Pollution NOTES For BS/MSC/MS/MPHIL/PHD etc...

Pollution 

The introduction of contaminants into the natural environment that causes adverse change. Pollution can take the form of chemical substances or energy, such as noise, heat or light. Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants. 

Environmental pollution is one of the most serious problems facing humanity and other life forms on our planet today. “Environmental pollution is defined as “the contamination of the physical and biological components of the earth/atmosphere system to such an extent that normal environmental processes are adversely affected.” Pollutants can be naturally occurring substances or energies, but they are considered contaminants when in excess of natural levels. Any use of natural resources at a rate higher than nature’s capacity to restore itself can result in pollution of air, water, and land. 

Environmental pollution is of different types namely air, water, soil, noise and light-weight. These cause damage to the living system. How pollution interacts with public health, environmental medicine and the environment has undergone dramatic change.   

1. Air pollution: 

Air pollution is a mixture of solid particles and gases in the air.  

Car emissions, chemicals from factories, dust, and pollen and mold spores may be suspended as particles.  

Ozone, a gas, is a major part of air pollution in cities. When ozone forms air pollution, it's also called smog.  

Some air pollutants are poisonous. 

Air pollution occurs when harmful or excessive quantities of substances are introduced into Earth's atmosphere. 

Sources of air pollution include gases, particulates, and biological molecules.”  

“Air pollution refers to the release of pollutants into the air that are detrimental to human health and the planet as a whole.” 

Primary and secondary air pollutants: 

A primary pollutant is an air pollutant emitted directly from a source. A secondary pollutant is not directly emitted as such, but forms when other pollutants (primary pollutants) react in the atmosphere. 

The primary pollutants are “directly” emitted from the processes such as fossil fuel consumption, volcanic eruption and factories.  The major primary pollutants are Oxides of Sulphur, Oxides of Nitrogen, Oxides of Carbon, Particulate Matter, Methane, Ammonia, Chlorofluorocarbons, Toxic metals etc.   

Examples of Primary Pollutants:    

1. Car exhaust, smokestacks (CO, SO2, NO)   

2. Particulate material (soot, ash)   

3. Toxic metals (lead, mercury)   

4. Volatile organic compounds (VOCs) (methane, propane, CFCs, etc.)    Secondary air pollutants:   

The secondary pollutants are not emitted directly. The secondary pollutants form when the primary pollutants react with themselves or other components of the atmosphere. Most important secondary level Air Pollutants are Ground Level Ozone, Smog and POPs (Persistent Organic Pollutants).   

Causes of air pollution: 

The burning of fossil fuels Sulfur dioxide emitted from the combustion of fossil fuels like coal, petroleum and other factory combustibles are one the major cause of air pollution. But, their overuse is killing our environment as dangerous gases are polluting the environment    Burning of Fossil Fuels:  

The combustion of fossil fuels emits a large amount of sulphur dioxide. Carbon monoxide released by incomplete combustion of fossil fuels also results in air pollution.   

 Automobiles:  

The gases emitted from vehicles such as jeeps, trucks, cars, buses, etc. pollute the environment. These are the major sources of greenhouse gases and also result in diseases among individuals.   

Agricultural Activities:  

Ammonia is one of the most hazardous gases emitted during agricultural activities. The insecticides, pesticides and fertilizers emit harmful chemicals in the atmosphere and contaminate it.   

Factories and Industries: 

Factories and industries are the main source of carbon monoxide, organic compounds, hydrocarbons, and chemicals. These are released into the air degrading its quality.   Mining Activities:  

In the mining process, the minerals below the earth are extracted using large pieces of equipment. The dust and chemicals released during the process not only pollute the air but also deteriorate the health of the workers and people living in the nearby areas.   

Domestic Sources: 

The household cleaning products and paints contain toxic chemicals that are released in   the air. The smell from the newly painted walls is the smell of the chemicals present in the paints. It not only pollutes the air but also affects breathing. 

Effects of Air Pollution: The hazardous effects of air pollution on the environment include:    Diseases: 

Air pollution has resulted in several respiratory disorders and heart diseases among humans. The cases of lung cancer have increased in the last few decades. Children living near polluted areas are more prone to pneumonia and asthma.    

 Global Warming:  

Due to the emission of greenhouse gases, there is an imbalance in the gaseous composition of the air. This has led to an increase in the temperature of the earth. This increase in earth’s temperature is known as global warming.     Acid Rain:  

The burning of fossil fuels releases harmful gases such as nitrogen oxides and sulphur oxides in the air. The water droplets combine with these pollutants, become acidic, and fall as acid rain which damages human, animal and plant life.   

 Ozone Layer Depletion:  

The release of chlorofluorocarbons (CFC), halons, and hydrochlorofluorocarbons in the atmosphere is the major cause of depletion of the ozone layer. The depleting ozone layer does not prevent the harmful ultraviolet rays coming from the sun and causes skin diseases and eye problems among individuals.   

 Effect on Animals:  

The air pollutants suspend on the water bodies and affect the aquatic life. Pollution also compels the animals to leave their habitat and shift to a new place.     

