages leaves of tobacco, tomato and pine and also the grape fruits. Besides, the PAN also blocks Hill's reaction of photosynthesis.

ACID RAIN

• Acid rain is precipitation containing harmful amounts of nitric and sulphuric acids formed primarily by nitrogen oxides and sulphur oxides released into the atmosphere.
• The coal and oil burned by power plants release SO2 into the air and automobile exhaust puts NO2 in the air. 
• Both SO2 and NO2 are converted into acids ( H2SO4 and HNO3 respectively) when they combine with water vapour in the presence of O2  in the atmosphere. These acids return to the earth as acid rain.

(I) NO + O3 NO2 + O2 

NO2 + O3  NO3 + O2

NO2 + NO3 N2O5

N2O5 + H2O  2HNO3

(II) 2SO2 + O2 2SO3 

• Pure rain has a pH of about 5.6 while the acid rain has pH below 5.6. 
• Acid rain is actually a mixture of H2SO4 and HNO3 (usually 60-70% H2SO4 and 30-40% HNO3).
• Acid rain affects the ability of the trees to tolerate cold temperatures and the weakened trees are killed by cold conditions and become more susceptible to diseases. 
• Acid rain leaches lead, mercury and calcium, from the soils and rocks and discharges them into rivers and lakes. The metals may become concentrated in fish and then passed on to people through food chain.
• Acid rain also damages building materials, including steel, paint, plastics, cement and marble.

GREENHOUSE EFFECT AND GLOBAL WARMING

• Usually carbon dioxide is not considered as a pollutant, but its higher concentration forms a thick layer above the earth's surface and checks the radiation of the heat from the earth's surface. Because of this, the temperature of the earth's surface increases, this is called "Green-house effect" or global warming.
• Main greenhouse gases are CO2, CH4, N2O, CFC. Excluding this SO2, NO2, O3, water vapour are also released from industries and agriculture which are responsible to increase the greenhouse effect.
• In this phenomenon, cover of CO2 layer around the earth, allows the short wavelength incoming solar radiation to come in but does not allow long wavelengths of outgoing heat radiation from warm surface of earth and keeps the earth warm. The consequent increase in the global mean temperature is referred to as global warming.

Fig.: The greenhouse effect

• Global warming has many fold effects as 
• Effect on weather and climate : There is an estimated increase in average temperature by 1.4 - 5.8 degree centigrade by the year 2100. Warming of  atmosphere increases its moisture containing capacity. All these are responsible for change in precipitation pattern. This climatic change is harmful for human health.
• Sea level change : Global warming is responsible for the increase in sea level and melting of glaciers and greenland ice sheets.
• Effects on range of species distribution : Due to increase in global warming, many species are expected to shift poleward or towards high elevation in mountain regions. 
• Food production : Increase in temperature causes extensive growth of weeds which ultimately decreases crop production.
• Some strategies should be followed to deal with global warming :
• Vegetation cover should be increased for photosynthetic utilization of CO2.
• Minimizing the use of fossil fuels to reduce greenhouse gas emissions.
• Reducing the use of nitrogen fertilizers to reduce nitrous oxide emissions.
• Chlorofluorocarbons should be replaced with some other substitute having little effect on global warming.

NOTES

• It has been observed that in the recent past, the level of CO2 in the atmosphere has increased from 280ppm to 368ppm from 1956 to 2002. If present growth rate is continued then the amount of CO2 will be double by 2020. Even
  2-3°C rise in temperature will lead  to melting of glaciers and ice caps of the polar region and consequently flood rivers, rise in sea levels and changes in cycle of rain. Islands may be submerged in sea water.
• Carbon-dioxide fertilization effect : Due to increased CO2 concentration, the rate of photosynthesis will increase (up to a few years). The response of the plants to elevated concentration of CO2 is known as the CO2 fertilization effect.
• The global mean temperature has increased by 0.6°C in the 20th century.
• Sea level has been raised by 1 to 2 mm per year during the 20th century.

