The effect of COVID-19 restrictions on atmospheric new particle formation in Beijing

Abstract

Abstract. During the COVID-19 lockdown, the dramatic reduction of anthropogenic emissions provided a unique opportunity to investigate the effects of reduced anthropogenic activity and primary emissions on atmospheric chemical processes and the consequent formation of secondary pollutants. Here, we utilize comprehensive observations to examine the response of atmospheric new particle formation (NPF) to the changes in the atmospheric chemical cocktail. We find that the main clustering process was unaffected by the drastically reduced traffic emissions, and the formation rate of 1.5 nm particles remained unaltered. However, particle survival probability was enhanced due to an increased particle growth rate (GR) during the lockdown period, explaining the enhanced NPF activity in earlier studies. For GR at 1.5–3 nm, sulfuric acid (SA) was the main contributor at high temperatures, whilst there were unaccounted contributing vapors at low temperatures. For GR at 3–7 and 7–15 nm, oxygenated organic molecules (OOMs) played a major role. Surprisingly, OOM composition and volatility were insensitive to the large change of atmospheric NOx concentration; instead the associated high particle growth rates and high OOM concentration during the lockdown period were mostly caused by the enhanced atmospheric oxidative capacity. Overall, our findings suggest a limited role of traffic emissions in NPF.

Underestimated Contribution of Heavy Aromatics to Secondary Organic Aerosol Revealed by Comparative Assessments Using New and Traditional Methods

“…With these approaches, the OOM precursors are segregated into aromatic OOMs, aliphatic OOMs, isoprene OOMs, terpene OOMs, undistinguished OOMs, and nitrophenols. Note that the calculations of nO eff and the DBE value assume that the nitrogen atoms are only associated with the nitrate group (−ONO 2 ), which is reasonable based on the current knowledge on N-containing organic formation, as widely reported in both field and laboratory studies. ,,− …”

Concentration and size distribution of atmospheric particles in southern Italy during COVID-19 lockdown period

“…For example, Tang et al (2021) did not observe a lockdown effect on new particle formation events in Beijing (China). Yan et al (2022) found unchanged formation rates of 1.5 nm particles in an urban area of Beijing (China), however, the particle survival probability was enhanced due to an increased particle growth rate during the lockdown period.

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Observations and Modeling of Gaseous Nitrated Phenols in Urban Beijing: Insights From Seasonal Comparison and Budget Analysis

“…The field measurements were performed at the west campus of Beijing University of Chemical Technology (BUCT, longitude 116.31°E and latitude 39.95°N). Detailed site descriptions have been recorded in previous studies (Liu et al., 2020; Ma et al., 2022; Yan et al., 2022). Briefly, BUCT is located in the western part of the Beijing metropolitan area (Figure S1 in Supporting Information ).…”

“…This instrument uses NO 3 − and its clusters (NO 3 (HNO 3 ) − and NO 3 (HNO 3 ) 2 − ) as reagent ions by ionizing HNO 3 gas using X‐rays. We adopted the same configuration described in previous studies (Yan et al., 2022). NPs, for example, C 6 H 5 NO 3 , react with the reagent ions to produce cluster ions (e.g., C 6 H 5 NO 3 (NO 3 ) − ) or deprotonated ions (e.g., C 6 H 4 NO 3 − ).…”