Using over 1000 chemical transport model simulations in the Beijing–Tianjin–Hebei region, we find that the emissions of primary inorganic PM
2.5 make the largest contribution to PM
2.5 concentrations and thus should be prioritized in PM
2.5 control strategies. Among the precursors, PM
2.5 concentrations are primarily sensitive to the emissions of NH
3, NMVOC+IVOC, and POA, and the sensitivities increase substantially for NH
3 and NH
x with the increase in emission reduction ratio.
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