Air Pollution Control: 

Following are the measures one should adopt to control air pollution:    Avoid Using Vehicles:  

People should avoid using vehicles for shorter distances. Rather they should prefer public modes of transport to travel from one place to another. This not only prevents pollution but also conserves energy.    Energy Conservation: 

A large number of fossil fuels are burnt to generate electricity. Therefore, do not forget to switch off the electrical appliances when not in use. Thus, you can save the environment at the individual level. Use of energy-efficient devices such CFLs also controls pollution to a greater level.  Use of Energy efficient appliances:   

Whether at the domestic level or at the industrial level, we must push for appliances that use energy efficiently, which result in complete combustion of fuel, as incomplete combustion causes air pollution.    Shifting industries:  

Another possible solution to reduce the harmful effects of air pollution is to shift the manufacturing plants, factories and industries to remote areas with a low level of population.    

 Using Modern Techniques:  

With technology making great advancements, there are now technologies available that can help reduce the release of pollutants in the air. Air filters, scrubbers, precipitators are just a few examples.    Shifting to Natural Gasses:   

Instead of using and exhausting fossil fuels, shifting to greener options is a no-brainer. For example, using CNG (compressed natural gas) instead of petrol or diesel is a great option.    

2. 10 Water pollution: 

Water pollution is the contamination of water bodies, usually as a result of human activities. Water bodies include for example lakes, rivers, oceans, aquifers and groundwater. Water pollution results when contaminants are introduced into the natural environment. “Water is essential to life. It need not be spelt out exactly how important it is. Yet water pollution is one of the most serious ecological threats we face today.”   

Water pollution happens when toxic substances enter water bodies such as lakes, rivers, oceans and so on, getting dissolved in them, lying suspended in the water or depositing on the bed. This degrades the quality of water. Not only does this spell disaster for aquatic ecosystems, the pollutants also seep through and reach the groundwater, which might end up in our households as contaminated water we use in our daily activities, including drinking.   

Sources of Water Pollution: 

Point and non-point sources:   

1. When pollutants are discharged from a specific location such as a drain pipe carrying industrial effluents discharged directly into a water body it represents point source pollution  

2. In contrast, non-point sources include discharge of pollutants from diffused sources or from a larger area such as runoff from agricultural fields, grazing lands, constriction site, abandoned mines and pits, etc.    

Causes of Water Pollution: 

The causes of water pollution vary and may be both natural and anthropogenic. However, the most common causes of water pollution are the anthropogenic ones, including:    Agrochemicals: 

Agrochemicals like fertilizers (containing nitrates and phosphates) and pesticides (insecticides, fungicides, herbicides etc.) washed by rain-water and surface runoff pollute water.   Storm water runoff:   

Carrying various oils, petroleum products, and other contaminants from urban and rural areas (ditches). These usually forms sheens on the water surface.    Sewage:   

Emptying the drains and sewers in fresh water bodies causes water pollution. The problem is severe in cities.   Mining activities:    

Mining activities involve crushing rocks that usually contain many trace metals and sulfides. The leftover material from mining activities may easily generate sulfuric acid in the presence of precipitation water.    Industrial Effluents:    

Industrial wastes containing toxic chemicals, acids, alkalis, metallic salts, phenols, cyanides, ammonia, radioactive substances, etc., are sources of water pollution. They also cause thermal (heat) pollution of water.   Burning of fossil fuels:   

The emitted ash particles usually contain toxic metals (such as As or Pb). Burning will also add a series of oxides including carbon dioxide to air and, respectively, water bodies.    Leaking landfills:   

May pollute the groundwater below the landfill with a large variety of contaminants (whatever is stored by the landfill).    Animal waste:   

Contribute to the biological pollution of water streams. Think of it this way: anything that can cause air pollution or soil pollution may also affect water bodies and cause innumerable ecological and human health issues   Effects of water pollution: 

The effects of water pollution are varied. They include poisonous drinking water, poisonous food animals (due to these organisms having bio-accumulated toxins from the environment over their life spans), unbalanced river and lake ecosystems that can no longer support full biological diversity, deforestation from acid rain, and many other effects. These effects are, of course, specific to the various contaminants. 

 Water bodies in the vicinity of urban areas are extremely polluted. This is the result of dumping garbage and toxic chemicals by industrial and commercial establishments.   

 Water pollution drastically affects aquatic life. It affects their metabolism, behavior, causes illness and eventual death. Dioxin is a chemical that causes a lot of problems from reproduction to uncontrolled cell growth or cancer. This chemical is bio-accumulated in fish, chicken and meat. Chemicals such as this travel up the food chain before entering the human body.    

 The effect of water pollution can have a huge impact on the food chain. It disrupts the food- chain. Cadmium and lead are some toxic substances, these pollutants upon entering the food chain through animals (fish when consumed by animals, humans) can continue to disrupt at higher levels.   

 Humans are affected by pollution and can contract diseases such as hepatitis through faucal matter in water sources. Poor drinking water treatment and unfit water can always cause an outbreak of infectious diseases such as cholera etc.   

 The ecosystem can be critically affected, modified and destructured because of water pollution.   Control of Water Pollution: 

Water pollution, to a larger extent, can be controlled by a variety of methods.  

Rather than releasing sewage waste into water bodies, it is better to treat them before discharge.  

Practicing this can reduce the initial toxicity and the remaining substances can be degraded and rendered harmless by the water body itself. If the secondary treatment of water has been carried out, then this can be reused in sanitary systems and agricultural fields.  

A very special plant, the Water Hyacinth can absorb dissolved toxic chemicals such as cadmium and other such elements.  

Establishing these in regions prone to such kinds of pollutants will reduce the adverse effects to a large extent.  Some chemical methods that help in the control of water pollution are precipitation, the ion exchange process, reverse, and coagulation. As an individual, reusing, reducing, and recycling wherever possible will advance a long way in overcoming the effects of water pollution.    

