The rapid decay of reactive oxygen and nitrogen species (RONS) in plasma-activated water (PAW) limits its biomedical applications. To address this issue

we propose a pH-mediated storage strategy. Our study reveals that prolonging air surface discharge time until the electrode temperature stabilizes at 140 ℃ can induce a dynamic transition from ozone-dominated to nitrogen oxide-dominated regimes

thereby altering RONS concentration trends. During storage

a neutral environment (pH=7) effectively suppresses H2O2 decomposition

while an alkaline environment (pH=10) slows NO2− and ONOO−/O2− decay rates through proton transfer. Acidifying the stored PAW to its initial acidic pH successfully restores its chemical activity

with neutral-stored PAW maintaining optimal anticancer efficacy. By implementing a pH regulation strategy based on "neutral/alkaline storage-acidic activation"

the bioactivity of PAW is preserved long-termly at room temperature. This work elucidates the critical roles of discharge mode transition and pH regulation in determining PAW dosage

providing a theoretical foundation for developing PAW with sustained high activity.