Most environmental acids from anthropogenic sources are from atmospheric sulfur (usually in the form of SOx). A substantial amount of environmental acidification does come from NOx forming nitric acid (from combustion sources of air pollutants).

The main result of the sulfur chemistry is to produce sulfurous (H2SO3) or, eventually, sulfuric (H2SO4) acid, which may or may not be dissolved in water (technically, the liquid solutions of sulfuric/sulfurous acid and water are called "sulfuric/ous acid solution" or "sulfuric/ous acid in solution" while the straight "acid" designation would be the gaseous forms of these chemicals).

The "aq" subscripts denote substances dissolved in liquid water or the liquid water itself (an "aqueous" solution); the "g" subscripts denote substances existing as gas molecules; the "v" subscript denotes water vapor (gaseous water).