ENVIRONMENT REVISION SERIES FOR PRELIMS

CHAPTER 1

Organisms and the Environment

The term ecology was coined by Ernst Haeckel.

Environment – Sum total of all biotic and abiotic factors that surround and potentially influence an organism.

There exist spatial and time scales of environment. Weather – Short term properties of the atmosphere at a given place and time. Climate – Average weather of an area over a long period. Temperature and

rainfall are the two most important factors that determine the climate of an area.

Climatic zones – Tropical, subtropical, temperate and arctic & Antarctic. Temperature and precipitation together determine the vegetation and soil

types. Microclimate represents the climatic conditions that prevail at a local scale, or

in areas of limited size.

Habitat – The place where an organism lives. It may refer to the place occupied by an entire biological community.

Ecological niche – It represents the range of conditions that it can tolerate, the resources it utilises and its functional role in the ecological system.

Environmental factors

Atmosphere – Layers are troposphere, stratosphere, mesosphere and thermosphere. Air contains gases like nitrogen, oxygen, carbon dioxide, Ozone, water vapour etc. Water vapour, Ozone and Carbon dioxide are essential for maintaining life on earth. In water, oxygen supply is regulated through diffusion from the air and the photosynthetic activity of aquatic plants.

Light –

Electromagnetic spectrum. In this, light waves in the range of 400-700 nm constitutes the visible range of the spectrum and is called photosynthetically active radiation.

Solar constant – Energy carried by the incoming radiation. It is equal to 2 cal cmˆ-2 minˆ-1.

UV radiation is absorbed by ozone. UV has three parts. UV-A in the range of 400-320 nm, UV-B in the range of 32-280 nm and UV-C in the range of 280-100 nm. Out of these three, UV-C is the most lethal.

The quality, intensity and duration of light is important to organisms.

Phenology refers to the timing of seasonal activities of plants in relation to change in environmental conditions.

In aquatic system, based on the penetration of light, it is divided into four states. 1. Littoral zone – rooted vegetation

2. Limnetic zone – Phytoplankton growth

3. Profundal zone – light doesn’t reach

4. Benthic zone – bottom of lakes and ponds

Temperature –

It is the degree of hotness or coldness of a substance. Vertical temperature gradient over Earth’s surface is called lapse rate. Animals can be cold blooded (ectotherms) or warm blooded (endotherms). Thermal stratification in lakes – Epilimnion (upper layer), thermocline (zone of

gradual change in temperature) and hypolimnion (lower layer of water).

Water –

The only inorganic liquid occurring naturally on earth. Water potential – Force with which soils hold water and it is quantified in

terms of pressure. Field capacity – The upper limit of water availability of a soil. Wilting point – The lower limit of water availability in soil.

Soil –

It is the uppermost weathered layer of the Earth’s crust. Is composed of minerals and partly decomposed organic matter. Soil aids plant growth by providing water, nutrients and anchorage. Soil profile – vertical layered structure of soil. It has four main horizons –

O,A,B,C.

Soils are made up of four components – mineral particles, organic matter, air and water.

Coarse sand (0.2-2 mm), fine sand (0.02-0.2 mm), silt (0.002-0.02 mm) and clay (<0.002 mm).

Soil organic matter consists of two parts – Detritus/Litter and Humus. Fire – through removal of plant cover, burning of litter mass present on soil

surface and loss of nutrients due to volatalisation. Biotic factors

Range of tolerance –

Acclimatisation – The gradual physiological adjustment to slowly changing new environmental conditions.

Ecological adaptations

Phenotype is the physical expression of the interaction between genotype of an organism and its environment.

The variations in phenotypes produced by the influence of local conditions of the habitat is called phenotypic plasticity.

Species having a wide range of distribution evolve genetically adapted local populations, which are called ecotypes.

