CBSE Class 12 Biology Revision Notes Chapter 16 - Environmental Issues
REVISION NOTES FOR CBSE CLASS 12 BIOLOGY CHAPTER 16
CHAPTER 16: ENVIRONMENTAL ISSUES
Air pollution and its control; water pollution and its control; agro chemicals and their effects; solid waste management; radioactive waste management; green house effect and climate change; impact and mitigation ozone layer depletion; deforestation; any one case study as success story addressing environmental issue.
¶ Pollution: Undesirable physical/chemical/biological characteristics of air/ water/ land which cause damage to the animals/plants/humans and architectural structures.
¶ Pollutants: Agents which cause pollution.
¶ Slash and Burn Agriculture (Jhum Cultivation): Farmers cut down trees and burn the plant remains. Ash is used as a fertilizer and the land is then used for farming or cattle grazing.
¶ Reforestation: Process of restoring a forest that was removed at some point of time in the past.
¶ Effluents: Something flowing over a large body of water (may be sewage or industrial effluents).
¶ CPCB: Central Pollution Control Board
¶ FOAM: Friends of Arcata Marsh
¶ JFM (Joint Forest Management): Introduced by the Government of India in 1980s to work closely with local communities for protecting and managing forests.
CONTROL OF AIR POLLUTION :
Air pollution can be controlled by following methods:
1. Electrostatic precipitator: This device is very efficient, used to remove particulate matter from air. This device can remove 99% particulates which are present industrial or thermal power plant's exhausts. In this device electrode wire at thousand volts are used and dust particles passed out through this device. Electrons released get attached to dust particles giving them negative charge. The collecting plates which are grounded attract these charged particles.
2. Scrubber: This device is used to remove gaseous pollutant like sulphur dioxide. The exhaust is passed through a spray of water and lime, which on reacting with sulphur dioxide form precipitate.
3. Catalytic converter: This is a device fitted in automobiles for emmission of gases. In catalytic converter metals like rhodium and platinum palladium act as catalyst. Only unleaded petrol can be used in vehicle in which catalytic converter is fitted.
BIOCHEMICAL OXYGEN DEMAND (BOD)
¶ BOD refers to the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidized by bacteria. The BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water.
¶ Indirectly, BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, more is its polluting potential.
¶ In the given figure, the effect of sewage on some important characteristics of a river is shown:
Harmful effects of algal bloom are:
1. Fish mortality.
2. Deterioration of water quality.
3. Toxic to animals and human beings.
BIOMAGNIFICATION
¶ It refers to increase in concentration of toxic substances at successive trophic levels.
¶ Biomagnification of DDT in an aquatic food chain is given below:
Eutrophication: It is the process of nutrient enrichment of water and subsequent loss of species diversity like fishes. Excess nutrients causes algal bloom which may cover the whole surface of water body and release toxins. It causes oxygen deficiency in water that leads to the death of aquatic animals like fishes.
Global Warming: Increase in the level of greenhouse gases is mainly responsible for global warming, (increase in mean global temperature due to trapping of infrared radiation). Carbon dioxide, Methane, CFCs. N₂O are the main gases that cause greenhouse effect.
1. Melting of glaciers
2. Over many years, this will result in a rise in sea level that can flood the coastal areas.
MEASURES TO CONTROL GLOBAL WARMING
1. Minimise the use of fossil fuel.
2. Improving efficiency of energy usage.
3. Reducing deforestration.
4. Planting trees.
CLIMATE CHANGE IMPACT AND MITIGATION
Human activities are changing the composition as well as behaviour of the atmosphere leading to its deterioration at global level. Climate change is phenomenon of seasonal changes over a period of time with accumulation of green house gases in the atmosphere. Since climate plays major role in the formation of natural ecosystem and the human economy, therefore we need to tackle this phenomenon. Due to climate change, we are facing new challenges for survival. More frequent and intense drought, storms, heat waves, rising sea level, melting of glaciers which can harm not only animals but also their habitat. Climate change will adversely affect our agriculture and thus our food supply.
Climate change mitigation refers to the effort to reduce or prevent the emission of green house gases. Climate change mitigation consists of actions which limit the magnitude or rate of long term climate change. We can achieve mitigation by increasing the capacity of carbon sink eg through reforestration. It is said that mitigation policies can substantially reduce the risk which are associated with human induced global warming. So we have to think about
¶ Phasing out of fossil fuel and switching on to low carbon energy sources.
¶ Use of renewable energy resources
¶ Expanding forest to remove greater amount of carbon dioxide from the atmosphere.
OZONE DEPLETION
¶ Ozone gas is continuously formed by the action of UV-rays on molecular oxygen and also degraded into molecular oxygen in stratosphere.
¶ The thickness of the ozone-layer in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU).
¶ Ozone layer absorbs the harmful UV-rays. These rays cause the skin cancer, damages genes, causes inflammation of cornea.
¶ Chlorofluorocarbon (CFCs) deplete the ozone layer. The part of atmosphere with lesser concentration of ozone is called ozone hole.
STEPS LEADING TO OZONE DEPLETION
¶ UV-rays split CFCs and release atomic chlorine (CI)
¶ UV-rays also split ozone into oxygen. (O3 →(UV rays)→O2+[O]
¶ Chlorine atoms trap oxygen atoms and ozone is not formed again from oxygen. This leads to depletion of ozone in the stratosphere.
Ozone Hole : Large area of thinned ozone layer over Antartica.
Control of Vehicular Air Pollution in Delhi: All the buses of Delhi were converted to run on CNG by the end of the 2002. Other steps to reduce air pollution in Delhi include.
1. Phasing out of old vehicles.
2. Use of unleaded petrol and low sulphur petrol and diesel.
3. Use of catalytic converters in vehicles.
4. Application of Euro-IV norms for vehicles from April 1, 2010.
Auto Fuel Policy: The Government of India has laid out a road map to cut down the vehicular air pollution in many cities of India. The goal is to reduce sulphur down to 35% of the fuel. The Bharat Stage II was applied to all automobiles in all cities from April, 1,2005. The cities like Delhi, Mumbai, Chennai, Kolkata have to meet Euro emission norms from April 1, 2005 and Euro IV Emission norms from April, 1, 2010.
Electronic Wastes (e-waste): e-wastes are irreparable computer and other electronic goods.
Disposal of e-wastes :
1. Burned in landfills
2. Incineration.
3. Recycling.
El Nino effect: Rise in temperature leading to deleterious changes in the environment and resulting in odd climatic changes is El Nino effect.
Adverse effect: Increased melting of polar ice, submerging of coastal areas, flood, loss of habitat leading to loss of biodiversity.
Comments
Post a Comment