Compilation of essays on ‘Pollution’. Find paragraphs, long and short essays on environmental pollution, air pollution, water pollution, noise pollution, motor vehicle pollution, thermal pollution, ground water pollution, marine pollution, oil pollution, particle pollution, soil pollution, trace metal pollution, radiation pollution, agricultural pollution, industrial pollution, agrochemical pollution, urban pollution & organic water pollution, especially compiled for teachers and students. All the essays are written in English Language for kids, students and teachers. Moreover, in this article we have included essays on almost all the types of pollution.
Essay on Pollution for Kids, Students and Teachers
- Essay on Environmental Pollution
- Essay on Air Pollution
- Essay on Water Pollution
- Essay on Noise Pollution
- Essay on Motor Vehicle Pollution
- Essay on Thermal Pollution
- Essay on Ground Water Pollution
- Essay on Marine Pollution
- Essay on Oil Pollution
- Essay on Particle Pollution
- Essay on Soil Pollution
- Essay on Trace Metal Pollution
- Essay on Radiation Pollution
- Essay on Agricultural Pollution
- Essay on Industrial Pollution
- Essay on Agrochemical Pollution
- Essay on Urban Pollution
- Essay on Organic Water Pollution
1. Essay on Environmental Pollution: [448 words]
Environmental pollution refers to any physical, chemical or biological alteration in the quality of air, water or soil to a degree that is harmful to living organisms. Pollution, is thus, direct or indirect change in any component of the biosphere that is harmful to the living components and in particular undesirable for man.
The agents that produce the state of pollution are called pollutants. A pollutant may thus include any chemical or geochemical substance, biotic component or its product or physical factor that is released intentionally by man into the environment in such a concentration that may have adverse harmful or unpleasant effects.
A source is the origin of a pollutant: at this point it has just entered the environment. What is important is what it can do and how it moves through the environment starting with what the pollutant can do, i.e., its properties.
Leaving aside the specific chemical and physical properties there are eight things that are important:
1. The persistence of the pollutant (the likelihood of it surviving in a state in which it can cause damage).
2. The lifetime of the pollutant (how long it’s active for).
3. Interactions (chemical or physical reactions with other substances). Here, one needs to distinguish between the primary pollutant one that has an effect unaltered and the secondary pollutant which comes through interactions with other pollutants or the environment.
4. Speciation – The number of forms a pollutant can take. The greater the speciation the more ways it can react with the environment.
5. Pollution loads – The amount of a pollutant that can be found in the environment. Two concepts are important: critical load (the amount of a pollutant that is needed before one can detect damage to an ecosystem) and target load – the amount of a pollutant that is permitted or tolerable. Target loads would change with changing knowledge or even public perception.
6. Dispersion – The ease with which a pollutant would spread throughout the environment.
7. The ability to bio accumulate – The ease with which a pollutant will stay in a target or environmental area and therefore build-up.
8. Ease of control – How simple will the pollution problem be to clean up? A simple solid spill will be easy to remove, a liquid less so and gases almost impossible to contain. There are also hidden issues here. For example, when the first oil tanker disaster occurred in 1967 (the Torrey Canyon running aground off the Isles of Sicilly) it was thought that the spill would be easy to contain. Unfortunately, it didn’t burn and attempts to clean off oil with detergents created more problems than the oil did.
2. Essay on Air Pollution: [150 + words]
Ambient air is a mixture of several gases including nitrogen (79%), oxygen (20%), carbon dioxide (0.03%), and several other inert gases such as argon, helium, krypton, neon and xenon. Unfortunately, the concentration levels of different gases show variations because some gases such as sulphur dioxide, carbon monoxide, emissions from volcanoes and swamps, salt spray, windblown dusts, etc. are continuously added to the air by the natural processes.
Thus, the air becomes polluted when its natural composition is disturbed either by natural or man-made sources or by both. In other words, when the presence of chemicals or their concentrations is high enough to harm organisms, ecosystems or any material in our ecosystem and even to the extent of changing the climate… is known as air pollution.
According to World Health Organisation (WHO) air pollution is defined as limited to situation in which the outdoor ambient atmosphere contains materials in concentration which are harmful to man and his surrounding environment. Every day, we breathe approximately 23,000 times, inhaling about 2000 litres of air. Along with air, we also breathe in a wide variety of pollutants released into the air by automobiles, factories, power plants and other sources.
About 70 per cent of the world’s urban residents breathe air that is unhealthy at least some of the time and an additional 10 per cent breathe air that is only marginally healthy. Several air pollution episodes have occurred in the past causing many deaths.
3. Essay on Water Pollution: [197 words]
Water pollution refers to any physical or chemical change in water, which could adversely affect its use for domestic, irrigation, industrial and recreational purpose or adversely affect the aquatic biota or any living organism.
The pollution of water may occur due to aquatic contaminants between two extremes:
(a) A body of water poisoned by toxic chemicals which may eliminate many living organisms or even exclude all forms of life.
(b) An over productive river or lake enriched with nutrients from sewage or fertilizer.
Like air pollutants, water pollutants come from a number of natural and man-made sources.
Broadly, these sources may be classified into two categories:
(i) Point sources:
These sources emit pollutants at discrete locations, usually a pipe that leads to a stream or a lake, e.g., factories, power plants and sewage treatment plants. They are easier to control because the source is located at specific places.
(ii) Non-point sources:
These sources emit general watershed run-off which is diffused and scattered, e.g., cropland, forests, urban and suburban lands, and roadways. Non-point water pollutants are generally more difficult to control because it is difficult to trace the various site of discharge.
4. Essay on Noise Pollution in English: [410 words]
Noise is any unwanted and unpleasant sound that causes discomfort.
The unit of measurement of noise is decibel (dB), which is one tenth of the larger unit called bel (B). A decibel is equal to the faintest sound that can be picked up and heard by the human ear. The World Health Organisation has fixed 45 decibels as the safe noise level for a city. However, a maximum duration of exposure to 90 dB noise level, without having the risk to suffer hearing loss, is 8 hours a day.
Noise comes from a variety of sources like aeroplanes, trains, trucks, buses, motor cycles, pneumatic drills, workshops and factories, radio, television sets, stereo system and public address systems. Noise levels of normal breathing, whispering, conversation, heavy automobile and jet aircraft are 10, 30, 60,100 and 120 dB respectively. Noise level of as low as 50 to 55 dB may delay or interfere with sleep. Noise in 80-90 dB range may cause irreversible changes and noise level of 160 dB can kill rat.
A continuous long-term exposure to noise levels as low as 55 dB can permanently damage hearing. Explosion (130 dB) and other extremely loud noises can cause instantaneous damage to the ear.
(i) The recognition of noise as a pollutant is rather new because its negative effects are subtle.
(ii) Depending upon the noise level and duration of exposure, hearing in man can either be impaired or lost completely and permanently, leading to deafness.
(iii) Loud and continuous noise causes rapid beating of the heart and raises cholesterol level resulting in permanent constriction of blood vessels. This leads to high blood pressure, and problems of blood circulation and even cardiac disturbances.
(iv) Loud noise causes peptic ulcers, gastro-intestinal problems, allergy, infertility, nervousness, etc.
(v) Noise makes the child irritable and hyperactive, and affects the development of child’s mental faculties. It has been established that there is an increased incidence of birth defects, still-births and unusually low weight among children born to mothers living near airports. People in noisy environment get tired and are irritable.
Many social conflicts and even lack of cooperation have been attributed to unwanted noise, which keeps individuals irritated, upset, imbalanced and fearful.
Noise, is thus a low killer. However, the movement against noise pollution is weak in India, because most of the people do not consider noise a pollutant, but rather a part of routine life.
5. Essay on Motor Vehicle Pollution: [250+ words]
No other mechanical product has made the same impact on the culture and lifestyle of the average person as the motor vehicle, especially the private car. The growth of motor vehicle really became noticeable in the years after the Second World War. This growth was a visible manifestation of the greater economic prosperity among wide sections of society.
