Glyoxal and methylglyoxal species are common in atmospheric aerosols and their speciation may be altered during cloud formation as water activity and pH change drastically, which may drive hydration, hydrolysis, and/or polymerization reactions. Water uptake during cloud formation was simulated by approximately 100-fold dilution of 40 wt. % glyoxal or methylglyoxal. Chemical speciation changes were monitored via high resolution quadrupole mass spectrometry and nuclear magnetic resonance spectroscopy. Results indicate that glyoxal and methylglyoxal polymers persist after dilution. Multiple polymer masses were observed for each organic due to hydration either of the monomer precursors or of the polymers themselves. The largest peaks in the mass spectra corresponded to dimers and trimers while polymers up to the hexamer for glyoxal and up to the octamer for methylglyoxal were also observed. Overall polymer kinetic behavior was consistent with sequential decomposition from large polymers to smaller ones and eventually to monomers.

Decomposition of glyoxal and methylglyoxal polymers in aerosols driven by dilution during cloud formation

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