Describe in detail about the concept of sustainable buildings

SUSTAINABLE BUILDINGS or sustainable architecture is architecture that seeks to minimize the negative environmental impact of buildings by efficiency and moderation in the use of materials, energy, and development space. Sustainable architecture uses a conscious approach to energy and ecological conservation in the design of the built environment. The idea of sustainability, or ecological design, is to ensure that our actions and decisions today do not inhibit the opportunities of future generations

Sustainable energy use

The most important and cost-effective element of an efficient heating, ventilating, and air conditioning (HVAC) system is a well-insulated building. A more efficient building requires less heat generating or dissipating power, but may require more ventilation capacity to expel polluted indoor air.

Significant amounts of energy are flushed out of buildings in the water, air and compost streams. Off the shelf, on-site energy recycling technologies can effectively recapture energy from waste hot water and stale air and transfer that energy into incoming fresh cold water or fresh air. Recapture of energy for uses other than gardening from compost leaving buildings requires centralized anaerobic digesters.

HVAC systems are powered by motors. Copper, versus other metal conductors, helps to improve the electrical energy efficiencies of motors, thereby enhancing the sustainability of electrical building components.

Site and building orientation have some major effects on a building's HVAC efficiency.

Passive solar building design allows buildings to harness the energy of the sun efficiently without the use of any active solar mechanisms such as photovoltaic cells or solar hot water panels. Typically passive solar building designs incorporate materials with high thermal mass that retain heat effectively and strong insulation that works to prevent heat escape. Low energy designs also requires the use of solar shading, by means of awnings, blinds or shutters, to relieve the solar heat gain in summer and to reduce the need for artificial cooling.

Windows are placed to maximize the input of heat-creating light while minimizing the loss of heat through glass, a poor insulator.

RENEWABLE ENERGY GENERATIONSolar panelActive solar devices such as photovoltaic solar panels help to provide sustainable electricity for any use. Electrical output of a solar panel is dependent on orientation, efficiency, latitude, and climate—solar gain varies even at the same latitude. Typical efficiencies for commercially available PV panels range from 4% to 28%. The low efficiency of certain photovoltaic panels can significantly affect the payback period of their installation.  This low efficiency does not mean that solar panels are not a viable energy alternative

Wind turbinesThe use of undersized wind turbines in energy production in sustainable structures requires the consideration of many factors. In considering costs, small wind systems are generally more expensive than larger wind turbines relative to the amount of energy they produce. For small wind turbines, maintenance costs can be a deciding factor at sites with marginal wind-harnessing capabilities. At low-wind sites, maintenance can consume much of a small wind turbine's revenue. Wind turbines

begin operating when winds reach 8 mph, achieve energy production capacity at speeds of 32-37 mph, and shut off to avoid damage at speeds exceeding 55 mph.  The energy potential of a wind turbine is proportional to the square of the length of its blades and to the cube of the speed at which its blades spin. Though wind turbines are available that can supplement power for a single building, because of these factors, the efficiency of the wind turbine depends much upon the wind conditions at the building site. For these reasons, for wind turbines to be at all efficient, they must be installed at locations that are known to receive a constant amount of wind (with average wind speeds of more than 15 mph), rather than locations that receive wind sporadically

Solar water heatingSolar water heaters, also called solar domestic hot water systems, can be a cost-effective way to generate hot water for a home. They can be used in any climate, and the fuel they use—sunshine—is free.[

There are two types of solar water systems- active and passive. An active solar collector system can produce about 80 to 100 gallons of hot water per day. A passive system will have a lower capacity.

There are also two types of circulation, direct circulation systems and indirect circulation systems. Direct circulation systems loop the domestic water through the panels. They should not be used in climates with temperatures below freezing. Indirect circulation loops glycol or some other fluid through the solar panels and uses a heat exchanger to heat up the domestic water.

