02 Nov 2022
 | 02 Nov 2022

Characteristics of Negative Cluster Ions in an Urban Environment 

Rujing Yin, Xiaoxiao Li, Chao Yan, Runlong Cai, Ying Zhou, Juha Kangasluoma, Nina Sarnela, Janne Lampilahti, Tuukka Petäjä, Veli-Matti Kerminen, Federico Bianchi, Markku Kulmala, and Jingkun Jiang

Abstract. Atmospheric cluster ions are important constituents in the atmosphere. Concentrations and compositions of cluster ions govern their effects on atmospheric chemistry, air quality, and human health. However, quantitative research on ion composition is rare, especially in an urban atmosphere where pollution levels and human populations are intense. In this study, we measure negative cluster ion compositions using an atmospheric pressure interface high-resolution time-of-flight mass spectrometer in urban Beijing. We demonstrate the feasibility of quantifying cluster ion compositions with simultaneous in-situ measurements by a neutral cluster and air ion spectrometer. The median concentrations of negative cluster ions smaller than 1.6 nm were 85 (61–112 for 25–75 %) cm-3, decreasing significantly with an increasing condensation sink (CS). These concentrations are far lower than those observed at comparatively clean sites due to the higher CS in polluted environments. The ions NO3- and HSO4-, together with organic ions with the adducts of NO3- and HSO4-, were the most abundant in urban Beijing, and the organic ions in the atmosphere were similar in composition to those oxygenated organic molecules charged in a chemical ionization mass spectrometer with NO3- as the reagent ions. It was shown that the ambient atmosphere is a natural ion-molecular reaction chamber with NO3- and HSO4- as the main reagent ions. Compared to the clean sites, negative cluster ions in Beijing are composed of more NO3- and CHON organic ions due to higher NOx concentrations and higher fractions of CHON molecules in overall oxygenated organic species. Using dynamic equilibrium equations to examine the fate of HSO4- and C3H3O4- in the atmosphere, we found that their main sources to be the ionization of H2SO4 and C3H4O4 by NO3- and their main loss being the condensational loss onto aerosol particles (73–75 %), followed by ion-molecule reaction losses (19 %), and ion-ion recombination losses (6–8 %).

Rujing Yin et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1108', Anonymous Referee #1, 31 Dec 2022
  • RC2: 'Comment on egusphere-2022-1108', Anonymous Referee #2, 19 Jan 2023

Rujing Yin et al.


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Short summary
The negative cluster ions with specific compositions are measured and quantified through the in-situ measurement of an atmospheric pressure interface high-resolution time-of-flight mass spectrometer and a neutral cluster and air ion spectrometer in urban Beijing. The governing factors of atmospheric negative cluster ion concentration and composition at polluted urban sites are revealed and the fate of two representative ions in the urban atmosphere is characterized.