In addition to the environmental problems caused by growing road traffic and attendant noise pollution, especially in urban areas, and land used for road construction, motor vehicles are responsible for producing a significant amount of pollutants at both a global and regional level. For example, the disposal of old motor vehicles requires disposal of millions of used tyres, old batteries and used oil and this will litter and contaminate the landscape.
At the same time, the millions of road vehicles in daily use pollute the atmosphere with potential health and environmental risk. Motor vehicles only harness 10-20% of the potential energy in their fuel; the rest is converted to heat and exhaust pollutants. It is now generally accepted that the emissions generated by fossil fuel (petrol and diesel)-powered motor vehicles have become a major source of environmental pollution, especially- air pollution. Much air pollution is produced by the combustion of fossil fuels.
Motor vehicle exhaust emissions generate carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOX), sulphur dioxides (SOx), hydrocarbons (HC) and particulate matter. These pollutants are harmful and have a deleterious effect on people and population.
Motor vehicles are responsible for about 85% of CO pollution, NOx is a major contributor to acid rain (see Acid rain) and CO2 is one of the main gaseous pollutants from motor vehicles and is perhaps the largest single contributor to global warming.
6. Essay on Thermal Pollution [500+ Words]
Warm effluents discharged into bays and estuaries may raise the water temperature. This reduces the solubility of oxygen, and the oxygenation may be further reduced by increased oxygen consumption by animals and bacteria, and by reduced vertical mixing due to thermal stratification. The effect may be that the underlying layers become deoxygenated and foul. Migratory fish, salmon may be discouraged from passing through the area.
Warm water may favour pests, such as shipworm and gribble, accelerating their growth and extending their breeding seasons, and it may also encourage the establishment of foreign pests. The fouling rate on ships’ hulls is likely to be raised. Waste heat discharged into the environment, raising temperature to an undesirable extent is referred to as thermal pollution. Electric power plants, steel mills, paper mills and refineries use large quantities of water for cooling.
The warm water when released into lakes or streams brings about many changes in the aquatic ecosystem. It is a form of water pollution, where the mean temperature of water body is increased by an anthropogenic activity. It is caused when thermal power plants dispose of their water in the water body for the purpose of cooling themselves.
i. Condenser cooling water released from electricity generating stations normally heated by 6-9°C.
ii. Urban heat island effect, also affects the temperature of the water bodies. Generally, cities raise temperature upto 5-8° C above the normal levels in summer.
iii. Changes in the configuration of urban channels. Which drains all warm water into the rivers?
iv. Changes in the degree of shading (by deforestation).
v. Changes in the volume of storm water run-off etc., which drains into the river or lake.
Effects of Thermal Pollution:
i. Spawning and growth of many fishes are adversely affected, e.g., Trout.
ii. Changes in plankton: At lower temperatures, diatoms which are not eutrophic plankton, flourish. At higher temperatures, blue-green algae grow very fast, producing algal blooms.
iii. Higher temperatures discourage oxygen solubility while increasing oxygen demand, i.e., faster depletion of oxygen in water.
iv. Thermal pollution lowers the dissolved oxygen content of water leading to fish kill,
v. Thermal pollution may affect species composition by killing heat-intolerant plants and animals, and hence the entire food chain,
vi. Increased temperatures may disrupt critical predator-prey relationships,
vii. Thermal pollution may increase susceptibility of fish and other aquatic organisms to parasites, pathogens, heavy metals and pesticides,
viii. Sharp changes in water temperature may cause thermal shock, a sudden death of fish that cannot escape the temperature change.
ix. Both sudden increase in temperature (when new plants open) and sudden decrease in temperature (when new plants are closed for short periods for repair) are detrimental to aquatic organisms.
Nuclear wastes from atomic reactors contain different kinds of reactive isotopes. Some of the wastes may retain their radioactivity upto 100,000 years.
It discharged into aquatic systems, these wastes adversely affect aquatic life, such as:
(i) Early hatching of fish eggs,
(ii) Failure of trout eggs to hatch,
(iii) Failure of salmon to spawn,
(iv) Increase in BOD,
(v) Change in diurnal and seasonal behaviour and metabolic responses of organisms.
(vi) Significant shift in algal forms and other organisms towards more heat tolerant forms. This leads to decrease in species diversity,
(vii) Affect changes in macrophytes, and
(viii) Migration of some aquatic forms.
7. Essay on Ground Water Pollution: [573 words]
Ground water is threatened with pollution from seepage of pits, refuse, dumps, septic tanks, transport accidents and different pollutants. Important sources of ground water pollution are sewage and other wastes. This gives birth to cholera, hepatitis, dysentery, etc. especially in areas with high water table.
Once a pollutant reaches the level of ground water, it contaminates the ground water and through this it reaches an aquifer where pollutant is able to contaminate the wider plume of water. When the groundwater becomes contaminated, it cannot cleanse itself of degradable wastes as flowing surface water is capable of. The reason behind this is that the ground water flows so slowly – usually less than 0.3 meter (1 foot) per day – that contaminants are not diluted and dispersed effectively.
Also, groundwater usually has much lower concentrations of dissolved oxygen (which helps decompose many contaminants) and smaller populations of decomposing bacteria. The cold water temperatures of groundwater also slow down chemical reactions that decompose wastes.
Thus, it takes hundreds to thousands of years for contaminated groundwater to cleanse itself of degradable wastes. On human time scale, non-degradable wastes (such as toxic lead, arsenic and fluoride) remain permanently, while slowly degradable wastes like DDT are there for decades.
Arsenic in Ground Water: A Natural Threat:
When a well is dug, the contaminated soil and rock with toxic arsenics (As) may reach the aquifers and contaminate the well water. This type of pollution has been mostly found in Bangladesh, China and India (West Bengal). Long-term exposure to arsenic in drinking water may cause premature deaths from cancer of the skin, bladder and lungs.
It is an urgent issue to implement the corrective measures to control this pollution because very large population is being affected by it. U.S researchers are experimenting with using nanoparticles of iron and zinc oxide to capture and remove arsenic from contaminated water.
Before implementing the action for curing the contaminated groundwater, we must take the following steps must be taken:
(i) Eliminating the source of pollution.
(ii) Monitoring drilling of the wells to determine how far, in what direction, and how fast the contaminated plume is moving.
(iii) Project future dispersion of the contaminant in the aquifer.
(iv) Finally make a strategy to clean up the contamination.
Since the final step of cleaning up of the contaminated aquifer is very expensive and finding out the source is also very difficult, prevention and increasing awareness among the locals is the most effective and cheapest way to protect ground water.
Because of the growing rate of pumping out water (mostly to irrigate crops) the natural rate of recharge of wells from precipitation is not sufficient enough to maintain the natural water table. This is found worldwide. The world’s three largest grain producers – India, China and the USA and also Saudi Arabia, Mexico and Pakistan have been overexploiting their aquifers, depleting their natural groundwater.
This depletion in ground water table is invisible and human beings are not able to assess the extent of damage. The replenishment of ground water takes hundreds to thousands of years and therefore, its high time human realised their folly of over pumping ground water.
When the water table gets lowered due to overexploitation of ground water along the coastal region, the saline sea water intrusion takes place making the well water unusable.
8. Essay on Marine Pollution: [300 + words]
The oceans are undergoing through a change in their temperature, chemical composition and salinity content. Naturally, the salt content must have kept on increasing throughout the geological history as more and more salt must have been washed into the oceans and as evaporation withdrew water leaving salt behind. Similarly, the pH content has also shown some change. The acidification of oceans is increasing.
Increasing acidification is a cause of concern as it:
(i) Determines the growth and survival of calcareous phytoplankton which will be adversely affected;
(ii) The growth and survival of coral reefs will be adversely affected;
(iii) The survival of some animals that have phytoplanktonic larvae will be adversely affected and
(iv) The cloud seeding and formation of clouds will be adversely affected.
