Carbonate radical ion as a key driver of rapid atmospheric sulfate formation

Abstract

Carbonate radical anion (\({{\rm{CO}}}_{{3}^{.-}}\)) is generally considered as a marginal intermediate that rarely regulates atmospheric-relevant reactions of significance. Unexpectedly, in this work, employing a suit of the in-field measurements, lab-based validations, improved kinetic numerical calculations, and chemical transport modeling, we demonstrate that \({{\rm{CO}}}_{{3}^{.-}}\) gives a significantly overlooked contribution (~54.4%) to overall secondary sulfate formation during dust storm-relevant episodes and ~236.3% increase of SO₂ uptake over mineral dust pathway during haze-relevant periods. GEOS-Chem modeling results further emphasize the important position of this radical ion in dust-driven SO₂ oxidation chemistry. Our finding leaves this active intermediate no longer a marginal oxidant currently prevailing in the framework of the atmospheric science community. More importantly, after considering this rapid dust-driven sulfate formation channel mediated by carbonate radicals during pollution episodes, this study provides a clear indication that high priority should be given to reducing alkaline soil dust emissions to achieve benefits for air quality.