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🧪 Chemistry  ·  Environmental Chemistry  ·  NEET & JEE

Methylmercury formed from inorganic mercury in sediments is far more hazardous to humans than Hg<sup>2+</sup> itself mainly because methylmercury:

Answer: Is lipid soluble, so it is absorbed and biomagnified up the aquatic food chain.

  • A Is highly water soluble and is therefore rapidly excreted by the kidneys
  • B Is lipid soluble, so it is absorbed and biomagnified up the aquatic food chain
  • C Decomposes quickly in sunlight
  • D Cannot cross biological membranes

Correct answer: B. Is lipid soluble, so it is absorbed and biomagnified up the aquatic food chain

Explanation: Lipid-soluble methylmercury passes easily through membranes, is retained in tissues and becomes concentrated at each trophic level (biomagnification), reaching toxic levels in fish consumed by humans, causing Minamata disease.

Classical (London) SmogSources: coal burningSO₂ + particulates + fogReducing typeConditions: cold, humid,early morning, winterVisibility: very low (fog)London, 1952 - ~4000 deathsHarms: eyes, lungs, bronchitisPhotochemical (LA) SmogSources: vehicles, industriesNOx + hydrocarbons + UVOxidising typeConditions: warm, sunny,afternoon, summerProducts: O₃, PAN, acroleinLos Angeles (common in cities)Harms: eyes, rubber cracking

Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.

Concept context

Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.

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