The most important problem affecting the marine environment is the disturbance of the marine ecology. Seacoasts are highly complex and dynamic system, sensitive to developmental pressures. With the growth of cities, towns, ports, industrial establishments and other developments, great expanses of the coasts have been altered to such an extent that they resemble only little with the original.
When rivers cross a long way to the sea, they carry a huge amount of sewage, garbage, agricultural discharge, biocides including heavy metals and ultimately meet the seas. Besides other materials that may cause marine pollution include discharge of oils and petroleum products and dumping of radionuclide wastes into sea. Huge quantity of plastic is being added to seas and oceans.
Thus, marine pollution is of four types and is caused by a variety of technology driven and anthropogenic factors:
a. Oil pollution caused by ballast voyages, and accidental spillage, tank washing by oil tankers, accidents, including collisions or shipwrecks resulting in oil leaks or loss of toxic cargoes, and also damage to undersea pipelines.
b. Disposal of domestic sewage, agricultural, industrial waste and biocides, direct drainage from coastal towns and industries, drainage via rivers from inland towns, industries, agricultural and pest control, waste tipping on the shoreline, often usefully applied for land reclamation may result in toxic or persistent pollutants entering the sea by seepage or erosion. Such a disposal of sewage, other wastes, coupled with other factors has led to algal blooms in the coastal waters.
c. Radioactive wastes and nuclear tests and experiments.
d. Plastic contamination that includes floating plastics; such as cans, bottles, etc.
e. Airborne pollution by solution of volatile materials from the atmosphere, or from rainfall or airborne dust.
9. Essay on Oil Pollution: [746 words]
There are several forms of oil pollution:
1. Floating slicks due to spilled oil (from ships, tankers or accidents)
2. Blowouts at offshore drilling rigs (when oil escapes under high pressure from a bore hole in the ocean floor).
3. Oil pollution from urban and industrial runoff from the land.
4. Particulate petroleum residue such as tar-balls.
5. Dumping of waste oil.
The Impact of Oil Pollution:
The impact of oil pollution is very disastrous as:
(a) It damages the marine flora and fauna by
(i) Reducing the penetration of sunlight and the level of dissolved oxygen,
(ii) By rendering feathers and gills ineffective by clogging them up.
(b) It posses serious threat to coastal ecosystem and seaweeds by killing the marine plants (damage to all marine flora & fauna).
(c) Hydrocarbons and benzpyrene accumulate in food chain and consumption of fish by man may cause cancer.
Control of Oil Pollution:
Since the main source of marine pollution is oil spill, efforts must be done to clear them.
There are four ways in which this can be done:
(i) Fence the floating oil and stop them from spreading by floating booms.
(ii) Remove the oil either through suction or through absorption with the help of skimmers and transfer it to tank for disposal
(iii) Break down the oil chemically by using chemical dispersants, but it also pollutes the sea.
(iv) Burn the oil- This will however have many unlikely consequences on the marine ecosystem as it raises the temperature and destroys the marine life.
(v) Oil Zapper.
Algae are microscopic plants that are usually aquatic, unicellular, and lack true stems, roots, and leaves. Algal blooms refer to a sudden eruption in the algal population; and occur in both marine and freshwater environments when an algal species out competes other species and reproduces rapidly. An algal bloom discolours the water due to the large number of algal cells.
Algal blooms are composed of phytoplankters which naturally produce bio toxins are called Harmful Algal Blooms, or HABs. (An algal bloom can still kill fish and other aquatic life by decreasing sunlight available to the water and by using up all of the available oxygen in the water, but a harmful algal bloom specifically produces harmful toxins.)
Though many types of algae can form blooms, freshwater harmful algal blooms have the ability to produce toxins that are dangerous to other organisms such as humans, dogs, and livestock. Most harmful algal blooms takes place in warm, slow moving, eutrophic waters and are formed by cyanobacteria (blue-green algae) which are now known to be photosynthetic bacteria.
Algal blooms can also be caused by haptopliytes, dinoflagellates, green algae, raphidophytes, euglenophytes, diatoms and cryptophytes, but though they can be a nuisance, they do not produce toxins like cyanobacteria do and have not been linked to any adverse human health effects
It is possible for blooms to appear quickly and form floating mats of various colours, however, not all blooms form mats on the surface. Some remain in the water column and discolour the water.
Blooms can be caused by several factors:
1. An increase in nutrients from the estuaries caused by high runoff from the land during monsoons can cause algae growth and reproduction to increase dramatically into a bloom just as fertilizing a lawn makes the grass grow faster.
2. Change in the environmental conditions so that certain algae can out compete the other algae for food, which can result in a bloom of the algae with the advantage. This environmental change can be related to the water quality, temperature, nutrients, sunlight, or other factors. Upwelling of cold water is one such environmental change. A strong upwelling is regularly observed in India during summer and the whole of southwest monsoon season but it is largely restricted to the continental shelf.
Upwelling is an important process in redistribution of nutrients in the oceanic regime. It causes profound increase in productivity of a region by increasing nutrient content in the euphotic zone. In the process, the cooler nutrient-rich waters from beneath are drawn upwards when offshore winds push the warm surface waters away from shore.
The plant life, particularly plankton, thrives here and not surprisingly such areas are associated with active fishery and also regular occurrence of algal blooms. In comparison to east coast, the west coast of India is known for its higher productivity, due to the frequent upwelling process, particularly in the southern region.
10. Essay on Particle Pollution: [878 words]
The capacity of particulate matter to produce adverse health effects in humans depends on its deposition in the respiratory tract. Particle size, shape, and density affect deposition rates. The most important characteristics influencing the deposition of particles in the respiratory system are size and aerodynamic properties. The aerodynamic diameter of a particle is the diameter of a unit density sphere having the same settling velocity as the particle in question, whatever its size, shape or density.
Particles between 2.5 and 10 micrometer in aerodynamic diameter correspond to the inhalable particles capable to be deposited, in the upper respiratory tract. Particles with aerodynamic diameter smaller than 2.5 micrometer (PM2.5), called fine particles, correspond to the respirable particle fraction capable of penetrating the alveolar region of the lung. Inhaled particles come in contact with surface of the respiratory system.
These particles pass the proximal airway (throat and larynx) of the respiratory tract, and deposit in the tracheobronchial conductive airway of the lungs (bronchial and bronchiolar airway) or in the gas exchange region (respiratory bronchioles, alveolar ducts, and alveoli of the lung parenchyma).
There are five mechanisms that influence particle deposition within the respiratory tract. The primary mechanisms are gravitational settling, impaction, and Brownian diffusion. Secondary mechanisms are electrostatic attraction and interception. These last two processes have minimal importance for inhalation and deposition of particulate matter.
Deposition by gravitational settling occurs as a result of the influence of gravity on particles suspended in the air. The settling rate of particles is directly proportional to particle size. This process is most important in the distal region of the bronchial airway and in proximal portions of the gas exchange region. Another mechanism of particle deposition is impaction.
Due to inertia airborne particles do not follow changes in direction or speed of airflow and they may impact on the wall of the airway. This mechanism occurs primarily in the throat and larynx with particles larger than 3 μm and increases with increasing particle size.
Brownian diffusion involves collision between gas molecules and micrometer- sized particles, which push the particle in an irregular manner. Brownian diffusion increases with decreasing particle size. This mechanism is predominant in the gas exchange alveolar region of the lung for particles smaller than 0.5 μm.
There are other factors that also influence particle deposition, including mode of breathing (oral breathing permit the passage of particles greater than 10 μm to the lung), physical activity (exercise), age, lung diseases (chronic obstructive lung disease), and ambient conditions (increase in temperature or the presence of other pollutants).
The ability of the lung trying to protect itself against inhaled particles, clearance, will determine the adverse health effects of particulate matter. There are two clearance mechanisms: the mucociliary system and the alveolar macrophages. Particles deposited in the ciliated region of the tracheobronchial airway, rise on the mucociliary ladder to be expelled by coughing or swallowing. Particles deposited on the terminal bronchioles are cleared by lung macrophages.
