Pollution : Effects & Measures

Pollution

Definition

An undesirable change in the physical, chemical and biological characteristics of the environment especially air, water, land and space that may adversely affect human population and the wild life, industrial processes, cultural assets (building and monuments), is called  pollution. 

The agents that pollute the environment or cause pollution are called pollutants.

Classifications

1. According to the form in which they persist after release into the environment

• Primary pollutants : These persist in the form in which they added to the environment e.g. DDT, plastic.
• Secondary pollutants : These are formed by interaction among the primary pollutants. e.g. peroxyacetyl nitrate (PAN) is formed by the interaction of nitrogen oxides and hydrocarbons. 

     2. According to their existence in nature.

• Quantitative pollutants : These occur in nature and become pollutant when there concentration reaches beyond threshold level e.g. carbon dioxide, nitrogen oxide. 
• Qualitative pollutants :  These do not occur in nature and are man-made. e.g. fungicide, herbicide, DDT etc.

     3. According to the nature of disposal.

• Biodegradable pollutants : Waste products which are degraded by microbial action e.g. Sewage. 
• Non Biodegradable pollutants : Pollutants which are not decomposed by microbial action e.g. plastic, glass, DDT, salts of heavy metal radioactive substances etc.

   

4. According to origin

 

1. Natural 
2. Anthropogenic

Causes of pollution

• Uncontrolled growth in human population
• Rapid industrialization
• Urbanization 
• Uncontrolled exploitation of nature
• Forest fires, radioactivity, volcanic eruptions, strong wind etc.

Types of pollution

Depending upon the area or the part of environment affected, pollution may be of the following types :

• Air pollution 
• Water pollution 
• Land pollution 
• Noise pollution
• Radioactive Pollution
• Thermal Pollution
• Space Pollution

Air Pollution

Air Pollution

Sources

i) Natural sources 

    

    (i) Ash from burning volcanoes, dust from storm, forest fires 

    (ii) Pollen  grains from flowers in air are natural sources of pollution 

ii)  Anthropogenic (human-made) sources                   

  (i) Power stations using coal or crude oil release CO2  in air 

 (ii) Also furnaces using coal, cattle dung cakes, firewood, kerosene, etc. 

 (iii) Steam engines used in railways, steamers, motor vehicles, etc. give out CO2. 

 (iv) So  do  motor and internal combustion engines which run on petrol, diesel, kerosene. etc.

(v) Vegetable oils, kerosene, and coal as household fuels 

(vi) Sewers and domestic drains emanating foul gases 

(vii) Pesticide residues in air

Major Air Pollutants

1. Carbon dioxide 

The increasing CO2  in the atmosphere is likely to have the following effects: 

(i) A rise in atmospheric temperature or  global warming due to greenhouse effect.  Also causes climate change. 

(ii) Reduced productivity of the marine ecosystem.

(iii) Due to Global warming,  the increased surface temperature would cause melting of continental and mountain glaciers  and thus would cause  flooding of coastal areas  of some countries. 

2. Sulphur dioxide

It is produced by the burning of coal in powerhouses and automobiles (car, trucks etc.).  It causes  chlorosis  and  necrosis  of plants, irritation in eyes and injury to the respiratory tract (asthma, bronchitis) in humans responsible for discoloration and deterioration of buildings. High concentration of sulphur dioxide in the atmosphere dissolves in rain drops to form sulphuric acid which causes  acid rain. 

3. Carbon monoxide 

Carbon monoxide is produced as a result of incomplete combustion of fossil fuels like coal, petroleum and wood charcoal.  Automobiles using diesel and petroleum are the major sources of carbon monoxide which gets added to the atmosphere.

4. Fluorides 

Upon heating„ rocks, soils and minerals that contain fluorides, give out hydrogen fluoride gas.  This is an extremely toxic gas, which causes serious injury to livestock and cattle. 

5. Oxides of nitrogen 

A few oxides of nitrogen, such as nitric oxide (NO), nitrous oxide (N2O) and nitrogen dioxide (NO2) are produced by natural processes as well as from thermal power stations, factories, automobiles and aircrafts (due to burning of coal and petroleum). They reduce the oxygen carrying capacity of blood, may cause eye irritation and skin cancer in human beings.

