The photochemistry of chromophoric pyruvic acid in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is known to be highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. This work explores how the photolysis (λ ≥ 305 nm) of 10-200 mM pyruvic acid at pH 1.0 consumes initial dissolved O2 concentrations in the range 0.11-1.3 mM (Figures 1 and 2). The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is also monitored in real time at air flow rates from 30.0 to 900.0 mL min-1. Under air saturated conditions and 30 mL min-1 flow of air, the estimated half-lives of O2(aq) consumed by the photolytic radicals is in the range 3-22 min. Therefore, the corresponding depths of penetration of O2(g) into water, x = 4.3 and 1.6 µm, are determined. Thus, accumulation and small coarse mode aqueous particles should not be O2-depleted in the presence of sunlight photons impinging this kind of chromophore. These results are of major tropospheric relevance for understanding the formation and growth of secondary organic aerosol.

Interfacial dissolved O2 consumption by photolyzed aqueous pyruvic acid

2019 Fall National Meeting

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