An early cellular response to an acute particulate exposure is damage to epithelial cells of respiratory tract, which also produce many different types of inflammatory mediators. The local pulmonary inflammation induced by PM10 could impact on the cardiovascular system via the local production of procoagulant factors in the lung or as a result of the effects of mediators released from the lungs which act on the liver, to increase the levels of procoagulant factors which could promote myocardial infarction.
The size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometers in diameter pose the greatest problems, because they can get deep into lungs, and some may even get into blood stream.
Exposure to such particles can affect both lungs and heart. Small particles of concern include “inhalable coarse particles” (such as those found near roadways and dusty industries), which are larger than 2.5 micrometers and smaller than 10 micrometers in diameter; and “fine particles” (such as those found in smoke and haze), which are 2.5 micrometers in diameter and smaller.
Particle pollution – especially fine particles – contains microscopic solids or liquid droplets that are so small that they can get deep into the lungs and cause serious health problems particle pollution exposure causes variety health problems, including-
(i) Increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing, for example;
(ii) Decreased lung function; aggravated asthma;
(iii) Development of chronic bronchitis; irregular heartbeat;
(iv) Nonfatal heart attacks; and
(v) Premature death in people with heart or lung disease.
People with heart or lung diseases, children and older adults are the most likely to be affected by particle pollution exposure. However, even if you are healthy, you may experience temporary symptoms from exposure to elevated levels of particle pollution.
Acute Particle Pollution Exposure Causes:
(i) Irritation to the eyes, nose, throat and lungs.
(ii) Neurological effects such as lightheadedness.
(iv) Exacerbate asthma and difficulty in breathing.
Chronic Particle Pollution Exposure Causes:
(i) Decreased lung function
(ii) Development of chronic bronchitis
(iii) Irregular heartbeat
(iv) Nonfatal heart attacks
(v) Premature death in people with heart or lung disease
(vi) Bladder Cancer
(vii) Heart Disease
(viii) Nervous System impairment
(x) DNA Damage
11. Essay on Soil Pollution: [522 words]
Soil pollution is defined as the presence in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents, which have adverse effects on the biological productivity of plant growth and animal health.
There are many different ways that soil can become polluted, such as:
(i) Seepage from a landfill
(ii) Discharge of industrial waste into the soil
(iii) Percolation of contaminated water into the soil
(iv) Rupture of underground storage tanks
(v) Excess application of pesticides, herbicides or fertilizer
(vi) Solid waste seepage
The most common chemicals involved in causing soil pollution are:
(i) Petroleum hydrocarbons
(ii) Heavy metals
(i) Soil pollution results from excessive use of insecticides, herbicides and fertilizers which adversely affect the physical, chemical and biological properties of the soil.
(ii) Agricultural discharge.
(i) Radioactive substances resulting from explosion of nuclear devices test explosions, mad rush for power plants and radioisotope used in medicine; industry and research are the main source of radioactive pollution. They penetrate the soil from where they enter into food chain and become concentrated in body tissues causing many harmful effects.
(ii) These substances are most toxic and exposure of Radioactive Isotopes to it may kill human as well as animal. The radioactive substances remain active as environment pollutant for very long period of time.
(iii) Radioactive isotopes ionizing radiations bring about genetic changes through mutation and can cause death of any organisms including man.
(iv) Soil pollutants bring about killing of soil dwelling animals that help in decomposition through consumption of plant debris.
(v) Many micro-organisms involved in nitrogen and phosphorus cycles may be adversely affected.
Industries, manufacturing a variety of chemicals, textiles, paper materials, steel and mixing operations, etc., release a wide variety of inorganic and organic pollutants like solvents, oils, grease, plastics, plasticizers, metallic wastes, phenols, toxins, heavy metals, etc. and when all these, in the form of industrial wastes, get mixed up in soil they are transferred to different organisms in food chain, and at any tropic level, a given toxicant may accumulate in higher amounts and cause undesirable and harmful effects.
Domestic and Urban Wastes:
It has been estimated that more than 15 million solid wastes are produced every year by more than 110 million urban dwellers in India. It has been found that the use of municipal waste water for irrigation purposes leads to substantial increase in accumulation of available zinc (Zn), copper (Cu), lead (Pb) and cadmium (Cd) in soils.
The accumulation has been found to be highest in soils receiving waste water of industrial towns. The crops grown on sewage-irrigated soils always contain higher amount of heavy metals. The leafy vegetables accumulate in higher amounts than other crops.
(i) It results in substantial decrease in agricultural production.
(ii) In some cases, the land becomes unusable for crop farming, e.g., formation of wasteland due to soil erosion.
(iii) Chemical pollutants (chemical fertilisers, pesticides, insecticides, etc.) after reaching the soil they also reach human and animal bodies through food chains and cause various diseases and cause several deaths.
12. Essay on Trace Metal Pollution: [728 words]
A variety of heavy or trace metals are naturally present at low concentrations and cycle through atmosphere, surface water, soil living creatures, oceans and sediments. As these metals are mined for industrial applications, part of them reaches the biosphere. These metals are present as contaminants in fossil fuels, coal and petroleum.
Combustion of these fuels releases substantial quantities of heavy metals into the biosphere either as particulate in the exhaust gases or ash that goes to soil and then water. The artificial flows of these metals have added to natural ones. Lead, mercury and cadmium are considered more dangerous for human beings and mammals.
Lead compounds added to gasoline to reduce knocking are emitted into the air with the exhaust as volatile lead halides (chlorides and bromides). About 75% of lead burnt in gasoline comes out as lead halides through tail pipe as exhaust gases. Of this about 40% settles immediately on the ground and the rest 60% gets into the air. The lead levels of air in air-quality guide of WHO are 2mg/m3. This level is already crossed in many countries of the world. Human beings are exposed through lead base points, pesticides, etc.
Effects of Lead:
(i) Children, painters, foundry and smelter workers, and typographers run a greater risk.
(ii) Lead is ingested via food, air and water. It is cumulative cellular poison and its chronic poisoning is difficult to diagnose. Symptoms of lead poisoning include loss of appetite, weakness, awkwardness, apathy and miscarriage.
(iii) It causes lesions of neuromuscular system, circulatory system, brain and gastrointestinal tract.
(iv) High lead level in blood interferes with the production or operation of a variety of enzymes that play important role in the human body.
(v) Many children risk mental retardation due to exposure to lead in air, water and soil, mainly from lead fuel burnt by vehicles. Several studies have found that at least half of the newborns in Mexico City have levels of lead in their blood high enough to impair mental or physical development.
(vi) The plants do not take metallic lead from soil but extract tetraethyl lead much more efficiently from air and soil. So increase in ingestion of lead through diet has become a more and significant pathway -for human exposure than through breathing.
Mercury is heavy, silvery metal that is liquid at room temperature. It is used in production of chlorine which, in turn, is used in production of plastics and caustic soda, used in manufacture of electrical goods and scientific instruments.
Mercury Poisoning and Its Effects:
In streams and lakes, inorganic mercury is converted into dimethyl and methyl mercury by aerobic bacteria. Dimethyl mercury evaporates from water whereas methyl mercury concentrates in the body in red blood cells and in the nervous system, and selectively attacks nerve cells. Symptoms of poisoning may appear after a week to a month after exposure.
These include numbers and tightening of lips, hands and feet, lack of motor coordination, disturbances of speech, constriction of visual field, impairment of hearing and emotional disturbances. This type of poisoning sometimes is called Minamata disease, named after a small fishing village in Japan where an outbreak of methyl mercury poisoning occurred in 1950s. Cases of fatal poisoning from ingestion of grain treated with organic mercurial fungicides have been documented in Iraq, Pakistan, Guatemala and USA.
Standards for air borne organic mercury compounds have been fixed in advanced countries. The levels of concentration of mercury in blood and brain to cause damage are known. The level of mercury in fish is 500 ppb on a wet weight basis. Fishing restrictions are enforced in lakes because of mercury contamination.
