Geosmin is the compound responsible for which earthy smell?

Geosmin is the compound responsible for which earthy smell?

• A. Ammonia
• B. Geosmin
• C. Methane
• D. Sulfur dioxide

Answer: (B)

The main idea here is that geosmin is the compound that gives soil its distinctive earthy odor, especially noticeable after rain. Geosmin is produced by soil-dwelling microbes, and it has an incredibly low odor threshold, so even tiny amounts in soil or water trigger that recognizable muddy scent. The other substances listed have different and unrelated smells: ammonia has a sharp, pungent odor; methane is odorless; sulfur dioxide has a sharp, irritating smell, not earthy. So geosmin is the true source of that earthy smell.

The main idea here is that geosmin is the compound that gives soil its distinctive earthy odor, especially noticeable after rain. Geosmin is produced by soil-dwelling microbes, and it has an incredibly low odor threshold, so even tiny amounts in soil or water trigger that recognizable muddy scent. The other substances listed have different and unrelated smells: ammonia has a sharp, pungent odor; methane is odorless; sulfur dioxide has a sharp, irritating smell, not earthy. So geosmin is the true source of that earthy smell.