SUSTAINABLE BUILDING MATERIALS

Recycled materials

Recycling items for building

Sustainable architecture often incorporates the use of recycled or second hand materials, such as reclaimed lumber and recycled copper. The reduction in use of new materials creates a corresponding reduction in embodied energy (energy used in the production of materials). Often sustainable architects attempt to retrofit old structures to serve new needs in order to avoid unnecessary development. Architectural salvage and reclaimed materials are used when appropriate. When older buildings are demolished, frequently any good wood is reclaimed, renewed, and sold as flooring. Any good dimension stone is similarly reclaimed. Many other parts are reused as well, such as doors, windows, mantels, and hardware, thus reducing the consumption of new goods. When new materials are employed, green designers look for materials that are rapidly replenished, such as bamboo, which can be harvested for commercial use after only 6 years of growth, sorghum or wheat straw, both of which are waste material that can be pressed into panels, or cork oak, in which only the outer bark is removed for use, thus preserving the tree. When possible, building materials may be gleaned from the site itself; for example, if a new structure is being constructed in a wooded area, wood from the trees which were cut to make room for the building would be re-used as part of the building itself.

Lower volatile organic compounds

Low-impact building materials are used wherever feasible: for example, insulation may be made from low VOC (volatile organic compound)-emitting materials such as recycled denim or cellulose insulation, rather than the building insulation materials that may contain carcinogenic or toxic materials such as formaldehyde. To discourage insect damage, these alternate insulation materials may be treated with boric acid. Organic or milk-based paints may be used. However, a common

fallacy is that "green" materials are always better for the health of occupants or the environment. Many harmful substances (including formaldehyde, arsenic, and asbestos) are naturally occurring and are not without their histories of use with the best of intentions. A study of emissions from materials by the State of California has shown that there are some green materials that have substantial emissions whereas some more "traditional" materials actually were lower emitters. Thus, the subject of emissions must be carefully investigated before concluding that natural materials are always the healthiest alternatives for occupants and for the Earth

GREEN BUILDING.

Green building (refers to a structure and using process that is environmentally responsible and resource-efficient throughout a building's life-cycle: from siting to design, construction, operation, maintenance, renovation, and demolition. This requires close cooperation of the design team, the architects, the engineers, and the client at all project stages.The Green Building practice expands and complements the classical building design concerns of economy, utility, durability, and comfort.

Although new technologies are constantly being developed to complement current practices in creating greener structures, the common objective is that green buildings are designed to reduce the overall impact of the built environment on human health and the natural environment by:

Efficiently using energy, water, and other resources Protecting occupant health and improving employee productivity Reducing waste, pollution and environmental degradationA similar concept is natural building, which is usually on a smaller scale and tends to focus on the use of natural materials that are available locally. Other related topics include sustainable design and green architecture. Sustainability may be defined as meeting the needs of present generations without compromising the ability of future generations to meet their needs. Although some green building programs don't address the issue of the retrofitting existing homes, others do. Green construction principles can easily be applied to retrofit work as well as new construction.

Goals of green buildingGreen building brings together a vast array of practices, techniques, and skills to reduce and ultimately eliminate the impacts of buildings on the environment and human health. It often emphasizes taking advantage of renewable resources, e.g., using sunlight through passive solar, active solar, and photovoltaic equipment, and using plants and trees through green roofs, rain gardens, and reduction of rainwater run-off. Many other techniques are used, such as using low-impact building materials or using packed gravel or permeable concrete instead of conventional concrete or asphalt to enhance replenishment of ground water.

On the aesthetic side of green architecture or sustainable design is the philosophy of designing a building that is in harmony with the natural features and resources surrounding the site. There are several key steps in designing sustainable buildings: specify 'green' building materials from local sources, reduce loads, optimize systems, and generate on-site renewable energy.

ENERGY EFFICIENCY OF GREEN BUILDINGS

Green buildings often include measures to reduce energy consumption – both the embodied energy required to extract, process, transport and install building materials and operating energy to provide services such as heating and power for equipment.

As high-performance buildings use less operating energy, embodied energy has assumed much greater importance – and may make up as much as 30% of the overall life cycle energy consumption. Studies show buildings built primarily with wood will have a lower embodied energy than those built primarily with brick, concrete, or steel.

