Comparative analysis of the impact of PM2.5 components on visibility, extinction and oxidative potential in beijing, China

The implementation of policies such as the “Clean Air Action Plan” has contributed to the ongoing enhancement of air quality in Beijing. This study investigates the characteristics of visibility, PM_2.5 concentration, and its components, as well as their effects on extinction, and oxidative potential (OPv) through observational data and the WRF-Chem model within the context of these emission reduction strategies. Analysis of data collected during the spring and summer of 2019 revealed that PM_2.5 concentrations were significantly higher in spring (48 µg/m³) compared to summer (35 µg/m³), primarily due to emissions related to heating and unfavorable meteorological conditions. While average visibility showed slight variation between the seasons (21.53 km in spring versus 20.99 km in summer), OPv was markedly elevated in summer. The chemical composition of PM_2.5 was found to exert a more substantial influence on visibility and OPv than mass concentration alone. Visibility appeared to be strongly influenced by relative humidity (RH), mainly when RH ≤ 60%. Conversely, PM_2.5 concentrations significantly affected visibility within the range of 40% ≤ RH < 60%. Nitrate contributed the most to the extinction coefficient (37%), followed by organic carbon (24%) and sulfate (15%). The contribution rates of various chemical components to atmospheric extinction were significantly altered depending on visibility levels. Secondary components were identified as the principal source of atmospheric extinction, comprising 41% of total extinction, and were also the predominant contributors to OPv. The findings of this study lay the groundwork for the development of more effective air quality management strategies in Beijing.