by Chris Woodford. Last updated: February 2, 2018.
What's beneath your feet? Maybe a wooden floor or a stone one... and, beneath that? Brick foundations, water pipes, power cables... and who knows what else. Keep going down and you'll come to soil, rocks, and the raw stuff of Earth. We imagine these basic foundations of our planet to be a kind of pristine, internal wilderness—but often that's far from the case. While we can see many of the changes we've made to the world, some of our impacts are virtually invisible, and land pollution is a good example. You might see factory smoke rising through the air or oil slicks drifting over the ocean, but you can't easily see the poisons that seep from underground mines, the garbage we tip into landfills by the truckload, or the way the very soil that feeds us is turning slowing to dust. Land pollution, in short, is a much bigger and more subtle problem than it might appear. How does it occur and what can we do about it? Let's take a closer look!
Photo: Mining is a major cause of land pollution. It's easy to point the finger at mine operators, but we all rely on fuels, metals, and other minerals that come from the ground, so we're all partly responsible for the damage that mining does. Photo by David Parsons courtesy of US DOE/NREL (US Department of Energy/National Renewable Energy Laboratory).
What is land pollution?
If you've read our articles on water pollution and air pollution, you'll know that pollution can be defined generally along these lines: it's the introduction into the environment of substances that don't normally belong there, which, in great enough concentrations, can have harmful effects on plants, animals, and humans. We can define land pollution either narrowly or broadly. Narrowly defined, it's another term for soil contamination (for example, by factory chemicals or sewage and other wastewater). In this article, we'll define it more widely to include garbage and industrial waste, agricultural pesticides and fertilizers, impacts from mining and other forms of industry, the unwanted consequences of urbanization, and the systematic destruction of soil through over-intensive agriculture; we'll take land pollution to mean any kind of long-term land damage, destruction, degradation, or loss.
Causes of land pollution
There are many different ways of permanently changing the land, from soil contamination (poisoning by chemicals or waste) to general urbanization (the systematic creation of cities and other human settlements from greenfield, virgin land). Some, such as huge landfills or quarries, are very obvious; others, such as atmospheric deposition (where land becomes contaminated when air pollution falls onto it) are much less apparent. Let's consider the main causes and types of land pollution in turn.
Humans produce vast quantities of waste—in factories and offices, in our homes and schools, and in such unlikely places as hospitals. Even the most sophisticated waste processing plants, which use plasma torches (electrically controlled "flames" at temperatures of thousands of degrees) to turn waste into gas, produce solid waste products that have to be disposed of somehow. There's simply no getting away from waste: our ultimate fate as humans is to die and become waste products that have to be burned or buried!
Chart: Although most of the waste we produce is relatively harmless and easy to dispose of (blue), around one fifth of it (orange, yellow, and green) is dangerous or toxic and extremely difficult to get rid of without automatically contaminating land.
Waste disposal didn't always mean land pollution. Before the 20th century, most of the materials people used were completely natural (produced from either plants, animals, or minerals found in the Earth) so, when they were disposed of, the waste products they generated were natural and harmless too: mostly organic (carbon-based) materials that would simply biodegrade (break down eventually into soil-like compost). There was really nothing we could put into the Earth that was more harmful than anything we'd taken from it in the first place. But during the 20th century, the development of plastics (polymers generally made in chemical plants from petroleum and other chemicals), composites (made by combining two or more other materials), and other synthetic (human-created) materials has produced a new generation of unnatural materials that the natural environment has no idea how to break down. It can take 500 years for a plastic bottle to biodegrade, for example. And while it's easy enough to recycle simple things such as cardboard boxes or steel cans, it's much harder to do the same thing with computer circuit boards made from dozens of different electronic components, themselves made from countless metals and other chemicals, all tightly bonded together and almost impossible to dismantle.
Nothing illustrates the problem of waste disposal more clearly than radioactive waste. When scientists discovered how to create energy by splitting atoms in nuclear power plants, they also created the world's hardest waste disposal problem. Nuclear plants produce toxic waste that can remain dangerously radioactive for thousands of years and, what's worse, will contaminate anything or anyone that comes into contact with it. Nuclear plants that have suffered catastrophic accidents (including the Chernobyl plant in the Ukraine, which exploded in 1986, and the Fukushima plant in Japan, which was damaged by an earthquake in 2011) are generally sealed with concrete and abandoned indefinitely. Not surprisingly, local communities object vociferously to having nuclear waste stored anywhere near them.
Photo: The world's biggest copper mine, Escondida Mine in Chile, is so big you can even see the scar on the landscape from space. But we all use copper (it's in the computer you're using right now) so is this actual "land pollution" or just very necessary land use? Photo by NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team courtesy of NASA Goddard Space Flight Center (NASA-GSFC).
