Fig. 1. Overview of the atmospheric acidity, nutrient, and trace element cycles.

Emissions of NH₃, NOx, SO₂, and dust influence atmospheric acidity (orange arrows). Dust, anthropogenic trace element emissions (abbreviated as Fe), and anthropogenic and biological sources of P, NH₃, and NO_x contribute to the atmospheric nutrient/trace element burden (blue arrows). The majority of sources are terrestrial, although ship-based emissions of Fe and NOx are important and marine emissions of dimethyl sulfide (DMS) are a substantial source of SO₂, particularly in the Southern Hemisphere. Acidity-driven atmospheric processing alters the labile nutrient flux to the ocean, either by affecting the gas-aerosol partitioning or by altering the labile fractions of Fe (L-Fe), P (L-P), and trace metals (L-TM). Organic nitrogen compounds (OrgN) are also generated during atmospheric processing but are not discussed here.