Cadmium is similar to zinc and occurs with it in nature. Unlike zinc, it is inimical to life. Even in small quantities it causes kidney defunction and bone demineralisation if combined with Ca deficiency. If inhaled it causes respiratory diseases. It is suspected to be carcinogenic.
Cadmium is used in electroplating, stabilizers, plastics, pigments, alloys and batteries. Most of these uses are dissipative and non-recyclable. A significant amount comes from smelting and reclamation of steel scrap and incineration of plastics. It is taken up in food by non-smokers. Smokers absorb it from cigarettes. It has exceedingly long life in body and accumulates building high body burden. Industrial workers in Japan suffered from acute poisoning by cadmium.
13. Essay on Radiation Pollution: [659 words]
Radioactivity and ionizing radiation are major pollutants. The significant additions to natural radiation exposure that civilization has produced and might produce in future are a matter of concern. The increase of radioisotopes in our environment has been due to fallout from nuclear bombs and emissions from industrial uses of nuclear energy. The decay of radioactive isotopes results in the release of three types of ionizing radiation, viz., alpha particles, beta particles and gamma rays.
Alpha particles are much larger and do not penetrate human skin, and hence are not of great biological hazards when exposure is external. These are dangerous only if emitted within the body. Beta particles are most dangerous when emitted within the body but energetic one can penetrate several meters of air and skin. Gamma rays can travel tens to hundreds of meters in air and can penetrate material much more readily than either alpha or beta particles.
(i) High doses of radiation, delivered within short period, can produce acute illness and death.
(ii) Acute exposure results in damage to bone marrow, spleen and gastrointestinal tract lining, and the central nervous system.
(iii) Red blood cell counts begin to drop slightly after exposure, results in fatigue, fever and sore throats.
(iv) The destruction of lining of gastrointestinal tract may result in vomiting and diarrhea, and ultimately death. Symptoms of vomiting, fatigue, fever, sore throat, temporary sterility of males and abortion of pregnancies in females may appear at low dose.
(v) At high dose death occurs within a week due to destruction of lining of gastrointestinal tract.
(vi) Chronic exposures to low levels of radiation are more common than acute exposures.
(vii) Ionising radiation can induce genetic changes, which can extend through many generations.
(viii) Delayed effects on survivors are exhibited in deformed children and production of cancer. The exposure to radiation has been well documented in genetic defects. Still births are the results of delayed effects.
Radioactive waste is classified as high-, intermediate- or low-level depending upon the activity of radionuclides present. Intermediate- and high-level radioactive wastes arise mainly from the nuclear industry in the form of spent fuel rods, highly irradiated reactor components and reprocessing wastes. The nuclear power plants are the dominant producer of low-level radioactive waste, but smaller quantities arise from other sources such as hospitals, (which use radiation medicine, X-ray equipments) universities and industrial facilities.
Selective concentration of natural decay series radionuclides generates radioactive waste in some non-nuclear industries (e.g., oil extraction and metal refining). Radium- or tritium containing wastes can also occur in the environment from the disposal of manufactured luminescent materials.
Solid low-level wastes are disposed of by burial in near-surface engineered repositories.
Handling and Management of Radioactive Wastes:
The radioactive wastes should be very carefully handled.
There are three methods for handling radioactive waste material:
(i) Dilute and Disperse:
Wastes of low radioactivity can be diluted to permissible levels for dispersal and diluted further in air, water and soil. Gaseous and liquid low-level radioactive wastes are disposed of by authorized discharges to the environment, with the aim of dispersion in the atmosphere or aquatic environment to give dilution to levels that present a negligible radiological hazard. There is danger of environmental contamination and accumulation in food chains.
(ii) Delay and Decay:
A radioactive material with a relatively short half-life can be retained in receptacles until radioactivity is dissipated due its natural decay.
(iii) Concentrate and Contain:
Wastes with high levels of radiation are concentrated into small volumes and stored away from areas of public use and wildlife habitats. A typical strategy would be to place the vitrified waste in a stainless-steel container which would be surrounded by bentonite clay and concrete. Upon the eventual failure of the near-field barriers, radionuclides will migrate through the host rock (known as the far field) and the rock type and repository depth would be selected to give long-term stability and a low rate of radionuclide migration.
14. Essay on Agricultural Pollution: [1417 words]
The western model of agriculture with its emphasis on productivity and growth has added many new sources of pollution. The excessive use of biocides (pesticides, herbicides or weedicides) and fertilizers have led to their accumulation in different components of the environment. The water runoff from agricultural lands pollutes lakes and streams causing eutrophication. The burning of rice straw after harvest of the crop causes air pollution.
In Punjab alone, more than 10 lac tonnes of paddy straw is burnt in paddy fields and it becomes difficult to travel through rural areas during end September to early October. The smoke causes several respiratory diseases like asthma and bronchitis. The dumping of agricultural wastes and cattle dung in improper ways creates unhealthy environment around human dwellings. The increased need for industrial goods in agriculture adds to industrial pollution. Agriculture itself is likely to be affected by non-agricultural sources of pollution.
Pesticides are the chemicals used for killing the plant and animal pests. It is a general term that includes bactericides, fungicides, nematicides, insecticides and also the herbicides or weedicides. The use of organic pesticides is very important for meeting the increasing food needs of the growing population and containing vector-borne diseases, particularly in developing countries.
Persistent organochlorine compounds, the use of which has been restricted in the western countries more than a decade ago, are still used in large amounts in India. Although the pesticides have greatly increased agricultural production and saved millions of lives from insect borne diseases, the use of certain pesticides has resulted in the pollution of the environment.
The contamination of food materials with pesticides is one of the major problems confronting man. The consumer runs the greatest risk of exposure to pesticides through the contaminated food. The intake of pesticides through food and other sources results in their accumulation in the body tissues of human beings.
Residents of different countries have been found to contain different levels of DDT, e.g., Netherlands 2.01, Germany 2.3, Great Britain 3.0, Denmark 3.1, Italy 10.1, Hungary 12.4, Poland 13.4, Israel 18.1 and India 28 ppm. It has been shown that these chemicals can be transferred from the mother to the foetus so that babies may be borne with insecticides in their tissues.
As children are considered to be more susceptible than adults, they are at a much greater risk. The problem of contamination of dairy products with pesticide residues is widespread. Most of the samples of popular brands of butter obtained from the different states in India have been found to be contaminated with DDT residues above 1.25 ppm. The maximum residue limit, although there is no prescribed limit for HCH, results showed its presence also at high levels.
The sources of contamination of dairy products in India are not clearly known. In addition to their agricultural usage, both DDT and HCH are extensively used for control of malaria. DDT at the dosage of 1 g/m2 twice a year and HCH at the dosage of 1.5 g/m2 thrice a year are sprayed inside the rural houses and cattle dwellings. There is a direct correlation between the usage of these insecticides for malaria control and the contamination of bovine milk.
Like insecticides, herbicide usage has become an integral part of modern agricultural practices. Among the different herbicides available in India, the demand for rice and wheat herbicides is more. Of the total herbicides available in India, 60 per cent are used in the Punjab state. At present, 90 per cent area under transplanted paddy and 45 per cent under wheat is treated with different herbicides in Punjab.
Since most of the herbicides are applied as pre-emergence or post-emergence in the early stages of crop, herbicide residues in grains, fruits and vegetables are likely to be negligible. However, some of the herbicides may adversely affect the soil micro flora.
Recently, Government of India of late has withdrawn the use of DDT in agriculture and use of HCH on vegetables, fruits, oilseeds and preservation of food grains. The residues of synthetic pyrethroids have been found to decline at a much faster rate than organochlorines.
That is why, the residues of organochlorine pesticides are still detectable, though at very low levels, in dairy products in certain countries even though these pesticides have not been in use there for the last about 15 years. It is well recognized that many of the hazards result through the improper usage of the pesticides.