OZONE DEPLETION

• Ozone is present in less quantity in the atmosphere. But at a height of 16 km to 25 km on earth, concentration of ozone is maximum in stratosphere.
• At normal temperature and pressure, thickness of ozone layer is 3mm. (But at poles thickness of ozone layer is 4mm).
• Due to depletion of ozone layer, harmful UV radiations penetrate to the earth which causes skin cancer (melanoma) and also acts as strong mutagens.
• Ozone hole was first discovered in 1985 over Antarctica by Nimbus-7 satellite.

Aerosols like C.F.Cs. (Chlorofluorocarbons) released into the atmosphere from refrigerators, air conditioners and jet planes deplete or reduce the ozone layer. This is called ozone depletion and these substances are called O.D.S. (ozone depleting substances). This thin layer of ozone is also known as the ozone hole.

                  

Number of pollutants like CFCs (15% of total depletion), nitrogen oxide (3.5%), CH4 and halogens (chlorine) cause depletion of the ozone layer. Maximum ODP (Ozone depleting potential) is of CFCs due to the release of chlorine.

NOTES

1. In this process, one chlorine atom converts one lakh O3 molecules into O2 by photodissociation.
2. The life time of CF2Cl2 (CFC-12) is 139 years while that of CFCl3 (CFC = 11) is about 77 years.

• Chemical process of ozone depletion-chain reaction

  

• Thickness of ozone layer is measured in Dobson unit (1 Du = 1ppb). The unit is named after G.M. Dobson, one of the first scientists to investigate atmospheric ozone.

    

• Ozone hole occurs mainly during spring time
  (Feb. - Apr.) and is lowest during (July - October).
• Shewood Rowland, Mario Molina with Paul Crutzen got Nobel prize (1995) for their research in chemistry on environment science.

NOTES

• First Earth Summit of United Nations Conference on  Environment and Development (UNCED) was  held at Rio-de-Janerio ( Brazil) in 1992.
• First International Conference on “Environment and Development” was held at Stockholm in 1972.
• Second International Conference on “ Environment and Development ” was held at New Delhi in 1985.
• Cyclone collector  is used for minimising air pollution.
• Most polluted city of the World is Tokyo (Japan).
• Most polluted city of India is Kolkata.
• Level of Suspended Particulate Matter (SPM) concentration is highest in the atmosphere of Kolkata.
• In Bihar and Andhra Pradesh, major source of air pollution is thermal power plants.
• Pittsburg city (USA) was once named as “smoke city ”.
• Automobile emission can be reduced by adding barium salts to the petrol.

NOISE POLLUTION

• Generally 80 dB or more than that, the unwanted sound is called noise pollution.
• Noise pollution is measured in dB.
• Noise pollution can cause damage to the heart, increase blood cholesterol and even raise blood pressure etc.
• Noise pollution can be controlled by reduction of noise level from the source, protection of human beings from noise and check of noise pollution.

WATER POLLUTION

• Water pollution is defined as the addition of some substances (organic, inorganic , biological, radiological) or factor
  (e.g., heat) which degrades the quality of water so that, it either becomes health hazard or unfit for use.
• Water pollution may be physical, chemical or biological.
• Physical pollution involves the changes in the physical properties of water, e.g., colour, taste, odour, temperature, turbidity, etc.
• Chemical pollution is caused due to a change in the chemical properties of water. They mainly include pH, dissolved O2, inorganic or organic  chemicals, heavy metals etc.

Inorganic chemicals include fluorides, chlorides, phosphates and nitrates and organic chemicals include phenols, dyes, pesticides and chloro compounds.

• Biological pollution is caused due to the presence of living organisms in water such as algae, fungi, bacteria, viruses, protozoans, insects etc.

SOURCES OF WATER POLLUTION AND EFFECTS OF WATER POLLUTANTS

• Water pollution is a serious health hazard in India, especially in villages. It is estimated that 50-60% of Indian population suffers from diseases caused by it. 30-40% of all deaths are believed to be due to it.
• The principal sources of water pollution and water pollutants are domestic sewage and industrial effluents.

