Air water and soil pollution: Kind, source quality parameters, effects on plants and ecosystems.

Air water and soil pollution: Kind, source quality parameters, effects on plants and ecosystems

INTRODUCTION
Pollution is the introduction of contaminants into an environment. These contaminants cause instability, disorder, harm or discomfort to the physical systems or living organisms therein. Pollution can take the form of chemical substances, or energy, such as noise, heat, or light energy. Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels. Pollution is often classed as point source or nonpoint source pollution.

Sometimes the term pollution is extended to include any substance when it occurs at such unnaturally high concentration within a system that it endangers the stability of that system. For example, water is innocuous and essential for life, and yet at very high concentration, it could be considered a pollutant: if a person were to drink an excessive quantity of water, the physical system could be so overburdened that breakdown and even death could result. 

MAJOR FORMS OF POLLUTION AND MAJOR POLLUTED AREAS

The major forms of pollution are listed below along with the particular pollutants relevant to each of them:

§  Air pollution, the release of chemicals and particulates into the atmosphere. Common air pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight.

§  Water pollution, by the release of waste products and contaminants into surface runoff into river drainage systems, leaching into groundwater, liquid spills, wastewater discharges, eutrophication and littering.

§  Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE, herbicides, pesticides and chlorinated hydrocarbons.

§  Radioactive contamination, resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment.

§  Noise pollution, which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.

§  Light pollution, includes light trespass, over-illumination and astronomical interference.

§  Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash or municipal solid waste.

§  Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.

The Blacksmith Institute issues annually a list of the world's worst polluted places. In the 2007 issues the ten top nominees are located in Azerbaijan, China, India, Peru, Russia, Ukraine and Zambia.

AIR POLLUTION

Air pollution is the human introduction into the atmosphere of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damage the environment. Air pollution causes deaths and respiratory disease. 

Air pollution is often identified with major stationary sources, but the greatest source of emissions is actually mobile sources, mainly automobiles. Gases such as carbon dioxide, which contribute to global warming, have recently gained recognition as pollutants by climate scientists, while they also recognize that carbon dioxide is essential for plant life through photosynthesis.

The gaseous cover on the surface of the earth is called atmosphere. The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet Earth.. It consists of gaseous mixtures such as nitrogen, oxygen, carbon dioxidemixed with water vapours and is collectively called air. According to Sytnick, (1985), the gaseous mass wchich forms the atmosphere is about 5.5 x 10¹⁵ tons. It also contains other gases in very minute quntitiy, dust particle, pollen grains etc., which are given in following tables :

Composition of Unpolluted Air

Consitituents	Volume
Nitrogen	78.09 %
Oxygen	20.94 %
Argon	0.93 %
Carbon dioxide	0.032 %
Neon	18 ppm
Helium	5.2 ppm
Methane	1.3 ppm
Krypton	1.0 ppm
Hydrogen	0.5 ppm
Nitrous oxides	0.25 ppm
Carbon mono-oxide	0.1 ppm
Ozone	0.02 ppm
Sulphure dioxide	0.001 ppm
Nitrogen dioxide	0.001 ppm

Pollutants

There are so many substances in the air which may impair the health of living beings, or reduce visibility. These arise both from natural processes and human activity. Substances not naturally found in the air or at greater concentrations or in different locations from usual are referred to as pollutants.

Pollutants can be classified as either primary or secondary. Primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption or the carbon monoxide gas from a motor vehicle exhaust.

Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone - one of the many secondary pollutants that make up photochemical smog.

Note that some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants.

Major primary pollutants produced by human activity include:

§  Sulfur oxides (SOx) especially sulfur dioxide are emitted from burning of coal and oil.

§  Nitrogen oxides (NOx) especially nitrogen dioxide are emitted from high temperature combustion. Can be seen as the brown haze dome above or plume downwind of cities.

§  Carbon monoxide is colourless, odourless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.

§  Carbon dioxide (CO₂), a greenhouse gas emitted from combustion.

§  Volatile organic compounds (VOC), such as hydrocarbon fuel vapors and solvents.

§  Particulate matter (PM), measured as smoke and dust. PM10 is the fraction of suspended particles 10 micrometers in diameter and smaller that will enter the nasal cavity. PM2.5 has a maximum particle size of 2.5 µm and will enter the bronchies and lungs.

§  Toxic metals, such as lead, cadmium and copper.

