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Environmental Issues — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYEnvironmental Issues1 Mark
MCQ
Increase of $\ce{BOD}$ in water leads to:
  • A
    Increase in the dissolved $O_2$ concentration.
  • ✓
    Decrease in the dissolved $O_2​$ concentration.
  • C
    Maintenance of dissolved $O_2$ concentration at the same level.
  • D
    No effect on dissolved $O_2​$ concentration.
✓

Answer

Correct option: B.
Decrease in the dissolved $O_2​$ concentration.
Organic loading is occurrence of excess organic matter inside water due to sewage disposal and eutrophication. This leads to an increase in biological oxygen demand $\ce{(BOD)}$ for putrefaction.
Explosive multiplication of alga leads to algal bloom. These conditions result in decrease in dissolved oxygen in water. Both toxicity due to algal toxins and decreased levels of dissolved oxygen kill aquatic animals.

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