DOMESTIC WASTES AND SEWAGE 

• Sewage containing human faeces, urine, kitchen and cloth washing, organic wastes, industrial wastes etc. is usually poured into water bodies which cause water pollution. 
• Villagers often wash their animals, clothes and take a bath in the same pond. Such water gets contaminated with infectious agents for cholera, typhoid, dysentery, jaundice and skin diseases. 
• Sewage provides food for decomposers, so the population of decomposers increases. 
• Decomposers/microorganisms causing decomposition of sewage take up most of the oxygen present dissolved in water. So, in this water, BOD (Biological oxygen demand or Biochemical oxygen demand) increases very much. 
• BOD is the amount of oxygen in milligrams required by microorganisms for five days to metabolise the waste present in one litre of water at 20°C . 
• B.O.D. of pure drinking water is less than 1ppm or mg/litre.
• A weak organic waste will have BOD below 1500 mg/litre, medium organic waste between 1500 – 4000 mg/litre while in strong waste above 4000 mg/litre. 
• The degree of water pollution is directly proportional  to BOD.
• Soil salinity can be measured by conductivity meter.
• Water having D.O. (dissolved oxygen) content below
  8.0 mgL–1 may be considered as contaminated and below
  4.0 mgL–1 as heavily polluted.
• D.O. is measured by Oximeter.
• B.O. D. ∝ input of organic wastes.
• Some organism like Daphnia, Trout and fishes are sensitive to water pollution, they are indicators of water pollution.
• Biotic index gives an idea of pollution of a particular water body. Any water body with a biotic index of more than 15 is clean, while index lower than 10 is polluted.
• C.O.D. (Chemical Oxygen demand) is the amount of oxygen required to oxidise all pollutant materials is one litre of water at 20°C in five days. The value of COD is much higher than BOD.
• In sewage, phosphorus and nitrogen compounds are present which are necessary for the growth of algae. In polluted water, these are accumulated which results into excessive growth of algae on water surface. Excessive growth of algae is called water bloom .
• Presence of extra nutrients brings about dense growth of plants and animals. The phenomenon is called eutrophication and lake is known as eutrophic lake. In this process, the presence of nutrients in lake stimulates growth of algae (algal bloom) which increases organic loading and brings about reduction in the oxygen content of water causing death of aquatic animals.
• Sewage produces foul odour and makes the water brownish and oily.

INDUSTRIAL EFFLUENTS (OR INDUSTRIAL DISCHARGES)

• Industries usually discharge waste water into ponds, lakes and rivers.
• Industrial wastewater contains heavy metals (mercury, lead, copper, arsenic and cadmium), inorganic pollutants (acids, alkalies and bleaching liquors), organic pollutants (phenol, naphtha, proteins, aromatic compounds, cellulose fibres etc.) 
• Industrial effluents are the most hazardous pollutants on land and water.
• Mercury  (Hg)
• It is released during combustion of coal, smelting of metallic ores, paper and paint industries. 
• Mercury is highly persistent. In water, it gets changed into water soluble dimethyl form [(CH3)2Hg] and enters the food chain (undergoes biomagnification).
• It kills fish and poisons the remaining fauna. Human beings feeding on such poisoned animals develop a crippling deformity called minamata disease which is characterized by impairment of various senses, diarrhoea, haemolysis, meningitis and death. 

The minimata disease was first detected in Japan. 

• Mercury inhibits chromosomal disjunction during gamete formation. So, it brings about genetic changes also.
• Biological magnification : The non biodegradable pollutant like Al, Hg, Fe, D.D.T., pesticides, phenolic compound ABS (Alkyl benzene sulphonate) are not decomposed by microorganisms.

These get accumulated in tissue in increasing concentration along the food chain and the phenomenon is called biological magnification. The highest concentration occurs in top consumer.

Example : Concentration of DDT in water body.

Fig. : Biomagnification of DDT in an aquatic food chain

In India, DDT was  banned for agricultural use in 1985. It is a chlorinated hydrocarbon and shows biomagnification . 