Although there are many responsible mining companies, and environmental laws now tightly restrict mining in some countries, mines remain among the most obvious scars on (and under) the landscape. Surface mining (sometimes called quarrying or opencast mining) requires the removal of topsoil (the fertile layer of soil and organic matter that is particularly valuable for agriculture) to get at the valuable rocks below. Even if the destruction of topsoil is the worst that happens, it can turn a productive landscape into a barren one, which is a kind of pollution. You might think a mine would only remove things from the land, causing little or no pollution, but mining isn't so simple. Most metals, for example, occur in rocky mixtures called ores, from which the valuable elements have to be extracted by chemical, electrical, or other processes. That leaves behind waste products and the chemicals used to process them, which historically were simply dumped back on the land. Since all the waste was left in one place, the concentration of pollution often became dangerously high. When mines were completely worked out, all that was left behind was contaminated land that couldn't be used for any other purpose. Often old mines have been used as landfills, adding the insult of an inverted garbage mountain to the injury of the original damage. But at least it saved damaging more land elsewhere.
Humans have been making permanent settlements for at least 10,000 years and, short of some major accident or natural disaster, most of the cities and towns we've created, and the infrastructure that keeps them running, will remain with us for thousands more years into the future. Not many of us would automatically classify cities and other human settlements as "land pollution"; people obviously need to live and work somewhere. Even so, urbanization marks a hugely important change to the landscape that can cause land pollution in a variety of subtle and not-so-subtle ways.
With over 7 billion people on the planet, it might come as a surprise to find that humans have urbanized only about 3 percent of Earth's total land surface , though almost a third of the total land area has been transformed if we include agriculture . Our impact on the planet extends much further than urbanization might suggest. In 1996, Herbert Girardet estimated that London, England has an ecological footprint (area of land needed to support it) some 125 times bigger than the city itself . Add up that effect for every major city in the world and you get an idea of how big an impact urbanization has had.
One of the problems of urbanization is that, by concentrating people, it concentrates their waste products at the same time. So, for example, crudely disposing of sewage from a big city automatically creates water or land pollution, where the same number of people and the same volume of sewage might not create a problem if it were created in 10 smaller cities or 100 small towns. Concentration is always a key factor when we talk about pollution. Having said that, it's important to remember that urbanization, when it works, can also help people to live very efficiently. Thus, New York has the lowest ecological footprint of any state in the USA, largely because people there have smaller homes and make greater use of public transportation .
Photo: Greenfield to brownfield: This once-green field will soon be a large housing estate. People need homes to live in, but they also need green spaces—and agricultural land to feed them.
Those of us who are lucky enough to live in rich countries take our basic survival for granted: aside from trips to the grocery store, we don't worry about where our food comes from or how it gets to us. The reality is that seven billion hungry people consume a vast amount of food. Feeding the world on such a scale is only possible because agriculture now works in an industrial way, with giant machines such as tractors and combine harvesters doing the work that hundreds of people would have done in the past, and chemicals such as fertilizers and pesticides (herbicides that kill weeds and insecticides that kill bugs) increasing the amount of food that can be grown on each piece of land. Unfortunately, most pesticides are by definition poisons, and many remain in the soil or accumulate there for years. One infamous and now widely banned pesticide, DDT, is not ordinarily biodegradable so it has remained in the environment ever since it was first used in the mid-20th century and even spread to such places as Antarctica . DDT is just one of many organic (carbon-based) chemicals that remain in the environment for years or decades, known as persistent organic pollutants.
Air pollution doesn't remain air pollution forever. Ideally it disperses, so the concentration of problematic chemicals becomes so low that it no longer constitutes pollution. Sometimes, though, it falls back to the ground and becomes either water pollution (if it enters the oceans, rivers, and lakes) or land pollution. Pollution created ("deposited") in water or land from existing pollution in the air (atmosphere) is known as atmospheric deposition. Land can become polluted by deposition in some very unexpected ways. For example, a corridor of land either side of a highway or freeway becomes systematically polluted over time with all kinds of harmful byproducts of road travel—everything from fuel spills and brake linings to dust worn from the pavement and heavy metal deposits (such as lead) washed from the engines. These chemicals accumulate in the soil where they can undergo reactions with one another and form substances that are even more toxic .
Two important things are worth noting about atmospheric deposition. First, it means no land on Earth—not even the most isolated island—can be considered completely safe from pollution: even if it's hundreds or thousand miles from the nearest factory or human settlement, even if no human has ever lived there, it could still be polluted from the air. Second, if you're doing something that causes pollution (maybe spreading weedkiller on your garden or perhaps running a factory where ash is discharged from a smokestack), the effects are not necessarily going to be confined to the place where the pollution is first produced. It's important to remember that pollution knows no boundaries.
Photo: Soil erosion turns fields into deserts. Photo by Jack Dykinga courtesy of US Department of Agriculture/Agricultural Research Service (USDA/ARS).
If you define "land pollution" as irreversible damage to the land, you have to include soil erosion as a type of pollution too. Many people think soil is soil, always there, never changing, ever ready to grow whatever crops we choose to bury in it. In reality, soil is a much more complex growing habitat that remains productive only when it is cared for and nurtured. Too much wind or water, destruction of soil structure by excessive plowing, excessive nutrients, overgrazing, and overproduction of crops erode soil, damaging its structure and drastically reducing its productivity until it's little more than dust. At its worst, soil erosion becomes desertification: once-productive agricultural areas become barren, useless deserts. How serious is the problem? In 2001, former UN Secretary General Kofi Annan warned the world that: "Drought and desertification threaten the livelihood of over 1 billion people in more than 110 countries around the world." . Deforestation doesn't only harm the place where the trees are cut down. A 2013 study by Princeton University researchers found that if the Amazon rainforest were completely destroyed, it would have a dramatic effect on the atmosphere, which would carry across to places like the United States, causing drought and potentially desertification there as well .