Strategies of adaptations in plants: 1. Adaptation to light regime:

a) Sciophytes – shade tolerant

b) Heliophytes – sun adapted

2. Adaptations to water scarcity and heat: a) Ephemerals – short life span

b) Xerophytes – growing in desert

c) Succulence – storage of water in leaves and stems

3. Adaptations in aquatic environments: a) Hydrophytes – plants permanently immersed in water. It has the presence of

aerenchyma (large air spaces). 4. Adaptations in saline environments:

a) Halophytes – special adaptations like pneumatophores (respiratory roots), vivipary (seeds germinate while on the trees).

5. Adaptations to oligotropic soil (soils containing low amounts of nutrients) – presence of mycorrhizae, which have mutualistic association of roots with fungi. Mycorrhizae can be divided into endomycorrhizae and ectomycorhizzae.

Strategies of adaptation in animals:

1. Migration – long/short distance movement of animals from one region to another. 2. Camouflage – Capacity to blend with surroundings. 3. Hibernation and aestivation. 4. Mimicry – mimicry in animals is of two types. In Batesian mimicry, the mimic is defenceless, but has anti – predatory marks. In mullerian mimicry the mimic shares the same defensive mechanism as the model 5. Warning colouration. 6. Adaptations to water scarcity – by lowering of water loss as much as possible and adapting to arid conditions. 7. Adaptations to cold –

i. Cold hardening with the help of ice nucleating proteins

ii.Avoiding freezing by accumulating glycerol or antifreeze proteins.

CHAPTER 2

Population, Biotic community and Succession

The individuals of a species living with a habitat constitutes a population. In other words, population is a group of individuals of the same species, inhabiting the same area and functioning as a unit of biotic community.

Populations have a number of attributes using which different populations can be compared.

1. Density – It is the total number of individuals present per unit area or volume at a given time. 2. Natality – The increase in number of individuals in a population under the given environmental conditions. 3. Mortality – Loss of individuals due to death in a population under the given environmental conditions. 4. Dispersal – Movement of organisms into and out of population, also called immigration and emigration.

5. Age distribution – pre reproductive, reproductive and post reproductive ages. 6. Biotic potential – The inherent maximum capacity of an organism to reproduce or increase in number is termed biotic potential. 7. Environmental resistance – The environmental check on population size is called environmental resistance.

Population growth – Increase in the size of population over a period of time. There are two basic population growth forms – J shaped growth form and S

shaped growth form.

The maximum number of individuals of a population that can be sustained indefinitely in a given habitat represents its carrying capacity.

Ecological interdependence and interactions

Members of the biotic community in an area are dependent on one another for their survival. For this, they interact with each other.

The interactions between populations of species in a community are broadly categorised into positive and negative interactions.

Positive interactions include mutualism and commensalism. Negative interactions include competition, predation, parasitism and

ammensalism. Competition can be interspecific or intraspecific. The parasites which remain outside the host are called ectoparasites.

Biotic community

Biotic community organisation results from interdependence and interactions amongst populations of different species in a habitat. Some of the common community characteristics include:

1. Species composition. 2. Dominance – communities are generally named after the dominant species. 3. Physiognomy and stratification – physiognomy refers to the external appearance or ‘look’ of the community. It is the total effect created by the combination of vertical structure and architecture of dominant species of vegetation. 4. Species diversity – it includes the total number of species present in a community and the relative abundance of these species. 5. Keystone and link species – The species having much greater influence on the community characteristics, relative to their low abundance or biomass, are called keystone species. Link species act as the connecting points in different areas such as food chain, nutrient cycling etc. 6. Ecotones and edge effect – The transition zone between two communities is known as ecotone. The tendency of increased variety and density of some organisms at the community border is known as edge effect.

In analysis of plant communities, the characteristics can be categorised as analytic and synthetic characters.

Analytic are directly observed while synthetic are derived from analytic. Analytic can be quantitative and qualitative.

Quantitative characteristics are frequency, density, cover, bio mass and leaf size.

