Chapter 14 Environmental Chemistry Solutions
Question - 11 : - . What are the major causes of water pollution? Explain.
Answer - 11 : -
Causes of water pollution:
тАв Pathogens: Pathogens include bacteria and other microorganisms that enter water from domestic sewage and animal excreta.
Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis ,
which cause gastrointestinal diseases.
тАв Organic wastes: Organic wastes when added to water, as these are biodegradable, bacteria decomposes organic matter and consume dissolved oxygen in water. When the concentration of dissolved oxygen of water is below 6 ppm, the growth of fish gets inhibited. Breakdown of the organic wastes by anaerobic bacteria produces chemicals that have a foul smell and are harmful to human health.
тАв Chemical pollutants: Some inorganic chemicals as an industrial wastes dissolve in water like cadmium, mercury nickel etc. These metals are dangerous to humans and other animals. These metals can damage kidneys and central nervous system,lever etc. Petroleum products pollute many sources of water.
Question - 12 : - What do you mean by Biochemical Oxygen Demand (BOD)?
Answer - 12 : - The amount of oxygen required by bacteria to breakdown the organic matter present in a certain volume of a sample of water is called Biochemical Oxygen Demand (BOD).
Question - 13 : - What are pesticides and herbicides? Explain giving examples.
Answer - 13 : -
Pesticides are the chemical compoundsused in agriculture to control the damages caused by insects, rodents, weedsand various crop diseases.
Example: Aldrin, Dilldrin, B.H.C etc.
Herbicides:┬аThese are thechemicals used to control weeds.
Example: Triazines.
Question - 14 : - What do you mean by green chemistry? How will it help in decreasing environmental pollution ?
Answer - 14 : -
Green chemistry is a way of thinkingand is about utilising the existing knowledge and principles of chemistry andother sciences to reduce the adverse effect of pollution.
For example:
┬╖┬а┬а┬а┬а┬а┬а┬а┬аAutomobile engines have been fittedwith catalytic converters which prevent the release of the vapours ofhydrocarbons and oxides of nitrogen into acrolein and peroxyacetyl nitrate.
┬╖┬а┬а┬а┬а┬а┬а┬а┬аCO2┬аhas replacedCFCs as blowing agents in the manufacture of polystyrene foam sheets.
Question - 15 : - What would have happened if the greenhouse gases were totally missing in the earthтАЩs atmosphere? Discuss.
Answer - 15 : -
The solar energy radiated back fromthe earth surface is absorbed by the green house gases. (CO2, CH4,O3, CFCs) are present near the earthтАЩs surface.
They heat up the atmosphere near the earthтАЩs surface and keep it warm. As aresult of these, there is growth of vegetation which supports the life. In theabsence of this effect, there will be no life of both plant and animal on thesurface of the earth.
Question - 16 : - A large number offish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.
Answer - 16 : - Excessive phytoplankton (organic pollutants such as leaves, grass trash etc.) present in water are biodegradable. Bacteria decomposes these organic matters in water. During this process when large number of bacteria decomposes these organic matters, they-consume the dissolved oxygen in water. When the level of dissolved oxygen falls below 6 ppm the fish cannot survive.
Question - 17 : - How can domestic waste be used as manure?┬а
Answer - 17 : - Domestic waste consists of biodegradable waste which can be converted into manure by suitable method.
Question - 18 : - For your agricultural field or garden you have developed a compost producing pit. Discuss the process in the light of bad odour, flies and recycling of wastes for a good produce.
Answer - 18 : -
The compost producing pit should be kept covered so that flies cannot make entry into it and bad odour is minimized.
The waste materials which are non-biodegradable like glasses, plastic bags, polybags, must be handed over to the vendors who can send them to the recycling plants.