Question

Indiscriminate disposal of used fluore­scence electric lamps causes mercury pollution in the environment. Why is mercury used in the manufacture of these lamps ?
1. A mercury coating on the inside of the lamp makes the light bright white
2. When the lamp is switched on, the mercury in the lamp causes the emission of ultra-violet radiations
3. When the lamp is switched on it is the mercury which converts the ultra-violet energy into visible light
4. None of the statement given above is.correct about the use of mercury in the manufacture of fluorescent lamps

Answer 1

Correct Answer - Option 2 : When the lamp is switched on, the mercury in the lamp causes the emission of ultra-violet radiations

The correct answer is When the lamp is switched on the mercury in the lamp causes the emission of ultra-violet radiations.

• Mercury pollution
  • Recently researchers have found that despite a decrease in seawater concentration of methylmercury, the amount of mercury found in fish is different among different species 
  • Joint research conducted by the Indian Institute of Technology, Hyderabad (IIT-H), Harvard University, and Fisheries and Oceans Canada (a Canadian government agency) has found that though there has been a decrease in the levels of mercury emission, the concentration of mercury in fish varies across different species.
  • Some species of fish have less mercury than before, while others have a very high concentration of mercury (tuna, salmon, and swordfish).
  • The researchers warn that human exposure to the toxin (methylmercury) through fish consumption is bound to increase as a result of climate change.

• Variation in Mercury Accumulation in Fish
• Three factors that can be attributed to the variation in accumulation of mercury in fish are:
  • Variations in the Temperature of the Seawater
    • Seawater temperatures may also alter mercury accumulation.
    • Fish metabolism is temperature-dependent, so as ocean temperature increases, fish experience higher metabolism, and more energy obtained from food are spent on maintenance rather than growth, leading to more methylmercury getting concentrated in predatory fish.
    • Changes in the amounts of mercury found in seawater as a result of pollution.
  • Overfishing
    • Leads to dietary changes among marine animals.
    • Cod relied more on lobsters and other large invertebrates (which are low in mercury), while the dogfish went for more squid and other cephalopods (which tend to be high in mercury).
    • Hence cod ended up with lower mercury levels than the dogfish.