Monday, April 30, 2012

6. Organisms and populations

Human population explosion increases the demand for food, water, home, electricity, roads, automobiles etc.
It leads to pollution of air, water and soil.

Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil. Agents that cause pollution are called as pollutants.
The Government of India has passed the Environment (Protection) Act, 1986 to control environmental pollution and protect and improve the quality of our environment.
AIR POLLUTION AND ITS CONTROL
Causes of air pollution:
§ Particulate & gaseous air pollutants from smokestacks of thermal power plants, smelters etc.
According to Central Pollution Control Board (CPCB), particulate size of less than 2.5mm in diameter (PM 2.5) causes greatest harm to human health. It causes respiratory problems, irritation, inflammations & damage to lungs and premature deaths.
§ Pollutants from automobiles.
Harmful effects of air pollution:
§ Air pollutants cause injury to all living organisms.
§ They reduce growth and yield of crops and cause premature death of plants.
§ Air pollutants affect the respiratory system.
Control of air pollution
§ Particulate matters must be separated/filtered out before releasing the harmless gases into the atmosphere.
§ Use of lead-free petrol or diesel.
§ Use of catalytic converters (having platinum-palladium & rhodium as the catalysts). It reduces emission of poisonous gases. This converts unburnt hydrocarbons to CO2 & water, and carbon monoxide and nitric oxide to CO2 and nitrogen gas, respectively. Motor vehicles having catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.
§ Phasing out of old vehicles
§ Use of low-sulphur petrol and diesel
§ Application of pollution-level norms for vehicles, etc.
§ In Delhi, compressed natural gas (CNG) in public transport (buses) is used. CNG is better than petrol & diesel because CNG burns most efficiently and very little of it is left unburnt. CNG is cheaper than petrol or diesel, cannot be siphoned off by thieves and adulterated like petrol or diesel. The main problem with switching over to CNG is the difficulty of laying down pipelines to deliver CNG through distribution points/pumps and ensuring uninterrupted supply.
Electrostatic precipitator: (For figure see TB page: 271)
-    It is the device widely used to remove particulate matter.
-    It can remove over 99% particulate matter present in the exhaust from a thermal power plant.
-    The electrons released from electrode wires (maintained at several thousand volts) attach to dust particles and give a negative charge. The collecting plates attract the charged dust particles.
-    The velocity of air between the plates must be low enough to allow the dust to fall.
-    A scrubber removes gases like SO2. In a scrubber, the exhaust is passed through a spray of water or lime.
-    Very small particulates are not removed by this precipitator.
In India, the Air (Prevention & Control of Pollution) Act (1981) was amended in 1987 to include noise as an air pollutant. Noise is undesired high level of sound.
Sources of noise pollution:
Music instruments, loudspeaker, crackers, industries etc.
Harmful effects of noise:
§ Noise causes psychological and physiological disorders.
§ The sound level above 150 dB (generated by takeoff of a jet plane or rocket) may damage ear drums.
§ Chronic exposure to relatively lower noise may damage hearing abilities of humans.
§ Sleeplessness, increased heartbeat & breathing, stress etc.
Control of noise pollution:
§ Use of sound absorbent materials in industries.
§ Delimitation of horn-free zones around hospitals & schools.
§ Permissible sound-levels of crackers and loudspeakers.
§ Delimit the timings of using loudspeakers.
Laws & policies in India to control vehicular pollution:
§ Auto fuel policy has laid out a roadmap to cut down vehicular pollution in Indian cities.
§ Euro II norms: It stipulates that sulphur be controlled at 350 parts-per-million (ppm) in diesel and 150 ppm in petrol. Aromatic hydrocarbons are to be contained at 42% of the concerned fuel. The goal is to reduce sulphur to 50 ppm in petrol and diesel and bring down the level to 35%. Vehicle engines will also need to be upgraded.
WATER POLLUTION AND ITS CONTROL
-    Water bodies are lifeline of all living organisms.
-    Due to human activities, the ponds, lakes, stream, rivers, estuaries and oceans are becoming polluted.
-    The Government of India has passed the Water (Prevention and Control of Pollution) Act, 1974 to safeguard our water resources.
Domestic Sewage and Industrial Effluents
-    A mere 0.1 % impurities make domestic sewage unfit for human use. They include suspended solids (sand, silt, clay etc), colloidal materials (faecal matter, bacteria, cloth, paper fibres etc) and dissolved materials (nutrients like nitrate, NH3, phosphate, Na, Ca etc).