Succession

The successive replacement of communities in an area over a period of time is known as ecological succession.

Succession can be primary as well as secondary. Primary succession is when succession occurs in a barren land whereas secondary succession is when succession occurs by replacing an existing stable community.

The plants that invade the bare land initially are called pioneer species and their assemblage forms the pioneer community.

The plant species which get established later, during the course of succession are known as late successional species.

The terminal stage of succession is represented by the climax community. The succession occurring in water bodies like ponds and lakes is called

hydrarch succession and that taking place in terrestrial areas with low moisture is known as xerarch. Xerarch succession

Hydrarch succession

CHAPTER 3

Ecosystem: structure and function

The term ecosystem was coined by Sir Arthur Tansley. Two major categories of ecosystems – terrestrial and aquatic. Ecosystem has two basic components – abiotic and biotic. Abiotic components

comprise inorganic materials and dead organic matter while biotic components include producers, consumers and decomposers. Producers produce their own food, consumers eat producers and decomposers live on dead organic matter or detritus.

Ecosystem structure and function

Important structural features are species composition and stratification. Another way to depict the ecosystem structure is through food relationships of producers and consumers.

Trophic structure may be described in terms of the amount of living material called standing crop, present in different trophic levels at a given time.

The amount of nutrients, such as nitrogen, phosphorous and calcium present in the soil at any given time, is referred to as the standing state.

The key functional aspects of the ecosystem are: 1. Productivity and energy flow. 2. Nutrient cycling

3. Development and stabilisation

Productivity – rate of biomass production

Primary productivity refers to the rate at which sunlight is captured by producers for the synthesis of energy – rich organic compounds through photosynthesis.

The total organic matter production is called gross primary production. Net productivity = Gross productivity – respiration

The magnitude of primary productivity depends on the photosynthetic capacity of producers and the prevailing environmental conditions.

Decomposition

Dead plant parts and animal remains are called detritus.

Processes involved in decomposition can be categorised as fragmentation of detritus, leaching and catabolism.

Nutrient immobilisation occurs when nutrients are incorporated in the biomass of microbes and thus become temporarily unavailable to other organisms.

The rate of decomposition of detritus is primarily regulated by the climatic factors (temperature and soil moisture) and the chemical quality of detritus.

Energy flow

The storage and expenditure of energy in the ecosystem is based on the two basic laws of thermodynamics, i.e., the first and second laws of thermodynamics.

The transfer of energy from one trophic level to the next is called food chain.

Food chain is of two types, grazing food chain and detritus food chain. Grazing food chain extends from producers through herbivores to carnivores. Detritus food chain begins with dead organic matter and passes through detritus feeding organisms in soil to organisms feeding on detritus – feeders.

Inter connected matrix of food chains is called food web. With reference to energy flow in an ecosystem, two aspects:

1. Energy flows in one way only. 2. Amount of energy flow decreases with successive trophic levels.

The respiration cost increases sharply along successive higher trophic levels. Due to this high energy loss, length of food chain in an ecosystem is limited to 3-4 trophic levels.

Ecological pyramids

Three types of ecological pyramids are usually compared: (i) Pyramid of numbers.

(ii) Pyramid of biomass

(iii) Pyramid of energy

While the pyramids of number and biomass can be inverted, the pyramid of energy is always upright.

Ecological efficiencies

Photosynthetic efficiency = (Gross primary productivity/incident total solar radiation) * 100

Net production efficiency = (Net primary productivity/gross primary productivity) * 100

Assimilation efficiency = (Food energy assimilated/Food energy ingested) * 100

Ecological efficiency =(Energy in biomass pdn in one level/energy in prev level) *100

First two are at the level of producer while last two are at the levels of consumer.

Nutrient cycling

Nutrient cycles involve storage and transfer of nutrients through various components of ecosystem so that the nutrients are repeatedly used.