To reduce operating energy use, designers use details that reduce air leakage through the building envelope (the barrier between conditioned and unconditioned space). They also specify high-performance windows and extra insulation in walls, ceilings, and floors. Another strategy, passive solar building design, is often implemented in low-energy homes. Designers orient windows and walls and place awnings, porches, and trees to shade windows and roofs during the summer while maximizing solar gain in the winter. In addition, effective window placement (daylighting) can provide more natural light and lessen the need for electric lighting during the day. Solar water heating further reduces energy costs.Onsite generation of renewable energy through solar power, wind power, hydro power, or biomass can significantly reduce the environmental impact of the building. Power generation is generally the most expensive feature to add to a building.

What are the different types of environmental pollution? How does it affect the nature?

Different Types of pollution are categorized based on the part of the environment which they affect or result which the particular pollution causes. Each of these types has its own distinctive causes and consequences. Categorized study of pollution helps to understand the basics in more detail and produce protocols for the specific types. Accordingly, the main types of pollution are: 

Water Pollution Air Pollution Soil Pollution Thermal Pollution Radioactive Pollution Noise Pollution Light Pollution

WATER POLLUTION  Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater). Water pollution occurs when pollutants are directly or indirectly discharged into water bodies without adequate treatment to remove harmful compounds.

Water pollution affects plants and organisms living in these bodies of water. In almost all cases the effect is damaging not only to individual species and populations, but also to the natural biological communities.

Sources of surface water pollution are generally grouped into two categories based on their origin.

Point source pollution - Point source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain.

Nonpoint sources - Nonpoint source pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. A common example is the leaching out of nitrogen compounds from fertilized agricultural lands. Nutrient runoff in stormwater from "sheet flow" over an agricultural field or a forest are also cited as examples of NPS pollution.Contaminated storm water washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of NPS pollution. However, this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, and is a point source.

Effects of water pollution.

The effects of water pollution are varied and depend on what chemicals are dumped and in which locations.Many water bodies near urban areas (cities and towns) are highly polluted. This is the result of both garbage dumped by individuals and dangerous chemicals legally or illegally dumped by manufacturing industries, health centers, schools and market places.

Death of aquatic (water) animals

The main problem caused by water pollution is that it kills life that depends on these water bodies. Dead fish, crabs, birds and sea gulls, dolphins, and many other animals often wind up on beaches, killed by pollutants in their habitat (living environment).

Disruption of food-chains

Pollution disrupts the natural food chain as well. Pollutants such as lead and cadmium are eaten by tiny animals. Later, these animals are consumed by fish and shellfish, and the food chain continues to be disrupted at all higher levels.

Diseases

Eventually, humans are affected by this process as well. People can get diseases such as hepatitis by eating seafood that has been poisoned. In many poor nations, there is always outbreak of cholera and diseases as a result of poor drinking water treatment from contaminated waters.

Destruction of ecosystems

Ecosystems (the interaction of living things in a place, depending on each other for life) can be severely changed or destroyed by water pollution. Many areas are now being affected by careless human pollution, and this pollution is coming back to hurt humans in many ways.

AIR POLLUTION

Air pollution is the introduction of chemicals, particulates, biological materials, or other harmful materials into the Earth's atmosphere, possibly causing disease, death to humans, damage to other living organisms such as food crops, or the natural or built environment.

The atmosphere is a complex natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth's ecosystems.

POLLUTANTS

An air pollutant is a substance in the air that can have adverse effects on humans and the ecosystem. The substance can be solid particles, liquid droplets, or gases. A pollutant can be of natural origin or man-made. Pollutants are classified as primary or secondary. Primary pollutants are usually produced from a process, such as ash from a volcanic eruption. Other examples include carbon monoxide gas

from motor vehicle exhaust, or the sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. Ground level ozone is a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants.

Major primary pollutants produced by human activity include:

Sulfur oxides (SOx) - particularly sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.[2] This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.

Nitrogen oxides (NOx) - Nitrogen oxides, particularly nitrogen dioxide, are expelled from high temperature combustion, and are also produced during thunderstorms by electric discharge. They can be seen as a brown haze dome above or a plume downwind of cities. Nitrogen dioxide is a chemical compound with the formula NO2. It is one of several nitrogen oxides. One of the most prominent air pollutants, this reddish-brown toxic gas has a characteristic sharp, biting odor.