6. Smog 

Smog is a mixture of smoke, dust particles and small drops of fog.  Smog may cause necrosis and develop a white coating on the leaves (silvering) of plants. 

7. Aerosol spray propellants 

Suspended fine particles in the air  are known as aerosols.  Aerosols  contain chlorofluorocarbon carbons (CFCs) and fluorocarbons used in refrigerants and aerosol cans.  They cause depletion of the ozone layer.

Effects of Air Pollution

Prevention and control of air  pollution 

There are two types of air pollutants—gaseous and particulate. 

Methods of controlling gaseous air  pollutants 

(i) Combustion.  

This technique is used for controlling those air pollutants that are in the form of organic gases or vapours. In this technique, the organic air pollutants are subjected to flame combustion technique (also known as catalytic combustion). In this technique, organic pollutants are converted into less harmful products and water vapour. 

(ii) Absorption.  

Absorption is a process in which a substance penetrates into another substance like scrubbers. In this technique, gaseous pollutants are passed through absorbing material like scrubbers.  These scrubbers contain a liquid absorbent.  This liquid absorbent removes the pollutants present in gaseous effluents.  Thus the air coming into scrubber is free from pollutants and it is discharged into atmosphere. 

(iii) Adsorption. 

Adsorption is a process in which a substance sticks to the surface of another substance (called absorbent). In this technique, gaseous effluents are passed through porous solid absorbent kept in containers.  The gaseous pollutants stick to the surface of the porous material and clean air passes through.  The organic and inorganic constituents of gaseous effluents are trapped at the interface of solid adsorbent by physical adsorbent. 

Methods to control particulate air  pollutants 

The particulate air pollutants such as dust, soot, fly ash etc. can be controlled by using fabric filters, electrostatic precipitators, wet scrubbers and mechanical devices etc. 

(i) Fabric filters.  

In this technique, gaseous emission containing dust, soot and fly ash is passed through porous fabric filters made of fabric  (cloth) (woven or filled fabric).  The particles of pollutants get trapped in this fabric and are collected in the filter and the gases free from the pollutant particles are discharged. 

(ii) Mechanical devices.  

There are many mechanical devices that clean the air of pollutants either due to 

(a) gravity in which the particles settle down by gravitational force; or by 

(b) sudden change in the direction of gas flow in which particles separate out due to greater momentum. 

(c) Electrostatic precipitators.  

In this technique, a gas or air stream containing aerosols in the form of dust, mist or fumes, is passed between the two electrodes of the electrostatic precipitator. During this process, the aerosol particles get precipitated on the electrodes.

Water Pollution

Any physical, biological or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired use is called water pollution.

Water Pollution

Sources of water  pollution

  (i) point sources; and 

  (ii) non-point sources.

(i) Point sources  

Those sources which discharge water pollutants directly into the water are known as point sources of water pollution. Oil wells situated near water bodies, factories. power plants, underground coal mines, etc. are point sources of water pollution. 

(ii) Non-point sources

Those sources which do not have any specific location for discharging pollutants, in the water body are known as non-point sources of water pollution. Run-offs from agricultural fields, lawns, gardens, construction sites, roads and streets are some non-point sources of water pollution.

Water Pollutants 

River, lake and sea water may be polluted in many ways. 

• Domestic sewage  discharged into rivers from areas located on its banks 
• Industrial wastes  effluents from urban areas containing high concentration of oil, heavy metals and detergents 
• Minerals, organic wastes  and crop dusting  from agricultural fields with phosphate and nitrogen fertilizers that reach lakes, rivers and sea (water becomes deoxygenated and poisonous, thus, cannot support aquatic life) 
• Chemical fertilizers, pesticides, insecticides, herbicides and plant remains Industrial waste water containing several  chemical pollutants,  such as calcium, magnesium, chlorides, sulphide, carbonates, nitrates, nitrites, heavy metals and radioactive waste from nuclear reactor. 
• Excretory wastes of humans and animals in water  bodies 
• Disposal of urban and industrial waste matter into water bodies.