• Lead (Pb)
• The sources of lead pollution are smelters, battery  industry, paint, chemicals and pesticide industry, automobile exhausts etc.
• Lead is a pollutant of air, soil and water. 
• It is used as anti-knock reagent in petrol and released by automobile exhausts. 
• Lead is a persistent pollutant and may show biological amplification or biomagnification. 
• It is mutagenic and causes anaemia, headache, vomiting, colic, loss of muscle power, bluish lines around the gums, loss of appetite and damage of liver, kidney and brain. 
• Cadmium (Cd)
• It is added to the environment  by metal industries, welding and electroplating, pesticides and phosphate industries. 
• Cd shows biological amplification and accumulates inside kidneys, liver, pancreas and spleen. 
• It causes itai-itai disease (a painful disease of the joints), hypertension, anaemia, diarrhoea and damages - liver and kidneys.

OIL 

• During extraction and transportation of oil from the sea to different parts, some of the oil spreads over the surface of water. Refineries also discharge a lot of oil present in their effluents into rivers. 
• Oil spreading on the surface of  water prevents its oxygenation and inhibits photosynthetic activity of aquatic plants. Animal life is destroyed due to reduced availability of oxygen, food and toxic effects of oil. 
• Oil spilled over the surface of water may catch fire and hence kill all organic life.

THERMAL POLLUTION  

• Hot water is produced by many industries, power generation plants and thermal power plants. 
• Thermal pollution is caused by the addition of hot water effluents in water bodies, it brings about rise  in water temperature. 
• Warmer water contains less oxygen. Therefore, there is a decrease in the rate of decomposition of organic matter. 
• In hot water, green algae are replaced by less desirable blue green algae. 
• Many organisms fail to reproduce in hot water, e.g., Salmon, Trout.

NOTES

High concentration of DDT disturbs calcium metabolism in birds, which causes thinning of egg shells and their premature breaking, eventually causing a decline in bird populations. 

Table : Important legislation for the protection of the environment

NOTES

• Fluorosis – 13 states in India possess high fluoride content in drinking water (more than 1.5 mg/l) which causes fluorosis in human.
• ABS (Alkyl Benzene Sulphonate) is the most harmful component of detergents causing water pollution.
• Maize (Zea mays) is a sensitive indicator of fluoride pollution.
• Ganga Action Plan started in 1985 for controlling pollution in Ganges.
• Reed plants (yellow iris) are used to purify water. This method of purifying water is called “Green method of water cleaning”. Yellow iris plant is less affected by herbicides, so reed beds are highly effective in those areas where pesticides are in use and provides microbiological methods of pesticide detoxification. These plants filter out particulate matter,  while the microbes living in association with the plants, decompose the organic wastes.
• Water hyacinth (Eicchornia) popularly known as Jalkumbhi or Kaloi, can purify water polluted by biological or chemical wastes. It can also filter out heavy metals like cadmium, mercury, lead and nickel as well as other toxic substances found in industrial waste waters.

RADIOACTIVE POLLUTION

• The property of sudden emission of the different particles (charged) and radiation (rays) by the decay of atomic nuclei is called radioactivity and the elements are called radioactive elements.
• The radioactivity of the atmosphere is increased by atomic power stations and atomic tests. Radioactivity contributes to the pollution of air, water as well as soil and it proves to be extremely harmful to the organisms.
• The various sources of radioactive materials are – 
• Natural sources : Cosmic rays, radiation from the earth such as Radium 224, Uranium 235, Uranium 238, Thorium 232, Radon 222, Potassium 40 and Carbon 14.
• Man made radiation : The radiations are released in the atmosphere during mining and purification of thorium and plutonium, and in producing nuclear weapons etc.

Nuclear reactor and nuclear fuels cause pollution by radioactive radiation. Nuclear fuels and coolants are the sources of radioactive radiation. Radioactive waste is also most important radioactive pollutants because these wastes are not dumped at particular or right place.

