Synergistic effects between SO2 and HCOOH on α-Fe2O3

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Surface Science

Background:

• Heterogeneous reactions on mineral aerosols are crucial for atmospheric chemistry, influencing particle properties and trace gas budgets.
• The impact of coadsorbed trace gases, particularly inorganic-organic pollutant synergies, on mineral aerosols is not well understood.

Purpose of the Study:

• To investigate the synergistic effects of formic acid (HCOOH) and sulfur dioxide (SO2) coadsorption on mineral aerosol surfaces.
• To elucidate the interaction mechanisms between HCOOH and SO2 during heterogeneous reactions on α-Fe2O3.

Main Methods:

• Utilized in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) to study gas-surface interactions.
• Examined the coadsorption of HCOOH and SO2 on α-Fe2O3 surfaces under controlled conditions.

Main Results:

• Coadsorption of SO2 significantly inhibited the heterogeneous reaction of HCOOH on α-Fe2O3.
• The amount of formate adsorbed decreased in the presence of SO2, while sulfate formation was unaffected.
• SO2 facilitated the catalytic decomposition of surface formate to CO2 on α-Fe2O3.

Conclusions:

• SO2 and HCOOH exhibit significant synergistic effects during coadsorption on mineral aerosols.
• The findings suggest a potential mechanism explaining atmospheric correlations between sulfate and carboxylate species.