Elevated Formation of Particulate Nitrate From N ₂ O ₅ Hydrolysis in the Yangtze River Delta Region From 2011 to 2019

Aerosol nitrate has become the most abundant compound during aerosol pollution in eastern China. The Chinese government implemented a stringent policy 2013–2017 to tackle pollution. However, response of nitrogen oxides (NOx) reduction is unclear owing limitation long-term measurement. Here, we performed 9-year continuous measurement compositions Shanghai and confirmed decrease species except nitrate. contribution fine particulate matter (PM2.5) increased significantly, reaching up 35% episodes after 2017. This contrast evident NOx emissions. We found that elevated dinitrogen pentoxide (N2O5) hydrolysis responsible for observed trend. Increased ozone decreased dioxide (NO) facilitated formation N2O5, proportion promoted uptake N2O5 eventually enhanced conversion efficiency NO2 Our results highlight importance synergic control