This study investigates aerosol “sensitivity regimes” to explore the effectiveness of abating gaseous precursors to mitigate aerosols over the Indo-Gangetic Plain (IGP). A new mechanistic insight is proposed by integrating ISORROPIA-II thermodynamical model with high-resolution simultaneous measurements of precursor gases (HCl, HNO3, and NH3) and inorganic constituents of PM1 and PM2.5, monitored for the first time in India using MARGA-2S instrument. The estimated aerosol acidity (pH) of PM1 and PM2.5 was 4.49±0.53 and 4.58±0.48, respectively. The sensitivity of phase-partitioning (ε) of Cl-, NO3-, and NH4+ to pH, ALWC, HCl, HNO3, and NH3 showed that fine aerosols fall in the ”HCl and HNO3 sensitive regime”, emphasizing that HCl and HNO3 reductions would be the most effective pathway to reduce aerosols in NH3-rich IGP. Since existing mitigation strategies over IGP are random and ineffective, this novel insight is the first step in providing a thermodynamically consistent “roadmap” to mitigate aerosols effectively.