Thursday, October 31, 2013

Aquatic ecosystems - Estuaries

ESTUARINE ECOSYSTEM
An estuary is a partially enclosed coastal area at the mouth of a river where sea water mixes  with fresh water. It is strongly affected by tidal action. Estuaries are usually nutrients in abundance. Estuaries are useful to human beings due to their high food potential. Hence, estuaries must be protected from pollution.

CHARACTERISTICS OF ESTUARINE ECOSYSTEMS
  1. Estuaries are transition zones that are strongly affected by tides of the sea.
  2. Water characteristics change periodically
  3. Living organisms in estuarine ecosystems have wide tolerance.
  4. Salinity in estuarine water is high during summer and lest during winter
STRUCTURE AND FUNCTION
Abiotic components
Temperature, pH, sodium and potassium salts and various nutrients.
Biotic components
  1. Producers: Ex - Marsh grass, sea-weeds, sea-grass and phytoplankton
  2. Consumers: Ex - Oysters, Crabs, Seabirds and small fish
  3. Decomposers: Ex - Bacteria, Fungi  and actinomycetes

Aquatic ecosystem - Oceans

MARINE ECOSYSTEMS ((OCEANS)
Oceans cover more than two third of the earth's surface. Ocean environment is characterized by a high concentration of salts and minerals. It supplies a large variety of sea products and drugs. Among others, it is a reservoir of magnesium, iron, phosphorus and natural gas.

ZONES OF THE OCEAN
Oceans have two major life zones.
  1. Coastal zone which is relatively warm, nutrient rich and shallow water.It is the zone of high primary productivity because of high sunlight.
  2. Open sea is the deep part of the sea that is vertically divided into three regions.
      1. Euphotic zone that receives abundant light and shows high photosynthetic activity
      2. Bathyal zone that receives low light and is usually geologically active
      3. Abyssal zone which is dark and very deep (~2000 to 5000m)
CHARACTERISTICS OF OCEAN ECOSYSTEM
  1. It occupies a large surface area with saline water
  2. Commercial activities like fishing and shipping are carried-out in oceans
  3. It is rich in biodiversity
  4. It helps moderate the temperature of earth.
STRUCTURE AND FUNCTION OF OCEAN ECOSYSTEMS
Abiotic components
Ex: Temperature, Light, NaCl, K, Ca, and Mg salts, Alkalinity

Biotic components
  1.  Producers: Ex: Phytoplankton (diatoms, unicellular algae, etc) and marine plants (sea weeds, chlorophyceal, Phaeophycaea)
  2. Consumers: They are heterotrophic macroconsumers and depend on producers for their food.
        1. Primary consumers (herbivores) feed on producers. Ex: Crustaceans, molluscs, fish
        2. Secondary consumers (Carnivores) feed on herbivores. Ex: Herring, sahd, mackerel, etc
        3. Tertiary consumers are the top consumers. They feed on small fishes. Ex: Cod, Haddock, etc.
  3. Decomposers: They decompose dead organic matter. Ex: Bacteria and some fungi.

Aquatic Ecosystems - River or Stream

RIVER OR STREAM ECOSYSTEM
Running water in a river or stream is usually well oxygenated as it absorbs oxygen from the air. River or stream is full of life with aquatic life.

CHARACTERISTICS
  1. It is fresh and freely flowing water system
  2. Due to constant mixing of water during the flow of water in a river, the dissolved oxygen content is high
  3. Rivers deposit large amount of nutrients.
 STRUCTURE AND FUNCTION
  1. Abiotic components Temperature, light, pH, nutrients, organic and inorganic compounds
  2. Biotic components
          1. Producers: Phytoplankton, algae, water grass, aquatic mass and other amphibious plants
          2. Consumers: Primary consumers feed on phytoplankton. Ex: Water      insects, Snails, Fish. Secondary consumers feed on primary consumers. Ex: Birds and mammals. 
          3. Decomposers: They decompose the dead plants and animals. Ex: Bacteria and Fungi.

Aquatic ecosystems - Lakes

LAKE ECOSYSTEM
Lakes are large shallow water bodies. They are used for various purposes and are supplied with water from rainfall, streams and melting snow.

TYPES OF LAKES
Some important types of lakes are:
  1. Oligotrophic lakes: They have low nutrient concentrations.
  2. Eutrophic lakes: They are over-nourished by nutrients like N and P.
  3. Dystrophic lakes: They have low pH, high humic acid content and brown waters
  4. Volcanic lakes: They receive waters from magma after volcanic eruption
  5. Meromictic lakes: They are rich in salts
  6. Artificial lakes: They are created due to construction of dams
ZONES OF LAKES
Depending on the depth and distance from the shore, lakes consist of the following four distinct zones:
  1. Littoral zone: It is the top layer of the lake. It has shallow water.
  2. Limnetic zone: Next to the littoral zone is the limnetic zone, where effective penetration of solar light takes place
  3. Profundal zone: It is the deep open water where it is too dark
  4. Benthic zone: This zone is found at the bottom of the lake.
CHARACTERISTICS OF THE LAKE ECOSYSTEM
  1. Lake is a shallow freshwater body
  2. It is a permanent water body with large water resources
  3. It helps in irrigation and drinking
STRUCTURE AND FUNCTION OF LAKE ECOSYSTEM
Abiotic components
Ex: Temperature, light, proteins and lipids, turbidity, oxygen and carbondioxide.
Biotic components
  1. Producers: They are green plants which might be freely floating, submerged or amphibious in nature. Ex: Phytoplanktons, algae and flagellates
  2. Consumers: Primary consumers (zooplanktons) feed on phytoplanktons. Ex: Ciliates, Protozoans, etc. Secondary consumers (carnivores) feed on zooplankton. Ex: Insects and smaller fish. Tertiary consumers feed on smaller fish. Ex: Large fish like game fish feed on small fish.
  3. Decomposers: They decompose dead plants and animals. Ex: Bacteria, Fungi and actinomycetes