Nutrient cycles are of two types – gaseous and sedimentary. For gaseous, the reservoir is in the atmosphere or the hydrosphere while for sedimentary, it is in the earth’s crust.

The input of nutrients into the ecosystem can occur either as wet deposition or as dry deposition.

In an undisturbed ecosystem, input of nutrients may approximately be equal to the output of nutrients.

The transfer of nutrients from the soil to plants by the process of nutrient absorption is known as uptake.

Retention = uptake – recycle

Nitrogen cycle

Phosphorous cycle

Major forest biomes in India are: 1. Tropical rain forest biome

Western Ghats and North Eastern Himalayas. Highest standing crop biomass among all biomes.

2. Tropical deciduous forest

Northern and southern parts of the country in plain and low hilly areas. Lush green in summer and leafless in winter.

3. Temperate broad leaf forest

15—2400 m altitude in the Western Himalayas. They never become leafless.

4. Temperate needle leaf/coniferous forest

1700-3000 m altitude. Canopy is cone shaped. Grassland ecosystems may be grassland or savannah ecosystem. Grassland ecosystems have treeless herbaceous plant cover, dominated by a

wide variety of grass species. Eg: “Prairie” in North America and “Steppe” in Russia.

The primary productivity in grassland is directly related to the amount of rainfall.

In Savannah, they have well developed grass cover, interspersed with scattered shrubs or small trees.

Savannahs occur in tropical areas with highly seasonal climate, having distinct wet and dry periods. Availability of soil moisture determines the species composition and productivity of savannahs and it may be modified by fire, soil nutrients and herbivores.

In desert biome, there is prolonged moisture scarcity. Desert biome can be classified into two – true desert and extreme desert. In

true desert, the amount of rainfall is less than 120 mm while in extreme desert, it is less than 70 mm.

Also based on temperature, deserts can be classified as hot and cold desert. Most of the deserts are distributed around the Tropic of Cancer and Tropic of

Capricorn, between 15° and 35° latitudes. The vegetation is dominated by three life forms:

i) Ephemeral annual herbs

ii) Typical succulent xerophytes

iii) Shrubs and small trees whose deep tap roots may reach the water table.

CHAPTER 4

Natural resources and their conservation

Any component of the natural environment that can be utilised by man to promote his welfare is considered as a natural resource.

Resources can be broadly classified as inexhaustible and exhaustible sources. Exhaustible resources can again be categorised as renewable and non – renewable sources.

Soil resource

Movement of water and air removes top soil from the land by the process of erosion.

Depletion of soil fertility occurs when natural vegetation is removed to develop agricultural systems.

Soil conservation practises include conservation tillage, organic farming, crop rotation, contour ploughing and strip cropping terraces.

STRIP FARMING

Water resources

Distribution of water in earth is in the following order: Oceans > Polar ice caps > Groundwater> Water in lakes and rivers > Soil > Atmosphere

About 84% of the total global evaporation occurs from ocean surface and 16% from land surface.

The total annual evaporation = total annual precipitation. Problems with water resources:

i. Due to over – use of surface water, nearby wetlands may dry up. ii. Over usage of groundwater can result in it also drying out. iii. Excessive irrigation in semi – arid and arid regions can cause salt

accumulation in the soil. iv. Depletion of groundwater leads to movement of saline sea water to

freshwater wells.

Conservation and management of water:

i. Reducing agricultural water wastage by increasing efficiency of irrigation. ii. Reducing water wastage in industry by recycling the used water. iii. Reducing domestic water wastage by constructing waste water treatment

plants and recycling the treated water. iv. Rainwater harvesting by employing practices to store rainwater and

recharge groundwater. v. Afforestation and protection of watershed to improve water economy.

Land resources

Land resources can be classified as forests, grasslands and wetlands. Forests:

They cover one - third of the earth’s total land cover. The functions of forests can be categorised as:

i) Productive – production of wood, fruits and a wide variety of compounds. ii) Protective – conservation of soil and water, prevention of drought etc. iii) Regulative – absorption release and storage of gases, water etc.

