Extended Data Fig. 6: Scatter plot of HCl:BC versus HCl:OC ratios for various type of burning as collected from literature, compared with measured ratios from the present observations from Delhi and Chennai.

The fuels for which the emission ratios are derived includes open biomass burning, biofuel burning, open burning of mixed garbage, and burning of plastic waste. The purple dots and corresponding square in the graph represents the HCl:BC and HCl:OC ratios for Delhi during the entire period and averaged over P1 period, respectively. The green dots and corresponding square are similar like purple colour but for period P2. The orange dots and corresponding square is again similar to purple and green dots but for Chennai representing the Bhogi period. The total HCl concentration was inferred from the particulate chloride observed during early morning hours when HCl was expected to partition into the particle phase. The squares represent the arithmetic mean of measured points during respective periods of measurements for corresponding sites and the error bars extend to the 10^th and 90^th percentiles.