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Contamination of aquatic environment by Polychlorinated Biphenyls (PCBs) can originate from

A. Sewage effluent

B. Waste incinerators

C. Toxic dumps

D. Thermal power plants

E. Transport sector

Choose the most appropriate answer from the options given below:


1. A, C, E only
2. A, B, D, E only
3. B, C, D only
4. A, B, C only

1 Answer

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Best answer
Correct Answer - Option 4 : A, B, C only

Contamination:

  • The act or state of making or being made impure by polluting or poisoning.
  • Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical bodynatural environmentworkplace, etc.
  • In environmental chemistry, the term "contamination" is in some cases virtually equivalent to pollution, where the main interest is the harm done on a large scale to humans, organisms, or environments
  •  An environmental contaminant may be chemical in nature, though it may also be a biological (pathogenic bacteria, virus, invasive species) or physical (energy) agent.

Aquatic Environment:

  • The aquatic environment can be defined as an interacting system of resources such as water and biota.
  • Aquatic environments include inland surface water, seas, and groundwater.
  • Aquatic ecosystems are generally divided into two types --the marine ecosystem and the freshwater ecosystem.
  • The largest water ecosystem is the marine ecosystem, covering over 70 percent of the earth's surface. Oceans, estuaries, coral reefs, and coastal ecosystems are the various kinds of marine ecosystems.
  • The freshwater environments—such as streams, rivers, and lakes—apart from their bacterial and algal populations contain fungal, protozoan, and viral populations, which interact and contribute to the functioning of the food web.

Polychlorinated Biphenyls (PCBs)

  • polychlorinated biphenyl (PCB) is an organic chlorine compound with the formula C12H10−xClx.
  • Polychlorinated biphenyls were once widely deployed as dielectric and coolant fluids in electrical apparatus, carbonless copy paper, and heat transfer fluids.
  • With the discovery of PCBs' environmental toxicity, and classification as persistent organic pollutants, their production was banned by United States federal law in 1978, and by the Stockholm Convention on Persistent Organic Pollutants in 2001.
  • The International Agency for Research on Cancer (IARC), rendered PCBs as definite carcinogens in humans. 
  • The hydrosphere is the main reservoir. The immense volume of water in the oceans is still capable of dissolving a significant quantity of PCBs.
  • As the pressure of ocean water increases with depth, PCBs become heavier than water and sink to the deepest ocean trenches where they are concentrated.
  • PCBs in the dielectrics of transformers, voltage regulators (variable voltage transformers), capacitors, and fluorescent light ballasts are the major industrial uses today.
  • The main uses of PCB are as a dielectric fluid in power transformers and capacitors, as hydraulic fluid, as heat-exchange fluid, and as a plasticizer, in paints, plastics, and sealants.
  • Large volumes of PCB have been emitted by the open burning or incomplete incineration of waste, and by leakage from landfill sites and in the vicinity of factories.
  • There has also been the release of it due to accidents, such as in spills of transformer oil.

Conclusion: We can conclude that PCBs are discharged from a number of sources such as Sewage effluent, incineration, land-fills i.e toxic dumps etc. Hence, option (4) is correct.

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