Aquatic ecosystem-Ponds

The aquatic ecosystem deals with water bodies. The major types of organisms found in aquatic environments are determined by the water's salinity.
Based on the salinity of water water bodies are classified into:
  1. Fresh water bodies (Ex: Ponds, streams, lakes and rivers)
  2. Salt water bodies (Ex: Oceans, Seas, Estuaries)
Pond is a freshwater aquatic ecosystem where water is stagnant. It receives enough water during rainy season. It contains several types of algae, aquatic plants, insects, fish and birds.
  1.  Pond is only seasonal
  2. It is a stagnant freshwater body
  3. Ponds get polluted easily due to limited amount of water
STRUCTURE AND FUNCTION OF POND ECOSYSTEM
Abiotic components
Ex:  Temperature, light, water, organic and inorganic components
Biotic components
  1. Producers: They are green photosynthetic organisms and are of two types. phytoplanktons are microscopic aquatic plants that freely float on the surface of water. Ex: Algae, small floating plants like volvox, pandorina, anabena and cosmarium. Microphytes are large floating plants and submerged plants. Ex: Hydrilla, Jussiaea, wolfina and demna.
  2. Consumers: Primary consumers are microscopic animals that freely float on the surface of water. They are called zooplanktons and they feed on phytoplanktons. Ex: Protozoa, very small fish, ciliates, flagellates and protozoans.Secondary consumers feed on zooplanktons. Ex: Insects like water beetles and small fish. Tertiary consumers feed on small fish. Ex: Large fish
  3. Decomposers: They decompose the dead plant and animal matter thereby releasing the nutrients to be reused by green plants. Ex: Fungi, Bacteria and flagellates.

Ecological Pyramids

Ecological Pyramids
The graphical representation of structure and function of tropic levels of an ecosystem, starting with producers at the top and each successive tropic level forming the apex is known as an ecological pyramid.
In a food chain starting from the producers to the consumers, there is a regular decrease in the properties (i.e., energy, biomass and the number of organisms) Since some energy is lost in each tropic level, it becomes progressively smaller at the top.

Ecological pyramids are of three types:
  1. Pyramid of Numbers
  2. Pyramids of Energy and
  3. Pyramid of Biomass
 Pyramid of Numbers It represents the number of individual organisms present in each tropic level.
Ex: A grassland Ecosystem
Producers are grass (small in size and large in number. Hence they occupy the first tropic level
The primary consumers are rats occupying the second tropic level. It is worthwhile to note that rats are less in number than grass.
Secondary consumers are snakes which occupy the third tropic level and they are lesser in number than rats.
Tertiary consumers are Eagles that occupy the next tropic level. This is the last tropic level where the number and size of the tropic level is the least as shown in the diagram.

 Pyramid of Energy It represents the amount of energy present in each tropic level. The rate of energy flow and the productivity at each successive tropic level is shown in the figure below.
At every successive tropic level, there is a heavy loss of energy (almost 90%) in the form of heat. Thus, at each tropic level only 10% is transferred. Hence there is a sharp decrease in energy at each and every successive tropic level as we move from producers to top consumers (carnivores).
Pyramid of  energy is depicted in the figure below.


 Pyramid of Biomass: It represents the total amount of biomass (mass or weight of biological material) present in each tropic level. Considering the example of a forest ecosystem, there is a steady decrease in the biomass from the lower tropic level to the higher tropic level. The producers (trees) contribute a major amount of the biomass. The next tropic level are the herbivores (insects and birds) and carnivores (snakes, foxes, etc). The top of the tropic level consists of very few tertiary consumers (Ex: Lions and Tigers) whose biomass is very low. The pyramid of biomass is shown below

Desertification

DESERTIFICATION
Desertification is a progressive destruction or degradation of arid or semi-arid lands to desert. Desertification leads to conversion of range-lands or irrigated croplands to desert like conditions in which agricultural productivity falls. Desertification is classified by devegetation, depletion of groundwater, salination and soil erosion.
EFFECTS OF DESERTIFICATION
  1. Almost 80% of the productive land in the arid and semi-arid regions is converted into desert.
  2. Approximately 600 million people are threatened by desertification.
CAUSES OF DESERTIFICATION
  1. Desertification: The process of denuding and degrading a forest land initiates the formation of a desert. Lack of vegetation prevents the rainfall from soaking into the ground resulting in poor recharge of groundwater. Eventually this results in soil erosion and loss of fertility.
  2. Over-grazing: Increase in cattle population coupled with repeated grazing at the same location results in depletion of vegetation in the area. Eventually, the land becomes loose and prone to soil erosion and formation of a desert.
  3. Water management: Over-utilization of groundwater, particularly in the coastal regions, results in saline water intrusion into aquifers thereby making water unfit for irrigation.
  4. Mining and quarrying:  These activities are responsible for loss of vegetative cover and denudation of extensive land area leading to desertification.
  5. Climate change: Climate change manifests in the form of failure of monsoons, irregular monsoons and frequent droughts thereby leading to desertification
  6. Pollution: Excessive use of fertilizers and pesticides to increase yield and disposal of toxic wastes into land leads to desertification.

Wednesday, October 30, 2013

Land degradation- Land slides, Soil erosion and Desertification

LAND DEGRADATION
Land degradation is the process of deterioration of soil or loss of fertility of soil.

EFFECTS OF LAND DEGRADATION

  1. Soil texture and structure are deteriorated
  2. Loss of soil fertility due to loss of valuable nutrients
  3. Increase in water logging, salinity, alkalinity and acidity problems
  4. Loss at a social, economic and biodiversity level
CAUSES OF LAND DEGRADATION
Population: With the increase in population, more land is needed for producing food, fibre, and fuel wood leading to increasing pressure on the limited land resources. Therefore the land gets degraded due to over exploitation

Urbanization: Increased urbanization due to population growth reduces the agricultural land. To compensate for loss of agricultural land, new lands comprising of natural ecosystems such as forests are cleared. Therefore, urbanization leads to deforestation which in-turn affects millions of plant and animal species.

Fertilizers and Pesticides: Increased application of fertilizers and pesticides are needed to increase farm output in new lands thereby leading to pollution of land, water and soil degradation.

Damage to top soil: Increase in food production generally leads to damage of top soil through nutrient depletion.

Water-logging, soil erosion, salination and contamination of the soil with industrial waste cause land degradation.

LANDSLIDES
Landslides are the downward movement of a slope composed of earth materials such as rock, soil or artificial fills. Landslides are also called rock-slide, debris-slide, slump, earth-flow or soil-creep. 
During construction of roads and mining activities huge portions of mountainous fragile areas are cut down and thrown into adjacent areas and streams. These land masses weaken the already fragile mountain slopes leading to man-induced landslides.