3. Soil Pollution: 

Soil contamination or soil pollution as part of land degradation is caused by the presence of xenon biotic chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste.   

Definition of Soil pollution:   

“Soil pollution refers to the contamination of soil with anomalous concentrations of toxic substances. It is a serious environmental concern since it harbors many health hazards.”   

“Soil pollution refers to anything that causes contamination of soil and degrades the soil quality. It occurs when the pollutants causing the pollution reduce the quality of the soil and convert the soil inhabitable for microorganisms and macro organisms living in the soil.” 

Causes of Soil Pollution: 

Soil pollution can be natural or due to human activity. However, it mostly boils down to the activities of the human that causes the majority of soil pollution such as heavy industries, or pesticides in agriculture.   

Industrial activities including mining, smelting and manufacturing; domestic, livestock and municipal wastes; pesticides, herbicides, fertilizers used in agriculture; petroleum-derived products that are released into or breakdown in the environment; fumes generated by transportation  all contribute to the problem. These include pharmaceuticals, endocrine disruptors, hormones and biological pollutants; "e-waste" from old electronics; and the plastics that are nowadays used in almost every human endeavor.    Natural Pollution of Soil:   

In some extremely rare processes, some pollutants are naturally accumulated in soils. This can occur due to the differential deposition of soil by the atmosphere. Another manner in which this type of soil pollution can occur is via the transportation of soil pollutants with precipitation water.  

Anthropogenic Soil Pollution: Almost all cases of soil pollution are anthropogenic in nature. A variety of human activities can lead to the contamination of soil.    Pesticides:   

Before World War II, the chemical nicotine chemical present in the tobacco plants was used as the pest controlling substance in agricultural practices. However, DDT was found to be extremely useful for malaria control and as pest control of many insects during World War II.     Inorganic Fertilizers:   

Excessive use of inorganic nitrogen fertilizers leads to acidification of soil and contaminate the agricultural soil.      Industrial Pollution:   

The incorrect way of chemical waste disposal from different types of industries can cause contamination of soil. Human activities like this have led to acidification of soil and contamination due to the disposal of industrial waste, heavy metals, toxic chemicals, dumping oil and fuel, etc.    Heavy Metals:   

The presence of heavy metals (such as lead and mercury, in abnormally high concentrations) in soils can cause it to become highly toxic to human beings. 

Effects of Soil Pollution: 

Soil pollution affects plants, animals and humans a like. While anyone is susceptible to soil pollution, soil pollution effects may vary based on age, general health status and other factors, such as the type of pollutant or contaminant inhaled or ingested. However, children are usually more susceptible to exposure to contaminants, because they come in close contact with the soil by playing in the ground; combined with lower thresholds for disease,( headaches, nausea, and vomiting, coughing, pain in the chest, and wheezing) this triggers higher risks than for adults. Therefore, it is always important to test the soil before allowing your kids to play there, especially if you live in a highly industrialized area.   

Control of Soil Pollution: 

Several technologies have been developed to tackle soil remediation. Some important strategies followed for the decontamination of polluted soil are listed below.  

 Excavation and subsequent transportation of polluted soils to remote, uninhabited locations.  

 Extraction of pollutants via thermal remediation the temperature is raised in order to force the contaminants into the vapor phase, after which they can be collected through vapors extraction.  

 Bioremediation or phytoremediation involves the use of microorganisms and plants for the decontamination of soil.  

 Mycoremediation involves the use of fungi for the accumulation of heavy metal contaminants.    

4. Thermal pollution: 

Thermal pollution, sometimes called "thermal enrichment," is the degradation of water quality by any process that changes ambient water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Other causes of thermal pollution include soil erosion.   

Cause of Thermal Pollution: 

Many human and natural factors contribute to the problem of thermal pollution.  

The single biggest cause of thermal pollution is probably cooling for industrial machinery and power plants.  

Water is an excellent, and free, cooling agent. This is why many industrial operations pull in relatively cool water to cool their machinery and let the relatively warm water flow back into the river or lake or sea.   

Thermal pollution also has some natural causes.  

Geothermal vents and hot springs introduce excess heat into bodies of water.  

Soil erosion, deforestation, and runoff from paved areas are other artificial sources of hot water.  

Deforestation eliminates shade, which exposes the water to sunlight.  

Water on hot paved surfaces gets hot, then runs off into nearby bodies of water, raising the water temperature. Retention ponds can also be a source of thermal shock because the relatively small and shallow bodies of water can absorb quite a bit of heat energy from the sun.  

Pumping that water directly into a river, lake, or bay causes a significant temperature increase, just like pouring a hot pitcher of water into a bathtub full of water causes the water to jump a few degrees Fahrenheit. 

Effects of Thermal Pollution: 

The effects of thermal pollution are diverse, but in short, thermal pollution damages water ecosystems and reduces animal populations. Plant species, algae, bacteria, and multi-celled animals all respond differently to significant temperature changes. Organisms that cannot adapt can die of various causes or can be forced out of the area. Reproductive problems can further reduce the diversity of life in the polluted area. The Effects of Thermal Pollution: The effects of thermal pollution are diverse, but in short, thermal pollution damages water ecosystems and reduces animal populations.   

