# Possible Missing Sources of Atmospheric Glyoxal Part I: Phospholipid Oxidation from Marine Algae
## 3 Results and Discussion
### SSML Analysis with Marine Aerosol Reference Tank (MART)
Although the chemistry in Figure 3a is well-supported, the solubility of glyoxal would likely preclude its facile transfer from the aqueous- to the gas-phase as was reported by [PERSON] et al. (2014) [46]. However, transport across the air-water interface could be facilitated through SSA formation due to the action of bubble bursting from breaking waves. Increased levels of organic carbon (OC) in the SSML are reported to directly correlate with the OC enrichment factor of SSA independent of chlorophyll \(a\) concentrations [63]. Detection of glyoxal on 3-5 July 2014 may represent that some critical level of OC was achieved that facilitated its enrichment in the SSA, and this happened to correspond with the July 1 st chlorophyll \(a\) peak that likely provided the substrate for glyoxal production. In thisvein, a similar trend was observed in the microcosm experiment where there was a burst of OC collected in the headspace on Day 5 (Figure 2b) following glyoxal detection on Days 3-4 (Figure 2a). Further evidence that there were ester-bound lipid substrates present in surface waters at that time comes from the measured enzyme activity within the channel that showed continuous lipase activity in bulk waters with a spike in stearase activity (-70 nM/h), specifically within the SSML on 4 July 2014 (Figure 5). The enrichment of hydrophobic OC (i.e., lipids) and the lipophilic nature of a bacterial cell membrane in the SSML may alter the solubility of molecules such as glyoxal that are formed at the surface in that environment. This may be especially true of the foam, which is highly enriched with organic matter but has a significantly lower water content than the SSML. As a result, glyoxal may be transferred to the atmosphere as OC enriched in the SSA. Despite the uncertainty regarding the exact mode of transport, it is clear that glyoxal may be capable of crossing the air-water interface. Figure 3: Proposed mechanism for the formation of marine glyoxal from the peroxidation of PUFA-containing phospholipids (**a**), which was validated by the ESI-MS/MS positive-ion mode characterization of PAPC (**b**), its oxidation product HO-PARC (**c**), and the corresponding short-chain degradation product HOOA-PC (**d**) that were found in the foam of the SSML. Figure 4: ESI-HR-MS/MS positive-ion spectra of peroxididized PLPC (**a**) and PAPC (**b**); and ozonides of PLPC (**c**). Figure 5: Measured lipase (stearase) activity in the sea surface microlayer (SSML; top of the striped bars) and bulk (top of the solid bars) waters of the wave channel during IMPACTS. Future work would improve the laboratory studies on the kinetics and pathways of glyoxal uptake and oxidation. The expansion of field campaigns should improve the understanding of glyoxal's interaction with SSA. The use of multiphase modeling incorporating factors like relative humidity, aerosol composition, and glyoxal's aqueous-phase reactions will help reduce model uncertainties in predicting its transport and transformation. Lastly, there needs to be a search for a link between glyoxal and secondary organic aerosols.