Transient oxidation of hazes a source of nutrients during the great oxidation event.

The transition period of the Great Oxidation Event (GOE) saw the emergence of transient physical and chemical processes. In this context, photochemical organic hazes may have evolved in an atmosphere containing low concentrations of oxygen (< 10/10 Present Atmospheric Level). This coexistence of organic aerosols and oxygen traces induced an atmospheric reactivity which has so far been unexplored. Here, we show that the progressive rise of oxygen around the GOE triggered oxidation of organic aerosols suspected to be present at that time. We estimate that such transient mechanisms would have persisted over 60 to 100 Myrs during the GOE and possibly extended during the Archean. The main chemical markers of aerosol oxidation observed are urea, oxalic acid and carboxylic acid derivatives. These oxygen-bearing organics identified could have served as nutrients by existing ecosystems. This input of oxidized organic matter, estimated between 10 and 10 g of C.yr based on aerosol production yields, has probably been significant compared to oxygenic photosynthesis. Such mechanisms could also have diversified the pool of available nutrients, constituting an interesting vector of biodiversity for the primitive ecosystem.