Carbon monoxide (CO)- CO is a colourless, odourless, toxic yet non-irritating 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.

Volatile organic compounds - VOCs are a well known outdoor air pollutant. They are categorized as either methane (CH4) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life of methane in the atmosphere. This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure. 1,3-butadiene is another dangerous compound often associated with industrial use.

Particulates, alternatively referred to as particulate matter (PM), atmospheric particulate matter, or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to combined particles and gas. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged worldwide, anthropogenic aerosols—those made by human activities—currently account for approximately 10 percent of our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.

Persistent free radicals connected to airborne fine particles are linked to cardiopulmonary disease

Toxic metals, such as lead and mercury, especially their compounds.

Chlorofluorocarbons (CFCs) - harmful to the ozone layer; emitted from products currently banned from use

These are gases which are released from air conditioners, refrigerators, aerosol sprays, etc. CFC's on being released into the air rises to stratosphere. Here they come in contact with other gases and

damage the ozone layer. This allows harmful ultraviolet rays to reach the earth's surface. This can lead to skin cancer, disease to eye and can even cause damage to plants.

Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with the formula NH3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.

Odours — such as from garbage, sewage, and industrial processes

Radioactive pollutants - produced by nuclear explosions, nuclear events, war explosives, and natural processes such as the radioactive decay of radon

EFFECTS OF AIR POLLUTION

Pollutants can affect human respiratory and cardiovascular systems. The young, the elderly and those with acute illnesses are at greater risk of such effects. Different pollutants have been associated with hospitalizations, increased respiratory and cardiovascular mortality, asthma exacerbation, decreased lung function, lung inflammation and changes in heart rate variability

Impacts range from minor breathing problems to premature death. The more common effects include changes in breathing and lung function, lung inflammation, and irritation and aggravation of existing heart and lung conditions (e.g. asthma, emphysema and heart disease)

Negative health effects increase as the concentrations of pollutants in the air increases. Even modest increases in concentration (e.g. PM2.5 and O3) can cause small but measurable increases in emergency room visits, hospital admissions, and premature death.

Ground-level ozone damages vegetation, including crops, flowers, shrubs and forests, by interfering with plants’ ability to produce and store food. This damage makes them more susceptible to disease, pests and environmental stresses.

Nitrogen oxides (NOx) and sulphur dioxide (SO2) can become acidic gases or particulates, and cause or accelerate the corrosion and soiling of materials. Together with ammonia, they are also the main precursors of acid rain. Acid rain affects soils and water bodies, and stresses both vegetation and animals.

Health impact of specific air pollutants

Some of these gases can seriously and adversely affect the health of the population and should be

given due attention by the concerned authority. The gases mentioned below are mainly outdoor air

pollutants but some of them can and do occur indoor depending on the source and the circumstances.

Tobacco smoke. Tobacco smoke generates a wide range of harmful chemicals and is a major

cause of ill health, as it is known to cause cancer, not only to the smoker but affecting passive

smokers too. It is well-known that smoking affects the passive smoker (the person who is in

the vicinity of a smoker and is not himself/herself a smoker) ranging from burning sensation

in the eyes or nose, and throat irritation, to cancer, bronchitis, severe asthma, and a decrease in

lung function.

Biological pollutants. These are mostly allergens that can cause asthma, hay fever, and other

allergic diseases. 

Volatile organic compounds. Volatile compounds can cause irritation of the eye, nose and

throat. In severe cases there may be headaches, nausea, and loss of coordination. In the longer

run, some of them are suspected to cause damage to the liver and other parts of the body.

Formaldehyde. Exposure causes irritation to the eyes, nose and may cause allergies in some

people.

Lead. Prolonged exposure can cause damage to the nervous system, digestive problems, and

in some cases cause cancer. It is especially hazardous to small children.

Radon. A radioactive gas that can accumulate inside the house, it originates from the rocks

and soil under the house and its level is dominated by the outdoor air and also to some extent

the other gases being emitted indoors. Exposure to this gas increases the risk of lung cancer.

