Environmental pollution and degradation
humans have spoilt environment by 1. excessive use of resources and 2. by polluting environment
Eutrophication of a water body occurs when plant nutrients such as nitrates and phosphates are released by the action of aerobic bacteria on organic wastes entering a water body . These nutrients promote growth of algae (algal bloom). Algae consume all the oxygen and aquatic organism die due to lack of oxygen.
Collapse of marine fishery : due to global warming animals have permanently moved to cooler northern regions. Smaller fish are able to move faster to cooler areas away and the elevated temperature is taking its toll on larger fish
Deforestation is a broad term. It includes lopping, felling, and removal of forest litter , browsing, grazing and trampling of seedlings. can also be defined as the removal or damage of vegetation in a forest to the extent that it no longer supports its natural flora and fauna. Forest cover of india is about 22.7%only instead of 33%.
The main causes of deforestation are:
- - agriculture;
- - shifting cultivation;
- - demand for firewood : Almost 44% of the total global wood produced fulfils the fuel requirements of the world
- - demand of wood for industry and commercial purposes;
- - urbanization and developmental projects;
- - other causes.
Deforestation affects both physical and biological components of the environment: - Soil erosion and flash flood : landslides, flood, washing of top soil - Climatic change - Loss of biodiversity
desertification: destruction of the biological potential of the land which can ultimately lead to desert like conditions. climate is dry , restoration is very slow, Caused due to : excessive felling of trees, high wind velocity , low precipitation, increasing aridity and extremes of temperatures Causes of land degradation - Deforestation - Overgrazing– About 20% of the world’s pasture and range lands have been damaged - Fuel wood consumption: Wood fuel is the primary source of energy in many developing regions - Agricultural mismanagement– Loss of soil due to water erosion, Soil salinization, water logging, chemical degradation - Industrialization and urbanization, road construction, mining and industry About 76.15% of the total Indian desert area has resulted from manmade desertification process. Another 19.5% of the total area is subjected to medium or slight desertification. This area is concentrated mostly along the eastern Rajasthan in the north-east to south-west zone parallel to the foothills of Aravalis.
Other pollutants : Tetraethyl lead, Oxides of iron, aluminum, manganese, magnesium, zinc
Prevention and control of air pollution
- - proper ventilation for disinfectants, fumigants, volatile organic compounds used in houses and buildings
- - Use of cleaner fuels such as biogas, kerosene, smokeless chullahs
- - species of trees such as baval (Acacia nilotica) which are least smoky should be planted and used. Charcoal is a comparatively cleaner fuel
Prevention and control of industrial pollution
- - use of cleaner fuels
- - employing environment friendly industrial processes
- - installing devices which reduce release of pollutants. Devices like filters, electrostatic precipitators, inertial collectors, scrubbers, gravel bed filters or dry scrubbers
- > Filters – Filters remove particulate matter from the gas stream. The medium of a filter may be made of fibrous materials like cloth, granular material like sand, a rigid material like screen, or any mat like felt pad. Baghouse filtration system is the most common one and is made of cotton or synthetic fibres ( for low temperatures) or glass cloth fabrics (for higher temperature up to 290 o C).
- > Electrostatic precipitators (ESP) - The emanating dust is charged with ions and the ionized particulate matter is collected on an oppositely charged surface. The particles are removed from the collection surface by occasional shaking or by rapping the surface. ESPs are used in boilers, furnaces, and many other units of thermal power plants, cement factories, steel plants, etc
- > Inertial collectors –It works on the principle that inertia of SPM in a gas is higher than its solvent and as inertia is a function of the mass of the particulate matter this device collects heavier particles more efficiently . ‘Cyclone’ is a common inertial collector used in gas cleaning plants.
- > Scrubbers– Scrubbers are wet collectors. They remove aerosols from a stream of gas either by collecting wet particles on a surface followed by their removal, or else the particles are wetted by a scrubbing liquid. The particles get trapped as they travel from supporting gaseous medium across the interface to the liquid scrubbing medium. Gaseous pollutants can be removed by absorption in a liquid using a wet scrubber and depends on the type of the gas to be removed e.g. for removal of sulphur dioxide alkaline solution is needed as it dissolves sulphur dioxide. Gaseous pollutants may be absorbed on an activated solid surface like silica gel, alumina, carbon, etc. Silica gel can remove water vapour . Condensation allows the recovery of many by products in coal and petroleum processing industries from their liquid effluents.
Control of vehicular pollution
- - emission standards for automobiles
- - To reduce emission of sulphurdioxide, sulphur content in diesel has been reduced to 0.05%.
- - Addition of lead in petrol has been banned
- - CNG is being encouraged for use in public transport vehicles.
- - Pollution control certificate is required
- W .H.O. (W orld Health Organization) has prescribed optimum noise level as 45 dB by day and 35 dB by night. Anything above 80 dB is hazardous.
- maintenance of vehicles.
- noise attenuation walls
- appropriate insulation
- not be permitted at night
- green belt of trees is an efficient noise absorber
- mercury causes Minamata disease
- Lead causes displexia
- cadmium poisoning causes Itai – Itai disease
Sources of soil pollution
- Plastic bags
- Agricultural sources like pesticide, fertilizer, herbicide.
- Non-ionizing radiations are constituted by the electromagnetic waves at the longer wavelength of the spectrum ranging from near infra-red rays to radio waves. These waves have energies enough to excite the atoms and molecules of the medium through which they pass, causing them to vibrate faster but not strong enough to ionize them. In a microwave oven the radiation causes water molecules in the cooking medium to vibrate faster and thus raising its temperature.
