Impact of Meteorology and Aerosol Sources on PM _2.5 and Oxidative Potential Variability and Levels in China

China has long-term high PM _2.5 levels, and its Oxidative Potential (OP) is worth studying as it may unravel the impacts of aerosol pollution on public health better than PM _2.5 alone. OP and PM _2.5 are influenced by meteorological factors, anthropogenic emissions sources and atmospheric aging. Although their impact on PM _2.5 have been studied, OP measurements only recently became available and on a limited scale, as they require considerable technical expertise and resources. For this, the joint relationship between PM _2.5 and OP for a wide range of meteorological conditions and emissions profiles remain elusive. Towards this, we estimated PM _2.5 and OP over China using the Danish Eulerian Hemispheric Model (DEHM) system with meteorological input from WRF weather forecast model. It was found that higher values of PM _2.5 and OP were primarily concentrated in urban agglomerations in the central and eastern regions of China, while lower values were found in the western and northeastern regions. Furthermore, the probability density function revealed that about 40 % of areas in China had an annual average PM _2.5 concentrations exceeding the Chinese concentrations limit; 36 % of the regions have OP below 1 𝑛𝑚𝑜𝑙 𝑚𝑖𝑛 ⁻¹ 𝑚 ⁻³, 41 % have OP between 1 and 2 𝑛𝑚𝑜𝑙 𝑚𝑖𝑛 ⁻¹ 𝑚 ⁻³, and 23 % have OP above 2 𝑛𝑚𝑜𝑙 𝑚𝑖𝑛 ⁻¹ 𝑚 ⁻³. Analysis of the simulations indicate that meteorological conditions and anthropogenic emission contributed 46 % (65 %) and 54 % (35 %) to the PM _2.5 concentration (OP) variability. The emission sensitivity analysis also highlighted PM _2.5 and OP levels are mostly determined by secondary aerosol formation and biomass burning.