Effects of Water Pollution

Prevention and control of water pollution

Water pollution can be controlled by

• Treating industrial effluents before discharging into rivers, separate channels for river and sewage water
• Avoid contamination of rivers, lakes and ponds by washing clothes, bathing.etc.
• Not throwing waste, food materials, paper, biodegradable vegetables and plastic into open drains.
• Setting up sewage water treatment plants
• Use of septic tanks in houses to avoid direct outlet of faecal matter and other wastes
• Effluents from distilleries and solid waste containing organic matter diverted to biogas plants to generate energy
• Maintenance or  safety standards  for the effluents discharged into the water system.

Soil Pollution

Addition of substances that change the quality of soil by making it less fertile and unable to support life is called soil pollution. 

Soil Pollution

Sources of soil pollution

Soil pollution is caused due to :

• Domestic sources : plastic bags, kitchen waste, glass bottles, and paper
• Industrial sources : chemical residue, fly ash, metallic waste, and
• Agricultural residues : fertilizers and pesticides.

Harmful effects of soil pollution

• Decrease in irrigated land thereby reduction in agricultural production.
• Decrease in soil productivity.
• Carry over of pollutants into the food chain.
• Damage to landscape

Control of Soil Pollution

• Judicious use of chemical fertilizers and pesticides.
• Proper and appropriate irrigation practices
• Conversion of farm wastes into compost and much use of bio fertilizers and manure in farming.
• Ensure use of pollution free or treated waste water only for irrigation. 
• Recycling of waste material for example plastic, metal and glass are recyclable and incineration of non recyclable, wastes.

Soil Erosion 

The process of detaching and removal of loosened soil particles by water (running water, ground water, rain, sea waves) and wind is known as soil erosion.  Soil may be eroded by water and wind, each contributing towards a significant amount of soil loss every year in our country. 

Soil Erosion

Types of soil erosion 

1. Wind erosion 

Erosion of large quantity of fine soil particles and sand from deserts by wind is known as wind erosion. It is spread over the cultivated land and thus, destroys fertility of that land. 

2. Sheet erosion 

When water moves over the land surface as a sheet, it takes away the topmost thin layer of soil.  This phenomenon occurs uniformly on the slopes of hilly areas, riverbeds and areas affected by floods.  This type of erosion is known as  sheet erosion. 

3. Gully erosion 

When water moves down the slope as a channel, it scoops out the soil and forms gullies which gradually multiply and spread over a large area.  This type of soil erosion is known as  gully erosion. 

Gully Erosion

Effects of soil erosion 

Soil erosion may have several adverse effects such as,

• The top layer of productive land may be washed away. 
• Roads, fences, bridges, trees and houses may get damaged. 
• Fine soil may be transported far away. 
• Crops and pasture lands may be destroyed either by being washed out or by getting covered with mud. 
• Flooded fields may take a long time to recover and fertilizers may also be washed out leading to reduction in agricultural yield. 
• Organic matter of the soil, residues or any applied manure, is relatively lightweight and can be readily washed off the field. Crop emergence, growth and yield are directly affected by the loss of natural nutrients and fertilizers in the soil. Seeds and plants can get disturbed or completely removed from the eroded soil. 
• Soil erosion changes the composition of soil leaving infertile rock behind. Soil quality, structure. stability and texture may also be affected.
• The breakdown of aggregates and the removal of smaller particles or entire layers of soil or organic matter can weaken the structure and even change the texture.  Textural changes can in turn affect the water-holding capacity of the soil making it more susceptible to extreme conditions, such as drought. 
• Sediment which reaches streams or water-courses due to soil erosion clog drainage and stream channels, deposit silt in reservoirs and reduce quality downstream water. 

Causes of Soil Erosion 

(i) Natural Sources 

Water Erosion:  

During rainfall, drops of rain can break down soil aggregates and disperse them.  The loosened soil particles are transported with the runoff water. If vegetation is depleted by drought, raindrops are free to hit the soil, causing erosion during rainfall. 