Continuous use of pesticides has many negative effects on the environment:
(i) Killing non-targeted organisms,
(ii) Bio magnification,
(iii) Building of immunities by the targeted pests,
(iv) Lower reproductive potential,
(v) Synergistic effects,
(vi) Toxic effects on water,
(vii) Pesticide residue in food and tissues,
(viii) Effects on vegetation and milk, and
(ix) Direct pesticide poisoning.
Pesticides have their impact on all three components of the Earth, i.e., lithosphere (soil), hydrosphere (water) and atmosphere (air).
Pesticides are toxic, hence it is assumed that their presence in soil will change or alter fundamental soil processes, such as:
(a) Organic matter decomposition,
(b) Nitrogen transformation,
(c) Sulphur transformation,
(d) Phosphate availability,
(e) Trace element availability, and
(f) Soil enzyme activity which influence soil fertility and productivity.
The presence of toxic chemicals in water also has significance as they are picked up by unicellular aquatic organisms like plankton and get accumulated in the body by a phenomenon called bio concentration or bio magnification.
The amount of pesticides released into the atmosphere, if larger than really required, pollutes the air.
The Role of Fertilizers in Pollution:
The consumption of fertilisers is increasing every year to restore soil fertility and to meet the food grains requirements of the ever increasing population. In India, the total consumption of nutrients in the form of fertilizers has increased from 66 thousand tonnes in 1951-52 to 26.49 million tonnes in 2010. The judicious use of chemical fertilizers and other chemicals increases the agricultural production but poor management may lead to environmental pollution problems.
These may result from excessive use of fertilizers, unbalanced use of nutrients or even incidental addition of toxic elements as impurities in the fertilizer materials.
High levels of nitrate nitrogen content in the surface waters results in eutrophication of water bodies. High concentration of nitrate in drinking water has been found to cause methaemoglobinaemia in infants, a fatal disease characterized by cyanosis in which blood pigment loses oxygen required by all human tissues. The incidence of cancer has been associated with nitrate through the formation of N-nitrosamines and nitrosamides which are extremely powerful carcinogenic agents.
Nitrate itself may be carcinogenic without the formation of nitrosamides. There is a positive correlation between nitrate uptake and gastric cancer.
This increase in the level of nitrate in ground waters has been attributed to the intensive use of nitrogenous fertilizers. Rising trend in fertilizer use for higher food grain production has been observed in India. This rising trend of nitrogenous fertilizer consumption has become a matter of serious concern to the environmentalists as ground water in the extensive farming belts of Punjab, Haryana and western U.P. has been found to contain very high amounts of nitrates.
Fertilizers can contribute to eutrophication, i.e., promotion of growth of plants, animals and micro-organisms in ponds, lakes and rivers. Nitrogen and phosphorus are the main nutrients involved in this type of pollution. Enrichment with nitrogen and phosphorus causes and increase in growth of algae and other aquatic weeds, which choke the water ways making water turbid and unpotable. When algae die, toxins are produced. The decomposing organic matter reduces oxygen content in water which may decrease or affect fish production.
There are a number of ways for reducing the nitrate leaching losses. The land management practices which decrease sediment runoff should be followed. High losses are likely when fertilizer input exceeds crop requirement. Therefore, the rate of application should be determined on the basis of soil and crop requirements. It has been found that as the amount of irrigation increases, while its frequency decreases, more nitrates are leached to deeper soil layers.
Therefore, nitrate leaching losses of nitrate-N is the application of balanced nutrients. Such a practice encourages better root and shoot growth. It is also possible to minimise losses of nitrogen and phosphorus by keeping the soil covered instead of bare fallow periods so as to reduce runoff losses. Use of organic manures, green manures and recycling of organic wastes can be extremely useful in controlling the nutrient losses and hence the Environmental Degradation.
15. Essay on Industrial Pollution: [230 words]
Industries differ in the type of pollution that can possibly be caused by them. Liquid effluents, solid wastes and gaseous emissions are common, resulting in impact on water-bodies, land and air, but thermal, radioactive and noise pollution are also associated with a few industries. Industries face a number of problems in their pollution abatement programmes. These include use of outdated technology, plant and equipment, financial burden and non-availability of suitable technology.
Industrial effluents vary in load, concentration of pollutants, toxic materials and are often nutritionally unbalanced. They are complex in composition and may contain biodegradable or non-biodegradable constituents, or both. The effluent of a unit may also show seasonal variation related with production and fluctuations within a day. Non-biodegradable components have to be tackled by physico-chemical methods, while biodegradable components can be tackled otherwise.
Pollutants can be classified as:
1. Readily degradable organics (e.g. from food industry).
2. Complex organics (e.g. from organo-chemical industry, pesticide industry).
3. Readable inorganics (e.g. from heavy metal industries and plating).
4. Inert inorganics (e.g. from coal mining and quarrying).
Objectives of pollution treatment include reduction of BOD/COD, heavy metal removal, hazardous wastes disposal, removal of nitrogen/phosphorus, removal of oil and grease, deodourisation, removal of air pollutants, solid waste disposal, etc. However, very often much of the effort is focussed on reduction of total organic carbon (TOC) or reduction in BOD/COD.
16. Essay on Agrochemical Pollution: [1534 words]
In recent decades, the use of inorganic fertilizers has increased dramatically at the expense of more traditional organic nutrient treatments. Between 1952 and 1985, the global use of fertilizers increased from 14 million tonnes to 125 million tonnes, an increase of almost 900 per cent.
Inorganic fertilizers are used in preference to organic treatments because the nutrients are in a more readily available form and are released rapidly after applications. Organic material releases its nutrients slowly, through decomposition processes, and only when conditions are suitable (warm and moist), not necessarily when crops need them.
Fertilizers are applied in a variety of forms—solution, suspension, emulsion and solid.
The solid forms vary in particle size from fine powder to coarse granules and are either spread evenly (broadcast) over the soil surface or mechanically placed, by drilling, into the rhizosphere; generally the rate of nutrient release decreases with increasing particle size.
Fertilizers are based on compounds of plant macronutrients (e.g. nitrogen, phosphorus and potassium) and micronutrients (e.g., zinc, copper, boron and molybdenum) and a variety of nutrient combinations are available depending on the nature of the nutrient problem.
There are five main fates of fertilizers applied to the soil—plant and animal uptake (immobilisation), adsorption and exchange in the soil (fixation) leaching and loss in soluble form through drainage, volatilisation and gaseous losses to the atmosphere (e.g. denitrification) and surface loss in solid form by runoff and erosion.
In terms of plant uptake, the percentage recovery of nutrient varies markedly between the different types of fertilizers. During the first year of application, the recovery of nitrogen from inorganic nitrogen fertilizers is about 50-65 per cent, whereas from organic manures it is only 20-32 per cent.
Similarly, the recovery of phosphorus and potassium from inorganic fertilizers is about 5-15 per cent and 75 per cent respectively.
In terms of fixation in the soil, many of the phosphorus and potassium fertilizers are of relatively low solubility and the nutrients released are often strongly adsorbed. In contrast, many of the nitrogen fertilizers are highly soluble, nutrient release is rapid and, in most soils, adsorption is limited.
The differences in degree of immobilisation by plants and animals and in the extent of fixation in the soil, help to explain why leaching losses of nitrogen are usually far greater than those of phosphorus and potassium.
Levels of nitrogen in drainage waters, for example, are often in the range 15-150 kg ha–1a–1, whereas levels of phosphorus are generally < 1 kg ha–1a–1; even in exceptional circumstances in eroded areas, phosphorus levels rarely exceed 10 kg ha–1a–1 (White 1987). Nitrogen losses of up to 30-35 per cent of that applied have been recorded for both leaching and denitrification.
Leaching is most common in coarse-textured and well-drained soils, whereas denitrification losses are greatest in fine-textured, waterlogged and poorly aerated soils. Similarly, surface losses are greatest at sites which ate most susceptible to surface runoff and erosion.
