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AP Environmental Science · Question of the Day

AP Environmental Science Question of the Day

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Thursday, November 5, 2026

After prolonged fertilizer use, a soil shows high nitrate but also increased emissions of nitrous oxide (N2O\text{N}_2\text{O}), a greenhouse gas, especially when soils are wet. Which nitrogen-cycle process is most associated with producing gaseous nitrogen forms from nitrate under low-oxygen conditions?

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Question of the Day

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After prolonged fertilizer use, a soil shows high nitrate but also increased emissions of nitrous oxide (N2O\text{N}_2\text{O}), a greenhouse gas, especially when soils are wet. Which nitrogen-cycle process is most associated with producing gaseous nitrogen forms from nitrate under low-oxygen conditions?

  1. Denitrification (correct answer)
  2. Nitrification
  3. Ammonification
  4. Assimilation

Explanation: Denitrification produces gaseous forms like nitrous oxide (N2O) from nitrate under low-oxygen, wet conditions, with bacteria using nitrate as an electron acceptor. This explains emissions after fertilizer use, as excess nitrate fuels the process (choice A). Nitrification produces nitrate but not gases, ammonification releases ammonium, and assimilation stores nitrogen. Wet soils promote anaerobic bacteria for denitrification. N2O's greenhouse gas role highlights environmental concerns.