Unfortunately, because soil erosion has so far affected developing countries more than the developed world, it's a problem that receives relatively little attention. Accelerating climate change will soon alter that. In a future of hotter weather and more intense storms, it will become increasingly difficult to maintain soil in a fertile and productive state, while heavy rainstorms and flash floods will wash away topsoil more readily. Meanwhile, agriculture may become impossible in coastal areas inundated by saltwater carried in by rising sea levels. We might think of global warming as an example of air pollution (because it's caused mostly by humans releasing gases such as carbon dioxide into the atmosphere). But if it leads to dramatic sea-level rise and coastal erosion, you could argue that it will become an example of land pollution as well.
Effects of land pollution
With luck and the right atmospheric conditions, air and water pollution disperse and disappear. What makes land pollution such a problem is that land is static, so land pollution stays exactly where it is until and unless someone cleans it up. Land that's polluted stays polluted; land that's urbanized almost invariably stays urbanized. As we've already see, plastics take hundreds of years to disappear while radiation can contaminate land for ten times longer. That means landfill sites and radioactive waste dumps remain that way pretty much indefinitely.
The simplest effect of land pollution is that it takes land out of circulation. The more land we use up, the less we have remaining. That might not sound a problem where there's plenty of land in rural areas, but it's certainly a concern where productive agricultural land is concerned, especially as the world's population continues to increase. The biggest problem comes when contaminated land is returned to use, either as building or agricultural land. Houses might be built on brownfield (former industrial) sites that haven't been cleaned up properly, putting future owners and their families at risk. Or people might get their water from rivers supplied by groundwater contaminated by landfill sites, mine workings, or otherwise polluted land some distance away. Illnesses such as cancer develop over years or decades for a variety of reasons and it's extremely difficult to prove that they've been caused by something like local environmental pollution, especially when people move homes during their lifetime. No-one knows how much land is contaminated, how contamination varies from one place to another, or how land contaminants react with one another once they enter watercourses and become water pollution. So the scale of the problem and its ultimate effects are impossible to determine.
However, we do know what effect individual pollutants have. We know, for example, that lead is a toxic heavy metal that has all kinds of unpleasant effects on human health; it's been implicated in developmental deficits (such as reductions in intelligence) in children . We know that some chemicals are carcinogenic (cancer-causing)  while others cause congenital defects such as heart disease . At the very least, it seems prudent not to introduce dangerous chemicals, such as persistent organic pollutants, into the environment where they may mat harm people's health for many years into the future.
Why does land pollution matter? Although Earth might seem a pretty big place, only about a third of its surface is covered in land, and there are now over seven billion people trying to survive here. Most of our energy (around 85 percent worldwide ) still comes from fossil fuels buried under the ground and, since we haven't yet figured out how to mine in space, so do all our minerals. Much of our food is grown on the surface of the planet; the water we need comes from the planet's surface too or from rocks buried just underground. In short, our lives are as intimately tied to the surface of Earth as the plants that grow from the ground. Anything that degrades, damages, or destroys the land ultimately has an impact on human life and may threaten our very ability to survive. That's why we need solutions to the problem.
What kind of solutions? Ideally, we'd look at every aspect of land pollution in turn and try to find a way of either stopping it or reducing it. With problems like waste disposal, solutions are relatively simple. We know that recycling that can dramatically reduce the need for sending waste to landfills; it also reduces the need for incineration, which can produce "fly ash" (toxic airborne dust) that blows may miles until it falls back to land or water. We'll always need mines but, again, recycling of old materials can reduce our need for new ones. In some countries, it's now commonplace to require mine operators to clean-up mines and restore the landscape after they've finished working them; sometimes mine owners even have to file financial bonds to ensure they have the money in place to do this. Greater interest in organic food and farming might, one day, lead to a reduction in the use of harmful agricultural chemicals, but that's unlikely to happen anytime soon. Even so, public concerns about food and chemical safety have led to the withdrawal of the more harmful pesticides—in some countries, at least. Meanwhile, international efforts, such as the United Nations Convention to Combat Desertification, are helping to focus attention on major problems like soil erosion.
Ideally, we don't just need to stop polluting land: we also need to clean up the many contaminated sites that already exist. Many former nuclear sites have already been cleaned up as much as possible; in the UK, for example, the Nuclear Decommissioning Authority is currently spending around £117 billion ($146,000 million) to clean up 17 former nuclear sites—and the figure keeps on rising . In the United States, a program called the Superfund has been decontaminating hundreds of polluted sites since 1980. Where sites can't be completely restored, it's possible to "recycle" them and benefit the environment in other ways; for example, a number of contaminated sites and former mines in the United States have now become wind farms or sites for large areas of solar panels.
New technologies will almost certainly make it easier to "recycle" polluted land in future. For example, the relatively new form of waste disposal called plasma gasification makes it possible to "mine" former landfills, converting the old waste into an energy-rich gas and a relatively safe solid waste that can be used as a building material. Bioremediation is another very promising land-cleaning technology, in which microbes of various kinds eat and digest waste and turn it into safer end-products; phytoremediation is a similar concept but involves using plants, such as willow trees, to pull contaminants from the soil.
