Gaseous and heterogeneous reactions of low-molecular-weight (LMW) unsaturated ketones with O3: Mechanisms, kinetics, and effects of mineral dust in tropospheric chemical processes

Mineral dust has a significant effect on the atmospheric heterogeneous chemistry and environmental risk prediction of VOCs. In this work, a comprehensive theoretical study for the gaseous and heterogeneous reactions process of four Low-Molecular-Weight (LMW) unsaturated ketones with O-3 has been provided for the first time. SiO2 is the main component of mineral dust, which shows better adsorption performance of these ketones and represents a good sinking of atmospheric LMW oxygenated VOCs. The gaseous reactions of LMW unsaturated ketones with O-3 are closely related to the formation of some strong oxidants and air pollution behaviors. The heterogeneous reactions of these ketones onto the surface of available mineral aerosols may compete with the corresponding gas phase reactions, especially in arid and semi-arid areas with frequent dust storms. Organic hydroperoxides and LMW carbonyl compounds generated in the title reactions may change the properties of aerosols, which have essential impacts on tropospheric chemistry and climate. The presence of SiO2 could accelerate the reactions of LMW unsaturated ketones with O-3 without changing their degradation mechanism. It also should be emphasized that the promoting effect of SiO2 clusters to CH2OO + H2O has been found in our computation. This may explain the high product yields of HMHP and H2O2 detected on SiO2 particles in the experiment. The effect of mineral particles on the O-3-initiated reactions has been probed at the molecular level and the pollution mechanism of VOCs has been better understood.