1. Decreased Dissolved Oxygen:    

Warm water holds less oxygen than cool water. If the oxygen level drops animals that cannot move to another area may begin to die. In deeper bodies of water, the injection of warm water can keep oxygen from dispersing into deep water, which is potentially good for bacteria but dangerous for aquatic animals. The decreased oxygen can cause algae blooms that pose a threat to aquatic plants and animals. This algae bloom problem is probably the most common and best-known side effect of thermal pollution.   

2. Loss of Biodiversity:   

The sudden heating can kill off vulnerable organisms or drive them away. This is one of many serious issues for threatened and endangered animal species. This loss can come from organisms dying from the hot water, being unable to reproduce as effectively as before, or simply leaving the area. We usually think of animals as casualties of water pollution, but multi- celled aquatic plants are also at risk when thermal pollution changes the local aquatic ecosystem.   

3. Ecological Impacts:   

The local aquatic ecosystem can be damaged by thermal pollution, especially if it is dramatic, as in copious amounts of warm water being dumped into a chilly pond or bay or river. “Thermal shock” can kill off insects, fish, and amphibians.   

5. Migration:  

Fish and amphibians may move away from the warm water to a more-suitable location, disrupting the ecosystem for animals that remain. Birds may also be forced to leave in search of areas with more food.    

6. Increased Toxins:   

Toxins in the water are more a side effect of dumping waste water than a direct effect of thermal pollution. Chemical pollution is an almost inevitable side effect of using water for cooling. Solvents, fuel oil, and dissolved heavy metals end up in the lake or river where the cooling water gets dumped. 

Nuclear hazards and human health risks: 

 These can be both beneficial and harmful, depending on the way in which they are used.  

 We routinely use X-rays to examine bones for fractures, treat cancer with radiation and diagnose diseases with the help of radioactive isotopes.  

 About 17% of the electrical energy generated in the world comes from nuclear power plants.  

 Radioactive substances when released into the environment are either dispersed or become concentrated in living organisms through the food chain.  

 Other than naturally occurring radioisotopes, significant amounts are generated by human activity, including the operation of nuclear power plants, the manufacture of nuclear weapons, and atomic bomb testing.  

 For example, strontium 90 behaves like calcium and is easily deposited and replaces calcium in the bone tissues. It could be passed to human beings through ingestion of strontium-contaminated milk.  

 Again another example is tritium, which is radioactive hydrogen.  

 The amount of tritium released from nuclear power plants to the atmosphere have reached as high as tens of thousands of curies in one year, and releases to bodies of water have measured as high as tens of millions of picocuries per liter.   

Nuclear accidents impact health: 

 Apart from the damage caused by fires and explosions, accidents also release radioactive materials which can cause radiation sickness.  

 Radiation exposure above a certain threshold, usually only received by workers and emergency teams in a stricken plant, causes acute radiation syndrome within hours of exposure.  

 Depending on the dose of radiation this ranges from skin rashes, vomiting and diarrhea, to coma and death. 

 Radiation damages DNA, especially as it assembles in dividing cells. That means tissues which contain many dividing cells, such as the gut lining, skin and bone marrow, are most at risk of damage.  

 High enough doses also damage brain cells and such doses are invariably fatal. 

Repeated Soil pollution: 

Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents, which have adverse effects on plant growth and animal health.  

Soil is the thin layer of organic and inorganic materials that covers the Earth's rocky surface.  

The organic portion, which is derived from the decayed remains of plants and animals, is concentrated in the dark uppermost topsoil.  

The inorganic portion made up of rock fragments, was formed over thousands of years by physical and chemical weathering of bedrock. Productive soils are necessary for agriculture to supply the world with sufficient food. There are many different ways that soil can become polluted, such as:  

• Seepage from a landfill  

• Discharge of industrial waste into the soil  

• Percolation of contaminated water into the soil  

• Rupture of underground storage tanks  

• Excess application of pesticides, herbicides or fertilizer  

• Solid waste seepage  

The most common chemicals involved in causing soil pollution are: 

• Petroleum hydrocarbons  

• Heavy metals  

• Pesticides  

• Solvents  

Types of Soil Pollution • Agricultural Soil Pollution  

i) pollution of surface soil  ii)  pollution of underground soil 

• Soil pollution by industrial effluents and solid wastes 

i) pollution of surface soil  ii)  disturbances in soil profile  

• Pollution due to urban activities  

i) pollution of surface soil  ii)  pollution of underground soil 

Causes of Soil Pollution 

Soil pollution is caused by the presence of man-made chemicals or other alteration in the natural soil environment. This type of contamination typically arises from the rupture of underground storage links, application of pesticides, and percolation of contaminated surface water to subsurface strata, oil and fuel dumping, leaching of wastes from landfills or direct discharge of industrial wastes to the soil. The most common chemicals involved are petroleum hydrocarbons, solvents, pesticides, lead and other heavy metals. This occurrence of this phenomenon is correlated with the degree of industrialization and intensities of chemical usage.  

