Ammonia gas concentrations over the Southern Ocean

Abstract

Ammonia is the only common, soluble, basic gas in the atmosphere and as such plays an important neutralising, sometimes rate-determining, role in the chemistry of acid gases such as SO₂, H₂SO₄ and HNO₃. It also constitutes a reservoir of labile nitrogen in the atmosphere and so must be included in any attempt to describe the cycling of nitrogen through the global environment. We report here values of ammonia concentration measured in Southern Ocean air which are considerably lower than any previously reported^1–5. For our analyses ammonia was collected on oxalic acid-impregnated filters and determined colormetrically. In air apparently devoid of contact with land for several thousands of kilometres of travel the mean concentration of ammonia gas was 0.06 μg m⁻³ (STP). Concentrations in air apparently affected by the Australian continent were several times higher than in the maritime air.