All these things offer hope for a better future—a future where we value the environment more, damage the land less—and realize, finally, that Earth itself is a limited and precious resource.
Photo: Bioremediation. Thankfully, microorganisms don't mind tackling the kind of waste we'd prefer to dump and ignore. Here, scientists at Oak Ridge National Laboratory in Tennessee are testing whether soils contaminated with toxic chemicals such as PCBs (polychlorinated biphenyls) can be cleaned up by bacteria. Photo courtesy of US Department of Energy.
Find out more
On this website
On other websites
- One fifth of China's farmland polluted by Jennifer Duggan. The Guardian, April 14, 2014.
- Likely Spread of Deserts to Fertile Land Requires Quick Response, U.N. Report Says by Elisabeth Rosenthal. The New York Times, June 28, 2007.
- Soil erosion as big a problem as global warming, say scientists by Tim Radford, The Guardian, February 14, 2004.
- Illness linked to contaminated land: BBC News, 23 June 2003. Can we ever truly know the health impacts linked with polluted land?
- Poisoned chalice: Cost-cutting over contaminated land sites for new schools could be putting lives at risk by Paul Humphries, The Guardian, Tuesday 22 October 2002. Are schoolchildren among those most at risk from contaminated land?
- New York Times: Superfund articles: A chronological list of stories covering the Superfund and land cleanup issues in the United States.
For adults and older readers
For younger readers
- Earth Matters by Lynn Dicks et al. Dorling Kindersley, 2008. A multi-award-winning book that takes us on a biome-by-biome tour of the world. Best for ages 8–10.
Clicking on the upward arrows will take you back to your place (where each item is referenced in the main text).
- [↑] The Growing Urbanization of the World: The Earth Institute at Columbia University, News Archive, 8 March 2005.
- [↑] Domesticating the World: Conversion of Natural Ecosystems by Gregory Mock, World Resources 2000–2001, World Resources Institute, September 2000. [Via Web Archive]
- [↑] The Gaia Atlas of Cities: New Directions for Sustainable Urban Living by Herbert Girardet. UN-HABITAT, 26 Apr 1996. See p24: "The footprint of cities".
- [↑] Why New York Has the Smallest Ecological Footprint of Any State by Vincent Pellecchia, TSTC Blog, July 20, 2015.
- [↑] Melting Glaciers: A Probable Source of DDT to the Antarctic Marine Ecosystem by Heidi N.Geisz et al, Environ. Sci. Technol., 2008, 42 (11), pp 3958–3962.
- [↑] See numerous publications on highway runoff by Professor Neil Ward and collaborators, University of Surrey.
- [↑] Secretary-general, in message on world day to combat desertification, warns livelihood of 1 billion people in 110 countries threatened: UN Convention to Combat Desertification, News Release, 7 June 2001. [Via Web Archive]
- [↑] If a tree falls in Brazil...? Amazon deforestation could mean droughts for western U.S. by Morgan Kelly, News at Princeton, 7 November 2013.
- [↑] Lead: U.S. Department of Labor, Occupational Safety & Health Administration. A good starting point if you want to find out about the health effects of lead.
- [↑] See Living Downstream: An Ecologist's Personal Investigation of Cancer and the Environment by Sandra Steingraber (Da Capo Press, 2010) for a lengthy discussion of this topic.
- [↑] See for example Effects of Environmental Exposures on the Cardiovascular System: Prenatal Period Through Adolescence by Suzanne M. Mone, et al. Pediatrics, April 2004, Volume 113, Issue Supplement 3y, May 1, 2011; and Chemical found in crude oil linked to congenital heart disease: Fetal exposure to solvents may damage heart: Science Daily, May 1, 2011.
- [↑] The BP Statistical Review of World Energy 2016 quotes fossil fuels accounting for ~85 percent of world primary energy consumption.
- [↑] The current estimated cleanup cost is £117 billion according to a UK Government Nuclear Decommissioning Authority estimate published in September 2016. That's a significant increase on previous estimates, including the £73 billion quoted in 2008 (see Nuclear clean-up costs 'to soar' by David Shukman, BBC News, 27 May 2008) and an earlier estimate of just £12 billion.
- [↑] US EPA: Success Stories and Case Studies on Siting Renewable Energy on Contaminated Land and Mine Sites: A list of projects and sites where contaminated land has been successfully reused for wind and solar projects. [Via Web Archive]
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Essay on Water Pollution!
Water pollution may be defined as deterioration of physical, chemical and biological characteristics of water through natural and anthropogenic activities to such an extent that it becomes harmful to human beings, plants and animal communities.
1. Importance of Water
2. Sources of Water
3. Uses of Water
4. Water Pollution
5. Sources of Water Pollution
6. Types of Water Pollutants
7. General Effects of Water Pollution
8. Classification of Water Pollution
9. Water Quality Parameters and Standards
Chemically speaking, water is a simple inorganic covalent molecule. It is formed, when hydrogen is burnt in oxygen or an electric spark is passed through a mixture of hydrogen and oxygen gas in the ratio 2: 1 (Vol. to Vol.)