Ozone. Exposure to this gas makes our eyes itch, burn, and water and it has also been

associated with increase in respiratory disorders such as asthma. It lowers our resistance to

colds and pneumonia.

Oxides of nitrogen. This gas can make children susceptible to respiratory diseases in the

winters.

Carbon monoxide. CO (carbon monoxide) combines with haemoglobin to lessen the amount

of oxygen that enters our blood through our lungs. The binding with other haeme proteins

causes changes in the function of the affected organs such as the brain and the cardiovascular

system, and also the developing foetus. It can impair our concentration, slow our reflexes, and

make us confused and sleepy.

Sulphur dioxide. SO2 (sulphur dioxide) in the air is caused due to the rise in combustion of

fossil fuels. It can oxidize and form sulphuric acid mist. SO2 in the air leads to diseases of the

lung and other lung disorders such as wheezing and shortness of breath. Long-term effects are

more difficult to ascertain as SO2 exposure is often combined with that of SPM.

SPM (suspended particulate matter). Suspended matter consists of dust, fumes, mist and

smoke. The main chemical component of SPM that is of major concern is lead, others being

nickel, arsenic, and those present in diesel exhaust. These particles when breathed in, lodge in

our lung tissues and cause lung damage and respiratory problems. The importance of SPM as

a major pollutant needs special emphasis as

a) it affects more people globally than any other pollutant on a continuing basis;

b) there is more monitoring data available on this than any other pollutant; and

c) more epidemiological evidence has been collected on the exposure to this than to any other

pollutant.

SOIL POLLUTIONDefinition: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 seepageThe most common chemicals involved in causing soil pollution are:• Petroleum hydrocarbons• Heavy metals• Pesticides• Solvents

Types of Soil Pollution

• Agricultural Soil Pollutioni) pollution of surface soilii) pollution of underground soil• Soil pollution by industrial effluents and solid wastesi) pollution of surface soilii) disturbances in soil profile• Pollution due to urban activitiesi) pollution of surface soilii) 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, 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 thesoil 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

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 more dire. Soilthat 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 itwould 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

What are the different types of air pollution? Mention their sources and the effects on the environment

AIR POLLUTION

Air pollution is the introduction of chemicals, particulates, biological materials, or other harmful materials into the Earth's atmosphere, possibly causing disease, death to humans, damage to other living organisms such as food crops, or the natural or built environment.

The atmosphere is a complex natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth's ecosystems.

SOURCES

There are various locations, activities or factors which are responsible for releasing pollutants into the atmosphere. These sources can be classified into two major categories.

Anthropogenic (man-made) sources:

These are mostly related to the burning of multiple types of fuel.

Stationary Sources include smoke stacks of power plants, manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices. In developing and poor countries, traditional biomass burning is the major source of air pollutants; traditional biomass includes wood, crop waste and dung

Mobile Sources include motor vehicles, marine vessels, and aircraft.

Chemicals', dust and controlled burn practices in agriculture and forest management'. Controlled or prescribed burning is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for foresters. Controlled burning stimulates the germination of some desirable forest trees, thus renewing the forest.

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

Waste deposition in landfills, which generate methane. Methane is highly flammable and may form explosive mixtures with air. Methane is also an asphyxiant and may displace oxygen in

an enclosed space. Asphyxia or suffocation may result if the oxygen concentration is reduced to below 19.5% by displacement.

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

Natural sources:

Dust from natural sources, usually large areas of land with few 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. Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health hazard. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after cigarette smoking.

Smoke and carbon monoxide from wildfires

Vegetation, in some regions, emits environmentally significant amounts of VOCs on warmer days. These VOCs react with primary anthropogenic pollutants—specifically, NOx, SO2, and anthropogenic organic carbon compounds—to produce a seasonal haze of secondary pollutants.[7]

Volcanic activity, which produces sulfur, chlorine, and ash particulates

POLLUTANTS

An air pollutant is a substance in the air that can have adverse effects on humans and the ecosystem. The substance can be solid particles, liquid droplets, or gases. A pollutant can be of natural origin or man-made. Pollutants are classified as primary or secondary. Primary pollutants are usually produced from a process, such as ash from a volcanic eruption. Other examples include carbon monoxide gas from motor vehicle exhaust, or the sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. Ground level ozone is a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants.

