Entangled iodine and hydrogen peroxide formation in ice

Area of Science:

• Environmental Chemistry
• Atmospheric Chemistry
• Chemical Oceanography

Background:

• Ice-core records indicate rising atmospheric hydrogen peroxide (H2O2) and iodine concentrations since the mid-20th century due to anthropogenic pollution.
• The specific chemical pathways responsible for the concurrent increase of these compounds in icy environments remain incompletely understood.

Purpose of the Study:

• To elucidate a novel and highly efficient synergistic mechanism for the simultaneous production of hydrogen peroxide and iodine species in acidic icy water.
• To identify key intermediates and reaction pathways involved in this process.

Main Methods:

• Investigated chemical reactions in simulated acidic icy water conditions.
• Utilized spectroscopic techniques to identify reaction intermediates, including IO2H.
• Quantified the production rates of hydrogen peroxide and iodine species.

Main Results:

• Demonstrated a synergistic mechanism for H2O2 and iodine production in acidic icy water.
• Identified IO2H as a key intermediate formed from I- and dissolved O2.
• Observed rapid recombination of I with I- to form I2- and subsequent disproportionation to I3-.
• Showed O2H radicals yielding H2O2 through reactions with I- and protons.

Conclusions:

• The identified mechanism provides a novel explanation for the concurrent increase of atmospheric H2O2 and iodine.
• This synergistic reaction in icy environments contributes to understanding pollutant cycling and atmospheric chemistry.
• Highlights the importance of ice-bound chemical processes in mediating the fate of anthropogenic pollutants.