EFFECTS OF LANDSLIDES:
  1. Landslides increase the turbidity of nearby streams, thereby reducing their productivity
  2. Destruction of communicative links
  3. Loss of habitat and biodiversity
  4. Loss of infrastructure and economic loss
CAUSES OF LANDSLIDES
  1. Removal of vegetation - Deforestation in slopes creates soil erosion leading to landslides
  2. Underground mining activities cause subsidence of the ground
  3. Movement of heavy vehicles in areas with unstable slopes causes landslides.
  4. Addition of weight by construction on slopes causes landslides.
  5. Over exploitation of groundwater also leads to landslides.
SOIL EROSION
Soil erosion is the process of removal of superficial layer of soil. Soil erosion removes soil components and litter.
HARMFUL EFFECTS OF SOIL EROSION

  1. Soil fertility is lost
  2. Loss of soil ability to hold water and sediment
  3. Sediment runoff can pollute water courses and kill aquatic life
TYPES OF SOIL EROSION
  1. Normal erosion: This is caused by the gradual removal of topsoil by natural processes. The rate of erosion is slow.
  2. Accelerated erosion: This is caused by man made activities. In this case, the rate of erosion is much faster than the rate of formation of soil.
CAUSES OF SOIL EROSION
  1. Water: Water affects soil erosion in the form of rain, run-off, rapid flow or wave action
  2. Wind: Wind is an important climate agent that carries away the fine particles of soil thereby contributing to soil erosion.
  3. Biotic agents: Overgrazing, mining and deforestation are the major biotic agents causing soil erosion. These processes disturb the top soil thereby exposing the soil to various physical forces inducing erosion
  4. Landslides cause soil erosion
  5. Construction of dams, buildings and roads removes the protective vegetal cover leading to soil erosion
SOIL CONSERVATION PRACTICES
  1. Conservational till farming or no-till farming: Traditionally, land is ploughed to make a planting surface. This disturbs the soil and makes it susceptible to erosion. The no-till farming method makes minimum disturbance to the top soil by making slits in the unploughed soil. Seeds, fertilizers and water are injected in these slits.
  2. Contour farming: In this method, crops are planted in rows along contours of gently sloped land. Each row acts as a small dam to hold soil thereby slowing water runoff.
  3. Terracing: In this method, steep slopes are converted into a series of broad terraces that run across the contour.This retains water for crops and reduces soil erosion by controlling runoff.
  4. Alley cropping or Agro forestry: This method involves planting crops in strips or alleys between rows of trees or shrubs that provide fruits and fuel wood. Hence, when the crop is harvested, the soil will not be eroded as the trees and shrubs remain on ground holding the soil particles.
  5. Wind breaks or shelter belts: In this technique, trees are planted in long rows along the boundary of cultivated land which block the wind and reduce soil erosion. Wind breaks help in retaining soil moisture, supply wood for fuel and provide habitat for birds.

Land as a Resource

LAND AS A RESOURCE
Land is a very valuable resource. It provides food, fibre, wood, medicine and other biological materials needed for food. Soil is a mixture of inorganic materials and (rocks and minerals) and organic materials (dead materials and plants). Top soil is classified as a renewable resource as it is continuously regenerated by natural processes at a very slow rate. However, if the rate of erosion is faster than the rate of renewal, the soil becomes a non-renewable resource.

Uses of land resources

  1. Land provides food, wood, minerals, etc
  2. Land nurtures plants and animals that provide us food and shelter
  3. Land may be used as watershed or reservoir. 
  4. Land acts as a dustbin for the wastes generated by modern society. 
  5. Land is used for constructing buildings and industries.

Alternate Renewable Energy Sources

USE OF ALTERNATE RENEWABLE ENERGY SOURCES

  1. Solar energy is renewable and does not cause environmental pollution
  2. Energy sources that create minimum pollution, are safe not prone to security threats and have universal availability have the best chance of large scale utilization in future.
  3. Hydro-electric power generation is expected to the existing ecological balance
  4. Apart from generating heat, hydel power plants critically endanger aquatic and terrestrial biotic
  5. Radioactive pollutants released from nuclear plants are chronically hazardous. Commissioning of Boiling Water Power Reactors (BWRs) result in accumulation of large number of radionuclides in water
  6. Dangerous radioactive waste cannot be buried in/land without the risk of polluting soil and underground water. The waste cannot be dumped in rivers as it poisons aquatic life and human beings.
  7. Burning of coal, oil, wood, dung cakes and petroleum products have well established environmental problems. The smoke produced causes respiratory and digestive problems leading to lung, stomach and eye diseases.
  8. Disposal of fly-ash requires large ash ponds and may pose a severe problem considering the limited availability of land. 
Hence non-conventional sources of energy are needed. The objectives of using alternate renewable energy sources are listed below:
  1. To provide more energy to meet the requirements of increasing population.
  2. To reduce environmental pollution and
  3. To reduce safety and security risks associated with the use of nuclear energy.
CASE STUDIES

Wind energy India is generating 1200 MW electricity using wind energy. The largest wind farm is in Kanyakumari in Tamil Nadu, which generates 380 MW electricity.

Hydrogen-Fuel cell car General motor company of china invented experimental cars that run on electric motors fueled by hydrogen and oxygen. These cars produce no emission and the only waste products being water droplets and water vapour.

Non-renewable energy sources

NON-RENEWABLE ENERGY SOURCES
  1. Coal: Coal is a solid fossil fuel formed in several stages as burried remains of land plants that lived 300-400 million years ago and were subjected to intense heat and pressure over millions of years.
Various stages of coal: The various stages of coal during formation of coal from wood are:
                                      i.  Wood
                                      ii  Peat
                                      iii  Lignite
                                      iv  Bituminous coal and
                                      v  Anthracite
Carbon content of anthracite is 90% and its calorific value is 8700 kcal. Carbon content of Bituminous coal, Lignite and Peat are 80%, 70% & 60% respectively. India has approximately 5% of the worlds coal. However, it is not of good quality as it has poor heat capacity.