Major primary pollutants produced by human activity include:

Sulfur oxides (SOx) - particularly sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.[2] This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.

Nitrogen oxides (NOx) - Nitrogen oxides, particularly nitrogen dioxide, are expelled from high temperature combustion, and are also produced during thunderstorms by electric discharge. They can be seen as a brown haze dome above or a plume downwind of cities. Nitrogen dioxide is a chemical compound with the formula NO2. It is one of several nitrogen oxides. One of the most prominent air pollutants, this reddish-brown toxic gas has a characteristic sharp, biting odor.

Carbon monoxide (CO)- CO is a colourless, odourless, toxic yet non-irritating 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.

Volatile organic compounds - VOCs are a well known outdoor air pollutant. They are categorized as either methane (CH4) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life of methane in the atmosphere. This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure. 1,3-butadiene is another dangerous compound often associated with industrial use.

Particulates, alternatively referred to as particulate matter (PM), atmospheric particulate matter, or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to combined particles and gas. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged worldwide, anthropogenic aerosols—those made by human activities—currently account for approximately 10 percent of our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.

Persistent free radicals connected to airborne fine particles are linked to cardiopulmonary disease

Toxic metals, such as lead and mercury, especially their compounds.

Chlorofluorocarbons (CFCs) - harmful to the ozone layer; emitted from products currently banned from use

These are gases which are released from air conditioners, refrigerators, aerosol sprays, etc. CFC's on being released into the air rises to stratosphere. Here they come in contact with other gases and damage the ozone layer. This allows harmful ultraviolet rays to reach the earth's surface. This can lead to skin cancer, disease to eye and can even cause damage to plants.

Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with the formula NH3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.

Odours — such as from garbage, sewage, and industrial processes

Radioactive pollutants - produced by nuclear explosions, nuclear events, war explosives, and natural processes such as the radioactive decay of radon

EFFECTS OF AIR POLLUTION

Pollutants can affect human respiratory and cardiovascular systems. The young, the elderly and those with acute illnesses are at greater risk of such effects. Different pollutants have been associated with

hospitalizations, increased respiratory and cardiovascular mortality, asthma exacerbation, decreased lung function, lung inflammation and changes in heart rate variability

Impacts range from minor breathing problems to premature death. The more common effects include changes in breathing and lung function, lung inflammation, and irritation and aggravation of existing heart and lung conditions (e.g. asthma, emphysema and heart disease)

Negative health effects increase as the concentrations of pollutants in the air increases. Even modest increases in concentration (e.g. PM2.5 and O3) can cause small but measurable increases in emergency room visits, hospital admissions, and premature death.

Ground-level ozone damages vegetation, including crops, flowers, shrubs and forests, by interfering with plants’ ability to produce and store food. This damage makes them more susceptible to disease, pests and environmental stresses.

Nitrogen oxides (NOx) and sulphur dioxide (SO2) can become acidic gases or particulates, and cause or accelerate the corrosion and soiling of materials. Together with ammonia, they are also the main precursors of acid rain. Acid rain affects soils and water bodies, and stresses both vegetation and animals.

Health impact of specific air pollutants

Some of these gases can seriously and adversely affect the health of the population and should be

given due attention by the concerned authority. The gases mentioned below are mainly outdoor air

pollutants but some of them can and do occur indoor depending on the source and the circumstances.

Tobacco smoke. Tobacco smoke generates a wide range of harmful chemicals and is a major

cause of ill health, as it is known to cause cancer, not only to the smoker but affecting passive

smokers too. It is well-known that smoking affects the passive smoker (the person who is in the

vicinity of a smoker and is not himself/herself a smoker) ranging from burning sensation in the

eyes or nose, and throat irritation, to cancer, bronchitis, severe asthma, and a decrease in lung

function.

Biological pollutants. These are mostly allergens that can cause asthma, hay fever, and other

allergic diseases. 