Water Erosion

Wind Erosion: 

Wind can move large amounts of soil.  Wind erosion is a serious means of soil erosion. Blowing soil not only leaves a degraded area behind but can also bury and kill vegetation where it settles.  Winds blow away the fine particles of soil during drought. 

Wind Erosion

(ii)  Anthropogenic (Produced by humans) 

• Extensive cutting down of forests and trees exposes the ground surface to the direct impact of rain and wind. For example, in the absence of proper vegetation cover there is no interception of rainfall and the falling rain strikes the soil surface directly resulting in the throwing up of loose soil particles in the air which are washed away by rainwater. 
• Construction work, mining, digging canals and ditches change the structure of soil.  This accelerates soil erosion due to high-speed winds as well as rainwater. 
• While making roads. soil is cut and massive digging of earth takes place.  This leads to soil erosion by water or wind. 
• Excessive use of plough, machines, fertilizers and irrigation may damage the land. 
• In many areas, trees and grasses are depleted because of overgrazing by animals. This makes the soil susceptible to erosion. 

Prevention of soil erosion 

Some methods to control soil erosion are discussed below. 

• The roots of the trees hold soil material together.  Therefore, we should protect our forests and trees from being cut down.  Afforestation means planting trees in place of cut-down forest trees. Planting of trees along river-side, waste lands and mountainous slopes reduces excessive erosion of soil that takes place in these regions. It is also effective in controlling wind erosion.
• Grazing by domesticated animals in a planned way reduces soil erosion by protecting vegetation cover specially on the hill slopes which are more prone to soil erosion. 
• Protected channels for water movement must be provided to stop soil erosion. If the waterways are properly maintained the speed of water gets reduced and soil erosion decreases. Dam should be constructed on rivers to control flooding and consequently soil erosion.  This can also be done by diverting water to dry areas through canals, in a planned way. 
• Obstructions known as bunds should be constructed in lands affected by gully erosion. 
• Terracing is a method of farming to conserve the thin soil layer on the mountain slopes.  This helps in controlling soil erosion and using water resources of these areas more economically and effectively for growing crops on these terraces. 
• Ploughing and tilling of land along the contour levels in order to cause furrows to run across the land slopes is known as the contour ploughing.  This method is most suited to areas that have a rolling landscape. 
• Windbreaks which means planting trees to protect bare soil from the full force of wind also help in preventing soil erosion by wind.  Windbreaks reduce the velocity of wind thereby decreasing the amount of soil that it can carry away.

Noise pollution 

Noise can be simply defined as “unwanted sound’’. It is generally higher in urban and industrial areas than in rural areas.  Workers using heavy machinery are exposed to high noise levels for long period of work hours every day. Intensity of sound is measured in a unit called  decibel  or  dB.  The lowest intensity of sound that human ear can hear is 20 dB.

Noise Pollution : Heavy Machinery at Construction

Sources of noise pollution 

The major sources of noise pollution are : 

• Use of loud speakers, loud music system and television at public places 
• Means of transport i.e. automobiles, railways, aircrafts, etc. 
• Heavy machines in industries fireworks.

Effects of noise pollution

• Inability to sleep, slow recovery from sickness. 
• Irritability and interference in communication. 
• Temporary loss of hearing, earache, sometimes even leading to permanent deafness. 
• Inability to concentrate, headache.
• Ringing of ears (a feeling, sound coming from within the ear in a very quiet environment). 
• Increased blood pressure, irregular heart beat.

Prevention and control of noise pollution

Following steps can be taken to control or minimize noise pollution : 

• Control the noise emanating from your radio and television. 
• Use automobile horn only in case of emergency. 
• Do not burn fire crackers as they are noisy and also cause air pollution. 
• Get all machinery and engines properly tuned and serviced at regular intervals and by the use of silencers. 
• Use of sound proof cabins and sound-absorbing materials in the walls. A  green belt of vegetation is an efficient absorber of noise. 
• Not playing loudspeakers during odd hours. It is legally banned and should be reported to the police immediately.