Disadvantages of using coal:
  1. Burning coal produces carbondioxide which is the main cause for global warming
  2. Coal contains impurities like Sulphur and Nitrogen which produce toxic gases when burnt.
  2.  Petroleum: Petroleum or crude oil is a thick liquid consisting of more than 100 cumbustible hydrocarbons with small amounts of S, O and N as impurities. Fossil fuels are mainly sormed by the decomposition of dead plants and animals that were buried under lakes and oceans  at a high temperature and pressure for millions of years. From the crude petroleum oil, various hydrocarbons are separated by fractional distillation of crude petroleum oil. At the present rate of usage, the world's crude oil reserves are expected to get over in the next 30 years.

LIQUIFIED PETROLEUM GAS (LPG)
The petroleum gas obtained during crackling and fractional distillation can be easily converted into liquid under high pressure as LPG. LPG is a colourless, odourless gas to which mercaptans are added to produce foul smell that aids in detection of LPG leaks.

NATURAL GAS Natural gas is found above the oil in oil well. It is a mixture of 50-90% methane and small amounts of other hydrocarbons. Its calorific value ranges between 12000 and 14000 kcal/m3.
     1. Dry gas: Natural gas containing low hydrocarbons like d ethane, it is called dry gas.
     2. Wet gas: Natural gas containing high hydrocarbons like propane and butane along with methane is called wet gas.
Natural gas is formed by decomposition of dead plants and animals buried under oceans at high temperature and pressure for millions of years.

NUCLEAR ENERGY:
Dr. Homi Bhabha was the father of nuclear power development in India. India has 10 nuclear reactors that produce 2% of India's electricity. Nuclear energy is produced by two types of reactions:

(i) Nuclear fission: Nuclear fission is a nuclear chain reaction in which the heavy nucleas is split into lighter nuclii by fast moving neutrons thereby releasing a large amount of energy.
Ex: Fission of Uranium235

(ii) Nuclear fusion: Nuclear fusion is a nuclear chain reaction in which lighter nucleus are combined together at extremely high temperatures to form heavy nucleus thereby releasing large amount of energy.
Ex: Fusion of Dueterium atoms to form helium with release of large amount of energy.

Nuclear power plants have been established in the following locations in India:
i.     Tarapur (Maharashtra)
ii     Rana Pratap Sagar (Rajasthan)
iii    Kalpakkam (Tamil Nadu)
iv    Narora (Uttar Pradesh)

Renewable energy sources

RENEWABLE ENERGY SOURCES:
Renewable energy sources are natural resources that can be regenerated continuously and are inexhaustible. They can be repeatedly used.

SOLAR ENERGY:
The energy that we get directly from the sun is called solar energy. Nuclear fusion occurring in the sun releases enormous amount of energy in the form of heat and light. Several techniques are available for collecting, converting and using solar energy.

METHODS OF HARVESTING SOLAR ENERGY
Listed below are the various devices used to harvest solar energy.
  1. Solar cells or Photovoltaic cells or PV cells: Solar cells consist of a p-type semiconductor (Silicon doped with Boron) and n-type semiconductor (Silicon doped with Phosphorus) in close contact with each other. When solar rays fall on the top p-type semiconductor, the electrons from the valence band move to the conduction band and cross the p-type junction into the n-type semiconductor. A potential difference is created causing an electric current to flow. These cells are widely used in calculators, electronic watches, street lights, water pumps  to radio and television.
  2. Solar battery: When several solar cells are connected in series, it forms a solar battery. These solar batteries generate enough electricity to run water pumps, street lights, etc. They are mainly used in remote areas where electricity supply is a problem.
  3. Solar heat collectors: Solar heat collectors consist of natural materials like stones, bricks, or materials like glass, which absorb heat during the day time and release it slowly in the night. It is generally used in cold places where houses are kept in hot condition using solar heat collectors.
  4. Solar water Heaters: It consists of an insulated box, in which is painted black on  the inside. It is provided with a glass lid to receive and store solar heat. The box contains a copper coil painted in black through which cold water flows in, gets heated in the copper coil and flows into a storage tank. Finally, water from storage tanks is supplied.
  5. Solar energy is currently used to power satellites, watches, calculators, etc
  6. A few applications of solar energy are: (i) solar water heater, (ii) solar cooker, (iii) solar dryer and (v) solar refrigerator.
WIND ENERGY:
Wind is defined as moving air. Energy recovered from the force of wind is called wind energy. Wind energy is harnessed by the use of wind mills.
  1. Wind mills: The  force of blowing wind strikes the blades of the wind mill thereby causing it to rotate continuously. This rotational energy of the blades is used to drive several machines like water pump, flour mill and electric generators.
  2. Wind farms: Several wind mills joined together in a definite pattern forms a wind farm. Wind farms  generate large amounts of electricity.
CONDITION The minimum speed required for satisfactory working of a wind generator is 15 kmph

ADVANTAGES:
  1. It does not cause any air pollution
  2. It is very cheap
OCEAN ENERGY
Ocean can be used for generating electricity:
  1. Tidal energy: Ocean tides produced by virtue of gravitational force of sun and moon possess enormous amounts of energy. Tidal energy can be harnessed by constructing a tidal barrage.
    During high tide, sea-water is allowed to flow into reservoir of the barrage and rotate the turbine thereby producing electricity.
    During low tide, when sea level is low, sea water stored in the barrage reservoir is allowed to flow into the sea thereby rotating the turbine again.

