Direct field evidence of autocatalytic iodine release from atmospheric aerosol

Abstract

Reactive iodine plays a key role in determining the oxidation capacity, or cleansing capacity, of the atmosphere in addition to being implicated in the formation of new particles in the marine boundary layer. The postulation that heterogeneous cycling of reactive iodine on aerosols may significantly influence the lifetime of ozone in the troposphere not only remains poorly understood but also heretofore has never been observed or quantified in the field. Here, we report direct ambient observations of hypoiodous acid (HOI) and heterogeneous recycling of interhalogen product species (i.e., iodine monochloride [ICl] and iodine monobromide [IBr]) in a midlatitude coastal environment. Significant levels of ICl and IBr with mean daily maxima of 4.3 and 3.0 parts per trillion by volume (1-min average), respectively, have been observed throughout the campaign. We show that the heterogeneous reaction of HOI on marine aerosol and subsequent production of iodine interhalogens are much faster than previously thought. These results indicate that the fast formation of iodine interhalogens, together with their rapid photolysis, results in more efficient recycling of atomic iodine than currently considered in models. Photolysis of the observed ICl and IBr leads to a 32% increase in the daytime average of atomic iodine production rate, thereby enhancing the average daytime iodine-catalyzed ozone loss rate by 10 to 20%. Our findings provide direct field evidence that the autocatalytic mechanism of iodine release from marine aerosol is important in the atmosphere and can have significant impacts on atmospheric oxidation capacity.

Climate changes modulated the history of Arctic iodine during the Last Glacial Cycle

“…Furthermore, atmospheric iodine can also be related to mineral dust by promoting iodate stability in the ice matrix and/or favouring the adsorption of iodine gas-phase molecules to dust particles during atmospheric transport 10 . On the other hand, ssa expelled from the ocean surface during wave breaking incorporate iodine in their composition and are a substrate where gaseous iodine species undergo heterogeneous recycling reactions [28][29][30] .…”

Iodine chemistry in the chemistry–climate model SOCOL-AERv2-I

“…However, the cross sections for photolysis of these species are recently measured and can be used to increase the accuracy of simulation (Lewis et al, 2020). Recent field evidence indicates that the recycling of iodine on sea-salt aerosol, and perhaps other types of aerosols, may be much faster than currently represented (Tham et al, 2021). Also, we did not include CF 3 I that also could modify the total concentration of iodine in the atmosphere.…”

“…and Tham et al (2021). It should be noted that the lack of recycling on sea-salt aerosols may affect the I y burden and the amount of stratospheric iodine injection.…”

Generalized Additive Models Analysis of the Atmospheric Pollutants Response to the Emission Reduction and Meteorology During the COVID-19 Lockdown in the North of Africa (Morocco)

“…This gure 1c and Figure S2 show the spatial distribution of PM 2.5 (particulate matter with aerodynamic diameter less than 2.5um) and PM 10 (particulate matter with aerodynamic diameter less than 10um), we observe that PM 2.5 and PM 10 have similar distribution and PM 2.5 and PM 10 increase in the North and East of the study area during LCD. This nding can be explained by two arguments: the increase in the ozone level over the Mediterranean Sea and Atlantic Ocean in the north and northwest (Figure S3), promotes the formation of sea salt particles like iodine by O 3 oxidation or OH radical oxidation (Sbai and farida 2019b;Tham et al, 2021). In addition, sea salt particle can be transported by the north-south or west-east direction wind and contribute to increase in PM.…”