In terms of the environmental problems associated with fertilizer use, perhaps the area which has received most attention in recent years, by way of research, is that of nitrate leaching.
In the last few decades, levels of nitrate in water supplies have increased dramatically, particularly in intensively cultivated areas where inputs of nitrogen fertilizers have been high. This association is not necessarily caused however, and may be indirect.
Nitrogen fertilizers are not the only source of leached nitrate, as illustrated by the Broad balk experiments carried out over a 150-year period at Rothamsted Experimental Station in southeast England. It was found that here much of the leached nitrate is derived from the vast reserves of organic nitrogen in the soil, rather than from fertilizers.
The main factors which influence the extent of nitrate leaching include land use, soil characteristics, and climate. In terms of land use, nitrate leaching tends to be greatest when there is no crop cover to utilise the nitrate released from fertilizers or organic reserves. With spring planted cereals, for example, the leaching risk is greatest during the wet autumn and winter period when the soil is left bare.
In order to maximise uptake and minimise leaching, fertilizers should be applied just before and during the period of maximum crop growth and large applications at any one time should be avoided. Tillage practices also have an effect on nitrogen losses through leaching and denitrification.
Tillage improves topsoil drainage and aeration and, as a result, rates of organic matter decomposition increase. Colbourn (1985) compared nitrogen losses by leaching and denitrification on conventionally cultivated and direct drilled land in southern England.
Leaching losses were considerably greater from the conventionally cultivated land, whereas denitrification losses were smaller. For both tillage regimes, however, maximum nitrogen losses occurred during the autumn period after the harvest and during the spring following fertilizer application.
In addition to the environmental problems associated with fertilizer application, a number of problems arise from the use of pesticides.
A wide range of pesticides has been developed (more than 450 compounds), the types most commonly used being insecticides, fungicides and herbicides; other varieties include nematicides, miticides, rodenticides and molluscicides. Pesticides behave in a variety of ways following application.
They may be degraded biologically or photochemicaily, adsorbed by organic matter, clay and oxides/hydroxides of iron and aluminium, washed into water courses by leaching (especially compounds with solubilities >10 mg such as simazine, bromacil and aldicarb) and surface runoff, or they may undergo volatilisation into the atmosphere (especially surface applied compounds and those of low solubility and vapour pressure such as organochlorines).
Ideally, pesticides should control only the target organism and persist for long enough to achieve this before degrading into harmless products. This is not always the case, however, and a number of environmental concerns arise from pesticide use.
These include persistence in the environment, toxicity in soil, vegetation and water supplies and impact beyond the target organism including bioaccumulation and its implications for human health. In fact, the degradation products of some pesticides may be as toxic as the original source chemical but are not often measured by standard assays.
The persistence and toxicity of many pesticide compounds and their degradation products are also dependent on a number of soil characteristics, notably clay and organic content and pH.
The environmental impacts of pesticide use were felt most strongly with the early generation of pesticides, particularly the organochlorine compounds and those containing heavy metals.
Generally, the organochlorine compounds are the most persistent of the pesticides and may survive for a number of years before they are degraded. Their residues have been found widely in soils, freshwater sediments, fish and cow’s milk.
Due to their high lipid solubility, they have also been found in the fatty tissues of animals. All of these findings have important implications for the ecology of food chains and, thus, for human health. An additional problem was that the effectiveness of organochlorine pesticides decreased as target organisms became resistant to them.
The more recently developed organophosphate and carbonate pesticides are much less persistent than the organochlorines, with a half-life of about six months, but are often more toxic. The phenoxyacetic acids, 2,4-D and 2, 4, 5-T, are also rapidly degraded but have been associated with animal and human growth and reproductive abnormalities.
In terms of management and remediation of the environmental problems associated with pesticide use, continued research and monitoring—with the aim of minimising effective persistence and toxicity and maximising specificity—are essential.
Attempts have been made to model the behaviour of pesticides in soils under different management regimes, with a view to reducing the risk of ground and surface water contamination.
In addition, the use of granular slow-release pesticides is being explored, together with ultra-low volume application techniques. The environmental problems may also be alleviated by adopting alternative, non-chemical strategies of pest, disease and weed control.
These include direct approaches, biological and cultural methods and habitat removal.
Direct approaches are aimed at clearly identified animals and plants and specific practices include hunting and hand-weeding. Biological methods involve the use of predatory species, preferably with a wide environmental tolerance range, to control the specific target organism.
Ideally, as the pest population grows, the predator population should follow, and vice versa; this is known as a density-dependence relationship.
If such a relationship does not exist, however, the predator itself may become a pest. Cultural methods involve the use of tillage, crop rotation, fertilizer application, liming and drainage techniques. These help to disturb the cycle of pests, diseases and weeds and to improve the resistance of crops to them.
Habitat removal is perhaps the least acceptable approach to pest, disease and weed control. The basis of this approach is that semi-natural vegetation acts as a refuge for many pests, diseases and weeds and that control may, therefore, be achieved through the removal of such habitats.
However, this approach fails to recognise both the conservation value of these habitats and the fact that they may be an important source of predators as well as pests.
Woodland and hedgerows in lowland arable areas, for example, are an important habitat for ladybirds, essential in the control of greenfly populations and for bees, important in plant pollination. They also act as shelter belts, thus helping to control soil erosion.
17. Essay on Urban Pollution: [1626 words]
Urban and industrial development has been associated with both physical degradation and chemical contamination of soils.
Problems of physical degradation include erosion, compaction and structural damage resulting from construction activities and opencast mineral extraction. Similarly, chemical problems result form waste disposal activities, discharge and spillage of liquid effluents and atmospheric emissions, including acid deposition.
Soils of urban and industrial environments are every bit as complex and variable in their characteristics as those in rural areas and merit classification in their own right. Hollis (1991), for example, suggests that the England and Wales soil classification system should be modified to include an ‘anthropogenic’ major soil group which could be subdivided on the basis of the types of contaminant materials present.
Physical disturbance and chemical contamination of soils in urban and industrial environments are not only recent phenomena.
Archaeological investigations have revealed the extensive accumulation of building and domestic waste, although much of this was relatively harmless. Since the Industrial Revolution of the eighteenth and nineteenth centuries, however, the amount and variety of waste materials have increased dramatically.
Furthermore, much of this waste is considerably greater than its early historical counterparts.
It is particularly important that any survey of contaminated sites should include an assessment of this historical legacy, since the response of soils to stored pollutants may be delayed for long periods of time. This type of delayed response is potentially very serious and is often referred to as the ‘chemical time-bomb’ effect.
Bridges (1991) identifies four major sources of soil contamination in urban and industrial environments—construction and demolition waste, metalliferous materials, power generation emissions and chemical and organic wastes.
During construction and demolition a range of materials are disposed-off in the soil environment, including broken bricks, tiles, glass, timber, piping, wiring and cables, insulation materials, mortar, concrete and plaster.
Once in the soil, these materials undergo a number of chemical changes. Plaster, for example, contains large amounts of gypsum and, at sites where the water table is high, the gypsum is dissolved and capillary actions may bring it into contact with new concrete structures, thus leading to serious corrosion problems.
Similarly, although the use of asbestos and its removal from existing buildings is now carefully controlled, significant quantities can be present in soils and overburden at sites with a long history of construction and demolition.
Metalliferous wastes, particularly heavy metals (e.g. lead, zinc, cadmium, copper, and nickel), are commonly found in soils of areas where ore extraction and smelting have occurred.
More locally, metal contamination occurs on land used for scrap metal dealing and munitions factories. In an attempt to provide systematic data or the extent of heavy metal contamination in urban soils in Britain, a national survey was commissioned by the Department of the Environment in 1981; 100 household gardens were sampled in each of 53 cities, towns and villages.
In most of these localities, total lead levels in the soil exceeded 200 mg kg-1, with values in excess of 500 mg kg-1 in industrial areas in the south and in former lead mining areas in the north. These values are considerably greater than the background levels of lead (usually < 100 mg kg–1) normally found in uncontaminated soils.