Deforestation is a serious issue related to the environment, which needs to be tackled at the earliest. Certain types of forest management methods are as follows:

1. Protection/conservation forestry – protection of degraded forests to allow recoupment of their flora and fauna.

2. Production/commercial forestry – It aims to fulfil the commercial demand, without causing denudation of natural forests, through intensive plantation in available land.

3. Social forestry – plant trees and shrubs on all unused and fallow land is used to provide fuelwood, fodder etc., and thereby reducing pressure on existing forests.

4. Agro forestry – woody species are grown in combination with herbaceous crops, either at the same time or in time sequence.

Grassland (rangeland):

About 37% of the total land area is available for grazing. Degradation or destruction of grassland is mainly related to over population.

Lack of plant cover causes soil erosion.

Desertification – it is the conversion of grassland to desert. Grassland management is done through protection from grazing, rotational

grazing, conservation of soil and water etc.

Wetlands:

Low-lying areas covered with shallow water are called wetlands. They are transitional zones between terrestrial and aquatic areas.

Wetlands are of two types – freshwater and salt water. Wetlands occupy almost 6% of the world’s land surface and provide crucial

environmental services. Freshwater wetlands includes:

i) Marshes – grass like plants dominate. ii) Swamps – trees or shrubs dominate. iii) Periodically flooded riverine forests.

Freshwater wetlands help control flooding by holding excess water. They also serve as groundwater recharging areas. They also help to clean and purify water run - off.

Saltwater wetlands are coastal wetlands and include highly productive estuaries which provide food and habitat for a large number of marine organisms.

Wetland conservation programmes are generally based on: i) Preparation of wetland inventories. ii) Identification of wetlands of critical importance for their protection. iii) Checking waste disposal in wetlands. iv) Reduction of excessive inflow of nutrients and silt into wetlands from surrounding uplands by keeping them under plant cover.

Energy resources

Energy resources can be broadly categorised as renewable and non – renewable sources.

Solar energy – direct solar energy is the radiant energy while indirect solar energy is energy obtained from materials that have previously incorporated the sun’s radiant energy.

Biomass energy is the most important energy source indirectly utilised from solar energy. It is obtained from those materials whose origin can be traced to photosynthesis.

Biogas produced from biomass is a mixture of 60% methane and 40% CO2. Other renewable energy sources include hydropower, wind energy,

geothermal energy, tidal energy etc.

Marine sources:

Marine sources can be classified broadly as living and non – living.

Marine algae have been used as a manure in many countries because of their high nutrient content.

Green, blue, red and brown algae are common in oceans. Red algae are used for the extraction of commercially important agar. Animal sources found in oceans include fishes, molluscs, crustaceans,

mammals etc. Fishes provide food, oil, fish protein etc. Demeral fish are ones which are found at the bottom of the sea and pelagic fish are the ones that are floating free in the water column.

Mineral resources: Minerals occur naturally in the earth’s crust, though not evenly distributed. The land that has been destroyed due to mining is known as derelict land or

mine spoil. Mineral conservation includes their recycling and reuse. The benefits of reuse

are greater than those of recycling.

Forests and wildlife laws

Forest Act 1927 – basic objectives include setting up and managing reserved forests, protected forests and village forest, control of movement of forest produce etc.

Wildlife (protection) Act 1972 – restriction and prohibition on hunting of animals, protection of specified plants, setting up and management of sanctuaries and national parks, control of trade and commerce in wildlife, wildlife products and trophies.

National forest policy 1988 –ensure environmental stability and maintenance of ecological balance, including atmospheric equilibrium, which are vital for all forms, human, animal and plant.

CHAPTER 5

Biodiversity

The term biodiversity refers to the totality of genes, species and ecosystems of a region.

