ENVIRONMENTAL ISSUES

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Water act- 1974 for prevention and control of pollution

Water pollutants a) Heavy metals (industrial waste) b) Sewage waste - contains biodegradable organic compounds, nitrates, phosphates and toxic metal ions (also human wastes)

BIOCHEMICAL OXYGEN DEMAND- The amount of organic matter in sewage water is estimated by measuring the Biochemical Oxygen Demand

The amount of oxygen needed by the biological organisms such as bacteria for the breakdown of organic matter by oxidation process is called BOD. After this process the demand for oxygen is increased by aquatic organisms

HARMFUL EFFECTS OF WATER POLLUTION

1) The microbes involved in biodegradation consumes a large amount of oxygen dissolved in water. It results in the decline of dissolved oxygen(OD) downstream from the point of sewage discharge which causes mortality of fishes and other organisms

2) Presence of large amounts of nutrients in waters also causes excessive growth of planktonic algae (algal bloom). - It imparts a distinct color to the water bodies - Deteriorates the water quality resulting in death of fishes. - Some bloom-forming algae are extremely toxic to human beings and animals.

3) some toxic substances (mercury, DDT etc) present in industrial waste waters, cause biological magnification in the aquatic food chain .Biomagnification is the accumulation of the harmful substances at successive trophic levels. Reason: The organism in each trophic level cannot metabolize or excrete the toxicant, and is thus passed on to the next trophic level.

4) Eutrophication: It is the natural aging of a lake by nutrient enrichment.

Young lake (water is cold and clear with some organisms)

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Streams and agricultural run-offs drains into the lake introduce nutrients (N2, P etc)

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Encourage the growth of aquatic plants and animals.

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Over centuries, the lake becomes shallower and warmer (with warm-water organisms)

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Marshy plants grows and fill in the original lake basin

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Large masses of floating plants (bog)

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lake is converted into land.

5) Cultural Eutrophication: It is the phenomenon where the aging process gets accelerated as effluents added from the industries and homes to lakes.

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GREENHOUSE EFFECT

The Greenhouse is a small glass house used for growing plants during winter. The glass panel lets the light in, but does not allow heat to escape. Therefore, the greenhouse warms up.

Greenhouse effect is a natural phenomenon responsible for heating of Earth’s surface and atmosphere. It maintains the present average temperature (150C). Without greenhouse effect, the average temperature at Earth surface would become –180C

Clouds and gases reflect about 1 /4 th of the incoming solar radiation, and absorb some of it. But almost half of incoming solar radiation falls on Earth’s surface heating it, while a small proportion is reflected back. Earth’s surface re-emits heat as infrared radiation. But a part of infrared is absorbed by atmospheric gases (CO2, CH4, etc.) and so cannot escape into space. These gases (greenhouse gases) radiate heat energy, and a major part of which again comes to Earth’s surface, thus heating it up again. These gases cause the greenhouse effect

Increase in the level of CFCs, N2O in addition to CO2, CH4 (greenhouse gases) irradiate more heat energy, has led to global warming (overheating of Earth).

Impacts of global warming

Deleterious changes in the environment resulting in odd climatic changes (e.g. El Nino effect).

Melting of polar ice caps.

Rise in sea level that submerges many coastal areas

Control of global warming:

Reduce the use of fossil fuel​​​​​​​

Improve efficiency of energy usage

Reduce deforestation and plant trees

Slowing down the growth of human population

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OZONE DEPLETION

The ozone layer is present in the stratosphere (16-50 Km). It acts as a shield absorbing 99.5% of harmful UV radiation from the sun

The thickness of the ozone is measured in terms of Dobson units (DU). 1 DU= 0.01 mm of the compressed gas at 00C and 760 mmHg pressure.

Ozone gas is continuously formed by the of UV rays on molecular oxygen, also degraded into molecular oxygen in the stratosphere

Formation of Ozone:- O2 + O= O3 Production & degradation of ozone should be balanced. But the balance is disrupted by CFCs.

CFCs (used as refrigerants) move upward and reach stratosphere. UV rays act on them releasing Cl atoms. In presence of Cl (catalyst), ozone degrades releasing molecular O2. This causes ozone depletion. It has formed ozone hole over the Antarctic region.

STEPS LEADING TO OZONE LAYER DEPLETION

UV radiations splits ozone and release atomic chlorine(CL)

UV rays also splits ozone into oxygen

chlorine traps oxygen and ozone is not formed again. This leads to depletion of ozone in atmosphere

Harmful effects:

UV-B causes mutation of DNA

Causes aging of skin, damage to skin cells and skin cancers.

A high dose of UV-B causes inflammation of cornea (snow blindness), cataract, etc.

DEFORESTATION

Deforestation: The conversion of forested areas to non-forested ones.

Slash & burn agriculture (Jhum cultivation) in the northeastern states of India. In this, the farmers cut down the trees of the forest and burn the plant remains. The ash is used as a fertiliser and the land is then used for farming or cattle grazing. After cultivation, the area is left for several years so as to allow its recovery. - In earlier days, enough time-gap was given for recovery. - With increasing population and repeated cultivation, this recovery phase is done away with, resulting in deforestation.

Consequences of deforestation:

؞ CO2 concentration in the atmosphere is enhanced because trees that could hold a lot of carbon in their biomass are lost with deforestation

؞ Loss of biodiversity due to habitat destruction

؞ Disturbs hydrologic cycle

؞ Soil erosion & Desertification

Reforestation: The process of restoring a forest

Bishnoi movement and Chipko Movement are examples for people’s participation in conservation of forests

 Government of India has instituted the Amrita Devi Bishnoi Wildlife Protection Award for individuals or communities from rural areas for protecting wildlife.

 In 1980s, Government of India has introduced the concept of Joint Forest Management (JFM) so as to work closely with the local communities for protecting and managing forests

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