• Other sources : Some of the radioactive elements (isotopes) are used in experimental laboratories for scientific researches which causes radioactive pollution. X-rays are also proved to have harmful effects.
• Harmful radiation are divided into two categories -
• Non-ionising components : Non-ionising components includes UV radiation. UV radiations are harmful for living beings. These radiations cause harm to the DNA, RNA and protein. Higher concentration of U.V radiation can cause xeroderma pigmentosum.
• Ionising components : X-rays, α-particles, β-particles etc. are ionising components. Ionising radiation are high energy radiations which release electrons from atoms and form a pair of negative and positive ions.
• Ionising radiation cause physical weakness and sudden death of living beings. The effects like hereditary changes, mutations, tumours, cancer and developmental changes are seen due to radiation.
• Excluding these, Iodine 131, Strontium - 90 are spreading in the environment through nuclear explosions and their effects remain for long duration. Iodine-131 reaches the human body through the food chain and causes harm to the bone marrow, WBC, Lymph nodes and spleen. Similarly, these lead to skin cancer, sterility and poorer eyesight. Strontium-90 leads to bone cancer and degeneration of tissues.
• In India, there are 4 atomic power plants – Narora, Tarapur, Kalpakkam and Rawat Bhata.

SOIL POLLUTION (SOLID WASTE)

• Unfavourable alteration of soil by addition or removal of substances and factors which decrease soil productivity, quality of plant  products and groundwater is called soil pollution. 
• Soil pollutants include pesticides, fertilizers, industrial wastes, salts, tin, iron, lead, copper, mercury, aluminium, plastics, paper, glass, broken bottles, discarded food etc.

PESTICIDES

• Pesticides include insecticides, fungicides, algicides, weedicides or herbicides, rodenticides etc. 
• Pesticides are generally broad-spectrum and affect other animals, man and even plants. They are hence, also called biocides.
• DDT (dichloro diphenyl trichloroethane), BHC (benzene hexachloride or gammexane), aldrin, dieldrin, endrin, heptachlor etc. are chlorinated hydrocarbons used as pesticides.
• Dieldrin is five times more toxic than DDT when ingested and 40 times more poisonous when absorbed.
• Endrin is the most toxic amongst chlorinated hydrocarbons.
• Chlorinated hydrocarbons are persistent, fat soluble and show biomagnification.
• DDT and other chlorinated hydrocarbons affect CNS, cause softening of brain, cirrhosis of liver (liver cancer), cerebral haemorrhage, cancer, hypertension, thinning of egg shells in birds, malformation of sex hormones, failure of gonad development.
• The population of certain birds (e.g. Bald eagle) has declined due to these biocides.
• The weedicides (or herbicides) are usually metabolic inhibitors which stop photosynthesis and other metabolic activities and hence kill the plants. 2,4-D, 2,4,5 -T, DCMU and CMU are weedicides.

FERTILIZERS

• Fertilizers contain plant nutrients, particularly N, P and K but the soil also gets polluted mainly due to organic pollutants present as impurities. 
• Excessive use of fertilizers cause soil deterioration through decrease of natural microflora (nitrogen fixing, nitrifying bacteria).
• Fertilizers added to soil enter the crop plants. Nitrogen fertilizers produce toxic concentration of nitrate in the leaves and fruits. When these leaves and fruits are eaten, nitrates change into nitrites by the activity of bacteria in the alimentary canal. The nitrites enter the blood and combine with haemoglobin to form methaemoglobin. As a result, oxygen transport is reduced. It gives rise to disease known as methemoglobinemia. In infants, it produces cyanosis (blue baby syndrome).

RADIOACTIVE WASTES

• The nuclear tests performed in sea pollute the sea water. 
• The animals and plants are affected by the remaining radioactivity of the wastes. Radioactive elements (eg. Cesium–137, strontium–90, Iodine–131) enter the human system.
• Cesium–137 accumulates inside the body muscles, Strontium–90 in bones while iodine–131 in thyroid.
• Cesium–137 brings about functional and genetic changes. Strontium–90 causes blood and bone cancer. Iodine–131 affects normal functioning of thyroid.