2 H2 + O2 → electric spark 2H2O
As regards to its physical state, it exists in three different states:
(a) Water liquid (Common water).
(b) Water solid (Ice).
(c) Water gas (Water vapour).
All these three physical states are inter-convertible and these depend upon the temperature.
1. Importance of Water:
Water is indispensible for sustenance of ail living organisms because of its several unique properties which are discussed below:
1. Universal Solvent:
Water is capable of solubilizing varieties of substances. By such a process a number of nutrients and ions can be transported into plant body.
2. Higher Specific and Latent Heat (Thermal properties):
Because of its higher specific heat, it can store a large quantity of thermal energy with a comparatively smaller rise in its own temperature. Such a storing of thermal energy is essential for the living organisms in water. Besides, it has a higher value of latent heat i.e. it requires large amount of heat for changing from ice to water and also it liberates large amount of heat for changing from water to ice.
3. Higher Viscosity:
Because of its higher viscosity, it protects the aquatic organisms against mechanical disturbances and helps the swimming and floating of living aquatic animals.
Since water is transparent, it allows the effective penetration of light whereby the submerged aquatic plants are able to photo-synthesize.
Pressure exerted by water at a particular depth modifies the shape and size of aquatic organism.
Water has this unique property which helps the aquatic organisms to float over its surface.
2. Sources of Water:
The fresh water required by man is obtained from two natural sources:
(a) Ground Water; and
(b) Surface Water.
(a) Ground Water:
Water present under the surface of the earth is known as ground water. The average magnitude of the total ground water content is about 210 billion m3 including recharge through infiltration, seepage and evapo-transpiration.
The storing of ground water takes place by the following mechanisms. The inter-molecular spaces between the soil particles are sufficient enough to allow the rain water molecules to pass through them. These water molecules get collected at different zones giving sub-surface water or ground water.
The spaces remaining in between soil particles are known as voids. Similarly, a part of the river water or streams can pass through the voids giving ground water. The ground water is usually of good quality and free from extraneous pollutions. So it can be used for drinking and for our day-to-day use.
It can be withdrawn for human consumption by the following ways:
(i) Wells (dug-well or bore-well);
(ii) Spring intake chamber; and
(iii) Infiltration galleries.
(b) Surface Water:
Water present over the surface of earth in rivers, lakes, ponds, seas and oceans is known as surface water. Water remains in solid state as ice near the poles or near the cold places where the temperature is below 00 C.
The humanity is largely dependent upon the surface water for day-to-day uses. The surface water contains a lot of pollutants, micro-organisms and mineral nutrients for the feeding of bacteria and virus. The surface water gets polluted by the run of water from agricultural Fields containing pesticides and fertilizers, soil particles, waste chemicals from industries and sewage from cities and rural areas. However, the surface water can be purified and reused.
The composition of water obtained from different sources is shown in Table 8.2.
Table 8.2: Chemical composition of ground water, river water and sea water
3. Uses of Water:
The water can be used for different purposes as mentioned below:
(i) Domestic use for drinking, cooking and cleaning, etc.
(ii) Irrigation for agriculture.
(iii) Power generation.
(iv) Industrial use for cooling, processing, cleaning, etc.
(v) For fisheries and acqua-culture.
(vi) For navigation.
(vii) Waste disposal.
4. Water Pollution:
Water is the most important constituent of the life support system because on one hand it is vital for the maintenance of all forms of life and on the other it helps in the movement, circulation and cycling of nutrients in the biosphere. Water is essential for power generation, navigation, irrigation of crops, disposal of sewage etc.
It may be noted that only one per cent of the total quantity of water of the hydrosphere is available to human beings and other biotic communities from various sources such as ground water, rivers, lakes, atmosphere and biological systems.
Coupled with population explosion, rapid industrialisation and unplanned urbanisation, are releasing a lot “of waste into water bodies thereby degrading the quality of water. Though water like other natural substances has self purifying capacity during recycling processes but when the foreign undesirable substances added to it exceed the tolerance level and self-purifying capacity of water, it gets polluted.
Thus water pollution may be defined as deterioration of physical, chemical and biological characteristics of water through natural and anthropogenic activities to such an extent that it becomes harmful to human beings, plants and animal communities. According to United States Public Health Services, water pollution means “the presence of any toxic substance in water that degrades the quality to constitute a hazard or impair its usefulness.
Water pollution may also be described as extraneous enrichment of chemicals which alter the physico-chemical environment changing the community composition and compelling some species or many species to disappear from the natural eco-system. The results of water pollution are evident whether measured by harms to the living resources or hazards to human health or reduction of immunities.
Anyway, water pollution is a global problem affecting both developed and developing countries. Human activities related with water pollution comprised mining, agriculture, stockbreeding, fisheries, urban human activities, various industries, such as manufacturing industry, domestic sewage etc.
5. Sources of Water Pollution:
Depending upon the specificity of waste discharge, the water pollution sources are categorised as:
(a) Point sources
(b) Nonpoint or diffused sources.
(a) Point sources:
Point sources are those which discharge pollutants from some specific location (such as pipeline, ditches and sewers) into water bodies.