Volatile organic compounds. Volatile compounds can cause irritation of the eye, nose and

throat. In severe cases there may be headaches, nausea, and loss of coordination. In the longer run,

some of them are suspected to cause damage to the liver and other parts of the body.

Formaldehyde. Exposure causes irritation to the eyes, nose and may cause allergies in some

people.

Lead. Prolonged exposure can cause damage to the nervous system, digestive problems, and in

some cases cause cancer. It is especially hazardous to small children.

Radon. A radioactive gas that can accumulate inside the house, it originates from the rocks and

soil under the house and its level is dominated by the outdoor air and also to some extent the other

gases being emitted indoors. Exposure to this gas increases the risk of lung cancer.

Ozone. Exposure to this gas makes our eyes itch, burn, and water and it has also been associated

with increase in respiratory disorders such as asthma. It lowers our resistance to colds and

pneumonia.

Oxides of nitrogen. This gas can make children susceptible to respiratory diseases in the

winters.

Carbon monoxide. CO (carbon monoxide) combines with haemoglobin to lessen the amount of

oxygen that enters our blood through our lungs. The binding with other haeme proteins causes

changes in the function of the affected organs such as the brain and the cardiovascular system, and

also the developing foetus. It can impair our concentration, slow our reflexes, and make us

confused and sleepy.

Sulphur dioxide. SO2 (sulphur dioxide) in the air is caused due to the rise in combustion of fossil

fuels. It can oxidize and form sulphuric acid mist. SO2 in the air leads to diseases of the lung and

other lung disorders such as wheezing and shortness of breath. Long-term effects are more

difficult to ascertain as SO2 exposure is often combined with that of SPM.

SPM (suspended particulate matter). Suspended matter consists of dust, fumes, mist and smoke.

The main chemical component of SPM that is of major concern is lead, others being nickel,

arsenic, and those present in diesel exhaust. These particles when breathed in, lodge in our lung

tissues and cause lung damage and respiratory problems. The importance of SPM as a major

pollutant needs special emphasis as

a) it affects more people globally than any other pollutant on a continuing basis;

b) there is more monitoring data available on this than any other pollutant; and

c) more epidemiological evidence has been collected on the exposure to this than to any other

pollutant.

Discuss in detail the global environmental issues

The main global environmental issues are discussed in detail below

1. GREENHOUSE EFFECT AND GLOBAL WARMING

The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases.

Solar radiation at the frequencies of visible light largely passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere. The mechanism is named after the effect of solar radiation passing through glass and warming a greenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing airflow, isolating the warm air inside the structure so that heat is not lost by convection

Global warming refers to an unequivocal and continuing rise in the average temperature of Earth's climate system. Since 1971, 90% of the warming has occurred in the oceans.Despite the oceans' dominant role in energy storage, the term "global warming" is also used to refer to increases in average temperature of the air and sea at Earth's surface. Since the early 20th century, the global air and sea surface temperature has increased about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980.Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.

The effects of an increase in global temperature include a rise in sea levels and a change in the amount and pattern of precipitation, as well as a probable expansion of subtropical deserts.Warming is expected to be strongest in the Arctic, with the continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent extreme weather events including heat waves, droughts and heavy rainfall; ocean acidification; and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the loss of habitat from inundation.

2. Ozone Layer depletion 

Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone inEarth's stratosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon is referred to as the ozone hole. In addition to these well-known stratospheric phenomena, there are also springtime polar tropospheric ozone depletion events.

The details of polar ozone hole formation differ from that of mid-latitude thinning, but the most important process in both is catalytic destruction of ozone by atomichalogens. The main source of these halogen atoms in the stratosphere is photo dissociation of man-made halocarbon refrigerants, solvents, propellants, and foam-blowing agents (CFCs, HCFCs, freons, halons). These compounds are transported into the stratosphere after being emitted at the surface.  Both types of ozone depletion have been observed to increase as emissions of halo-carbons increased.

