Work

Measurement report: Variations and environmental impacts of atmospheric N 2 O 5 concentrations in urban Beijing during the 2022 Winter Olympics

Year: 2025

Type: article

Abstract: . The chemistry of nitrate radical (NO3) and dinitrogen pentoxide (N2O5) plays a pivotal role in tropospheric nighttime chemistry. Given their close linkage to precursor variations, emission reduction during the 2022 Beijing Winter Olympics likely affected NO3 and N2O5 behavior. In this study, we measured N2O5, NO2, O3, etc. during and after the Olympics, and compared pollutant levels as well as the contributions of reaction pathways to the loss of NO3 and N2O5. Throughout the entire observation period, NO3 production rate averaged 0.5 ± 0.4 ppbv h⁻¹, and the N2O5 mixing ratio could reach up to 875 pptv within 1 min, indicating their active production. The relatively long τ(N2O5) at night, with an average of 11.9 ± 11.8 minutes, suggested a slow rate of N2O5 loss during the winter season. Despite low NO (below 3 ppbv), it dominated NO3 loss (79.0 %). VOCs oxidation contributed 0.2 %, mainly from styrene. During the Olympics, emission reductions led to decreased NO and VOCs, which in turn reduced their reaction with NO3. The heterogeneous uptake of N2O5, another NO3 loss pathway, accounted for 20.8 % during the event and 10.6 % afterward. This uptake is crucial for NO3 removal at night, and would be essential for winter nitrate formation in urban Beijing.

Source: Atmospheric chemistry and physics

DOI: 10.5194/acp-25-16331-2025