Bromine is present naturally as bromide salts in evaporite deposits. Bromine is also present in soils and in marine algae that synthesize organic bromine compounds. Other natural sources of bromine come from polar regions, salt lakes, and volcanoes.
The primary natural source of bromine to the atmosphere is sea spray aerosols. Smaller fluxes originate from volcanic emissions and biomass burning. The primary atmospheric sinks are sea spray deposition and photochemical reactions, which release gaseous bromine.