- At higher doses (up to 100 rem), the cells might damage
- Radiation damage can be divided into two types: (a) somatic damage (also called radiation sickness) and (b) genetic damage.
- somatic radiation damage include reddening of the skin, loss of hair , ulceration, fibrosis of the lungs, the formation of holes in tissue, a reduction of white blood cells, and the induction of cataract in the eyes. This damage can also result in cancer and death.
- Genetic damage refers to damage to cells associated with reproduction. This damage can subsequently cause genetic damage from gene mutation resulting in abnormalities. Genetic damages are passed on to next generation.
- Contact transmission: Some diseases can be transmitted by either direct physical contact with the infected person or the causative agent can be transmitted to the host indirectly by contact with the infected articles.
- Vehicle transmission:(a) Pathogenic organisms are transmitted through water , food, etc. When the water is infected at the source, it spreads the infection to large populations. eg Pathogens causing Cholera, Typhoid and Hepatitis. (b) Many chemical pollutants such as food additives, adulterants, poisonous industrial waste, pesticides and metals get mixed with water including underground water and are consumed by humans and animals resulting in diseases.
- Vector transmission:Vector is a carrier of pathogen. Mosquito spend a part of their life cycle in water and is Vector for disases such as malaria, yellow fever , encephalitis, filaria and dengue.
- Typhoid - Salmonella typhi
- Cholera - Vibrio cholerae
- Bacterial Diaorhoe - Shigellaspp
- Leptospirosis - Leptospira
- Bilharzia - Schistosomaspp
- Filaria - Wuchereria
- Dengue - Barbo
The tumors can be either benign or malignant. benign tumors are not harmful. malignant tumors are cancerous herbicides like 2,4-dichlorophenoxyacetic acid (2,4-D) has been associated with a 200-800% increase of NHL(Non-Hodgkin’ s L ymphoma)
Blue Baby disease nitrogenous fertilizers increased levels of nitrates this causes methaemoglobinaemia particularly in bottle fed infants who are very sensitive to this pollutant Methaemoglobin is formed when iron in the haemoglobin molecule is oxidized from Fe 2 + (ferrous) to Fe 3 + (ferric) form. Due to reduced carrying capacity for oxygen the babies gradually acquire a blue tinge and hence the name – “Blue Baby disease”
Arsenic is associated with copper, iron and silver ores. Arsenic is emitted from fossil fuel burning. Liquid effluents from fertilizer plants also contain arsenic. Ground water contamination with arsenic is very common If a person drinks water contaminated with arsenic for about 10 years, dark spot develop on the upper chest, back and arms known as melanosis.The next stage is keratosis in which palms become hard and patient may suffer from diarrohea, stomach pain, breathing problems
Mining especially of zinc and metallurgical operations, electroplating industries, etc. release cadmium in the environment It may cause hypertension, liver cirrhosis, brittle bones, kidney damage and lung cancer . Itai-itai disease Problems of heavy metal toxicity can be prevented by avoiding the use of utensils made from materials containing these heavy metals or use of drinking water and consuming fish having these heavy metals.
- Black lung disease is the common name for pneumoconiosis (CWP) or anthracosis, a lung disease of older workers in the coal industry ,
- Environmental degradation also increasing vulnerability to natural disasters. Natural disasters can not be prevented but their damaging impact can be reduced
- Flood : outbreak of epidemics like diarrhea, cholera, jaundice or viral infections. may affect soil characteristics and may turn them infertile. The floodwater can be reduced by reducing the run-off water through afforestation. Construction of dams . Measurement of intensity of rainfall in the catchment area provide sufficient clue to hydrology engineers to calculate the possible submergence area along a river well before the flooding occurs. Land use planning. No major development should be permitted in flood prone areas. Deforestation in the catchments areas should be discouraged.
- Drought :low rainfall, drying of rivers, lakes, reservoirs. As per Meteorological Department if rainfall is deficient by more than 10% of the annual average rainfall, the condition is said to be that of drought. water conservation measures, economizing water consumption, reusing the wastewater for inferior uses, sowing low water-consuming crop, Rain water harvesting.
- Earthquake : outbreak of epidemics like cholera, diarrhoea, and infectious diseases. Utilities such as water supply , sewerage, communication lines, power -lines, transportation network, and railways get damaged. build by laws and safety requirements. Physical characteristics of soil should be analysed in order to ensure the strength to withstand the earthquake.
- Cyclone: generally followed by heavy rains causing floods, Warning and evacuation is done along the projected path, mudslide or landslide, in the coastal areas may cause sea waves to enter on land, cause saline water contamination of soil
No development should be permitted in cyclone – prone areas, Coastal green belt has been found very effective in minimizing the effects of cyclones Tsunami: warnings to endangered coasts immediately after an earthquake and several hours before the arrival of the tsunami. As the waves approach the continental coasts, friction with the increasingly shallow bottom reduces the velocity of the waves. This results in increased wave height up to 50 meter
Epidemics Outbreaks of communicable disease. Mad Cow Disease (Bovine spongiform encephalopathy) caused by an infectious agent that has a long incubation period, between two and five years
Desertification : The land that has lost its productivity (ability to grow plants) is called a desert. principal causes are over cultivation, overgrazing, deforestation, and salt accumulation due to irrigation
Important ozone depleting chemicals : Carbon tetrachloride, Methyl chloroform, HCFC-22, CFCs A small amount of uv-radiation is necessary for well-being of human beings and other organisms, such as uv-B promote synthesis of vitamin-D. UV-radiation also act as a germicide to control microorganisms