[Impacts of Anthropogenic Emission Reduction on Urban Atmospheric Oxidizing Capacity During the COVID-19 Lockdown].

In recent years， regional compound air pollution events caused by fine particles （PM） and ozone （O） have occurred frequently in economically developed areas of China， in which atmospheric oxidizing capacity （AOC） has played an important role. In this study， the WRF-CMAQ model was used to study the impacts of anthropogenic emission reduction on AOC during the COVID-19 lockdown period. Three representative cities in eastern China （Shijiazhuang， Nanjing， and Guangzhou） were selected for an in-depth analysis to quantify the contribution of meteorology and emissions to the changes in AOC and oxidants and to discuss the impact of AOC changes on the formation of secondary pollutants.

Modeling particulate nitrate in China: Current findings and future directions.

Particulate nitrate (pNO) is now becoming the principal component of PM during severe winter haze episodes in many cities of China. To gain a comprehensive understanding of the key factors controlling pNO formation and driving its trends, we reviewed the recent pNO modeling studies which mainly focused on the formation mechanism and recent trends of pNO as well as its responses to emission controls in China. The results indicate that although recent chemical transport models (CTMs) can reasonably capture the spatial-temporal variations of pNO, model-observation biases still exist due to large uncertainties in the parameterization of dinitrogen pentoxide (NO) uptake and ammonia (NH) emissions, insufficient heterogeneous reaction mechanism, and the predicted low sulfate concentrations in current CTMs.