The -hydroxyalkyl-hydroperoxides [R-(H)C(-OH)(-OOH), -HH] produced in the ozonolysis of unsaturated organic compounds may contribute to SOA aging. -HHs inherent instability, however, hampers their detection and a positive assessment of their actual role. Here we report, for the first time, the rates and products of the decomposition of the -HHs generated in the ozonolysis of atmospherically important monoterpenes -pinene (-P), dlimonene (d-L), -terpinene (-Tn) and -terpineol (-Tp) in water:acetonitrile (W:AN) mixtures. We detect -HHs and multifunctional decomposition products as chloride-adducts by online electrospray ionization mass spectrometry. Experiments involving D 2 O and H 2 18 O instead of H 2 16 O, and an OH-radical scavenger show that -HHs decompose into gem-diols + H 2 O 2 rather than free radicals. -HHs decay mono-or bi-exponentially depending on molecular structure and solvent composition. e-fold times,  1/e , in water-rich solvent mixtures range from  1/e = 15-45 min for monoterpene-derived -HHs to  1/e > 10 3 min for the -Tp

Multiphase and heterogeneous photochemistry is an emerging component of atmospheric and air pollution research. It is primarily driven by reactions of photochemically produced free radicals in the particle phase with...

Glyoxal is an important precursor of aqueous secondary organic aerosol (aqSOA). Its photooxidation to form organic acids and oligomers and reactions with reduced nitrogen compounds to form brown carbon (BrC) have been extensively investigated separately, although these two types of reactions can occur simultaneously during the daytime. Here, we examine the reactions of glyoxal during photooxidation and BrC formation in premixed NH 4 NO 3 + Glyoxal droplets. We find that nitrate photolysis and photosensitization can enhance the decay rates of glyoxal by a factor of ∼5 and ∼6 compared to those under dark, respectively. A significantly enhanced glyoxal decay rate by a factor of ∼12 was observed in the presence of both nitrate photolysis and photosensitization. Furthermore, a new organic phase was formed in irradiated NH 4 NO 3 + Glyoxal droplets, which had no noticeable degradation under prolonged photooxidation. It was attributed to the imidazole oxidation mediated by nitrate photolysis and/or photosensitization. The persistent organic phase suggests the potential to contribute to SOA formation in ambient fine particles. This study highlights that glyoxal photooxidation mediated by nitrate photolysis and photosensitization can significantly enhance the atmospheric sink of glyoxal, which may partially narrow the gap between model predictions and field measurements of ambient glyoxal concentrations.