A soil pollutant is any factor which deteriorates the quality, texture and mineral content of the soil or which disturbs the biological balance of the organisms in the soil. Pollution in soil has adverse effect on plant growth. Pollution in soil is associated with  

• Indiscriminate use of fertilizers  

• Indiscriminate use of pesticides, insecticides and herbicides  

• Dumping of large quantities of solid waste  

• Deforestation and soil erosion  

Indiscriminate use of fertilizers 

Soil nutrients are important for plant growth and development. Plants obtain carbon, hydrogen and oxygen from air and water. But other necessary nutrients like nitrogen, phosphorus, potassium, calcium, magnesium, sulfur and more must be obtained from the soil. Farmers generally use fertilizers to correct soil deficiencies. Fertilizers contaminate the soil with impurities, which come from the raw materials used for their manufacture. Mixed fertilizers often contain ammonium nitrate (NH4NO3), phosphorus as P2O5, and potassium as K2O. For instance, As, Pb and Cd present in traces in rock phosphate mineral get transferred to super phosphate fertilizer. Since the metals are not degradable, their accumulation in the soil above their toxic levels due to excessive use of phosphate fertilizers, becomes an indestructible poison for crops.  

The over use of NPK fertilizers reduce quantity of vegetables and crops grown on soil over the years. It also reduces the protein content of wheat, maize, grams, etc., grown on that soil. The carbohydrate quality of such crops also gets degraded. Excess potassium content in soil decreases Vitamin C and carotene content in vegetables and fruits. 

The vegetables and fruits grown on over- fertilized soil are more prone to attacks by insects and disease. Indiscriminate use of pesticides, insecticides and herbicides 

Plants on which we depend for food are under attack from insects, fungi, bacteria, viruses, rodents and other animals, and must compete with weeds for nutrients. To kill unwanted populations living in or on their crops, farmers use pesticides. The first widespread insecticide use began at the end of World War II and included DDT (dichlorodiphenyltrichloroethane) and gammaxene. Insects soon became resistant to DDT and as the chemical did not decompose readily, it persisted in the environment. Since it was soluble in fat rather than water, it biomagnified up the food chain and disrupted calcium metabolism in birds, causing eggshells to be thin and fragile. As a result, large birds of prey such as the brown pelican, ospreys, falcons and eagles became endangered. DDT has been now been banned in most western countries. Ironically many of them including USA, still produce DDT for export to other developing nations whose needs outweigh the problems caused by it.  

The most important pesticides are DDT, BHC, chlorinated hydrocarbons, organophosphates, aldrin, malathion, dieldrin, furodan, etc.  

The remnants of such pesticides used on pests may get adsorbed by the soil particles, which then contaminate root crops grown in that soil.  

The consumption of such crops causes the pesticides remnants to enter human biological systems, affecting them adversely. An infamous herbicide used as a defoliant in the Vietnam War called Agent Orange (dioxin), was eventually banned.  

Soldiers' cancer cases, skin conditions and infertility have been linked to exposure to Agent Orange.  

Pesticides not only bring toxic effect on human and animals but also decrease the fertility of the soil.  

Some of the pesticides are quite stable and their bio- degradation may take weeks and even months.  

Pesticide problems such as resistance, resurgence, and health effects have caused scientists to seek alternatives. Pheromones and hormones to attract or repel insects and using natural enemies or sterilization by radiation have been suggested. 

Dumping of solid wastes 

In general, solid waste includes garbage, domestic refuse and discarded solid materials such as those from commercial, industrial and agricultural operations. They contain increasing amounts of paper, cardboards, plastics, glass, old construction material, packaging material and toxic or otherwise hazardous substances. Since a significant amount of urban solid waste tends to be paper and food waste, the majority is recyclable or biodegradable in landfills. Similarly, most agricultural waste is recycled and mining waste is left on site.  

The portion of solid waste that is hazardous such as oils, battery metals, heavy metals from smelting industries and organic solvents are the ones we have to pay particular attention to. These can in the long run, get deposited to the soils of the surrounding area and pollute them by altering their chemical and biological properties. They also contaminate drinking water aquifer sources. More than 90% of hazardous waste is produced by chemical, petroleum and metal-related industries and small businesses such as dry cleaners and gas stations contribute as well.  

Solid Waste disposal was brought to the forefront of public attention by the notorious Love Canal case in USA in 1978. Toxic chemicals leached from oozing storage drums into the soil underneath homes, causing an unusually large number of birth defects, cancers and respiratory, nervous and kidney diseases. 

Deforestation 

Soil Erosion occurs when the weathered soil particles are dislodged and carried away by wind or water. Deforestation, agricultural development, temperature extremes, precipitation including acid rain, and human activities contribute to this erosion. Humans speed up this process by construction, mining, cutting of timber, over cropping and overgrazing. It results in floods and cause soil erosion.  

Forests and grasslands are an excellent binding material that keeps the soil intact and healthy. They support many habitats and ecosystems, which provide innumerable feeding pathways or food chains to all species. Their loss would threaten food chains and the survival of many species. During the past few years quite a lot of vast green land has been converted into deserts. The precious rain forest habitats of South America, tropical Asia and Africa are coming under pressure of population growth and development (especially timber, construction and agriculture). Many scientists believe that a wealth of medicinal substances including a cure for cancer and aids, lie in these forests. Deforestation is slowly destroying the most productive flora and fauna areas in the world, which also form vast tracts of a very valuable sink for CO2. 

Pollution Due to Urbanisation Pollution of surface soils: 

Urban activities generate large quantities of city wastes including several Biodegradable materials (like vegetables, animal wastes, papers, wooden pieces, carcasses, plant twigs, leaves, cloth wastes as well as sweepings) and many non-biodegradable materials (such as plastic bags, plastic bottles, plastic wastes, glass bottles, glass pieces, stone / cement pieces). On a rough estimate Indian cities are producing solid city wastes to the tune of 50,000 - 80,000 metric tons every day. If left uncollected and decomposed, they are a cause of several problems such as  • Clogging of drains:  

Causing serious drainage problems including the burst / leakage of drainage lines leading to health problems.  