INDUSTRIAL WASTES

• Wastes of the industries are dumped over the soil. They contain a number of toxic substances including cyanides, acids, chromates, alkalies and metals like mercury, copper, zinc, lead, cadmium etc. 
• The industrial pollutants increase the toxicity level of the soil. 
• Heavy metals destroy useful microorganisms of the soil. 
• In 1970, some 200 people died in Japan by Cd pollution of soil due to itai–itai disease.

MUNICIPAL SOLID WASTE

• It includes wastes from kitchen, offices, stores, hospitals, schools etc. It generally comprises paper, food waste, plastics, glass etc.
• Burning reduces the volume of the wastes, although open dumps serve as a breeding ground for rats and fill. Sanitary landfills are adopted as a substitute for open burning dumps.

ELECTRONIC WASTE

• It includes irreparable computers, mobile and other electronic goods. It is a valuable source for secondary raw materials.
• It represents two percent of America's trash in landfills, but it equals to a larger percent of overall toxic waste.
• Recycling is the only solution for the treatment of e-wastes provided it is carried out in an environment friendly manner.

CONTROL MEASURE FOR SOIL POLLUTION

• Soil pollution can be checked by improving the disposal of wastes, appropriate use of chemical fertilizers and use of biological pest control.
• The most important measures to check land degradation is restoration of forest, crop rotation, improved drainage etc. 

AGROCHEMICAL AND THEIR EFFECTS

• Organic farming is a form of agriculture which avoids or largely excludes the use of synthetic fertilizers and pesticides, plant growth regulators and livestock feed additives.
• Possible organic farmers rely on crop rotation, crop residues, animal manures and mechanical cultivation to maintain soil productivity, to supply plant nutrients and to control weeds, insects etc. Harmful effects of the use of agrochemicals in modern farming are -
• About half of the nitrate in the artificial fertilizers used on crops is dissolved by rains.
• The constant use of artificial fertilizers, together with a lack of crop rotation reduces soil fertility year by year.
• The pesticides and fertilizers residuals that persists in the soil are harmful to the beneficial soil micro-organism and earthworms, thereby, resulting in the degradation of soil fertility.

DEGRADATION BY IMPROPER RESOURCE UTILIZATION AND MAINTENANCE

• Degradation of natural resources can occur by improper resource utilization practices like soil erosion and desertification and water logging and soil salinity.
• Soil erosion is the loss of protective vegetation through deforestation, overgrazing, ploughing and fire which makes soil vulnerable to being swept away by wind and water. Erosion will remove the topsoil first.
• Without soil and plants, the land become desert like and is unable to support life, this process is called desertification.
• Irrigation without proper drainage of water leads to water logging in the soil. Water logging limits oxygen to roots and prevent CO2 from diffusing away. Besides-affecting the crops, water logging draws salts to the surface of the soil which is then deposited as a thin crust on the land surface. This increased salt content is unfavourable to the growth of crops.

DEFORESTATION

• Deforestation is the falling down or removal of forest trees.
• The major causes of deforestation are Jhuming (shifting cultivation), construction of hydro electric projects, forest fires, construction of roads and railways and canals, over grazing of cattle in forest areas etc.
• In slash and burn agriculture, the farmers cut down the trees of the forest and burn the plant remains. The ash is used as fertilizer and the land is used for farming and cattle grazing. After cultivation, the area is left for several years. This allows the soil to recover and become rich and fertile again. The farmers then move on to the other areas and repeat the process. It is also called shifting cultivation.
• Impact of deforestation are -
• Shrinking fuel food
• Decrease in the availability of timber
• Soil erosion
• Drought, loss of biodiversity and germplasm
• Increases atmospheric CO2 content which causes global warming.
• Uprooting and loss of livelihood of tribals.
• Reforestation or afforestation is planting more trees.
• Conservation of forest can be done by-
• Sustained yield block cutting
• Van mahotsava (a special function of tree plantation).
• Chipko movement (a movement initially meant for protecting trees but now meant for preservation of environment including habitat and wildlife. It was started in Chamoli district in 1973 by Sundar Lal Bahuguna). 
• The government of India has recently instituted the 'Amrita Devi Bishnoi Wildlife Protection Award' for individuals or communities from rural areas that have shown extraordinary courage and dedication in protecting wildlife.