  2. Ocean thermal energy There is a large temperature difference between surface level and deep water level of tropical oceans. This temperature difference can be utilized to generate electricity. This energy is called ocean thermal energy. A necessary condition is that temperature difference of at least 20C is required between surface water and deep water. The technique used here is that the relatively hot surface temperature of the ocean is used to boil a low boiling liquid like ammonia. The high vapor  pressure of the liquid formed by boiling is used to turn the blades in a turbine and generate electricity. The cool waters in the deep sea are used to cool and condense the vapor into liquid.
Geo-thermal energy:
Temperature of the earth increases at the rate of  20 - 75C per km. Down below the earths surface, high pressure and high temperature steam fields exist in many places. The energy harnessed from high temperature present inside the earth's surface is called geothermal energy.
  1. Natural Geysers: In some places, steam comes out of ground through cracks naturally in the form of natural geysers.
  2. Artificial Geysers: Sometimes, a hole is drilled up to the hot region and by sending a pipe in it, the steam is made to rush-out through the pipe with very high pressure.
The steam coming out of natural or artificial geysers is made to rotate the turbine of a generator to produce electricity.
    BIOMASS ENERGYBiomass is organic matter produced by plants or animals. It is used as a source of energy. Biomass is generally burnt for heating, cooling and industrial purposes.
    Ex: wood, crop residues, seeds, cattle dung, sewage, agricultural wastes, etc.
    Biomass may be converted into energy in any of the following types:
    1.   Biogas: Biogas is a mixture of gases such as methane, carbondioxide, hydrogen sulphide, etc. It contains about 65% of methane gas as a major constituent. Biogas is obtained by the anaerobic fermentation of animal dung or plant wastes in the presence of water.
    2.   Biofuels: Biofuels are the fuels, obtained by the fermentation of biomass. Examples are Ethanol, Methanol.
                     (i)   Ethanol: Ethanol can be produced by sugarcane. Its calorific value is less when compared to petrol and therefor produces much less heat than petrol.
                     (ii)   Methanol: Methanol can be easily obtained from ethanol or sugar containing plants. Its calorific value is also too low when compared to gasoline and petrol.
                     (iii)   Gasohol: Gasohol is a mixture of ethanol and gasoline.
    3.  Hydrogen fuel: Hydrogen can be produced by thermal dissociation or photolysis or electrolysis of water. It possesses high calorific value. It is non polluting as the product of combustion is water.
    Disadvantages of Hydrogen fuel
    (i)  Hydrogen is highly flammable and explosive in nature.
    (ii)  Safe handling is required
    (iii)  It is difficult to store and transport.

Energy resources, Growing energy needs, Renewable and non-renewable energy sources

ENERGY RESOURCES
Energy may be defined as "any property which can be converted into work"
Energy is defined as "the capacity to do work"

Energy is available on earth in a number of forms and some forms may be used immediately while others might require some transformation. It is difficult to imagine Life without energy. All the developmental activities in the world are directly or indirectly dependent on energy. Both energy production and energy utilization indicate a country's progress.

GROWING ENERGY NEEDS
Energy is essential to the existence of mankind. All industrial processes like mining, transport, lighting, heating and cooling in buildings need energy. With the growing population, the world is facing an energy deficit. Lifestyle change from simple  to a complex and luxurious lifestyle adds to this energy deficit. Almost 95% of commercial energy is available from fossil fuels like coal and natural gas. These fossil fuels will not last for more than a few years.Hence, we must explore alternative fuel/energy options.

RENEWABLE AND NON-RENEWABLE ENERGY ENERGY SOURCES
Based on continual utility, natural resources can be classified into two types:
Renewable energy sources: These resources can be generated continuously and are inexhaustible. 
Ex: Wood, Solar energy, Wind energy, Hydro power, tidal energy, Geo-thermal energy, etc
Merits of Geo-thermal energy:
  1. Unlimited supply
  2. Provides energy security
  3. Fits in the concept of sustainable development
  4. Reliable and devices are modular in size
  5. Decentralized energy production
 Non-renewable energy sources: Non-renewable energy sources are natural resources, that cannot be regenerated once they are exhausted. They cannot be used again.
Ex: Coal, Petroleum, Natural gas and Nuclear fuels

Tuesday, October 29, 2013

Effects of modern agriculture - Fertilizer Pesticide problems, Water logging, Salinity

AGRICULTURE
Agriculture is an art, science and industry of managing the growth of plants and animals for human use. Agriculture includes preparation of soil for cultivation of crops, harvesting crops, breeding and raising livestock, dairying and forestry.
The two major types of agriculture are:

  1. Traditional agriculture and
  2. Modern or Industrialized agriculture
MODERN AGRICULTURE
Modern agriculture makes use of hybrid seeds of single crop variety, technologically advanced  equipment, fertilizers, pesticides and water to produce large amounts of single crop.

Problems using fertilizers
  1. Micronutrient imbalance: Chemical fertilizers used in modern agriculture contain Nitrogen, Phosphorus and Potassium (N,P,K) which are macronutrients. Excess use of fertilizers in fields causes micronutrient imbalance. Ex: Excessive use of fertilizers in Punjab and Haryana caused deficiency of micronutrient Zinc thereby affecting productivity of soil.
  2. Nitrate pollution: Excess Nitrogenous fertilizers applied in fields leach deep into the soil contaminating the groundwater. If the concentration of nitrate in drinking water exceeds 25 mg/L it leads to a fatal condition in new-born babies. This condition is termed "Blue Baby Syndrome"
  3. Eutrophication: The application of excess fertilizers in fields leads to wash off of the nutrient loaded water into nearby lakes causing over-nourishment. This is called "Eutrophication". Eutrophication causes the lakes to be attacked by "algal blooms". Algal blooms use nutrients rapidly and grow fast. Their life is short, they die and pollute water thereby affecting aquatic life in the lake. 
Problems in using Pesticides:
In order to improve crop yield, pesticides are used indiscriminately in agriculture. Pesticides are of two types:
  1. First generation pesticides that use Sulphur, Arsenic, Lead or Mercury to kill pests
  2. Second generation pesticides such as  Dichloro Diphenyl Trichloroethane (DDT) used to kill pests. These pesticides are organic in nature. Although these pesticides protect our crops from severe losses due to pests, they have several side-effects as listed below:
      1. Death of non-target organisms: Several insecticides kill not only the target species but also several beneficial not target organisms
      2. Pesticide resistance: Some pests that survive the pesticide generate highly resistant generations that are immune to all kinds of pesticides. These pests are called "superpests"
      3. Bio-magnification: Most pesticides are non-biodegradable and accumulis ate in the food chain. This is called bio-accumulation or bio-magnification. These pesticides in a bio-magnified form are harmful to human beings.
      4. Risk of cancer: Pesticide enhances the risk of cancer in two ways (i) It acts as a carcinogen and (ii) It indirectly suppresses the immune system.
WATER LOGGING
If water stands on land for most of the year, it is called water logging.
In water logged conditions, pore-voids in the soil get filled with water and soil-air gets depleted. In such a condition the roots of plants do not get enough air for respiration. Water logging also leads to low mechanical strength of soil and low crop yield.