• Barrier to movement of water:  

Solid wastes have seriously damaged the normal movement of water thus creating problem of inundation, damage to foundation of buildings as well as public health hazards.  

• Foul smell:  

Generated by dumping the wastes at a place.  

• Increased microbial activities: Microbial decomposition of organic wastes generate large quantities of methane besides many chemicals to pollute the soil and water flowing on its surface  

• When such solid wastes are hospital wastes they create many health problems:  

As they may have dangerous pathogen within them besides dangerous medicines, injections.  Pollution of Underground Soil 

Underground soil in cities is likely to be polluted by  

• Chemicals released by industrial wastes and industrial wastes  

• Decomposed and partially decomposed materials of sanitary wastes  

Many dangerous chemicals like cadmium, chromium, lead, arsenic, selenium products are likely to be deposited in underground soil. Similarly underground soil polluted by sanitary wastes generate many harmful chemicals.These can damage the normal activities and ecological balance in the underground soil Causes in brief: 

• Polluted water discharged from factories  

• Runoff from pollutants (paint, chemicals, rotting organic material) leaching out of landfill  

• Oil and petroleum leaks from vehicles washed off the road by the rain into the surrounding habitat  

• Chemical fertilizer runoff from farms and crops  

• Acid rain (fumes from factories mixing with rain)  

• Sewage discharged into rivers instead of being treated properly  

• Over application of pesticides and fertilizers  

• Purposeful injection into groundwater as a disposal method  

• Interconnections between aquifers during drilling (poor technique)  

• Septic tank seepage  

• Lagoon seepage  

• Sanitary/hazardous landfill seepage  

• Cemeteries  

• Scrap yards (waste oil and chemical drainage)  

• Leaks from sanitary sewers  

Effects of Soil Pollution 

Agricultural 

• Reduced soil fertility  

• Reduced nitrogen fixation  

• Increased erodibility  

• Larger loss of soil and nutrients  

• Deposition of silt in tanks and reservoirs  

• Reduced crop yield  

• Imbalance in soil fauna and flora Industrial  

• Dangerous chemicals entering underground water  

• Ecological imbalance  

• Release of pollutant gases  

• Release of radioactive rays causing health problems  

• Increased salinity  

• Reduced vegetation Urban 

• Clogging of drains  

• Inundation of areas  

• Public health problems  

• Pollution of drinking water sources  

• Foul smell and release of gases  

• Waste management problems 

Environmental Long Term Effects of Soil Pollution 

When it comes to the environment itself, the toll of contaminated soil is even direr. Soil that has been contaminated should no longer be used to grow food, because the chemicals can leech into the food and harm people who eat it. If contaminated soil is used to grow food, the land will usually produce lower yields than it would if it were not contaminated. This, in turn, can cause even more harm because a lack of plants on the soil will cause more erosion, spreading the contaminants onto land that might not have been tainted before.  

In addition, the pollutants will change the makeup of the soil and the types of microorganisms that will live in it. If certain organisms die off in the area, the larger predator animals will also have to move away or die because they've lost their food supply. Thus it's possible for soil pollution to change whole ecosystems  Effects of soil pollution in brief: •  

Pollution runs off into rivers and kills the fish, plants and other aquatic life  

• crops and fodder grown on polluted soil may pass the pollutants on to the consumers  

• polluted soil may no longer grow crops and fodder  

• Soil structure is damaged (clay ionic structure impaired)  

• corrosion of foundations and pipelines  

• impairs soil stability  

• may release vapours and hydrocarbon into buildings and cellars  

• may create toxic dusts • may poison children playing in the area Control of soil pollution 

The following steps have been suggested to control soil pollution. To help prevent soil erosion, we can limit construction in sensitive area. In general we would need less fertilizer and fewer pesticides if we could all adopt the three R's: Reduce, Reuse, and Recycle. This would give us less solid waste. 

Reducing chemical fertilizer and pesticide use 

Applying bio-fertilizers and manures can reduce chemical fertilizer and pesticide use. Biological methods of pest control can also reduce the use of pesticides and thereby minimize soil pollution. 

Reusing of materials  

Materials such as glass containers, plastic bags, paper, cloth etc. can be reused at domestic levels rather than being disposed, reducing solid waste pollution. Recycling and recovery of materials 

This is a reasonable solution for reducing soil pollution. Materials such as paper, some kinds of plastics and glass can and are being recycled. This decreases the volume of refuse and helps in the conservation of natural resources. For example, recovery of one tonne of paper can save 17 trees. 

Reforesting 

Control of land loss and soil erosion can be attempted through restoring forest and grass cover to check wastelands, soil erosion and floods. Crop rotation or mixed cropping can improve the fertility of the land. Solid waste treatment 

Proper methods should be adopted for management of solid waste disposal. Industrial wastes can be treated physically, chemically and biologically until they are less hazardous. Acidic and alkaline wastes should be first neutralized; the insoluble material if biodegradable should be allowed to degrade under controlled conditions before being disposed. 

As a last resort, new areas for storage of hazardous waste should be investigated such as deep well injection and more secure landfills. Burying the waste in locations situated away from residential areas is the simplest and most widely used technique of solid waste management. Environmental and aesthetic considerations must be taken into consideration before selecting the dumping sites.  