Radioactive Pollution

Radioactive is a phenomenon of spontaneous emission of proton (Alpha particle), electrons (beta particles) and gamma rays (shortwave electromagnetic waves) due to disintegration of atomic nuclei of some elements. These causes radioactive pollution.

Radioactive Container

Radioactivity : Radioactivity is a property of set an elements radium, thorium uranium etc.) spontaneously emit protons, electrons, and gamma rays by disintegration of their atomic nuclei.

Types of radiations

• Non-ionizing radiation affect only those components which absorb them and have low penetrability.
• Ionizing radiations have high penetration power and cause breakage of macro molecules.

Types of radiation particle

• Alpha particles can be blocked by a piece of paper and human skin.
• Beta particles can penetrate through skin, while can be blocked by some piece of glass and metal.
• Gamma rays can penetrate easily to human skin and then cell on its way through, reaching far, and can only be blocked by very thick, strong, massive piece of concrete.

Sources

Natural

• They include cosmic rays from space and terrestrial radiations from radio-nuclides present in earth's crust such as radium-224, uranium-238, thorium-232, potassium-40, carbon-14, etc.

Man-made

• Nuclear power plants
• Nuclear weapon
• Transportation of nuclear material
• Disposal of nuclear waste
• Uranium mining
• Radiation therapy

Effects

• The effects of radioactive pollutant depend upon

1. half-life
2. energy releasing capacity
3. rate of diffusion
4. rate of diffusion of pollutants

 Control Measures

• Prevention is the best control measure as there is no cure available for radiation damage.

1. All safety measures should be strictly enforced. Leakage of radioactive elements should be totally checked.
2. Safe disposal of radioactive waste.
3. Regular monitoring through frequent sampling and quantative analysis.
4. Safety measures against nuclear accidents.
5. Nuclear explosions and use of nuclear weapons should be completely banned.
6. Appropriate steps should be taken to protect from occupational exposure.

E-Waste

• The discarded and end-of-life electronic products ranging from computers, equipment used in Information and Communication Technology (ICT), home appliances, audio and video products and all of their peripherals, are popularly known as Electronic waste (E-waste).
• E-waste is not hazardous if it is stocked in safe storage or recycled by scientific methods or transported from one place to the other in parts or in totality in the formal sector. The e-waste can, however, be considered hazardous if recycled by primitive methods.

Electronics Hardware Wastes

Solid Waste

Solid wastes are the discarded (abandoned or considered waste-like) materials. Solid waste means any garbage, refuse, sludge from a wastewater treatment plant, or air pollution control facility and other discarded materials including solid, liquid, semi-solid, or contained gaseous material, resulting from industrial, commercial, mining and agricultural operations, and from community activities. But it does not include solid or dissolved materials in irrigation return flows or industrial discharges.

Garbage heap

Plastic Waste

Plastic are considered to be one of the wonderful inventions of 20th century. They are widely used as packing and carry bags because of cost and convenience. But plastics are now considered as environmental hazard due to the "Throw away culture".

A Boy playing in plastic wastes

Sources of generation of waste plastics

• Household
• Health and medicare
• Hotel and catering
• Air/rail travel

Types

• Solid wastes are classified depending on their source:

1. Municipal Waste
2. Hazardous Waste and
3. Biomedical Waste or Hospital Waste

Thermal Pollution

Thermal pollution is the rise or fall in the temperature of a natural aquatic environment caused by human influence. This has become an increasing and the most current pollution, owing to the increasing call of globalization everywhere.

Thermal pollution is caused by either dumping hot water from factories and power plants or removing trees and vegetation that shade streams, permitting sunlight to raise the temperature of these waters, release of cold water which lowers the temperature. Like other forms of water pollution, thermal pollution is widespread, affecting many lakes and vast numbers of streams and rivers in various parts of the world.