CAUSES OF WATER LOGGING
  1. Excessive water supply to the croplands
  2. Heavy rain
  3. Poor drainage
MEASURES TO PREVENT WATER LOGGING
  1. Avoid and prevent excessive irrigation
  2. Sub-surface drainage technology
  3. Bio-drainage by trees like Eucalyptus
SALINITY
Water not absorbed by soil, is evaporated leaving behind a thin layer of dissolved salts in the top soil. This is called salinity of the soil. Saline soils are characterized by accumulation of soluble salts like sodium chloride, calcium chloride, magnesium chloride, sodium sulphate, sodium carbonate and sodium bicarbonates. Saline conditions are exhibited when pH is greater than 8.0

PROBLEMS IN SALINITY
  1. Saline soils yield less crop
In order to remedy the condition of saline soils the following two techniques may be used:
  1. Salt deposit is removed by flushing with good quality water
  2. By using a sub-surface drainage system, the salt water is flushed out slowly.
CASE STUDIES
Canal irrigation in Haryana resulted in rising water table followed by water logging and salinity causing  low crop productivity thereby huge economic losses.
Similarly the "Indira Gandhi Canal Project" in Rajasthan converted a big area into a "water soaked waste land".

In Delhi, accumulation of pesticides and DDT in the body of mothers caused premature deliveries or low birth weight infants.

Food centre at Center for Science and Environment  (CSE) India reported Pepsi and Coca-Cola companies sold soft drinks with a pesticide content 30-40 times higher than EU guidelines permit. At the reported concentrations the pesticides damage the nervous system.

Dams - Benefits and problems

DAMS - BENEFITS AND PROBLEMS
Dams are built across rivers to store water for irrigation, hydroelectric power generation and flood control. The dams built to serve more than one purpose are called "multi-purpose dams". These dams were called the "temples of modern India" by the country's first Prime Minister, Jawaharlal Nehru.

BENEFITS OF DAMS

  1. Dams are built to control flood and store flood water
  2. Sometimes dams are used for diverting part or all of the water from river into a channel.
  3. Dams are used mainly for drinking and agricultural purposes.
  4. Dams are built for generating electricity
  5. Dams are used for recreational purposes
  6. Navigation and fishery can be developed in the dam areas
PROBLEMS OF DAMS Dams may face problems upstream or downstream as listed below: 
Upstream problems
  1. Displacement of tribal people
  2. Loss of non-forest land
  3. Loss of forests, flora and fauna
  4. Landslides, sedimentation and siltation occurs
  5. stagnation and waterlogging around reservoirs retards plant growth
  6. Breeding of vectors and vector-borne diseases
  7. Reservoir Induced Seismicity (RIS) causes earthquakes
  8. Navigation and aquaculture activities can be developed in the dam area
Downstream problems
  1. Water logging and salinity due to over irrigation
  2. Reduced water flow and silt deposition in rivers
  3. Salt intrusion at river mouth
  4. Since the sediments carrying nutrients gets deposited in the reservoir, the fertility of the land along the river gets reduced
  5. Due to structural defects or faulty design of the dam may cause sudden dam failure leading to collapse and destruction to life and property.

Conflicts over water

CONFLICTS OVER WATER
Water is essential for our existence and is fast becoming scarce. Rapidly increasing population and limited water resources  give rise to conflicts over water.
Conflict through use: Unequal distribution of water leads to inter-state or international disputes.
Examples:
International conflicts

  1. Conflict over water from the Indus between India and Pakistan
  2. Conflict over water from the Colorado river between Mexico and USA
  3. Conflict over water from the Shatt-al-Arab between Iran and Iraq
  4. Conflict over water from the Bhramaputra between India and Bangladesh

National conflicts

  1. Sharing of Cauvery water between Karnataka and Tamilnadu
  2. Sharing of Krishna water between Karnataka and Andhra Pradesh
  3. Sharing of Siruveni water between Tamilnadu and Kerala
Construction of dams or power stations:
For hydroelectric power generation, dams are built across the rivers, and this initiates conflicts between the states.

Conflict through pollution:
Rivers are also used for industrial purposes. They act as reservoirs for supply of fresh water and also a receptor of waste water and rubbish from the industry. Water crossing borders that has been polluted by wastes from one country develops into an international conflict.

Management of water conflicts
  1. Concerted efforts are required to enforce laws that check these practices to control water pollution
  2. In order to overcome the problem of sharing river water in a country, the concept of interlinking of rivers has been suggested
  3. Rivers should be nationalized, the National Water Authority and River Basin Authority should be given powers to ensure equitable distribution of basin water.

Natural resources: Droughts

Drought is scarcity of water. Drought occurs due to:
  1. inadequate rainfall
  2. late arrival of rains and
  3. excessive withdrawal of groundwater
Scarcity of water for normal needs of agriculture, livestock, industry or human population may be termed as drought.
Drought is understood from dry weather which persists long enough to produce a serious hydrological imbalance, leading to damage of plants, animals and human life.

TYPES OF DROUGHT
Droughts are classified into four types:
  1. Meteorological Drought occurs when the total amount of rainfall is less than 75% of normal rainfall. This drought will be severe if the rainfall is less than 50% of the normal rainfall
  2. Hydrological Drought occurs when the total amount of rainfall is less than the average rainfall. It is generally associated with reduction of statistical average of water reserves available in the source such as aquifers, lakes and reservoirs.
  3. Agricultural Drought occurs due to the shortage as well as the timing of  overall rainfall. This form of drought reduces groundwater and reservoir levels. Agricultural Drought affects cropped plants.
  4. Socio-economic Drought occurs due to reduction in the availability of food and social security of people in the affected areas. Socio-economic drought leads to famine.
CAUSES OF DROUGHT
  1. When annual rainfall is below normal and less than evaporation, drought occurs
  2. High population also leads to drought. Population growth leads to poor land use and worsens the situation
  3. Intensive cropping pattern and over-exploitation of scarce water resources by digging wells or bore-wells for high productivity has turned drought prone areas into desert. Ex:- Over exploitation of water resources for sugarcane in Maharashtra has prevented the state from drought recovery for the past 30 years.
  4. Deforestation leads to desertification and drought. Deforestation leads to the top soil exposed to erosion by heavy rains, wind and the sun. Thus the top layer of soil rich in nutrients gets washed away making the soil unproductive. Eroded soils exhibit a droughty tendency.
EFFECTS OF DROUGHT:
  1.  Drought causes hunger, malnutrition and scarcity of drinking water. It also degrades the quality of drinking water
  2. Drought causes widespread crop failures leading to acute shortage of food thereby adversely affecting human and livestock populations
  3. Drought indicates the initiation of desertificarion
  4. Raw materials for agro-based industries are critically affected during drought thereby retarding industrial and commercial growth.
  5. Drought accelerates degradation of natural resources
  6. Drought leads to large scale migration to urban areas thereby creating slums.
DROUGHT MANAGEMENT :
  1. Indigenous knowledge in control of droughts and desertification is very useful for dealing with drought problems
  2. Rainwater harvesting program is very useful technique used to conserve water and control drought
  3. Construction of large capacity reservoirs is essential in drought prone areas
  4. Modern irrigation techniques (drip irrigation) is very useful to conserve water and avoid wastage
  5. Afforestation activities improve the potential of water in drought prone areas
  6. Mixed cropping and dry farming are suitable methods that minimize the risk of crop failure in dry and drought prone areas.

