- A Reactive nitrogen compounds produced industrially are sometimes thought to be used mainly within agricultural fertilizer formulations, with little further environmental consequence beyond the treated farm field in general practice as frequently described
- B Reactive nitrogen from fertilizers and combustion cascades through multiple systems: ammonia contributes to PM2.5 and acid deposition; nitrate leaches to water causing eutrophication; N2O is a powerful greenhouse gas and destroys stratospheric ozone
- C Reactive nitrogen is sometimes thought to affect mainly highly localized soil chemistry at the point of application, with little broader cascading effect on regional air or water quality observed in most textbook accounts during normal conditions
- D The nitrogen cascade phenomenon is sometimes thought to occur mainly within largely enclosed aquatic freshwater systems such as ponds, rarely extending into the surrounding atmosphere or land as generally observed in typical laboratory settings
Correct answer: B. Reactive nitrogen from fertilizers and combustion cascades through multiple systems: ammonia contributes to PM2.5 and acid deposition; nitrate leaches to water causing eutrophication; N2O is a powerful greenhouse gas and destroys stratospheric ozone
Explanation: Nitrogen cascade (Galloway): once N is 'fixed' industrially or biologically, reactive N keeps cycling and causing successive environmental effects: (1) Eutrophication of water bodies; (2) Acidification of soil and water; (3) PM2.5 formation from NH3 (human health); (4) N2O emissions from soil denitrification (climate warming + ozone destruction); (5) NOx from combustion (smog, ozone). Reactive N is difficult to 'denitrify' completely.
Concept context
Pollution, global warming, ozone depletion, deforestation, and sustainability. Important for NEET and general awareness.