Hot Smoke

Major sources

• power plants creating electrify from fossil fuel
• water as a cooling agent in industrial facilities
• deforestation of the shoreline
• soil erosion

Ecological Effects - Warm Water

The change in temperature impacts organisms by

1. decreasing oxygen supply, and
2. affecting ecosystem composition

Warm water contains less oxygen. Elevated temperature typically decreases the level of dissolved oxygen (DO) in water. So there is decrease in rate of decomposition of organic matter. Green algae are replaced by less desirable blue green algae. Many animals fail to multiply. It also increases the metabolic rate of aquatic animals results in consumption of more food in a shorter time than if environment were not changed. An increase metabolic rate may result in food source shortages, causing a sharp decrease in population.

Ecological Effects - Cold Water

Thermal pollution can be caused by the release of very cold water from the base of reservoirs into warmer rivers. This affect fish (particularly their eggs and larvae), macro invertebrates.

Space Pollution

• Space Debris, also known as orbital debris, space junk and space waste, is the collection of defunct objects in orbit around the Earth.
• This includes everything from spent rocket stages, old satellites, fragments from disintegration, erosion and collision.

Space Debris

Effects

• Debris poses a growing threat to satellites and could prevent the use of valuable orbits in the future.
• Many pieces of debris are too small to monitor but too large to shield satellites against.

Types of orbits

1. Low Earth Orbit (altitude between 160 km and 2000 km from the Earth's surface)
2. Medium Earth Orbit (2000 km to 36000 km)
3. Geostationary Earth Orbit (35786 km and above)
4. High Earth Orbit (above 36000 km)

Debris in LEO (Low Earth Orbit)

• Satellites in LEO are many different orbitals planes providing global coverage and the 15 orbits per day typical of LEO satellites result in frequent approaches between object pairs.
• After space debris is created, the orbital plane's direction will change over time, and thus collisions can occur from virtually any direction. This leads to cascading effect.

Debris at higher altitudes

• At higher altitudes, where atmospheric drag is less significant, orbital decay takes much longer.
• This issue is especially problematic in the valuable GEO orbits where satellites are often clustered to share the same orbital paths.

Earth Surrounded by debris

Sources of debris

• Dead spacecrafts
• Boosters
• Lost equipment

Clearance of space debris

i) Tug like satellites

• It drag the debris to a safe altitude in order to burn up in the atmosphere.
• It creates an electron emission to create a difference in potential between the debris as negative and itself as positive.
• The satellite then uses its own thrusters to propel itself along with the debris to a safer orbit.

ii) Electrodynamic tethers

• It provides a simple and reliable alternative to the conventional rocket thrusters.
• It works on the basic principle of Lorentz force and Fleming's Left hand rule.
• Magnetic force is exerted on a current carrying wire in a direction perpendicular to both the flow of current and the magnetic field.

iii) Laser Brooms

• The laser broom uses a powerful ground based laser to ablate the front surface off debris and thereby produce a rocket like thrust that slows the object.
• With continued application the debris will eventually decrease their altitude enough to become subject to atmospheric drag.
• Additionally, the momentum of photons in the laser beam could be used to impart thrust in the debris directly.

iv) Solar Sails

• The Solar sails uses the pressure from sunlight to navigate an object, just like a naval sail uses wind.
• This way debris can be navigated out of orbit and bum into the atmosphere.

v) Space nets

• Space nets or umbrellas are satellites which eject a huge net that fishes or collects the debris and is later disposed off into a graveyard orbit.

vi) Collector Satellite

• The most commonly used collector satellite is the sling sat.
• It has two extended arms which collect the debris as it is in motion.

Bio-Geo Chemical Cycle in an Eco-System

Bio-Geo Chemical Cycle

Nutrients Cycle

It describes the nutrients movement from the physical environment to the living organisms and recycles back to the same physical environment. To maintain the sustainable ecosystem and to balance the nutrient cycle, this movement of nutrients from the environment into organisms & again back to the environment is necessary.

