Gas that triggers ozone destruction
Scientists at the Universities of Leeds and York have discovered that the majority of ozone-depleting iodine oxide observed over the remote ocean comes from a previously unknown marine source. The research team found that the principal source of iodine oxide can be explained by emissions of hypoiodous acid (HOI) – a gas not yet considered as being released from the ocean – along with a contribution from molecular iodine (I2). Since the 1970s when methyl iodide (CH3I) was discovered as ubiquitous in the ocean, the presence of iodine in the atmosphere has been understood to arise mainly from emissions of organic compounds from phytoplankton - microscopic marine plants. This new research, which is published , builds on an earlier study which showed that reactive iodine, along with bromine, in the atmosphere is responsible for the destruction of vast amounts of ozone – around 50 per cent more than predicted by the world’s most advanced climate models – in the lower atmosphere over the tropical Atlantic Ocean. The scientists quantified gaseous emissions of inorganic iodine following the reaction of iodide with ozone in a series of laboratory experiments. They showed that the reaction of iodide with ozone leads to the formation of both molecular iodine and hypoiodous acid. Using laboratory models, they show that the reaction of ozone with iodide on the sea surface could account for around 75 per cent of observed iodine oxide levels over the tropical Atlantic Ocean.
