2.3.22 (HL)—Human impacts on nitrogen cycle

Deforestation, fertilizer, aquaculture, sewage and combustion add or redirect reactive nitrogen, which can cause eutrophication and air or water pollution.

Identify the activity, nitrogen form and receiving store. Excess inputs can exceed plant uptake, move downstream or deposit from air; effects depend on dose and pathway.

Fertilizer nitrate not taken up by crops leaches into a lake, stimulating algae and later oxygen depletion.

A pathway from excess nitrogen to algal growth, decomposition and reduced oxygen, with timing and evidence.

Correlation with farming is not enough; trace the nitrogen form and mechanism to the impact.