About 70% of the identified species are animals while 30% are plants. Among the total, 61% of known species are insects.

Levels of biodiversity

Biological diversity includes three hierarchical levels: i) Genetic diversity

ii) Species diversity

iii) Community and ecosystem diversity

Genetic diversity refers to the variation of genes within species; the differences could be in alleles, in entire genes or in chromosomal structures. The amount of genetic variation is the basis of speciation. Genetic diversity within a species often increases with environmental variability.

Simplest measure of species diversity is species richness, i.e, the number of species per unit area.

Diversity at the level of community and ecosystem has three perspectives: i) Alpha diversity – within community diversity. ii) Beta diversity – between community diversity

iii) Gamma diversity – diversity of the habitats over the total geographical area.

There are two gradients of biodiversity – latitudinal and altitudinal. As we move from high to low latitudes, biodiversity increases. As we move from lower to higher altitudes, biodiversity decreases.

In India, the most biodiversity-rich zones are the Western Ghats and the North – East. About 33% of the flowering plants recorded in India are endemic to the country. The endemics are mainly concentrated in north-east, Western Ghats, north-west Himalaya and Andaman and Nicobar islands.

Uses of biodiversity

Source of food and improved varieties. i) Source of new crops. ii) Source material for breeding improved varieties. iii) source of new biodegradable pesticides.

Drugs and medicines: i) Morphine which is used as an analgesic. ii) Quinine used for treating malaria. iii) Taxol – anticancer drug from the bark of the yew tree.

Aesthetic and cultural benefits – eg: Tulsi, pipal, khejri etc. Ecosystem services – climate control by forests and oceanic systems, natural

pest control etc.

Threats to biodiversity

Habitat loss and fragmentation. Disturbance and pollution. Introduction of exotic species – new species entering a geographical region are

called exotic or alien species. Invasive species are considered second only to habitat destruction as a major cause of extinction of species. Eg: introduction of nile perch into lake Victoria.

Extinction of species: i) Natural extinction

ii) Mass extinction

iii) Anthropogenic extinction

More species have gone extinct from the islands than from the mainland or the oceans.

The characteristics of species particularly susceptible to extinction are: i) Large body size (Bengal tiger, lion and elephant) ii) Small population size (Blue whale)

iii) Low reproductive rate (Giant panda) iv) Feeding at high trophic levels in the food chain (Bald Eagle, Bengal tiger)

v) Fixed migratory routes and habitat (Whooping crane)

vi) Localized and narrow range of distribution (woodland caribou)

The IUCN red list is a catalogue of taxa that are facing the risk of extinction. It recognizes eight red list categories of species: extinct, extinct in the world, critically endangered, endangered, vulnerable, lower risk, data deficient and not evaluated.

Conservation of biodiversity

Basic strategies employed to conserve biodiversity can be broadly classified as in-situ and ex-situ methods.

In – situ methods:

Protected areas – Areas of land and/or sea, especially dedicated to the population of natural and associated cultural resources. Important examples are national parks and wildlife sanctuaries. The Jim Corbett National park was the first national park established in India.

Biosphere reserves – Here, people form an integral component of the system. It can be divided into three areas. The core area is the undisturbed part of the reserve where no activities are carried out. The buffer zone is the area where research and activities are being carried out. In the transition zone or the outermost part of the reserve, there happens an active cooperation between the local people and reserve management.

The main functions of biosphere reserves are conservation, development, scientific research, monitoring and education.

Another traditional strategy for the protection of biodiversity is sacred forests and sacred lakes.

Ex – situ methods:

The common methods include botanical gardens, zoos, conservation stands and gene, pollen, seed, seedling, tissue culture and DNA banks.

In vitro conservation is common, where there is the preservation of crops by storing in liquid nitrogen at a temperature of -196°C (Cryopreservation).

Arboreta – botanical gardens where specific tree and shrub species are cultivated.