§  Chlorofluorocarbons (CFCs), harmful to the ozone layer emitted from products currently banned from use.

§  Ammonia (NH₃) emitted from agricultural processes.

§  Odors, such as from garbage, sewage, and industrial processes

§  Radioactive pollutants produced by nuclear explosions and war explosives, and natural processes such as radon.

Secondary pollutants include:

§  Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog, such as nitrogen dioxide.

§  Ground level ozone (O₃) formed from NOx and VOCs.

§  Peroxyacetyl nitrate (PAN) similarly formed from NOx and VOCs.

Minor air pollutants include:

§  A variety of persistent organic pollutants, which can attach to particulate matter are known as minor hazardous air pollutants. Some of these are regulated in USA under the Clean Air Act and in Europe under the Air Framework Directive..

Sources

Sources of air pollution refer to the various locations, activities or factors which are responsible for the releasing of pollutants in the atmosphere. These sources can be classified into two major categories which are :

Anthropogenic sources : Its include human activity mostly related to burning different kinds of fuel.

§  "Stationary Sources" as smoke stacks of power plants, manufacturing facilities, municipal waste incinerators.

§  "Mobile Sources" as motor vehicles, aircraft etc.

§  Marine vessels, such as container ships or cruise ships, and related port air pollution.

§  Burning wood, fireplaces, stoves, furnaces and incinerators .

§  Oil refining, and industrial activity in general.

§  Chemicals, dust and controlled burn practices in agriculture and forestry management.

§  Fumes from paint, hair spray, varnish, aerosol sprays and other solvents.

§  Waste deposition in landfills, which generate methane.

§  Military, such as nuclear weapons, toxic gases, germ warfare and rocketry.

Natural sources

§  Dust from natural sources, usually large areas of land with little or no vegetation.

§  Methane, emitted by the digestion of food by animals, for example cattle.

§  Radon gas from radioactive decay within the Earth's crust.

§  Smoke and carbon monoxide from wildfires.

§  Volcanic activity, which produce sulfur, chlorine, and ash particulates.

Emission factors

Air pollutant emission factors are representative values that attempt to relate the quantity of a pollutant released to the ambient air with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of pollutant divided by a unit weight, volume, distance, or duration of the activity emitting the pollutant (e.g., kilograms of particulate emitted per megagram of coal burned). Such factors facilitate estimation of emissions from various sources of air pollution. In most cases, these factors are simply averages of all available data of acceptable quality, and are generally assumed to be representative of long-term averages.

Indoor Air Quality (IAQ) or Indoor Air pollution

It refers to the physical, chemical, and biological characteristics of air in the indoor environment within a home, building, or an institution or commercial facility. Indoor air pollution is a concern in the developed countries, where energy efficiency improvements sometimes make houses relatively airtight, reducing ventilation and raising pollutant levels. Indoor air problems can be subtle and do not always produce easily recognized impacts on health. Different conditions are responsible for indoor air pollution in the rural areas and the urban areas.

In the developing countries, it is the rural areas that face the greatest threat from indoor pollution, where some 3.5 billion people continue to rely on traditional fuels such as firewood, charcoal, and cowdung for cooking and heating. Concentrations of indoor pollutants in households that burn traditional fuels are alarming. Burning such fuels produces large amount of smoke and other air pollutants in the confined space of the home, resulting in high exposure. Women and children are the groups most vulnerable as they spend more time indoors and are exposed to the smoke. Daily averages of pollutant level emitted indoors often exceed current 

WHO guidelines and acceptable levels. Although many hundreds of separate chemical agents have been identified in the smoke from biofuels, the four most serious pollutants are particulates, carbon monoxide, polycyclic organic matter, and formaldehyde. Unfortunately, little monitoring has been done in rural and poor urban indoor environments in a manner that is statistically rigorous.

In urban areas, exposure to indoor air pollution has increased due to a variety of reasons, including the construction of more tightly sealed buildings, reduced ventilation, the use of synthetic materials for building and furnishing and the use of chemical products, pesticides, and household care products. Indoor air pollution can begin within the building or be drawn in from outdoors. Other than nitrogen dioxide, carbon monoxide, and lead, there are a number of other pollutants that affect the air quality in an enclosed space.

