Oxidation mechanisms study of molecules of interest for indoor air and atmospheric chemistry

Chemical species emitted in indoor environments by humans (skin emission and breath) and their activities (cooking, use of detergents and personal care products), or by building and furnishing materials, have a direct impact on air quality. In addition, these species exhibit an indirect impact through their gas phase reactions with atmospheric oxidants (e.g. hydroxyl radicals), leading to the formation of Oxygenated Volatile Organic Compounds (OVOCs) and Secondary Organic Aerosol (SOA), which can directly affect human health. They can also be transferred outside (through infiltration or ventilation), where they can further react to produce ozone and SOA, potentially having an additional impact on health and climate change. The COST action INDAIRPOLLNET aimed to identify and rank species emitted indoors, according to different criteria such as their health impact, or their reactivity with atmospheric oxidants (OH, O3, Cl and NO3). This work highlighted an important knowledge gap, as more than 800 compounds have been measured indoors, but only a limited number have relevant information to enable ranking. For instance, less than 65% of the molecules have a reported rate constant with OH. In this context, a FAGE (Fluorescence Assay by Gas Expansion) instrument, measuring the total OH reactivity (sum of OH loss rates due to reactions with trace gases), has been used to measure missing rate constants with OH, and to investigate oxidation mechanisms of species of interest that may impact human health, or react quickly with OH. The oxidation of furan, N,N-dimethylformamide and 1.2-diethoxyethane has been studied via two complementary approaches: laboratory experiments and modelling (using INCHEM-Py box model). The experiments were conducted in the DouAir simulation chamber, coupled with a Proton Transfer Reaction-Mass Spectrometer, -monitoring the primary VOCs and their oxidation products -, and with the FAGE instrument. In a second step, these experiments were simulated with INCHEM-Py. Experimental findings confirm the formation of butenedial, 5-hydroxyfuran-2(5H)-one, 4-oxobut-2-enoic acid, 2-hydroxy-5-carboxyfuran and maleic anhydride as the main oxidation products for the furan + OH reaction, and the formation of dimethylnitramine when N,N-dimethylformamide is oxidized by OH radicals. Oxidation products for the reaction of 1.2-diethoxyethane + OH are presented for the first time. In addition, the kinetic of this last reaction was studied using the FAGE technique, yielding a measured rate coefficient of (5.3 ± 0.4) × 10-11 cm3.mol-1.s-1, in good agreement with the value of (5.8 ± 0.6) × 10-11 cm3.mol-1.s-1 reported by Porter et al. 1997. The modelling of these experiments is ongoing to allow to derive and/or validate complete oxidation mechanisms for these three species.