Weak acids enhance halogen activation on atmospheric water's surfaces

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Chemical Kinetics

Background:

• Marine aerosol particles play a crucial role in atmospheric chemistry.
• Iodine species are significant components of marine aerosols and influence air quality.
• Heterogeneous reactions on aerosol surfaces are key processes in the atmosphere.

Purpose of the Study:

• To investigate the effect of alkanoic acids on iodine emissions during heterogeneous ozonation of iodide.
• To understand the mechanism by which organic acids influence iodine species production.
• To assess the implications for iodine chemistry in marine boundary layers.

Main Methods:

• Cavity ring-down spectroscopy was used to measure emissions of I(2)(g) and IO·(g).
• Experiments simulated the heterogeneous ozonation of interfacial iodide in the presence of alkanoic acids.
• Controlled laboratory conditions were used to mimic marine aerosol environments.

Main Results:

• Emissions of molecular iodine (I(2)(g)) were enhanced several-fold by undissociated alkanoic acids.
• Emissions of the iodine monoxide radical (IO·(g)) were unaffected by the presence of these organic acids.
• Alkanoic acids were found to efficiently supply interfacial protons (H(+)(s)), promoting I(2)(g) formation.

Conclusions:

• Undissociated alkanoic acids on water surfaces enhance I(2)(g) emissions during iodide ozonation.
• Organic acids in marine aerosols can significantly increase iodine emissions.
• This process has implications for iodine production in marine boundary layers and atmospheric chemistry.