Volatile organic compounds originate mainly from solvents and chemicals. The main indoor sources are perfumes, hair sprays, furniture polish, glues, air fresheners, moth repellents, wood preservatives, and many other products used in the house. The main health effect is the imitation of the eye, nose and throat. In more severe cases there may be headaches, nausea and loss of coordination. In the long term, some of the pollutants are suspected to damage to the liver and other parts of the body.

Tobacco smoke generates a wide range of harmful chemicals and is known to cause cancer. It is well known that passive smoking causes a wide range of problems to the passive smoker (the person who is in the same room with a smoker and is not himself/herself a smoker) ranging from burning eyes, nose, and throat irritation to cancer, bronchitis, severe asthma, and a decrease in lung function.

Pesticides, if used carefully and the manufacturers, instructions followed carefully they do not cause too much harm to the indoor air.

Biological pollutants include pollen from plants, mite, hair from pets, fungi, parasites, and some bacteria. Most of them are allergens and can cause asthma, hay fever, and other allergic diseases.

Formaldehyde is a gas that comes mainly from carpets, particle boards, and insulation foam. It causes irritation to the eyes and nose and may cause allergies in some people.

Asbestos is mainly a concern because it is suspected to cause cancer.

Radon (Rn) gas, a carcinogen, is exuded from the earth in certain locations and trapped inside houses. Due to modern houses having poor ventilation, it is confined inside the house causing harm to the dwellers.

Effects of air pollution

The important effects of air pollutants are as follows :

1.   Atmospheric particles can scatter and absorbed sunlight, thus reduce the visibility. Reduced visibility is aesthetically unidesirable and it is also dangerous for aircrafts and motors. In general cities receive above 15 to 20 % less solar radiation than rural areas and the reduction of sunlight can become as high as one third in the summer and two-third in winter. The reduction in sunlight is largely due to fuel combustion for industrial and household heating purpose.

2.   The effects of particulate matter include corrosion of metals, erosion and soiling of buildings, soulptures and painted surfaces and soiling of clothings and draperies, damage of electric equipments etc.

3.   The toxic effects of particulate matter on animals and human beings can be classified as :

·      Intrinsic toxicity due to chemical or physical properties - Carbon monoxide in congested areas remove 5 to 10 %of blood from circulation. Although body tissues extract only 25 % of O₂ from the blood, the heart needs 75%. So there is little margin for safety.

·        Interference with clearance mechanism in the respiratory tracts - Chronic bronchitis and emphysma have also been found to caused by SO_2. a 24 hour exposure to about 0.2 ppm of SO₂ may cause serious health problems. Lung cancer has also been found to correlated with air pollution. Polycyclic aromatic hydrocarbons (PAH) are found to related to the pathogenesis of lung cancer.

·        Toxicity due to abosrbed toxic substance – Many toxic particles includings metal dusts, asbestos, aromatic hydrocarbons have been discovered in a polluted urban atmosphere. Lead from vehicle exhaustsa, resulting from the use of tetraethyl lead as an anti knock additive to petrol, may build up to dangerous levels in urban areas adacent to busy road complexes. Lead in high doses kills outright. In lower doses (in dense traffic areas) it shortens life span and causes deterioration of nervous system. Retarded children have a higher lead conteneet in their body than the normal ones.

4.   Benzpyrenes – Their concentrations are extremely small but they play a role in higher cancer rates in urban areas as compared to rural areas. Peroxy acetyl nitrates (PAN) or photochemical smog may constitute a serious problem where high levels of vehicular emmissions occur in cities experiencing bright sunlight and ambient temperatures above 21^oC.

5.   The small solid particles can serve as carriers for microorganisms and other infective agents and therby spread diseases. Large dust particles are trapped in nose and throat and very tiny particles which stay in the lungs may start an ugly chain of events leading to serious illness and deaths.

6.   Air pollution causes coughing, sneezing, thickening of secretion of mucus and narrowing or complete closure of glottis due to presence of gases, especially SO_2, nitrogen dioxide and oxidaqnts. The silicon particles may cause ‘silicosis’ and fibrous particles ‘fibrosis’. It is suspected that some pollutants can start the growth of lung cancer.

7.   Effect of SO₂ – SO₂ can damage materials and properties mainly through their conversion into the highly reactive H₂SO_4. It causes discolouration and physical deteriation of building materials and sculptures. Deterioration and fading are also produced in fabrics as cotton, nylon, leather and paper. It accelerates corrosion of metals, especially iron, steel and zinc. SO₂ and H₂SO₄ both are capable of causing irritation in respiratory tracts of animals and human beings and high concentrations of SO₂ cause severe heart and lung diseases.