-    Solids are easy to remove. Removal of dissolved materials, organic compounds and toxic metal ions are most difficult.
-    Domestic sewage contains biodegradable organic matter. It is decomposed by microorganisms, which can multiply using these organic substances as substrates and hence utilize some of the components of sewage.
-    The amount of biodegradable organic matter in sewage water is estimated by measuring Biochemical Oxygen Demand (BOD).
-    During biodegradation, microorganisms consume a lot of O2. It results in a sharp decline in dissolved O2. This causes death of aquatic organisms.
-    Presence of large amounts of nutrients in waters also causes excessive growth of planktonic algae (algal bloom). It imparts a distinct colour to the water bodies and deteriorates the water quality resulting in death of fishes. Some bloom-forming algae are extremely toxic to human beings and animals.
-    The water hyacinth (Eichhornia crassipes) is the most problematic aquatic weed (Terror of Bengal’). They grow faster than our ability to remove them. They grow abundantly in eutrophic water bodies. It leads to an imbalance in the ecosystem dynamics of the water body.
-    Sewage from homes & hospitals may contain undesirable pathogens and its disposal into water causes serious diseases (dysentery, typhoid, jaundice, cholera, etc).
-    Industrial (petroleum, metal, paper manufacturing, chemical manufacturing, etc.) waste water contains toxic substances like heavy metals (mercury, cadmium, copper, lead, etc.) and organic compounds.
-    Some toxic substances (mercury, DDT etc) present in industrial waste waters, cause biological magnification (Biomagnification) in the aquatic food chain.
-    Biomagnification is the accumulation of the toxicant at successive trophic levels. The organism in each trophic level cannot metabolize or excrete the toxicant, and is thus passed on to the next trophic level.
Biomagnification of DDT in an aquatic food chain:
Water (DDT: 0.003 ppb) → zooplankton (0.04 ppm) → small fish (0.5 ppm) → large fish (2 ppm) → birds (5 ppm).
-    DDT disturbs calcium metabolism in birds, which causes thinning of eggshell and their premature breaking. It causes decline in bird populations.
Eutrophication:
-    It is the natural aging of a lake by nutrient enrichment.
-    In a young lake the water is cold and clear. With time, streams draining into the lake introduce nutrients (N2, P etc), which encourage the growth of aquatic organisms.
-    As the lake’s fertility increases, plants and animals grow rapidly, and organic remains are deposited on the lake bottom. Thus the lake grows shallower and warmer, with warm-water organisms.
-    Marsh plants take root in the shallows and fill in the original lake basin. Eventually, the lake becomes a bog, finally converting into land.
-    Depending on climate, size of the lake and other factors, the eutrophication may span thousands of years. However, pollutants like effluents from the industries and homes accelerate the aging process. This phenomenon is called Cultural or Accelerated Eutrophication.
-    The prime contaminants are nitrates and phosphates, which act as plant nutrients. They overstimulate the growth of algae, causing unsightly scum and unpleasant odors, and robbing the water of dissolved oxygen vital to other aquatic life. At the same time, other pollutants flowing into a lake may poison whole populations of fish; whose decomposing remains further deplete the water’s dissolved oxygen content.
-    Heated (thermal) wastewater from electricity-generating units (e.g. thermal power plants) eliminates organisms sensitive to high temperature. It may enhance the growth of plants and fish in extremely cold areas but, only after causing damage to the indigenous flora and fauna.
Integrated Waste Water Treatment
-    It includes artificial and natural processes.
-    An example is the town of Arcata, situated along the northern coast of California. Collaborating with biologists from the Humboldt State University, the townspeople created an integrated waste water treatment process within a natural system.
-    The cleaning occurs in two stages
a.    Sedimentation, filtering and chlorine treatments. After this stage, lots of dangerous pollutants like dissolved heavy metals still remain. To combat this, an innovative approach was taken.
b.    The biologists developed a series of six connected marshes over 60 hectares of marshland. Appropriate plants, algae, fungi and bacteria were seeded into this area, which neutralize, absorb and assimilate the pollutants. Hence, as the water flows through the marshes, it gets purified naturally. The marshes also constitute a sanctuary, with a high level of biodiversity in the form of fishes, animals and birds that now reside there. A citizens group called Friends of the Arcata Marsh (FOAM) is responsible for the upkeep and safeguarding of this wonderful project.