Incineration of other wastes is expensive and leaves a huge residue and adds to air pollution. Pyrolysis is a process of combustion in absence of oxygen or the material burnt under controlled atmosphere of oxygen. It is an alternative to incineration. The gas and liquid thus obtained can be used as fuels. Pyrolysis of carbonaceous wastes like firewood, coconut, palm waste, corn combs, cashew shell, rice husk paddy straw and saw dust, yields charcoal along with products like tar, methyl alcohol, acetic acid, acetone and a fuel gas. 

Anaerobic/aerobic decomposition of biodegradable municipal and domestic waste is also being done and gives organic manure. Cow dung which releases methane into the atmosphere, should be processed further in 'gobar gas plants' to produce 'gobar gas' and good manure.  

Natural land pollution: 

Land pollution occurs massively during earth quakes, landslides, hurricanes and floods. All cause hard to clean mess, which is expensive to clean, and may sometimes take years to restore the affected area. These kinds of natural disasters are not only a problem in that they cause pollution but also because they leave many victims homeless. 

 

Nitrogen Cycle Definition 

“Nitrogen Cycle is a biogeochemical process which transforms the inert nitrogen present in the atmosphere to a more usable form for living organisms.”  

Furthermore, nitrogen is a key nutrient element for plants. However, the abundant nitrogen in the atmosphere cannot be used directly by plants or animals. Read on to explore how the Nitrogen cycle makes usable nitrogen available to plants and other living organisms.  

What is Nitrogen Cycle?  

Nitrogen Cycle is a biogeochemical process through which nitrogen is converted into many forms, consecutively passing from the atmosphere to the soil to organism and back into the atmosphere. It involves several processes such as nitrogen fixation, nitrification, denitrification, decay and putrefaction. 

The nitrogen gas exists in both organic and inorganic forms. Organic nitrogen exists in living organisms, and they get passed through the food chain by the consumption of other living organisms.  

Inorganic forms of nitrogen are found in abundance in the atmosphere. This nitrogen is made available to plants by symbiotic bacteria which can convert the inert nitrogen into a usable form – such as nitrites and nitrates.  

Nitrogen undergoes various types of transformation to maintain a balance in the ecosystem. Furthermore, this process extends to various biomes, with the marine nitrogen cycle being one of the most complicated biogeochemical cycles. 

Stages of Nitrogen Cycle 

Process of Nitrogen Cycle consists of the following steps – Nitrogen fixation, Nitrification, Assimilation, Ammonification, and Denitrification. These processes take place in several stages and are explained below:  

Nitrogen fixation  

It is the initial step of the nitrogen cycle. Here, Atmospheric nitrogen (N2) which is primarily available in an inert form, is converted into the usable form -ammonia (NH3).  

During the process of Nitrogen fixation, the inert form of nitrogen gas is deposited into soils from the atmosphere and surface waters, mainly through precipitation. Later, the nitrogen undergoes a set of changes, in which two nitrogen atoms get separated and combines with hydrogen to form ammonia (NH4+).  

The entire process of Nitrogen fixation is completed by symbiotic bacteria which are known as Diazotrophs. Azotobacter and Rhizobium also have a major role in this process. These bacteria consist of a nitrogenase enzyme which has the capability to combine gaseous nitrogen with hydrogen to form ammonia.  

Nitrogen fixation can occur either by the atmospheric fixation- which involves lightening or industrial fixation by manufacturing ammonia under high temperature and pressure condition. This can also be fixed through man-made processes, primarily industrial processes that create ammonia and nitrogen-rich fertilizers. Types of Nitrogen Fixation 

1. Atmospheric fixation:  

A natural phenomenon where the energy of lightning breaks the nitrogen into nitrogen oxides and is then used plants.  

2. Industrial nitrogen fixation: Is a man-made alternative that aids in nitrogen fixation by the use of ammonia. Ammonia is produced by the direct combination of nitrogen and hydrogen, and later, it is converted into various fertilisers such as urea.  

3. Biological nitrogen fixation: We already know that nitrogen is not usable directly from the air for plants and animals. Bacteria like Rhizobium and blue-green algae transform the unusable form of nitrogen into other compounds that are more readily usable. These nitrogen compounds get fixed in the soil by these microbes.  Nitrification 

In this process, the ammonia is converted into nitrate by the presence of bacteria in the soil. Nitrites are formed by the oxidation of Ammonia with the help of Nitrosomonas bacterium species. Later, the produced nitrites are converted into nitrates by Nitrobacter. This conversion is very important as ammonia gas is toxic for plants. The reaction involved in the process of Nitrification is as follows: 

2NH4+ + 3O2 → 2NO2– + 4H+ + 2H2O 

2NO2– + O2 → 2NO3– Assimilation  

Primary producers – plants take in the nitrogen compounds from the soil with the help of their roots, which are available in the form of ammonia, nitrite ions, nitrate ions or ammonium ions and are used in the formation of the plant and animal proteins. This way, it enters the food web when the primary consumers eat the plants.  

Ammonification  

When plants or animal die, the nitrogen present in the organic matter is released back into the soil. The decomposers, namely bacteria or fungi present in the soil, convert the organic matter back into ammonium. This process of decomposition produces ammonia which is further used for other biological processes.  

Denitrification  

Denitrification is the process in which the nitrogen compounds makes its way back into the atmosphere by converting nitrate (NO3-) into gaseous nitrogen (N). This process of the nitrogen cycle is the final stage and occurs in the absence of oxygen. Denitrification is carried out by the denitrifying bacterial species- Clostridium and Pseudomonas, which will process nitrate to gain oxygen and gives out free nitrogen gas as a byproduct. 