Toxic metals may exist in the soil in a number of forms including adsorbed cations, attached to clay and humus colloids and organo-metallic chelates. Their availability to plants depends on a number of soil characteristics, particularly cation exchange capacity (CEC), pH and the interdependence effects of other metals.
In soils with a low CEC, the metals are not retained effectively and are likely to be either leached from the soil or taken up by plants, while, in soils with a high CEC, they are likely to be fixed in the soil through adsorption processes.
Similarly, the mobility and availability of heavy metals is considerably greater in acidic soils (pH < 5.5) than in near neutral or alkaline soils. Once mobilised, the metals may enter the food chain either through water supplies and aquatic organisms, or through arable produce and grazing animals.
The effects of toxic metals in soils on human health are unclear and it is, therefore, difficult to establish threshold concentrations above which toxicity problems are likely to occur. However, a number of countries have devised such threshold values, although these vary markedly in response to differences in environmental policy and legislation.
The Dutch government, for example, has a system with three levels — an acceptable reference or background value, an indicative value for further investigation, and an indicative value for clean-up.
A number of soil contaminants are derived from the power generation industry, including SO2 (sulphur dioxide) from coal-fired power stations, and radionuclides from nuclear power stations and weapons testing. The anthropogenic radionuclides most commonly found in soils are those of caesium (137Cs and 134Cs). Much of the research in this field has occurred since the accident at Chernobyl in Ukraine in 1986, which resulted in large quantities of radionuclides being deposited across wide areas of Europe, including Britain.
The behaviour of radionuclides in soils depends on a number of soil characteristics, particularly clay content and mineralogy, organic content, CEC, pH, NH4 (ammonium) content and nutrient status. The radionuclidesa are immobilised most strongly in soils with a high ECE and near neutral pH values, where they are adsorbed on to clays, especially micaceous varieties, and humic materials.
They are least well retained in acidic soils with a low CEC, where they may be available for plant uptake. Such conditions are widespread in upland areas of northern and western Britain where the milk and meat of grazing cattle and sheep were contaminated following the Chernobyl accident. In northern Scandinavia, reindeer herds grazing on slow growing lichen heath were similarly affected.
The problem of radionuclide entry into the food chain from acid soils in Britain was not anticipated because much of the early research here had focused on clay soils with near neutral pH values where radionuclides are relatively immobile than the other contaminants.
These include derivatives of detergents, fertilizers and pesticides, paints, dyestuffs, battery chemicals and leather tanning agents, to name but a few. Even silicon chip manufacture involves the use of chemical components and leakage of solvents used in this process led to the contamination of drinking water in
Silicon Valley, California. In recent years, particular concern has arisen regarding the production of dioxins; these are a particularly toxic group of chemicals and are associated with the manufacture of several organic pesticides.
In the Italian town of Seveso, for example, an area of 1,800 ha was affected by dioxin contamination in 1976 and 700 people were evacuated; subsequently, the contaminated soil had to be excavated and removed.
A major event which publicized the issue of chemical contamination of soils was the Love Canal disaster near Niagara, USA.
Here, extensive dumping of chemicals over a 30-year period led to severe soil contamination by migrating leachates and gases, with serious health implications for local people. This persuaded the US government to release funds to implement the Comprehensive Environmental Response Compensation and Liability Act of 1980 (CERCLA).
A number of organic wastes may lead tc soil contamination. At Times Beach, Missouri, for example, the land was so badly contaminated by dioxins from waste oils, derived from the manufacture of the defoliant ‘agent orange’ that it was purchased by the Federal government.
Spillage of oils and related wastes is common on land used for storage and maintenance of motor vehicles and for fuel storage. Sewage sludge, often applied to agricultural land adjacent to urban and industrial areas, often contains high concentrations of heavy metals.
The PCBs (polychlorinated biphenyls) are a group of organic solvents commonly implicated in soil contamination. These are used as dielectric fluids in transformers and are often released during the break-up of electrical equipment.
Management of contaminated soils is a difficult prospect as the guidelines on threshold toxicity levels of contaminant materials and on the vulnerability of soils to pollution, are still being developed and refined. Management options depend to a large extent on the geological and hydrological characteristics and size of the contaminated area.
Such areas vary dramatically from large designated landfill sites with records of waste disposal activities, to former industrial sites with a long and unclear history of pollution.
Management options also depend on the nature of the contamination problem and whether it can be contained at the affected site, or whether leachates and gases threaten areas beyond it. Furthermore, it may be possible to treat the contamination on site, or it may be necessary to remove and relocate the contaminated soil.
Bridges (1991) outlines a number of management approaches to the problem of contaminated soil. These include the use of physical stabilisation barrier, thermal and microbiological techniques. Stabilisation techniques involve treatment to reduce the solubility and mobility of the waste materials.
This is achieved through the application of cement, lime, gypsum, silicate materials, epoxy-resins, polyesters or asphalt; these act as binding agents and help to stabilise the ‘landform’ within which the contaminated waste is stored.
Barrier systems usually rely on physical containment using steel or concrete pilling to prevent downward and lateral migration of toxic materials. Similarly, layered cover systems are often used to prevent upward migration of contaminants.
Thermal techniques involve heating contaminated soil in rotary kilns or furnaces, whereas microbiological techniques involve the inoculation of waste materials with microbiological communities. Both of these techniques aim to convert the toxic waste materials into less harmful forms.
Other approaches to the management of contaminated soil include chemical treatments which may be used to hydrolyse or oxidise contaminants into less dangerous products; similarly, acidic or alkaline wastes may be neutralized. In addition, physical methods may be employed to separate out contaminants according to particle size or density.
18. Essay on Organic Water Pollution: [438 words]
It is essential that the amount of oxygen present in any aquatic system be sufficient not only to minimally support life but also to facilitate the natural behavior of species. This is particularly important for locomotion, feeding, and reproduction. Oxygen exists in water in a dissolved state at a level equal to its saturation concentration, which is mostly dependent on temperature.
It is not very soluble in water and can be easily depleted. Oxygen occurs in water primarily through being absorbed from the atmosphere. It also enters through surface water runoff and from photosynthesis, although these sources are not as consistent.
Organisms vary considerably in their oxygen requirements. Fish require the highest levels, invertebrates somewhat lower levels, and bacteria the least. Because fish have the highest requirement, it is often prudent to use them as a gauge to determine acceptable aquatic oxygen levels. It should be remembered, however, that all species require oxygen; even plant life (producers) requires oxygen at night.
It is most likely that more fish kills result from low or depleted oxygen conditions than from any other reason. Within the class of fishes (i.e., class Osteichthyes) the requirement also varies depending on the species, stage of development, level or type of activity, temperature, and other factors. A more desirable species like trout or salmon generally has a higher oxygen requirement than a more tolerant species such as carp or catfish.
The typical needs of a well-rounded warm-water fish population might be greater than 5ppm for 16 or more hours a day with not less than 3 ppm for up to 8 hours a day. This would be higher for a cold water species perhaps on the order of 6 ppm for 16 hours per day.
Any existing aquatic system would be considered polluted when the dissolved oxygen (DO) content can no longer support the existing (or prior) well-balanced ecosystem. A low or depleted dissolved oxygen environment may result from a wide variety of both simple and complex conditions.
Some of the more common are:
(i) Accidental or intentional sewage discharge,
(ii) Polluted surface water runoff,
(iii) Wastewater discharges with problematic biochemical oxygen demand,
(iv) Waste water discharges with problematic chemical oxygen demand, and
(v) Elevated temperature.
All of these are highly regulated, with the exception of surface water runoff. It is now generally thought that the majority of low DO conditions in the Long Island Sound, for example, have been either caused by, or maintained by polluted wastewater discharges and surface water runoff. These discharges are received both directly and indirectly by the Sound itself, as well as through the many tributaries that feed it.