Biodiversity hotspots

The concept of hotspots was developed by Norman Myers in 1988. There are two key criteria for determining a hotspot: i) Number of endemic species. ii) Degree of threat, which is measured in terms of habitat loss.

Tropical forests appear in 15 hot spots, Mediterranean – type zones in 5 and 9 hotspots are mainly or completely made up of islands.

There are three biodiversity hotspots in India – Western Ghats, Eastern Himalayas and Indo – Burma.

The main effort to conserve biodiversity was the Earth summit held in 1992 in Rio de Janerio. The convention had three key objectives: i) Conservation of biological diversity

ii) Sustainable use of biodiversity and

iii) Fair and equitable sharing of benefits arising out of the utilization of genetic resources.

ENVIRONMENT REVISION SERIES FOR PRELIMS CHAPTER 6

Pollution and global environmental change

Pollution is an undesirable change in physical, chemical or biological characteristics of our air, land or water, caused by excessive accumulation of pollutants.

Kinds of pollution

A) Based on the part of environment where it occurs, it can be air pollution, water pollution or soil pollution. B) In terms of origin, it can be natural or anthropogenic pollution. C) According to the physical nature of the pollutants, it can be gaseous, dust, thermal, noise or radioactive pollution. D) From the ecosystem point of view, it can be biodegradable and non-biodegradable pollution.

Air pollution: Sources, types and effects

The sources of air pollution can be natural or anthropogenic. Anthropogenic sources can again be classified as fixed and mobile sources.

The pollutants can be primary or secondary. Primary pollutants are those which exist in the form in which they are released into the atmosphere whereas secondary pollutants are those which are formed by the reaction of primary pollutants.

Primary air pollutants

1) Particulate matter – It comprises solid particles or liquid droplets. Generally, particles with diameter less than I micrometer stay suspended in atmosphere for weeks.

2. Carbon monoxide – A product of incomplete combustion of fossil fuels. It is highly poisonous and reduces the oxygen carrying capacity of blood.

2) Hydrocarbons or Volatile Organic Carbons (VOCs) – produced by the decomposition of organic matter. Some of them are carcinogenic in nature. They contribute to the generation of secondary pollutants.

3) Sulphur dioxide – produced when sulphur containing coal is burnt. It causes respiratory problems and contributes to production of acid rain. 5) Nitrogen oxides – produced by combustion of fossil fuels at high temperatures in automobile engines. They cause reddish brown haze (brown air), which causes heart and lung problems

Secondary air pollutants

1) Photochemical smog – Warm conditions and intense solar radiation. Composed mainly of ozone, peroxy acetyl nitrate (PAN) and nitrogen oxides. When solar radiation is intense, brown air and when intensity is less, grey air. Ozone and PAN is formed from hydrocarbons and Nitrogen oxides. Ozone is corrosive and also causes lung problems. PAN damages chloroplasts and inhibits electron transport system. 2) Acid rain – ways in which acids from the atmosphere are deposited on the earth. Two types of deposition: (i) Wet deposition – acidic water received through rain, fog and snow. (ii) Dry deposition – acidic gases and particles in the atmosphere, which settle down on the ground.

Nitrogen oxides, VOCs and sulphur dioxide contribute to the formation of acidic particles in the atmosphere. pH f acid rain is below 5.6 and could be as low as 4 or below.

Control of air pollution

i) Suitable fuel selection and its efficient utilization. ii) Modifications in industrial processes. iii) Correct selection of manufacturing site. iv) Zoning for industrial set up

Control of particulate matter is done with the help of arresters and scrubbers. The different types of arresters are: a) Cyclonic – using centrifugal force

b) Filter – using filer material c) Electrostatic precipitator

Control of gaseous pollutants is done through combustion, absorption and adsorption.

Control of automobile exhaust is done by incorporating a more efficient engine, catalytic converter filters, good quality fuels etc.