Nitrogen Cycle in Marine Ecosystem  

The process of the nitrogen cycle occurs in the same manner in the marine ecosystem as in the terrestrial ecosystem. The only difference is that it is carried out by marine bacteria.  

The nitrogen-containing compounds that fall into the ocean as sediments get compressed over long periods and form sedimentary rock. Due to the geological uplift, these sedimentary rocks move to land. Initially, it was not known that these nitrogen-containing sedimentary rocks are an essential source of nitrogen. But, recent researches have proved that the nitrogen from these rocks is released into the plants due to the weathering of rocks.  

Importance of Nitrogen Cycle Importance of the nitrogen cycle are as follows:  

1. Helps plants to synthesize chlorophyll from the nitrogen compounds.  

2. Helps in converting inert nitrogen gas into a usable form for the plants through the biochemical process. 

3. In the process of ammonification, the bacteria help in decomposing the animal and plant matter, which indirectly helps to clean up the environment.  

4. Nitrates and nitrites are released into the soil, which helps in enriching the soil with necessary nutrients required for cultivation.  

5. Nitrogen is an integral component of the cell, and it forms many crucial compounds and important biomolecules.  

Nitrogen is also cycled by human activities such as combustion of fuels and the use of nitrogen fertilizers. These processes increase the levels of nitrogen-containing compounds in the atmosphere. The fertilizers containing nitrogen are washed away in lakes and rivers and results in eutrophication.  

Conclusion  

• Nitrogen is abundant in the atmosphere, but it is unusable to plants or animals unless it is converted into nitrogen compounds.  

• Nitrogen-fixing bacteria play a crucial role in fixing the atmospheric nitrogen into nitrogen compounds that can be used by the plants.  

• The plants absorb the usable nitrogen compounds from the soil through their roots. Then, these nitrogen compounds are used for the production of proteins and other compounds in the cell.  

• Animals assimilate nitrogen by consuming these plants or other animals that contain nitrogen. Humans consume proteins from these plants and animals, and then, the nitrogen assimilates into our system.  

• During the final stages of the nitrogen cycle, bacteria and fungi help decompose organic matter, where the nitrogenous compounds get dissolved into the soil which is again used by the plants.  

• Some bacteria then convert these nitrogenous compounds in the soil and turn it into nitrogen gas. Eventually, it goes back to the atmosphere.  

• These set of processes repeat continuously and thus maintain the percentage of nitrogen in the atmosphere.   The carbon cycle 

 The movement of carbon from one area to another is the basis for the carbon cycle.   

 Carbon is important for all life on Earth.  

 All living things are made up of carbon.   

 Carbon is produced by both natural and human-made (anthropogenic) sources. 

 

Natural sources of carbon 

 Carbon is found in the atmosphere mostly as carbon dioxide.  Animal and plant respiration place carbon into the atmosphere.  When you exhale, you are placing carbon dioxide into the atmosphere.  

 Carbon is found in the lithosphere in the form of carbonate rocks. Carbonate rocks came from ancient marine plankton that sunk to the bottom of the ocean hundreds of millions of years ago that were then exposed to heat and pressure.    

 Carbon is also found in fossil fuels, such as petroleum (crude oil), coal, and natural gas.    

 Carbon is also found in soil from dead and decaying animals and animal waste.  

 Carbon is found in the biosphere stored in plants and trees. Plants use carbon dioxide from the atmosphere to make the building blocks of food during photosynthesis.  

 Carbon is found in the hydrosphere dissolved in ocean water and lakes.    

 Carbon is used by many organisms to produce shells. Marine plants use carbon for photosynthesis. The organic matter that is produced becomes food in the aquatic ecosystem. 

Natural Carbon Releases into the Atmosphere  

 Carbon is released into the atmosphere from both natural and man-made causes. Here are examples to how nature places carbon into the atmosphere.    

 Gases containing carbon move between the ocean’s surface and the atmosphere through a process called diffusion.  

 Volcanic activity is a source of carbon into the atmosphere. 

How Do Humans Place Carbon in the Atmosphere? Humans place carbon into the atmosphere in a variety of ways.   

   

Deforestation.  When we cut down trees and forests, they can no longer remove carbon dioxide from the air.  This results in additional carbon dioxide placed in the atmosphere.  

Wood burning. When we burn wood, the carbon stored in the trees becomes carbon dioxide and enters the atmosphere.  

Combustion of fossil fuels. We extract fossils fuels (coal, oil, and natural gas) from the ground and burn them for energy at power plants.  The burning of fossil fuels is called combustion. Fossil fuel combustion releases carbon dioxide into the atmosphere.    

How Much Carbon Is in the Atmosphere?   

Climate scientist Charles Keeling measured atmospheric carbon dioxide levels between 1958-2005  at the Mauna Loa Observatory on the northern slopes of Earth’s largest volcano in Hawaii.  His data,  shown below, show the steady increase of carbon dioxide levels in the atmosphere. 

 

How Much Carbon Do Humans Emit?   

Nature absorbs 788 billion tonnes of carbon every year. Natural absorptions roughly balance natural emissions.  Humans upset this balance. While some of our human-produced carbon dioxide emissions are being absorbed by the ocean and land plants, around half of our carbon dioxide emissions remain in the air.