1.Gaseous Cycles

a). Water Cycle

Hydro Cycle

The continuous circulation of water in the atmosphere & earth systems which is driven by solar energy. Water on our planet is stored in reservoirs like atmosphere, oceans, rivers, lakes, dams, glaciers, groundwater etc. Water moves from one reservoir to another by the processes of evaporation, condensation, transpiration, deposition, running infiltration and flowing water.

b). Carbon Cycle

Carbon Cycle

Carbon exists in the atmosphere mainly in the form of carbon compound like CO₂, CO etc. Carbon cycle involves a continuous exchange of carbon between atmosphere and organisms. Carbon used in the photosynthesis from atmosphere by the plants & then moves to animals. By the process of respiration & decomposition of dead organic matter, it returns backs to the atmosphere.

Fossils fuels such as coals, oil, natural gas are organic component that were buried before decomposition & were transformed by time & geological process into fossil fuels. When they are burned, carbon stored in them released back into the atmosphere as carbon dioxide.

c). Nitrogen Cycle

Nitrogen Cycle

Nitrogen exists in the atmosphere is abundant. The largest constituent of air by volume, also the most essential constituents of protein and is a basic building block of all the living organism.

Nitrogen as an elemental form can’t be used directly. It is used to be fixed i.e. converted to nitrogen compound (nitrites or nitrates, ammonia) before it can be taken up by plants.

Nitrogen fixation takes place by:

I. By micro-organisms (bacteria & blue green algae)

Certain micro-organisms are capable of fixing atmospheric nitrogen into ammonium ions. These include free living nutrifying bacteria (e.g. Aerobic azotobacterial & Anerobic Clostridium) and symbiotic nutrifying bacteria living in association with leguminous plants symbiotic bacteria living in non-leguminous root module plants (e.g. Rhizobium) as well as blue-green-algae (e.g. Anabaena Spirulina).

Plant's Root: host to nitrogen fixation bacteria

Certain quantity of soil nitrates, being highly soluble in water, is lost to the system by being transported away by surface run-off (or) ground-water. The special denitrifying bacteria which converts the nitrates/nitrites to elemental nitrogen. This nitrogen escapes into the atmosphere, this forms the nitrogen cycle.

II. By using industrial process (Fertilizers)

In modern day, farmers have started using industrial processed fertilizers which can turn ammonia into nitrates just like those produced by soil bacteria. Plants can use these nitrates directly, and human industry can produce them in large quantity.

III. By atmospheric phenomenon (Lightening & Thunderstorm)

The production of nitrogen oxides NO₂ by lightening flashes has been computed from a model of gaseous molecular reaction occurring as heated lightening- channel air cools by mixing surrounding ambient air. The effect of ozone on the production of nitrogen, is that ozone gas oxidizes NO to NO₂ mainly at the end of the cooling process.

2. Sedimentary Cycle

The element involved in the sedimentary cycle normally does not the cycle through the atmosphere but follows a basic pattern of flow through erosion, sedimentation, mountain building volcanic activity & biological transport through excreta of the marine bird.

a). Phosphorus Cycle

Phosphorus occurs in large amounts as a mineral in phosphate rocks and enters the cycle from the means of erosion and mining. The nutrients considered to be the main cause of excessive growth of rooted & free-floating microscopic plant in lakes. Phosphorus found in the form of phosphates on land. These phosphorous deposited in the in the continental shelf of the oceans, after millions of years the crustal plates rise from the sea floor & expose the phosphate on land. Later weathering will release them from rock and the cycles geochemical phase begin again.

b). Sulphur Cycle

Sulphur Cycle

The Sulphur reservoir is in the soil & sediments where it is locked in organic (coal, oil) and inorganic deposits (Pyrite Rocks, Sulphides and Organic Sulphur). It is released by weathering of rocks, erosional runoff & decomposition of organic matter & is carried to terrestrial & aquatic ecosystem in salt solution.

Almost all the sulphur cycle are sedimentary except Hydrogen Sulphides(H₂S) and Sulphur Dioxide (SO₂) add a gaseous component to its normal sedimentary cycle.

Activities like volcanic eruptions, combustion, of fossil fuels from surface of ocean and gases released by decomposition enable sulphur to enter in the atmosphere. Atmospheric Hydrogen Sulphides also gets oxidised into sulphur dioxide. Atmospheric sulphur dioxide is carried back to the earth after being dissolved in rainwater as weak sulphuric acid.