CASE STUDIES AS SUCCESS STORIES ADDRESSING ENVIRONMENTAL ISSUES

A CASE STUDY OF CONTROLLING VENTRICULAR AIR POLLUTION

• Automobile exhaust is a significant source of air pollution in the urban context. In 1990, Delhi ranked fourth among the 41 most polluted cities in the world. 
• Air pollution problem in Delhi has become so serious that a public interest litigation (PIL) has been filed under Article 21 of the constitution of India regarding air pollution in Delhi. After being consulted very strongly by the supreme court, under its directives the govt. was asked to take, within a specified time period, appropriate measures including switching over the entire fleet of public transport i.e. buses from diesel to compressed natural gas (CNG). 
• The result is that air quality of Delhi has improved considerably with a substantial fall in pollutant gases between 1997-2005.

A CASE STUDY OF INTEGRATED WASTE WATER TREATMENT

• Arcata is a small city located on Humboldt Bay, in the coastal redwood country of Northern California. They created an integrated waste water treatment process within a natural system.
• As a result of this process of cleaning, the water flows through the marshes get purified naturally.
• The marshes also comprise, a sanctuary a citizen group called Friends of the Arcata Marsh (FOAM) which are responsible for the maintenance and protection of this project. Arcata's story has become a landmark in an alternative, wastewater treatment.

A CASE STUDY OF REMEDY FOR PLASTIC WASTE

• Plastics are used because they are easy and cheap to make and they can last a long time. Unfortunately, these qualities can make plastic a huge pollution problem.
• In collaboration with R.V. College of  Engineering and Bangalore city corporation, Ahmed Khan (57 years old) proved that blend of polyblend (a fine powder of recycled modified plastics)  and bitumen, when used to lay road, enhanced the bitumen's water repellent properties and helped to increase the road life by a factor of three.
• Using Khan's technique by the year 2002, more than 40 kms of roads in Bangalore have already been laid.

NOTES

World earth day – 22nd April  

World environment day – 5th June

International day for the preservation of the ozone layer or Ozone day – 16th September 

IMPORTANT ABBREVIATIONS

N.E.E.R.I. - National Environmental Engineering Research Institute, Nagpur

I.U.C.N. - International Union for Conservation of Nature and Natural Resources, Switzerland

C.P.C.B. - Central Pollution Control Board

U.N.E.P. - United Nations Environment Programme

O.D.P. - Ozone Depleting Potential (It is maximum in CFCs)

I.A.P. - Indices of Atmospheric Pollution [prepared with the help of lichens (sensitive to SO2)] 

C.N.G. - Compressed  Natural Gas

C.T.B.T - Comprehensive Test  Ban Treaty

C.S.E. - Centre for Science and Environment

I.W.P. - Indices of Water Pollution

Biology Study Notes

• The Living World
• Biological Classification
• Plant Kingdom
• Animal Kingdom
• Morphology of Flowering Plants
• Anatomy of Flowering Plants
• Structural Organisation in Animals
• Cell : The Unit of Life
• Biomolecules
• Cell Cycle and Cell Division
• Transport in Plant
• Mineral Nutrition
• Photosynthesis in Higher Plants
• Respiration in Plants
• Plant Growth and Development
• Digestion and Absorption
• Breathing and Exchange of Gases
• Body Fluids and Circulation
• Excretory Products and their Elimination
• Locomotion and Movement
• Neural Control and Co-ordination
• Chemical Coordination and Integration
• Reproduction in Organism
• Sexual Reproduction in Flowering Plants
• Human Reproduction
• Reproductive Health
• Principles of Inheritance and Variation
• Molecular Basis of Inheritance
• Evolution
• Human Health and Disease
• Strategies for Enhancement in Food Production
• Microbes in Human Welfare
• Biotechnology: Principles and Processes
• Biotechnology and its Application
• Organism and Population
• Ecosystem
• Biodiversity and its Conservation
• Environmental Issues

Study Notes for NEET/AIIMS/JIPMER