-    Ecological sanitation is a sustainable system for handling human excreta, using dry composting toilets. This is a practical, hygienic, efficient and cost-effective solution to human waste disposal. The key point to note here is that with this composting method, human excreta can be recycled into a resource (as natural fertiliser), which reduces the need for chemical fertilisers. There are ‘EcoSan’ toilets in many areas of Kerala & Sri Lanka.
SOLID WASTES
-    Solid wastes refer to everything that goes out in trash.
-    Municipal solid wastes are wastes from homes, offices, stores, schools, hospitals, etc., that are collected and disposed by the municipality.
-    The municipal solid wastes include paper, food wastes, plastics, glass, metals, rubber, leather, textile, etc.
-    Burning reduces the volume of the wastes, although it is generally not burnt to completion and open dumps often serve as the breeding ground for rats and flies.
-    Sanitary landfills were adopted as the substitute for open-burning dumps. In a sanitary landfill, wastes are dumped in a depression or trench after compaction, and covered with dirt every day.
-    Landfills are also not really much of a solution since the amount of garbage generation especially in the metros has increased so much that these sites are getting filled too. Also there is danger of seepage of chemicals, etc., from these landfills polluting the underground water resources.
All wastes can be categorized into 3 types –
(a)    Bio-degradable
(b)    Recyclable
(c)    Non-biodegradable
-    It is important that all garbage generated is sorted. What can be reused or recycled should be separated out. Kabadiwallahs & rag-pickers help to separate materials for recycling.
-    The biodegradable materials can be put into deep pits in the ground and be left for natural breakdown. That leaves only the non-biodegradable to be disposed off.
-    We are increasing the use of non-biodegradable products. E.g. plastic packets of eatables such as biscuit packet, milk and water in polybags, packed fruits and vegetables (in polystyrene and plastic packaging) etc.
-    State Governments are trying to push for reduction in use of plastics and use of eco-friendly packaging. We can use carrying cloth or other natural fibre carry-bags instead of polythene bags for shopping.
-    Hospital wastes contain disinfectants and other harmful chemicals, and also pathogenic micro-organisms. The incinerators are used to dispose hospital wastes.
-    Irreparable computers and other electronic goods are known as electronic wastes (e-wastes). They are buried in landfills or incinerated.
-    Over half of the e-wastes generated in the developed world are exported to developing countries, mainly to China, India and Pakistan, where metals like copper, iron, silicon, nickel and gold are recovered during recycling process.
-    Developed countries have specifically built facilities for recycling of e-wastes. Recycling in developing countries often involves manual participation thus exposing workers to toxic substances present in e-wastes. Recycling is the only solution for the treatment of e-waste, provided it is carried out in an environment friendly manner.
Polyblend: A Remedy for Plastic Waste
-    Ahmed Khan (A plastic sack manufacturer in Bangalore) developed Polyblend. It is a fine powder of recycled modified plastic. Polyblend is mixed with the bitumen and is used to lay roads.
-    Blend of Polyblend and bitumen enhances the bitumen’s water repellant properties and helps to increase road life.
AGRO-CHEMICALS AND THEIR EFFECTS
-    In the wake of green revolution, use of inorganic fertilisers, pesticides, herbicides, fungicides, etc. has increased manifold for enhancing crop production.
-    These are toxic to non-target organisms that are important components of the soil ecosystem. These can be biomagnified in the terrestrial ecosystems.
-    Chemical fertilisers cause eutrophication.
Integrated Organic Farming
-    It is a cyclical, zero-waste procedure, where waste products from one process are cycled in as nutrients for other processes. This allows the maximum utilization of resource and increases the efficiency of production.
-    Ramesh Chandra Dagar (a farmer in Sonipat, Haryana) included bee-keeping, dairy management, water harvesting, composting and agriculture in a chain of processes, which support each other and allow an extremely economical and sustainable venture.
-    There is no need of chemical fertilisers, as cattle excreta (dung) are used as manure. Crop waste is used to create compost, which can be used as a natural fertilizer or can be used to generate natural gas for satisfying the energy needs of the farm.
-    Dagar has created the Haryana Kisan Welfare Club, with a membership of 5000 farmers to spread information on the practice of integrated organic farming.
RADIOACTIVE WASTES
-    Use of nuclear energy has two very serious problems:
Accidental leakage. E.g. incident in the Three Mile Island and Chernobyl incidents
Safe disposal of radioactive wastes.
-    Radiation from nuclear waste is extremely damaging to organisms, because it causes mutations at a very high rate. At high doses, nuclear radiation is lethal but at lower doses, it creates various disorders, such as cancer.
