What is the environment what kind of substances are the main pollutants of environment?
Answers
Any constitutes constitutes of the environment environment
which directly or indirectly affects the
growth and development of an
organisms is called environmental or
ecological factor
E.g. climatic factor, biotic factor, fire,
edhapic (related to soil) factors
CHAPTER 3 ENVIRONMENTAL POLLUTION
1. AIR POLLUTION
The presence of one or more contaminants like dust, smoke, mist and odour in the atmosphere which are injurious to human beings, plants and animals.
Common air pollutants sources & their effects:
Substance Nature Sources Health effects Environmental effects
Carbon
monoxide
(CO)
Colourless, odourless, poisonous gas.
Formed during incomplete combustion of
fuels 2C + O2 → 2CO
Cigarette smoking, incomplete
burning of fuels, motor vehicle
exhaust
Causes headaches, anemia, coma,
irreversible brain cell damage &
death
Increases the globe temperature
Nitrogen
dioxide
(NO2)
Reddish-brown irritating gas & gives
photochemical smog,
Can be converted to nitric acid
NO2 + Moisture → HNO3
Fuels burning in vehicles,
industrial plants
Lung irritation & damage HNO3 acid deposition damage
trees, soils, & aquatic life. It
corrode metals, stones on
buildings, statues, monuments
etc.
Sulphur
dioxide
(SO2)
Colourless, irritating gas. Formed by
combustion of coal & oil. Can be
converted to sulphuric acid in atmosphere
Burning of coal, industrial
process
Breathing problems Reduce visibility, acid deposition
on trees, soils & aquatic life
Suspended
particulate
matter
(SPM)
Includes variety of particles & droplets
(aerosols).
Burning coal in industries, diesel
in vehicles, agriculture, unpaved
roads, etc
Nose & throat irritation, lung
damage, bronchitis, asthma, cancer
Reduce visibility, acid deposition,
H2SO4 droplets damage trees,
soils & aquatic life
Ozone (O3) Highly reactive irritating, unpleasant
odour gas. A major component of
photochemical smog.
Nitrogen oxides, chemical
reaction with volatile organic
compounds
- Moderates the climate
Photochemic
al smog
Brownish smoke formed during
automobile traffic
Formed due to chemical reaction
among nitrogen oxides
& hydrocarbon
Breathing problems, cough, eye,
nose & throat irritation, heart
diseases,
Damage plants & trees. Smog
reduce visibility
Lead (Pb) Solid toxic metal Paint, smelters, lead manufacture,
storage batteries, leaded petrol
Brain & nervous system damage,
mental retardation in children,
digestive & other health problems,
cause cancer
Can harm wild life
Chromium Solid toxic metal , Paint, smelters, chromium
manufacture, chromium plating
Perforation of nasal septum, chrome
holes, ulcer, central nervous system
disease, cancer.
1. Infectious agents :
Example: Bacteria, viruses, protozoa and parasitic worms.
Sources: Human and animal wastes.
Effects: Variety of diseases.
2. Oxygen demanding wastes:
Example:Animal manure and plant debris that can be decomposed by aerobic bacteria.
Sources: Sewage, paper mills, and food processing facilities.
Effects: Wastes can degrade quality by depleting water of dissolved oxygen, make aquatic life to die
3 .In organic Chemicals:
Example: Water soluble inorganic chemicals. Compounds of toxic metals such as lead, arsenic and
selenium. Salts such as Nacl in water.
Sources: Surface runoff, industrial effluents, household cleansers
Effects: skin cancers & neck damage
Damage nervous system, liver & kidneys
Lower crop yields, Harm fish & other aquatic life
Accelerate corrosion of metals
4. Organic Chemicals:
Examples: Oil, gasoline, plastics, pesticides, cleaning solvents, detergents
Sources: Industrial effluents, household cleansers, runoff from farms
Effects: Causes nervous system damage, cancer, harm fish & wild life.
5. Radio active materials:
Example: radioactive isotopes of iodine, radon, uranium,cesium,and thorium
Sources: Nuclear power plants, mining, nuclear weapons production.
Effects; genetic mutation, birth defects, and certain cancers.
6.Point and non-point sources of water pollution
Point sources: These are discharged pollutants at specific locations through pipes, ditches or sewers
eg: factories, sewage treatment plants
Non-point sources: They are usually large areas or air shed that pollute water by runoff
Eg: runoff of chemical from cropland to surface water.
Testing of river water:
Dissolved oxygen (DO) = It is the amount of oxygen dissolved in a givn quantity of water at a particular
pressure & temperature.
Biochemical Oxygen Demand (BOD) = It is the amount of oxygen required for the biological decomposition
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Forms of pollution
Air pollution: the release of chemicals and particulates into the atmosphere. Common gaseous pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles.
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