Secondary organica aerosol formation from the reactions of 2,5-dimethylfuran with OH radicals and ozone

Biomass is a significant renewable energy source and is expected to grow in importance in the transition away from fossil energy sources at a relatively low cost. Lignocellulosic biomass, which is the most abundant biomass, has critical importance as sustainable production of chemicals and fuels. Catalytic production methods of converting lignocellulosic biomass into furan derivatives have been improved significantly. One of these furan derivatives, 2,5-dimethylfuran (2,5-DMF), has attracted interest as a potential biofuel due to its physicochemical properties, in some aspects better than gasoline and ethanol, such as the low pollutant emissions in its combustion. However, before 2,5-DMF can be accepted as an alternative transport fuel, some outstanding problems, as its atmospheric fate, must be resolved.

2,5-DMF can be degraded by the main tropospheric oxidants, resulting in furan derivatives such as furanones which are efficient precursors of SOA. To this end, the present study had the aim of analyzing the OH radical photooxidation and ozonolysis of 2,5-DMF, characterizing the conditions that lead to the formation and growth of new particles. Factors such as relative humidity (RH), NOx and SO₂ level and pre-existing inorganic seed particles, which could influence in SOA formation, has been assessed. The study was carried out in two different chambers at (296±1) K and atmospheric pressure. Results for OH-photooxidation indicate that SOA yields decrease (from 6.2 to 0.4%) with the rise of 2,5-DMF concentration (from10 to 1000 ppb). In the absence of NOx and under high relative humidity (RH) conditions (60%), higher aerosol yields are favored. SOA formation is dependent on the initial seed surface for two kinds of inorganic seed particles ((NH₄)₂SO₄ and CaCl₂), being the effect slightly greater for CaCl₂. The ozonolysis only generates particles in the presence of SO₂ and the increase of relative humidity from 0 to 15% lowers the particle number and particle mass concentrations. The water-to-SO₂ rate constant ratio of the Criegee intermediate was derived from the SOA yield in experiments with different relative humidity values.

The obtained results provide detailed daytime chemistry about SOA formation from 2,5-DMF oxidation and improves our understanding of the chemical evolution of biomass burning plumes. Moreover, these results could be integrated into air quality simulation models, especially in developing countries which are suffering severe fine particulate matter pollution.