On the discrepancy between background atmospheric ammonia gas measurements and the existence of acid sulfates as a dominant atmospheric aerosol

From the knowledge of NH₄⁺ and H⁺ concentrations in precipitation (during rainy periods) and aerosol particles (when it is not raining) over the continental United States and in ocean water along the coasts, the atmospheric NH₃ gas concentration can be inferred by assuming Henry's law equilibrium. It is found that this method gives NH₃ concentrations which are in some cases considerably lower than those obtained through direct measurements. NH₃ is thus estimated to vary geographically and temporally with the mid-west region being a dominant source of this trace gas. Oceanic areas exhibit much lower concentrations. These findings are consistent with the existence of acid sulfates as a dominant atmospheric aerosol, with soil chemistry and with previous investigations concerning with the association of the molecular forms of sulfate aerosols with air mass history.