Heterogeneous NO reactions on atmospheric aerosols at four Chinese sites: improving model representation of uptake parameters

Heterogeneous reactivity of NO on aerosols is a critical parameter in assessing NOx fate, nitrate production, and particulate chloride activation. Accurate measurement of its uptake coefficient ( NO ) and representation in air quality models are challenging, especially in the polluted environment. With an in situ aerosol flow-tube system, the NO was directly measured on ambient aerosols at two rural sites in northern and southern China. The results were analyzed together with the NO derived from previous field studies in China to obtain a holistic picture of NO uptake and the influencing factors under various climatic and chemical conditions. The field-derived or measured NO was generally promoted by the aerosol water content and suppressed by particle nitrate. Significant discrepancies were found between the measured NO and that estimated from laboratory-determined parameterizations. An observation-based empirical parameterization was derived in the present work, which better reproduced the mean value and variability of the observed NO . Incorporating this new parameterization into a regional air quality model (WRFCMAQ) has improved the simulation of NO, nitrogen oxides, and secondary nitrate in the polluted regions of China.