Natural resources-Floods

A flood is an overflow of water, whenever the magnitude of flow of waterexceeds the carrying capacity of the channel within its banks.

CAUSES OF FLOODS
  1. Heavy rainfall, melting of snow (ice), sudden release of water from dams often causes floods in the low lying coastal area.
  2. Prolonged heavy rainfall can also cause the overflowing of lakes and rivers resulting in floods
  3. Reduction in carrying capacity of river channels due to accumulation of sediments or obstructions built on flood ways.
  4. Deforestation, overgrazing, mining increases the run-off from rains causing floods.
  5. Removal of dense and uniform forest cover over the hilly zones leaqds to occourrence of floods.
EFFECT OF FLOODS:
Due to floods:
  1. Water spreads in the surrounding areas and submerges them
  2. Plain surfaces get eroded and silted with mud and sand thereby affecting cultivable land areas.
  3. Extinction of civilization in some coastal areas also occurs.
FLOOD MANAGEMENT:
  1. Floods can be controlled by constructing dams or reservoirs
  2. Channel management and embankments also control floods
  3. Encroachment of flood ways should be banned
  4. Flood hazard may be reduced by forecasting or flood warning
  5. Flood hazard may be reduced by reduction of runoff and this can be achieved by increasing infiltration through appropriate afforestation in the catchment area.
 

Natural resources: Water resources - Use and Over-use





NATURAL RESOURCES:

Natural resources are the sources which are useful to man or those than be transformed into a useful product. Natural resources are of two types:
  1. Renewable resources and
  2. Non-renewable resources
WATER RESOURCES:
 Water is the most abundant, inexhaustible renewable resource. It covers 70%  of the globe in the form of oceans, rivers, lakes, etc. Of this 70%, only 3% is available as freshwater. From this 3%, roughly 2% is frozen in polar icecaps and only a fraction of the remaining 1% is used as drinking water (potable). 90% of the water is utilized for agricultural purposes in India.

USE OF SURFACE AND GROUND WATER
Consumptive use: In such uses, water is completely utilized  and cannot be reused.
Ex: Domestic, industrial and irrigation
Non-consumptive use:In such uses,water is not completely utilized and is reused
Ex: Hydropower plant

Other uses:
  1. Water is used for domestic purposes like drinking, bathing, cooking, washing. etc.
  2. Water is used in commercial establishments like hotels, theaters, educational institutions, offices, etc.
  3. Almost 60-70% of fresh water is used for irrigation
  4. 20-30% of water is used for industrial operations by refineries, iron & steel industries, paper & pulp industries, etc.
  5. Water plays a key role in sculpting the earths surface, moderating climate and diluting pollutants.
OVER-UTILIZATION OF SURFACE & GROUND WATER
The rapid increase in population and industrial growth led to severe demand on water resources. After using all available surface water resources to the maximum, human beings began using groundwater to meet their needs.
  1. The increased extraction of groundwater far in excess of the natural recharge led to decreased groundwater level. The erratic and inadequate rainfall caused reduction in storage of water in reservoirs. This also led to decrease of groundwater.
  2. Building construction activities seal permeable soil zone and reduce the area for percolation of rainwater thereby increasing surface runoff.
  3. If groundwater withdrawal rate is higher than recharge rate, sediments in aquifers get compacted resulting in sinking of overlaying land surface. This is called land subsidence which leads to structural damage in buildings, fracture in pipes and reverses the flow of canals leading to tidal flooding.
  4. Over-utilization of groundwater in arid and semi-arid regions for agriculture disturbs equilibrium of reservoir in the region causing problems like lowering of water table and decreased pressure in aquifers coupled with changes in speed and direction of water flow.
  5. Over utilization of groundwater in coastal areas leads to rapid intrusion of salt water from the sea thereby rendering it unusable for drinking and agriculture.
  6. Over-utilization of groundwater lads  to decrease in water level thereby causing earthquake, landslides and famine. 
  7. Over-utilization of groundwater leads to drying-up of dug wells as well as bore wells.
  8. Due to excess use of groundwater near agricultural fields, agricultural water that contains nitrogen as a fertilizer percolates rapidly and pollutes the groundwater thereby rendering the water unfit for potable use by infants. (Nitrate concentration exceeding 45 mg/L).

E.S. - Definition, scope & importance, need for public awareness

DEFINITION OF ENVIRONMENTASL STUDIES
The word environment is derived from the french word 'environ' meaning surroundings. Hence, everything surrounding us is called "ENVIRONMENT".
Every organism is surrounded by materials and forces that constitute its environment. It is the environment from where every organism must derive its requirement. The environment creates favourable conditions for the existence and development of living organisms.
The survival of any organism requires a steady supply of materials and removal of wate products from its environment.
The degradation of the environment has become a serious problem for the existence of human beings. Pollution of soil, water and air causes harm to living organisms as well as loss to valuable natural resources.
Environmental studies involves educating the people for preserving the quality of environment.
The scope of environmental studies include:
1. Developing an awareness and sensitivity to the total environment and its related problems
2. Motivating people for active participation in environmental protection and improvement
3. Developing skills for active identification and development of solutions to environmental problems
4. Imbibe and inculcate the necessity for conservation of natural resources
5. Evaluation of environmental programmes in terms of social, economic, ecological and aesthetic factors.

