Fig. 4: Temporal trends in oxidation rates and influencing factors for aerosol aqueous sulfate formation pathways in selected urban areas in 2005, 2009, 2013, 2017, and 2019, compared with that in 2001.

a H2O2 pathway, b NO2 pathway, c O3 pathway, and d TMI pathway. The dot charts represent the change rate of oxidation rates (upper axis). The bar charts indicate the change of the influencing factors, shown by 100% stacked bar charts (lower axis). Source data are provided as a Source Data file.