Thebromine cycle is abiogeochemical cycle ofbromine through theatmosphere,biosphere, andhydrosphere.
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Bromine is present naturally as bromide salts inevaporite deposits. Bromine is also present in soils and inmarine 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 issea spray aerosols. Smaller fluxes originate from volcanic emissions and biomass burning.[1] The primary atmospheric sinks are sea spray deposition andphotochemical reactions, which release gaseous bromine.
Bromine is used in flame retardants, pesticides, lighter fuel,antiknocking agents, and for water purification.[3] The organic form of this element is used as flame retardants commercially and in pesticides. These chemicals have led to an increase in thedepletion of thestratospheric ozone layer. Some countries use bromine to treat drinking water, similar tochlorination. Bromine is also present as impurities emitted fromcooling towers.[1]
Winter sea ice is a significant atmospheric contribution of bromine.[4] Organic bromine gases such asCH3Br,CH2Br2, CH2IBr are emitted by microorganisms in sea ice and snow at ten-fold higher rates than from other environments. In polar areas, decreasing sea ice releases bromine and at the Arctic and Antarcticboundary layer, bromine is released in the spring when the ice melts.
Inorganic bromine is found in the atmosphere and is quickly cycled between its gas and its particulate phase. Bromine gas (Br2) undergoes anautocatalytic cycle known as the 'bromine explosion', which occurs in the ocean and salt lakes such as theDead Sea, where a high quantity of salts are exposed to the atmosphere. Bromine contributes to 5-15% oftropospheric ozone layer losses.[1]
