Iodinepools

Iodinepools are the natural reservoirs of iodine and its compounds within the Earth’s system, encompassing atmospheric iodine species, dissolved iodine in seawater, iodine-bearing minerals, soils and sediments, and organic iodine in living organisms. The term describes the interconnected pools and the fluxes that move iodine among air, water, rock, and biota as part of the global iodine cycle.

The largest pool is dissolved iodine in the oceans, where iodide (I-) and iodate (IO3-) circulate with salinity and temperature. The atmosphere contains iodine primarily as molecular iodine (I2) and organoiodine compounds. Terrestrial reservoirs include soils, peat, and sediments, which store iodine mainly in organic matter and minerals; iodine-bearing rocks and minerals contribute smaller but long-term storage. Biota, from algae to higher plants and animals, accumulate iodine and can export it back to soils or water.

Iodine cycles through streams and rivers, is released from oceans by volatilization, and is deposited back to surface environments by precipitation and scavenging. Photochemical reactions, microbial processes, and oxidation–reduction reactions govern speciation. Burial in sediments and incorporation into organic matter provide longer-term storage. Volcanic and hydrothermal activity can inject iodine into the atmosphere.

Human interactions affect iodine pools through nutrition programs (iodized salt), industrial emissions, and atmospheric transport of anthropogenic organoiodine compounds. Iodine-131 from nuclear incidents and iodine-129 as a long-lived tracer illustrate the relevance of iodine pools for environmental monitoring and radiological safety.

Researchers study iodine pools using mass balance approaches, time-series observations, and speciation analyses to understand the global cycle, climate interactions, and ecosystem responses.