8.   The toxic effects of CO on human beings or animals arise from its reversible combination with haemoglobin in the blood. Haemoglobin has much greater affinity with CO and it lessens the oxygen carrying capacity of blood. It also reduces the dissociation of oxyhaemoglobin.

9.   A continued increase in excess unabsorbed CO₂ could have a catastrophic warming effect on the atmosphere, melting of polar ice, change in the ecosystems of seas and even floods on an undreamed scale. 

10.  Effect of NO₂ – Nitrogen oxides are known to produce fading the textile dyes, deterioration of cotton and nylon and corrosion of metals due to production of particulate nitrates. It affects lungs, heart, liver and kidney at higher concentrations (15 to 50 ppm for two hours). Besides, it is considered to be a major factor in causing eye irrittaion.

11.  Effects of air pollutants on plants – SO₂ has been found to affect vegetation adversely even at the concentration below 0.032 ppm. It is suspected that sulphur dioxide pollution in urban and industrial areas of industrialised countries has a major impact on the respiratory condition of the population and also has significant effects on the crops and other vegetations of the surrounding rural areas. High concentration of SO₂ over short period of time can produce leaf injury, such as necrosis in plants or brownish colouration in the tips of pine needles. Lower concentrations over long period lead to chronic leaf injury such as gradual chlorosis. NO₂ also causes leaf injury and reduction of growth in several NO₂ sensitive plants. Some plants produce volatile tarpenbes. In urban areas, ethylene (a hydrocarbon) is known to inhibit the plant growth.

Reduction efforts

There are various air pollution control technologies and urban planning strategies available to reduce air pollution.

Efforts to reduce pollution from mobile sources includes primary regulation (many developing countries have permissive regulations), expanding regulation to new sources (such as cruise and transport ships, farm equipment, and small gas-powered equipment such as lawn trimmers, chainsaws, and snow mobiles), increased fuel efficiency (such as through the use of hybrid vehicles), conversion to cleaner fuels (such as bioethanol, biodiesel, or conversion to electric vehicles).

WATER POLLUTION

Water pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater caused by human activities, which can be harmful to organisms and plants which live in these water bodies. Water pollution is a major problem in the global context. It has been suggested that it is the leading worldwide cause of deaths and diseases, and that it accounts for the deaths of more than 14,000 people daily.

Although natural phenomena such as volcanoes, algae bloom, storms, and earthquakes also cause major changes in water quality and the ecological status of water. Water is typically referred to as polluted when it impaired by anthropogenic contaminants and either does not support a human use (like serving as drinking water) or undergoes a marked shift in its ability to support its constituent biotic communities. Water pollution has many causes and characteristics.

Sources

The primary sources of water pollution are generally grouped into two categories based on their point of origin. Point-source pollution refers to contaminants that enter a waterway through a discrete "point source". Examples of this category include discharges from a wastewater treatment plant, outfalls from a factory, leaking underground tanks, etc.

The second primary category, “non-point source” pollution, refers to contamination that, as its name suggests, does not originate from a single discrete source. Non-point source pollution is often a cumulative effect of small amounts of contaminants gathered from a large area. Nutrient runoff in stormwater from sheet flow over an agricultural field, or metals and hydrocarbons from an area with high impervious surfaces and vehicular traffic are examples of non-point source pollution. The primary focus of legislation and efforts to curb water pollution for the past several decades was first aimed at point sources. As point sources have been effectively regulated, greater attention has come to be placed on non-point source contributions, especially in rapidly urbanizing/ suburbanizing or developing areas.

Contaminants

The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical or sensory changes. While many of the chemicals and substances that are regulated may be naturally occurring (iron, manganese, etc) the concentration is often the key in determining what is a natural component of water, and what is a contaminant. Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry include acidity, electrical conductivity, temperature, and eutrophication.

Contaminants may include organic and inorganic substances.

