A global budget for atmospheric NH3

We provide an assessment of the global sources of NH₃ in the atmosphere, which indicates an annual flux of about 75 Tg of N as NH₃. The emissions from land are dominated by the release of NH₃ during the hydrolysis of urea from the urine of domestic animals (32 TgN/yr) and by emanations from soils in unmanaged ecosystems (10 TgN/yr) and from fertilized agricultural soils (9 TgN/yr). Emissions from the sea surface may approach 13 TgN/yr. The total annual source of NH₃ is in reasonable agreement with estimates of global NH ₄ ⁺ deposition from the atmosphere, the major fate of atmospheric NH₃. As an alkaline atmospheric species, NH₃ emitted to the atmosphere each year can neutralize only about 32% of the annual production of H⁺ in the atmosphere from natural and anthropogenic sources.