-    It has been recommended that storage of nuclear waste, after sufficient pre-treatment, should be done in suitably shielded containers buried within the rocks, about 500 m deep below the earth’s surface. However, this method of disposal is meeting stiff opposition from the public.
GREENHOUSE EFFECT & GLOBAL WARMING
-    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 (15oC).
-    Without greenhouse effect, the average temperature at Earth surface would have been a chilly (–18oC).
-    Clouds and gases reflect about 1/4th 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 greenhouse gases has led to global warming (overheating of Earth leading).
-    During the past century, the temperature of Earth has increased by 0.60C, most of it during the last 3 decades.
Impacts of global warming:
§ Deleterious changes in the environment resulting in odd climatic changes (e.g. El Nino effect).
§ Melting of polar ice caps, Himalayan snow caps etc.
§ Over many years, this will result in a 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
International initiatives are also being taken to reduce the emission of greenhouse gases into the atmosphere.
OZONE DEPLETION IN THE STRATOSPHERE
-    ‘Bad’ ozone is formed in the lower atmosphere (troposphere). It harms plants and animals.
-    The ‘good’ ozone is found in the stratosphere. It acts as a shield absorbing ultraviolet radiation from the sun.
-    UV rays are highly injurious since they cause mutation.
-    The thickness of the ozone (O3) in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU).
-    Ozone is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere.
-    Production & degradation of ozone in the stratosphere should be balanced. But the balance is disrupted due to ozone degradation by chlorofluorocarbons (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 oxygen (O2). This causes ozone depletion. It has formed ozone hole over the Antarctic region.
-    UV radiation of wavelengths shorter than UV-B, are almost completely absorbed by Earth’s atmosphere. But, UV-B causes mutation of DNA. It 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. It permanently damages the cornea.
-    The Montreal Protocol (an international treaty in Canada, 1987) was signed to control the emission of ozone depleting substances. Subsequently many more efforts have been made and protocols have laid down definite roadmaps, separately for developed and developing countries, for reducing the emission of CFCs and other ozone depleting chemicals.
DEGRADATION BY IMPROPER RESOURCE UTILISATION AND MAINTENANCE
Soil erosion and desertification:
-    Human activities like over-cultivation, deforestation, grazing and poor irrigation practices, leads to soil erosion. It results in arid patches of land and desertification.
-    Increased urbanization also creates desertification.
Water logging and soil salinity:
-    These are the problems as a part of Green Revolution.
-    Irrigation without proper drainage of water leads to water logging in the soil.
-    It draws salt to the surface of the soil. The salt is deposited on the land surface or collects at the plant roots. This damages the agriculture.
DEFORESTATION
§ It is the conversion of forested areas to non-forested ones.
§ Almost 40% forests have been lost in the tropics, compared to only 1% in the temperate region.
§ National Forest Policy (1988) of India has recommended 33% forest cover for the plains and 67% for the hills. But we have only 19.4% of forest cover (it was about 30% at the beginning of 20th century).
Reasons of deforestation:
§ Conversion of forest to agricultural land.
§ For timber, firewood, cattle ranching etc.
§ Slash & burn agriculture (Jhum cultivation) in the north-eastern 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 that once existed in the past. It may occur naturally in a deforested area. However, we can speed it up by planting trees.
People’s Participation in Conservation of Forests
Bishnoi movement
§ In 1731, the king of Jodhpur in Rajasthan asked to arrange wood for constructing a new palace. The minister and workers went to a forest near a village, inhabited by Bishnois. The Bishnois thwarted them from cutting down the trees. A Bishnoi woman Amrita Devi hugged a tree. Sadly, the king’s men cut down the tree along with Amrita Devi. Her three daughters and hundreds of other Bishnois followed her, and thus lost their lives saving trees.
§ Government of India has instituted the Amrita Devi Bishnoi Wildlife Protection Award for individuals or communities from rural areas for extraordinary courage and dedication in protecting wildlife.
Chipko Movement of Garhwal Himalayas
§ In 1974, local women participated to protect trees from the axe of contractors by hugging them.
Realizing the significance of participation by local communities, the Government of India in 1980s has introduced the concept of Joint Forest Management (JFM) so as to work closely with the local communities for protecting and managing forests. In return for their services to the forest, the communities get benefit of various forest products (e.g., fruits, gum, rubber, medicine, etc.), and thus the forest can be conserved in a sustainable manner.


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