Water pollution: Sources, Types and Effects

The sources in water pollution can be broadly classified as point and non-point sources.

The types of pollutants can be categorized as biological, chemical and physical. These pollutants are generated by different sources and activities:

i) Municipal wastewater

ii) Industrial wastewater

iii) Surface run off from land

iv) Oil spills

Effects of water pollution

Effects on aquatic ecosystem: decreased dissolved oxygen (DO) content, which in turn results in reduced photosynthetic activity. a) BOD – measure of the oxygen required for degradation of biodegradable organic materials. b) COD – measure of oxygen required for degradation of total organic materials in the aquatic system

Biological magnification – by accumulation of non-biodegradable pollutants in the tissues of organisms.

Eutrophication – due to excess availability of nutrients, which causes profuse growth of algae (algal bloom). They release toxins and cause deficiency of oxygen in the water. The process of nutrient enrichment of water and consequent loss of species diversity is referred to as eutrophication.

Effects on human health – various diseases caused by pathogens. Also, due to heavy metal contamination like mercury poisoning, diseases like Minamata disease.

Groundwater pollution – Various elements cause various diseases:

i) Nitrate – methameoboglobinemia or blue-baby syndrome

ii) Flouride – skeletal flourosis

iii) Arsenic – black foot disease

iv) Cadmium – Itaita disease

Improving water quality

Industrial and municipal waste waters are treated in Effluent Treatment Plant (ETP). i) Primary treatment – separation of large debris by sedimentation

ii) Secondary treatment – biological process carried out in oxidation ponds, resulting in formation of sludge or biosolid. Iii) Tertiary treatment – physic chemical process.

Soil pollution

Soil pollution usually results from different human activities like waste dumping, use of agrochemicals, mining operation (open cast mining) and urbanization.

Noise pollution

Noise pollution can be defined as the loud disturbing sound dumped into the ambient atmosphere without regard to the adverse effects it may have.

Sound level is the logarithm of theratio of ambient intensity to the reference intensity. Its unit is decibel. Sound above 120 db causes noise pollution.

Noise affects heartbeat, peripheral circulation and breathing pattern.

Environmental laws for controlling pollution

i) The environment (protection) act, 1986

ii) The insecticide act, 1968

iii) The water (prevention and control of pollution) act 1974

iv) The air (prevention and control of pollution) act 1981

Global environmental change

Gases like CO2, CH4, N20 and CFCs are radiatively active gases (also called greenhouse gases) because they can absorb long wave infrared radiation.

Greenhouse flux – downward flux of radiation from the atmosphere, which keeps the earth warm.

Greenhouse effect – phenomenon of high temperature on earth even during night times due to the greenhouse flux.

Excessive increase in the concentration of the greenhouses gases result in enhanced greenhouse effect, which in turn causes global warming.

The increasing abundance of greenhouse gases in the atmosphere has the following effects: i) CO2 fertilization effect ii) Global warming

iii) Depletion of ozone layer in the stratosphere.

CO2 fertilization effect

It is the response of pants to elevated concentrations of CO2. Due to this, rate of photosynthesis will increase, stomatal conductance will decrease. Thus, transpiration decreases and water efficiency increases.

Global warming

i) Effect on weather and climate – temperature changes are expected to be most marked in regions of middle and higher altitudes. ii) Sea level change. iii) Effects on range of species distribution. iv) Food production – eruption of plant diseases and pests, growth of weeds and increases basal rate of transpiration of plants.

Ozone depletion

Ozone shield is present in the stratosphere. Absorption of UV-radiation by ozone layer increases exponentially with its

thickness. Decline in the thickness of ozone layer is called ozone hole.

International initiatives for mitigating global change are: i) Montreal protocol – phasing out of ozone depleting substances. ii) Kyoto protocol – reduce overall greenhouse emissions to a level at least 5% below the 1990 level by the commitment period 2008-2012.