Organic water pollutants are:

§  Insecticides and herbicides, a huge range of organohalide and other chemicals

§  Bacteria, often is from sewage or livestock operations

§  Food processing waste, including pathogens

§  Tree and brush debris from logging operations

§  VOCs (volatile organic compounds), such as industrial solvents, from improper storage

§  DNAPLs (dense non-aqueous phase liquids), such as chlorinated solvents, which may fall at the bottom of reservoirs, since they don't mix well with water and are more dense

§  Petroleum Hydrocarbons including fuels (gasoline, diesel, jet fuels, and fuel oils) and lubricants (motor oil) from oil field operations, refineries, pipelines, retail service station's underground storage tanks, and transfer operations. Note: VOCs include gasoline-range hydrocarbons.

§  Detergents

§  Various chemical compounds found in personal hygiene and cosmetic products

§  Disinfection by-products (DBPs) found in chemically disinfected drinking water

Inorganic water pollutants include:

§  Heavy metals including acid mine drainage

§  Acidity caused by industrial discharges (especially sulfur dioxide from power plants)

§  Pre-production industrial raw resin pellets, an industrial pollutant

§  Chemical waste as industrial by products

§  Fertilizers, in runoff from agriculture including nitrates and phosphates

§  Silt in surface runoff from construction sites, logging, slash and burn practices or land clearing sites

Transport and chemical reactions of water pollutants

Most water pollutants are eventually carried by the rivers into the oceans. In some areas of the world the influence can be traced hundred miles from the mouth by studies using hydrology transport models. Advanced computer models such as SWMM or the DSSAM Model have been used in many locations worldwide to examine the fate of pollutants in aquatic systems.

Many chemicals undergo reactive decay or chemically change especially over long periods of time in groundwater reservoirs. A noteworthy class of such chemicals are the chlorinated hydrocarbons such as trichloroethylene (used in industrial metal degreasing and electronics manufacturing) and tetrachloroethylene used in the dry cleaning industry. Both of these chemicals, which are carcinogens themselves, undergo partial decomposition reactions, leading to new hazardous chemicals (including dichloroethylene and vinyl chloride).

Groundwater pollution is much more difficult to abate than surface pollution because groundwater can move great distances through unseen aquifers. Non-porous aquifers such as clays partially purify water of bacteria by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity: however, in some cases, the pollutants merely transform to soil contaminants. Groundwater that moves through cracks and caverns is not filtered and can be transported as easily as surface water. In fact, this can be aggravated by the human tendency to use natural sinkholes as dumps in areas of Karst topography.

There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. Some of these secondary impacts are:

§  Silt bearing surface runoff from can inhibit the penetration of sunlight through the water column, hampering photosynthesis in aquatic plants.

§  Thermal pollution can induce fish kills and invasion by new thermophilic species. This can cause further problems to existing wildlife.

Effects of Water Pollution

Water Pollution comes from many different sources and can effect many different things. The effects of water pollution are not only devastating to people, but they can kill animals, fish, and birds. Furthermore, the effects of water pollution pose a serious threat to society today and in the future.

Effects of Untreated Human Waste

Normally, human waste goes through various treatment plants to become uncontaminated, but during a heavy rain storm, human waste can back up and overflow into rivers or the water supplies. This waste can also cause disease and it can rob the water of oxygen which kills the wildlife that lives in the water.

Effects of Run-Off Pollution

When rain runs off the land it picks up dirt and silt and carries them into the water. When the dirt and silt (sediment) settle in the water body they enter, these sediments can keep sunlight from reaching aquatic plants, plants that live in and grow in the water. When the sun can't reach the plants, they die. The sediments can also clog fish gills, and some other organisms that live on the bottom of the body of water.

Effects of Oil Pollution and Antifreeze

When oil is spilled into the water, the effects on the ecosystem and its components are devastating. Some animals, such as birds, mammals, and fish may and can be killed if they ingest oil. Many may die from eating oil contaminated prey. Birds may die if the oil coats their feathers. They can neither fly nor stay warm. Furthermore, when oil coats the feathers they can become sick and die. Oil and antifreeze can cause the water to have a bad odor and leave a sticky film on the surface of water that kills animals and fish. Oil is one of the most devastating pollutants of water. Contaminated Ground Water Effects When contaminated water seeps into the ground it can have serious effects. People can get very sick and have the possibility of developing liver or kidney problems, cancer or other illnesses, depending on if contaminated water seeps into the ground

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Fertilizers and Other Chemicals