IMPORTANCE OF ENVIRONMENTAL STUDIES
In the industrialized era that we live today, every component that we intake - be it, air, water or food are contaminated by industrial activities. THERE IS NO ZERO POLLUTION. To minimize this problem, knowledge of environmental studies is essential. An in-dept study of environmental studies will help us in the following ways:
1. We will begin to appreciate and adopt the idea of "DEVELOPMENT WITHOUT DESTRUCTION OF THE ENVIRONMENT"
2. Knowledge about "VARIOUS TYPES OF ENVIRONMENTS & DIFFERENT ENVIRONMENTAL HAZARDS"
3. Playing an effective role in protecting the environment by "DEMANDING CHANGES IN LAW AND ENFORCEMENT SYSTEMS".
4. Having a "POSITIVE IMPACT" on "QUALITY OF LIFE".
5. Creating a "CONCERN AND RESPECT FOR THE ENVIRONMENT".

NEED FOR PUBLIC AWARENESS:
Increasing population, Urbanization  and poverty have generated pressure on the natural resources and lead to a degradation of the environment. TO PREVENT THE ENVIRONMENT FROM FURTHER DEGRADATION, the supreme court has ordered and initiated environmental protection awareness through government and non-government agencies to take part in protecting our environment.
Environmental pollution cannot prevented by laws alone. Public participation is equally important with regard to environmental protection.
Environmental Education (EE) is a process of learning by giving an overall perspective of knowledge and awareness of the environment. It sensitizes the society about environmental issues and challenges interested individuals to develop skills and expertise thereby providing appropriate solutions.
Climate change, loss of biodiversity, declining fisheries, ozone layer depletion, illegal trade of endangered species, destruction of habitats, land degradation, depleting ground water supplies, introduction of alien species, environmental pollution, solid waste disposal, storm water and sewage disposal pose a serious threat to ecosystems in forest, rural, urban and marine ecosystems.
Both formal and informal education on the environment will give the interested individual the knowledge, values, skills and tools needed to face the environmental challenges on a local and global level.


Kyoto Protocol

The Kyoto Protocol is a protocol to the United Nations Framework Convention on Climate Change (UNFCCC or FCCC), aimed at fighting global warming. The UNFCCC is an international environmental treaty with the goal of achieving "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

The Protocol was initially adopted on 11 December 1997 in Kyoto, Japan and entered into force on 16 February 2005. As of July 2010, 191 states have signed and ratified the protocol.

Under the Protocol, 37 countries ("Annex I countries") commit themselves to a reduction of four greenhouse gases (GHG) (carbon dioxide, methane, nitrous oxide, sulphur hexafluoride) and two groups of gases (hydrofluorocarbons and perfluorocarbons) produced by them, and all member countries give general commitments. Annex I countries agreed to reduce their collective greenhouse gas emissions by 5.2% from the 1990 level. Emission limits do not include emissions by international aviation and shipping, but are in addition to the industrial gases, chlorofluorocarbons, or CFCs

The benchmark 1990 emission levels were accepted by the Conference of the Parties of UNFCCC were the values of "global warming potential" calculated for the IPCC Second Assessment Report. These figures are used for converting the various greenhouse gas emissions into comparable CO2 equivalents (CO2-eq) when computing overall sources and sinks.

The Protocol allows for several "flexible mechanisms", such as emissions trading, the clean development mechanism (CDM) and joint implementation to allow Annex I countries to meet their GHG emission limitations by purchasing GHG emission reductions credits from elsewhere, through financial exchanges, projects that reduce emissions in non-Annex I countries, from other Annex I countries, or from annex I countries with excess allowances
Each Annex I country is required to submit an annual report of inventories of all anthropogenic greenhouse gas emissions from sources and removals from sinks under UNFCCC and the Kyoto Protocol. These countries nominate a person (called a "designated national authority") to create and manage its greenhouse gas inventory. Virtually all of the non-Annex I countries have also established a designated national authority to manage its Kyoto obligations, specifically the "CDM process" that determines which GHG projects they wish to propose for accreditation by the CDM Executive Board.


The objective is the "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

The objective of the Kyoto climate change conference was to establish a legally binding international agreement, whereby all the participating nations commit themselves to tackling the issue of global warming and greenhouse gas emissions. The target agreed upon was an average reduction of 5.2% from 1990 levels by the year 2012. According to the treaty, in 2012, Annex I countries must have fulfilled their obligations of reduction of greenhouse gases emissions established for the first commitment period. The Protocol expires at the end of 2012.
The five principal concepts of the Kyoto Protocol are:

Commitments to the Annex-countries.
Dividing the countries in different groups is one of the key concepts in making commitments possible, where only the Annex I countries in 1997, were seen as having the economic capacity to commit themselves and their industry. Making only the few nations in the Annex 1 group committed to the protocols limitations.

Implementation.
In order to meet the objectives of the Protocol, Annex I countries are required to prepare policies and measures for the reduction of greenhouse gases in their respective countries. In addition, they are required to increase the absorption of these gases and utilize all mechanisms available, such as joint implementation, the clean development mechanism and emissions trading, in order to be rewarded with credits that would allow more greenhouse gas emissions at home.
Minimizing Impacts on Developing Countries by establishing an adaptation fund for climate change.
Accounting, Reporting and Review in order to ensure the integrity of the Protocol.
Compliance. Establishing a Compliance Committee to enforce compliance with the commitments under the Protocol.

The targets apply to the four greenhouse gases carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, and two groups of gases, hydrofluorocarbons and perfluorocarbons. The six GHG are translated into CO2 equivalents in determining reductions in emissions.

Annex I countries can achieve their targets by allocating reduced annual allowances to major operators within their borders, or by allowing these operators to exceed their allocations by offsetting any excess through a mechanism that is agreed by all the parties to the UNFCCC, such as by buying emission allowances from other operators which have excess emissions credits.

The Protocol defines three flexibility mechanisms to meet emission limitations. They are:
International Emissions Trading (IET),
the Clean Development Mechanism (CDM),
and Joint Implementation (JI)
The world's top ten emitters of GHGs for 2005.
China
United States
European Union
Indonesia
India
Russia
Brazil
Japan
Canada
Mexico

The Protocol also reaffirms the principle that developed countries have to pay billions of dollars, and supply technology to other countries for climate-related studies and projects. The principle was originally agreed in UNFCCC.

non-Annex I Parties belonged in the low-income group, with very few classified as middle-income. They are not obligated by the limits of emissions in the Kyoto Protocol. Fast growing economy countries like China, South Africa, India and Brazil are still in this non-obligated group