Some common point sources of water pollution include:
(ii) Sewage treatment plants,
(iv) Hazardous waste sites;
(v) Leakage from oil storage tanks.
The pollutants from point sources are of definite identity with almost a fixed volume and composition. The level of pollution can be controlled by suitable experimental modulation.
(b) Non-point or diffused sources:
Non-point sources of water pollution are widely scattered and discharge pollutants over larger areas.
Some common nonpoint sources of water pollution are:
(i) run off from agricultural fields;
(ii) live-stock feed lots;
(iii) Storm run off from urban streets; and
(iv) parking lot and streets into surface water and seepage into ground water.
It is difficult and expensive to identify and control the discharges from non-point sources. It may be noted that major pollution involve non-point source pollution.
6. Types of Water Pollutants:
Water pollutants may be classified into the following categories:
1. On the Basis of Pollutant Sources:
Water pollutants are divided into the following classes on the basis of pollutant sources:
(a) Industrial pollutants:
Different industrial pollutants include chlorides, sulphides, carbonates, nitrites, nitrates of heavy metals such as mercury, lead, zinc, arsenic etc., organic compounds synthesized for industrial purposes, radioactive wastes etc.
(b) Agricultural pollutants:
These are chemical fertilizers pesticides, insecticides and herbicides, synthetic chemical compounds, weeds and plant remains.
(c) Urban pollutants:
These contain chemicals from automobile exhaust, chemicals from lime and chemical fertilizers used in the lawns and gardens within city, chemicals from urban sewage, household sewage etc.
(d) Natural pollutants:
The natural pollutants include volcanic dusts, sediments due to weathering and erosion, debris caused by landslide, decayed and decomposed organic matter etc.
2. On the Basis of Physical and Chemical Characteristics:
On such a basis, water pollutants are divided into two categories:
(a) Physical pollutants:
Pollutants changing the physical characteristics such as colour, taste, turbidity, sediments, oil and grease content, dissolved and suspended solid etc.
(b) Chemical pollutants:
These are chlorides, sulphites, sulphates, sulphides, carbonates, nitrates of heavy metals like mercury, lead, cadmium etc., pesticides, herbicides, insecticides and several other chemical compounds.
3. On the Basis of Degradation Nature:
On such basis, water pollutants are of two types:
(a) Degradable pollutants; and
(b) Non degradable pollutants.
(a) Degradable pollutants:
These pollutants can be broken down by biological means such as decomposers or microorganisms. Such pollutants are also known as organic pollutants, e.g. leaf litters, sewage, garbage, plants and animals.
(b) Non-degradable pollutants:
These pollutants cannot be degraded by biological means. These are also known as inorganic pollutants, e.g. chemical pollutants and solid toxic substances.
7. General Effects of Water Pollution:
Water pollution induces irreparable damage to all types of living organisms including man.
Some detrimental effects of water pollution are outlined below:
1. Polluted water is the major cause for the spreading of epidemics and several dreaded diseases like cholera, tuberculosis, jaundice, dysentery, typhoid etc.
2. The consumption of water contaminated by fibres as asbestos causes lung cancer and stomach diseases called Asbestosis.
3. The consumption of water contaminated with mercury causes Minamata disease.
4. The polluted water contaminated with toxic chemicals causes death of aquatic organisms (both plants and animals).
5. Polluted water damages crops and decreases agricultural productivity.
6. Heavily polluted water decreases soil fertility and kills soil micro-organisms.
7. Polluted water containing basic salts increases alkalinity of the soil.
8. Increase in the concentration of inorganic and organic nutrients in water bodies causes eutrophication which leads to rapid growth in population of plants and animals beyond controllable unit.
9. Contamination of sea water due to oil slicks resulting from leakage of crude oil from huge oil tankers and due to discharge of industrial and urban wastes causes ecological disasters in littoral eco-systems because of mass death of sea organisms.
8. Classification of Water Pollution:
On the basis of sources and storage of water, water pollution nay be divided into the following categories:
1. Ground water pollution;
2. River water pollution;
3. Lake water pollution; and
4. Sea water pollution.
1. Ground Water Pollution:
Ground water (which lies below the surface of earth) acts as very good reservoir by virtue of large pore space in earth materials, as a Conduit which can transport water over long distances and as a mechanical filter which improves water quality by removing suspended solids and bacterial contamination. It is the recommended source of rural domestic use which is replenished by precipitation through rain, snow, slit and hail. The composition of ground water is given in Table 5.2.
In order to meet the high demands of increasing population there is continuous and non-interrupted interactions in between humanity and environment along with release of a lot of extraneous materials (wastes). These extraneous materials (wastes) are constantly added into ground water reservoirs at an alarming rate causing the pollution of ground water. Once the ground water is polluted, it is difficult to restore the original water quality of the aquifer.
The extent of ground water pollution depends on the factors like rainfall pattern, depth of water table, distance from the source of contamination, soil properties (like structure, texture and filtration rate).
(A) Sources of Contamination of Ground Water:
Ground water is threatened with pollution from the following sources:
1. Industrial wastes:
The hazardous effluents released from industries, contain toxic heavy metals, ions and a number of organic and inorganic species. These contaminate the ground water and severely pollute it.