Water, from rain, runs down the slopes of the land which may include farm areas that use fertilizers, pesticides, and other farming chemicals. After that they travel down into the rivers, lakes, or oceans. Fertilizers and some chemicals may cause plants to grow quicker. With the growth of more plants, more bacteria will grow (bacteria eat dead plants). Bacteria need oxygen to survive and if there are more bacteria in a river than normal, there is less oxygen for fish and some of them may die. In addition, some fish in the Great Lakes suffer from tumors and the populations of some species in these waters are declining. Other chemicals besides farming chemicals effect humans as well. Nitrates in drinking water can cause diseases to infants that might cause them death. Cadmium (a metal in sludge-derived fertilizer) can be absorbed by crops, and if people ingest this in sufficiently it can cause diarrheal disorders, liver, and kidney damage. The culprit is suspected to be inorganic substances such as mercury, arsenic, and lead. Also, other chemicals can cause problems with the taste, smell, and the color of water. Pesticides, PCB's, and PCP's (polychlorinated phenols) are some examples that are toxic to all life. Pesticides are used in farming, forestry, and homes. PCB's can still be found as insulators in old electrical transformers, and PCP's can be found in products such as wood preservatives. They are very toxic and that is what makes them a threat to our ecosystem.

Effects of Factory Pollution

Many factories have pipes that drain chemicals into rivers or streams. These chemicals can damage aquatic life as they are carried downstream. Furthermore, the added chemicals can warm the river, which decreases the amount of oxygen that the fish need to live.

Effects of Garbage from Private Offices and Homes

Many people today dump their garbage into streams, lakes, rivers, and oceans. Some examples of this garbage are cans, paper, furniture, and other household products. When people dump cleaning products into the ecosystem they are endangering its inhabitants. When plastic is dumped in lakes, ducks are at risk because they might be strangled and when dumped in the ocean, dolphins might be killed. Aluminum cans can cut the animals and fish.

Effects of Eutrophication

Eutrophication is the fertilization of surface water by nutrients that were previously scarce. Eutrophication, occurs when lake water is artificially supplemented with nutrients, which causes abnormal plant growth. The cause of eutrophication can be runoff of chemical fertilizers from fields. Eutrophication can produce problems such as bad tastes and odors as well as green scum algae. Also, the growth of rooted plants increases, which decreases the amount of oxygen in the deepest waters of the lake. A common chemical change is the precipitation of calcium carbonate in hard waters. Eutrophication makes some lakes void of life.

Effects of Acid Rain

The effects of acid rain are most clearly seen in lakes, streams, rivers, oceans, and other bodies of water. Acid rain directly falls on water, but it can flow into rivers after it falls on land. Lakes and streams become acidic (pH value goes down) when the water and the land around it can not neutralize the acid rain. Animals that live in the water environment are hurt and possibly killed. Some fish can only tolerate a certain amount of acid before dying. The more acid rain that falls, the life in the bodies of water decreases. Furthermore, animals that eat prey that is affected will be killed because they will be consuming acid.

SOIL POLLUTION

Soil contamination 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 tanks, application of pesticides, 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 intensity of chemical usage.

The concern over soil contamination stems primarily from health risks, both of direct contact and from secondary contamination of water supplies. Mapping of contaminated soil sites and the resulting cleanup are time consuming and expensive tasks, requiring extensive amounts of geology, hydrology, chemistry and computer modeling skills.

The United States, while having some of the most widespread soil contamination, has actually been a leader in defining and implementing standards for cleanup. Other industrialized countries have a large number of contaminated sites, but lag the U.S. in executing remediation. Developing countries may be leading in the next generation of new soil contamination cases.

Each year in the U.S., thousands of sites complete soil contamination cleanup, some by using microbes that “eat up” toxic chemicals in soil, many others by simple excavation and others by more expensive high-tech soil vapor extraction or air stripping. At the same time, efforts proceed worldwide in creating and identifying new sites of soil contamination, particularly in industrial countries other than the U.S., and in developing countries which lack the money and the technology to adequately protect soil resources.

Microanalysis of soil contamination

To understand the fundamental nature of soil contamination, it is necessary to envision the variety of mechanisms for pollutants to become entrained in soil. Soil particulates may be composed of a gamut of organic and inorganic chemicals with variations in cation exchange capacity, buffering capacity, and redox poise. For example, at the extremes, one has a sand component, a coarse grained, inert, and totally inorganic substance; whereas peat soils are dominated by a fine organic material, made of decomposing organic material and highly active. Most soils are mixtures of soil subtypes and thus have quite complex characteristics.