Plants takes sulphur in the form of sulphates & incorporated in the autotrophs as protein. This sulphur carried back to the soil through the excretion of decomposition of dead organic material.

Ecosystem : Its significance

Ecosystem

What is an ecosystem?

The interaction and interrelationship between the living community (plants, animal and organisms) in relation to each other and non-living community (soil, air and water) is defined to an ecosystem. Hence, an ecosystem is structural & functional unit of biosphere. It is made up of living and non-living beings and their physical environment. In other words, natural ecosystem is defined as a network of interaction among the organisms and their environment. Nutrient cycles and energy flow keep these living and non-living components connected in an ecosystem.

The way it works?

It literally means humans, the other animals, plants and micro-organisms are woven into interdependent network that we, and they, depend on food, water, clean air, reproductions and a place to call habitat. Plants help filter our water and stem to rise, insects pollinate the crops, other animals help to build the soil & control pest.

Significance of an ecosystem

Ecosystem is a part of natural environment consisting pf a community of living beings & the physical environment both constantly interchanging materials and energy between them. It is the sum total of the environment or part of nature.

Components

Atmosphere

The atmosphere refers to a productive blanket of glasses, surrounding the earth. It sustains; life on earth. It saves the earth from the hostile environment of outer space. The atmosphere composed of nitrogen and oxygen in large quantity along with small percentage of other gases such as argon, CO2 and other gases.

Layers of Atmosphere

Hydrosphere

The hydrosphere comprises all water resources, such as ocean, seas, rivers, lakes, reservoirs, ice-caps, glaciers and groundwater.

Lithosphere

The lithosphere is the outer mantle of the solid earth which contains minerals occurring in the earth’s crust and the soil.

Biosphere

The biosphere constitutes the realm of living organisms and their interaction with their environment (atmosphere, hydrosphere, lithosphere).

The study of ecosystem is considered to be the multidisciplinary in nature. It has confined two issues, of sanitary and health; & concerned with pollution control, biodiversity conservation, waste management & conservation of natural resources.

Functions

• Energy flow
• Nutrient Cycle

Energy Flow

The metabolism of all the organisms depends upon the energy content. This energy flow from the producers to the top level consumer that is called energy flow. Energy flow is unidirectional i.e. it always flows in single direction from lower trophic level to higher. Producers to herbivores then to the carnivores.

Energy Flow

Trophic levels

Trophic Level Table

Autotrophs

               Producers (i.e. Green plants)

Heterotrophs

               1) Primary Consumers (i.e. Herbivores)

               2) Secondary Consumers (i.e. Carnivores)

               3) Tertiary Consumers (i.e. Carnivores)

               4) Quaternary Consumers (i.e. Top Carnivores)

Trophic level interaction involves the following concepts

1)     Food Chain

2)     Food Web

Food Chain

Food Chain

The sequential flow of food energy in the form of getting eaten or being eaten. The plant converts solar energy into chemical energy by the process of photosynthesis. Small herbivores consume the plants and convert into animal matter. These herbivores are eaten by large carnivores animals.

Grazing food chain

Terrestrial Feeding mechanisms

Sunlight → Plants → Caterpillars → Lizards snake

Aquatic Feeding Mechanism

Sunlight → Phytoplankton → Zoo Plankton  → Fish Aquatic → Large Animals

Detritus Food Chain

Dead organic matters → Earthworms → Hen → Hawk

Food Web

A Food web shows, all possible transfer of energy and nourishment among the organisms in an ecosystem. An ecosystem may consists of several integrated food chain.

For e.g. Grasses may serve food for rabbit or grasshopper, goat, cow etc. Similar herbivores may many other carnivores animals.

The food availability & preferences of the organisms may shifts seasonally e.g. Human beings consumes watermelon in summer and peacher in the winter. Thus there are interconnected network of feeding mechanisms (or) interrelation which makes the food web.

Food Web