2. Agricultural wastes:
Excessive use of fertilizers, pesticides, insecticides, herbicides etc add a lot of chemical to ground water. Besides agricultural processing wastes and animal wastes are also significantly polluting ground water.
3. Domestic Wastes:
The primary factors responsible for deteriorating the ground water quality are pathogenic organisms, oxygen demand, nutrients and solids from domestic wastes.
4. Run-off from urban areas:
Rapid urbanisation releases a lot of effluents which contains large concentration of oils, greases, nutrients, heavy metals and detergents. The detergents being soluble can pass through the soil and pollute ground water.
5. Soluble Effluents:
Soluble effluents can easily pass through and pollute the ground water. The extent of pollution is more prominent in sandy soils and humid regions having high water table condition.
Other sources of ground water pollution may include:
(a) Earthen septic tanks;
(b) Seepage pits;
(c) Barnyard manures;
(d) Urban and rural garbage’s;
(e) Mine spills;
(f) Refuse dumps;
(g) Leaching and downward movement of pollutants.
(B) Detrimental Effects of Ground Water Pollution:
(1) Effects on human beings:
(i) Polluted ground water helps in spreading of epidemics and chronic diseases like typhoid, jaundice, dysentery, diarrhea, hepatitis etc.
(ii) Polluted ground water contaminated with toxic metals like Hg, Pb, Cd, Cr, Cu, etc. and cyanides causes stomach and skin diseases in man.
(iii) Polluted ground water contaminated with fibers (i.e., asbestos) causes fatal diseases like asbestosis and lung cancer.
(iv) Polluted ground water containing more than 0.3 ppm of iron becomes extremely harmful for drinking purpose.
(2) Effects on Plants:
(i) Polluted ground water disturbs plant metabolism severely and hence, has adverse effect on ecosystem.
(ii) Contaminated ground water increases acidity or alkalinity of the soil.
(iii) Polluted ground water decreases soil fertility by killing bacteria and micro-organisms.
(iv) Polluted ground water used for irrigation purpose severely damage crop productivity.
(C) Control of Ground Water Pollution:
The level of pollutants in ground water can be minimised by the following manner:
1. The contaminant water sources should be carefully surveyed.
2. The toxic industrial effluent should be properly treated before their disposal.
3. The location of wells for drinking water supplies should be decided with utmost caution.
4. The uppermost aquifier should not be tapped for drinking water wells.
5. The location of industrial and municipal disposal sites should be carefully selected keeping in view the ground water level and flow pattern in the area.
2. River Water Pollution:
River water is one of the forms of surface water. It usually contains ions like chloride ion
(Cl–), sulphate ion (SO2-4), sodium ion
(Na+), Magnesium ion (Ng+), Calcium ion (C 2+ a)’ Potassium ion
(K+) etc. in those areas which are free from industrial and urban influences. When concentrations of these ions exceeds their threshold values due to exogenous addition of effluents from industries, discharges of urban sewages, discharges from agricultural Fields etc. The river water gets polluted and causes a number of potential hazards to living organisms. Some Indian rivers and their major sources of pollution are given in Table 8.3.
(A) Sources of River Water Pollution:
The chief sources of river water pollutions are as follows:
1. Discharge from urban sewage water.
2. Industrial effluents carrying industrial waste water.
3. Washing and dumping of industrial solid wastes.
4. Non degradable and long lasting pollutants from tanneries.
5. Wastes from sugar factory, beet-sugar refining, meat packing, distilleries.
6. Agricultural wastes containing fertilizers, insecticides, fungicides, etc.
7. Decomposed plants and animals.
8. Radioactive materials.
9. Surface run-off.
10. Atmospheric gases.
11. Acid rain containing sulphuric acid, nitric acid etc.
The nature and extent of river water pollution depends on a number of factors, few of which may be outlined as follows:
(i) Hygienic and health situation of communities residing near river.
(ii) Physical, chemical and biological characteristics of waste water entering into river.
(iii) Vegetation, soil type and degree of weathering of rock.
(iv)Waste water disposal system and technique.
(v) Extent of internal mechanism to cause self purification.
(vi) Hydrological characteristics of diluting biocides.
River pollution takes place mainly in two ways:
(1) Through point source;
(2) Through non-point sources.
The point source includes discharge of urban sewage drains and industrial effluents at specific points into rivers. The Mon- point sources involve discharge of pollutants, mainly from agricultural fields through surface run-off.
(B) Types of River Water Pollutants:
According to U.S. Department of Heath, Education and Welfare (HEW), river water pollutants are classified into eight types:
1. Sewage and Waste:
It includes a number of chemical substances brought down by the sewage drains of urban and industrial areas.
2. Infectious agents:
These include germs and viruses which cause several diseases.
3. Plant nutrients and dissolved substances:
These are chemical fertilizers.
4. Particulate matters:
These are soil and mineral particles.
5. Mineral and Chemical substances:
These include salts, acids, alkalis, oil, grease etc.
6. Organic chemical exotics:
These include synthetic materials like pesticides, insecticides, herbicides, rodenticides etc.
7. Radio active substance.
(C) Detrimental Effects of River Water Pollution:
Same as ground water pollution.