There is also a great diversity of soil porosity, ranging from gravels to sands to silt to clay (in increasing order of porosity), pore size, and pore tortuosity (both in decreasing order). Finally there is a wide spectrum of chemical bonding or adhesion characteristics: each contaminant has a different interaction or bonding mechanism with a given soil type.

On balance, some contaminants may literally drain through soils such as sand and gravel and move to other soils or deeper aquifers, while polar or organic chemicals discharged into a clay soil will have a very high adsorption. Thus most soil contamination is the result of pollutants adhering to the soil particle surface, or lodging in interstices of a soil matrix. Clearly the equilibrium reached is a dynamic one, where new pollutants may lodge on new soil particles and the action of groundwater movement may over time transport some of the soil contaminants to other locations or depths.

Soil contamination results when hazardous substances are either spilled or buried directly in the soil or migrate to the soil from a spill that has occurred elsewhere. For example, soil can become contaminated when small particles containing hazardous substances are released from a smokestack and are deposited on the surrounding soil as they fall out of the air. Another source of soil contamination could be water that washes contamination from an area containing hazardous substances and deposits the contamination in the soil as it flows over or through it.

Effects on human health

The major concern is that there are many sensitive land uses where people are in direct contact with soils such as residences, parks, schools and playgrounds. Other contact mechanisms include contamination of drinking water or inhalation of soil contaminants which have vaporized. There is a very large set of health consequences from exposure to soil contamination depending on pollutant type, pathway of attack and vulnerability of the exposed population. Chromium and obsolete pesticide formulations are carcinogenic to populations. Lead is especially hazardous to young children, in which group there is a high risk of developmental damage to the brain,while to all populations kidney damage is a risk.

Chronic exposure to at sufficient concentrations is known to be associated with higher incidence of leukemia. Obsolete pesticides such as mercury and cyclodienes are known to induce higher incidences of kidney damage, some irreversible; cyclodienes are linked to liver toxicity. Organophosphates and carbamates can induce a chain of responses leading to neuromuscular blockage. Many chlorinated solvents induce liver changes, kidney changes and depression of the central nervous system. There is an entire spectrum of further health effects such as headache, nausea, fatigue (physical), eye irritation and skin rash for the above cited and other chemicals.

Effects on ecosystem

Not unexpectedly, soil contaminants can have significant deleterious consequences for ecosystems. There are radical soil chemistry changes which can arise from the presence of many hazardous chemicals even at low concentration of the contaminant species. These changes can manifest in the alteration of metabolism of endemic microorganisms and arthropods resident in a given soil environment. The result can be virtual eradication of some of the primary food chain, which in turn have major consequences for predator or consumer species. Even if the chemical effect on lower life forms is small, the lower pyramid levels of the food chain may ingest alien chemicals, which normally become more concentrated for each consuming rung of the food chain. Many of these effects are now well known, such as the concentration of persistent DDT materials for avian consumers, leading to weakening of egg shells, increased chick mortality and potentially species extinction.

Effects occur to agricultural lands which have certain types of soil contamination. Contaminants typically alter plant metabolism, most commonly to reduce crop yields. This has a secondary effect upon soil conservation, since the languishing crops cannot shield the earth's soil mantle from erosion phenomena. Some of these chemical contaminants have long half-lives and in other cases derivative chemicals are formed from decay of primary soil contaminants.

Cleanup options

Microbes can be used in soil cleanup. Cleanup or remediation is analyzed by environmental scientists who utilize field measurement of soil chemicals and also apply computer models for analyzing transport and fate of soil chemicals. Thousands of soil contamination cases are currently in active cleanup across the U.S. as of 2006. There are several principal strategies for remediation:

§  Excavate soil and remove it to a disposal site away from ready pathways for human or sensitive ecosystem contact. This technique also applies to dredging of bay muds containing toxins.

§  Aeration of soils at the contaminated site (with attendant risk of creating air pollution)

§  Bioremediation, involving microbial digestion of certain organic chemicals. Techniques used in bioremediation include landfarming, biostimulation and bioaugmentation soil biota with commercially available microflora.

§  Extraction of groundwater or soil vapor with an active electromechanical system, with subsequent stripping of the contaminants from the extract.

§  Containment of the soil contaminants (such as by capping or paving over in place).