Aqueous chemistry can play a vital role in secondary organic aerosol (SOA) formation and aging. A novel analytical approach that allows for simultaneous photo-oxidation and atomization of reacting bulk solutions coupled to an aerosol mass spectrometer (AMS) investigates aqueous OH oxidation of ambient biogenic SOA, cloud water from a biogenic environment, glyoxal, and mixtures of glyoxal with α-pinene SOA components. This is the first study of aqueous oxidative aging of ambient SOA and cloud water organics. Starting with an AMS-based observational framework, we show that aqueous oxidation of biogenic SOA in the presence of glyoxal can better represent observed atmospheric aging than when glyoxal is absent. Oxidation of glyoxal alongside semi-volatile SOA components leads to the production of highly oxidized SOA.