(D) Control of River Water Pollution:
The level of pollutants in river can be minimised by adopting the following procedures:
1. The contaminant water sources should be properly surveyed.
2. The toxic industrial effluents and urban sewage wastes should be properly treated before their disposal.
3. The use of biofertilizers should be given preference over chemical fertilizers.
4. The use of pesticides, insecticides, herbicides, rodenticides etc. should be minimised.
3. Lake Water Pollution:
In addition to ground water pollution and river water pollution, water masses in different lakes are also under going pollution due to rapid industrialisation and unplanned urbanisation. The pollution of lake water also causes a number of hazards to both plants and animals including human beings.
(A) Sources of Lake Water Pollution:
The lake water is polluted by the following sources:
1. Toxic and hazardous effluents from industries.
2. Surface run off, rivulets and streams bringing inorganic nutrients from agricultural fields.
3. Waste sludge’s from factories as well as washings and dumping of tailings.
4. Siltation of lakes due to dumping of enormous quantities of sediments.
5. Discharge of organic wastes from hills and toxic effluents from urban areas.
6. Decomposed plant and animal matters.
7. Wastes from house boats, hotels and homes.
8. Illegal constructions and building materials.
9. Excess quantity of excreta from migratory birds.
10. Eutrophication: The abundance of nutrients causes uncontrolled growth of plants and animals.
11. Acid rain
(B) Detrimental Effects of Lake Water Pollution:
Same as those of ground water.
(C) Control of Lake Water Pollution:
In order to control the level of pollutants in lake water, the following preventive measures should be adopted:
1. The contaminant water sources should be properly surveyed-
2. The toxic industrial effluents and urban sewage wastes should be properly treated before their entry into lakes.
3. Visitors should be advised not to add non-degradable pollutants into lakes.
4. The lake sites should be properly cleaned time to time.
Natural Water and Its Quality:
Water is one of the abundantly available resource which is an essential ingredient of animal and plant life. It is distributed in nature as rain water, river water, spring water, ground water, sea water, lake water etc.
Rain water is considered to be the purest form because it is produced by the process of natural distillation. However, it may be associated with dissolved gases like C02, S02, NH3 etc. in urban and industrial areas. The rain water in hilly areas and snow melting’s of mountains flow in the rivers. The original river water is pure but as it flows through the planes towards the sea, it gets polluted due to the addition of industrial effluents, agricultural run-off, urban sewage etc.
The natural water usually contains three types of substances:
1. Ion dispersed substances (inorganic substances)
2. Colloidal and molecular substances.
3. Suspended particulates.
1. Ion dispersed substances:
Naturally occurring water contain ionic compounds like CaCl2, MgCl2, CaSO4, MgSO4 Ca (HCO3)2, Mg (HCO3)2, Ha2SO4 and NACI in their ionic forms. Sometimes, the natural water is also associated with NH4+ (ammonium ion), NO3_ (nitrate ion), NO2– (nitrite ion) and HNO3 (nitric acid). The presence of nitrogen containing ions in water indicates that water is polluted.
2. Colloidal and Molecular Substances:
Substances of both organic and inorganic origin are present in water in colloidal state.
The contamination of natural water by organic substances may be due to:
(a) Dying of and decaying of organisms dwelling in water;
(b) Industrial discharges. The inorganic substances in colloidal forms are the compounds of silicon, aluminum and iron.
3. Suspended particulates:
The suspended particulates include the particles of sand and clay of different size, remnant of plants and other substances retrained from the surface. The greatest concentration of such substances in surface waters is usually observed during flood.
Some important functions of water in regulating the physiological activities in human beings may be outlined as follows:
(a) It acts as a regulator of body temperature.
(b) It acts as a carrier of nutrients to tissues and removes waste materials from them.
(c) It maintains electrolyte balance of the body by the maintenance of osmotic pressure.
(d) It acts as a solvent for the secretory and excretory products.
All the characteristics functions of water are due to:
(i) The amphoteric nature of water.
(ii) The tendency of water to solubulise a wide spectrum of compounds.
(iii) The tendency of water molecules to form intermolecular hydrogen bonding.
The total body water constitutes about 60% to 70% of body weight.
9. Water Quality Parameters and Standards:
Based on criteria and requirement, quality standards are prescribed which indicate the current state of knowledge of various constituents present in water. Since the quality standards are continuously revised with up to date information’s about the effects of constituents on proposed uses, these should not be used as absolute limits. However, these can be used as guidelines for preliminary judgments.
The specific purpose for which the water is used usually controls the requisite water quality. For example, water used in food industries will need to meet standards similar to drinking water but water for industrial operations can contain much higher concentrations of impurities.
The parameters for water quality characterisation are listed in Table 8.4. The permissible limits prescribed by United States Public Health Drinking Water Standards (UPSH) and Indian Standard Institution (ISI) are listed simultaneously for comprison. These refers to domestic water supplies for drinking water.
Table 8.5 illustrates the water quality characteristics of natural water that have been used as a source for various industrial operations.
Table 8.6: Raw Water Standards (Maximum Concentration of Constituents In Raw Water Supplied For Various Industries, MG/1. (Lamb, 1985; Clark Etal., 1977).