CFCs and other contributory substances are referred to as ozone-depleting substances (ODS). Since the ozone layer prevents most harmful UVB wavelengths (280–315 nm) of ultraviolet light (UV light) from passing through the Earth's atmosphere, observed and projected decreases in ozone have generated worldwide concern leading to adoption of the Montreal Protocol that bans the production of CFCs, halons, and other ozone-depleting chemicals such as carbon tetrachloride andtrichloroethane. It is suspected that a variety of biological consequences such as increases in skin cancer, cataracts, damage to plants, and reduction of plankton populations in the ocean  may result from the increased UV exposure due to ozone depletion.

Three forms (or allotropes) of oxygen are involved in the ozone-oxygen cycle: oxygen atoms (O or atomic oxygen), oxygen gas (O2 or diatomic oxygen), and ozone gas (O3 or triatomic oxygen). Ozone is formed in the stratosphere when oxygen molecules photodissociate after absorbing an ultraviolet photon whose wavelength is shorter than 240 nm. This converts a single O2 into two atomic oxygen radicals. The atomic oxygen radicals then combine with separate O2 molecules to create two O3 molecules. These ozone molecules absorb UV light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom then joins up with an oxygen molecule to regenerate ozone. This is a continuing process that terminates when an oxygen atom "recombines" with an ozone molecule to make two O molecules.

2 O3 → 3 O2 chemical equation

The overall amount of ozone in the stratosphere is determined by a balance between photochemical production and recombination.

Ozone can be destroyed by a number of free radical catalysts, the most important of which are the hydroxyl radical (OH·), the nitric oxide radical (NO·), atomic chlorine ion (Cl·) and atomic bromine ion (Br·). The dot is a common notation to indicate that all of these species have an unpaired electron and are thus extremely reactive. All of these have both natural and man-made sources; at the present time, most of the OH· and NO· in the stratosphere is of natural origin, but human activity has dramatically increased the levels of chlorine and bromine. These elements are found in certain stable organic compounds, especially chlorofluorocarbons (CFCs), which may find their way to the stratosphere without being destroyed in the troposphere due to their low reactivity. Once in the stratosphere, the Cl and Br atoms are liberated from the parent compounds by the action of ultraviolet light, e.g.

CFCl3 + electromagnetic radiation → CFCl2 + Cl

The Cl and Br atoms can then destroy ozone molecules through a variety of catalytic cycles. In the simplest example of such a cycle,a chlorine atom reacts with an ozone molecule, taking an oxygen atom with it (forming ClO) and leaving a normal oxygen molecule. The chlorine monoxide (i.e., the ClO) can react with a second molecule of ozone (i.e., O

3) to yield another chlorine atom and two molecules of oxygen. The chemical shorthand for these gas-phase reactions is:

Cl + O3 → ClO + O2: The chlorine atom changes an ozone molecule to ordinary oxygen

ClO + O3 → Cl + 2 O2:

The ClO from the previous reaction destroys a second ozone molecule and recreates the original chlorine atom, which can repeat the first reaction and continue to destroy ozone.

The overall effect is a decrease in the amount of ozone, though the rate of these processes can be decreased by the effects of null cycles. More complicated mechanisms have been discovered that lead to ozone destruction in the lower stratosphere as well.

A single chlorine atom would keep on destroying ozone (thus a catalyst) for up to two years (the time scale for transport back down to the troposphere) were it not for reactions that remove them from this cycle by forming reservoir species such as hydrogen chloride (HCl) and chlorine nitrate (ClONO2).

On a per atom basis, bromine is even more efficient than chlorine at destroying ozone, but there is much less bromine in the atmosphere at present. As a result, both chlorine and bromine contribute significantly to overall ozone depletion. Laboratory studies have shown that fluorine and iodine atoms participate in analogous catalytic cycles. However, in the Earth's stratosphere, fluorine atoms react rapidly with water and methane to form strongly bound HF, while organic molecules containing iodine react so rapidly in the lower atmosphere that they do not reach the stratosphere in significant quantities.

On average, a single chlorine atom is able to react with 100,000 ozone molecules before it is removed from the catalytic cycle. This fact plus the amount of chlorine released into the atmosphere yearly by chlorofluorocarbons (CFCs) and hydrofluorocarbons (HCFCs) demonstrates how dangerous CFCs and HCFCs are to the environment