Abstract. In this work we report the study of the ozonolysis of 2,5-dihydrofuran and 2,3-dihydrofuran and the reaction conditions leading to the formation of secondary organic aerosols. The reactions have been carried out in a Teflon chamber filled with synthetic air mixtures at atmospheric pressure and room temperature. The ozonolysis only produced particles in the presence of SO₂. Rising relative humidity from 0 to 40 % had no effect on the production of secondary organic aerosol in the case of 2,5-dihydrofuran, while it reduced the particle number and particle mass concentrations from the 2,3-dihydrofuran ozonolysis. The water-to-SO₂ rate constant ratio for the 2,3-dihydrofuran Criegee intermediate was derived from the secondary organic aerosol (SOA) yields in experiments with different relative humidity values, k_H2O/k_SO2 =  (9.8 ± 3.7) × 10⁻⁵.

The experimental results show that SO₃ may not be the only intermediate involved in the formation or growth of new particles in contrast to the data reported for other Criegee intermediate–SO₂ reactions. For the studied reactions, SO₂ concentrations remained constant during the experiments, behaving as a catalyst in the production of condensable products.

Computational calculations also show that the stabilised Criegee intermediates from the ozonolysis reaction of both 2,5-dihydrofuran and 2,3-dihydrofuran may react with SO₂, resulting in the regeneration of SO₂ and the formation of low-volatility organic acids.