Seasonal Characteristics of New Particle Formation and Growth in Urban Beijing

Abstract

Understanding the atmospheric new particle formation (NPF) process within the global range is important for revealing the budget of atmospheric aerosols and their impacts. We investigated the seasonal characteristics of NPF in the urban environment of Beijing. Aerosol size distributions down to ∼1∼1 nm and H 2 SO 4 concentration were measured during 2018-2019.2018-2019. The observed formation rate of 1.5 nm particles (J 1.5 ) is significantly higher than those in the clean environment, e.g., Hyytiala;Hyytiala, whereas the growth rate is relatively lower. Both J 1.5 and NPF frequency in urban Beijing showed a clear seasonal variation with maxima in winter and minima in summer, while the observed growth rates were generally within the same range around the year. We show that ambient temperature is a governing factor driving the seasonal variation of J 1.5 . In contrast, the condensation sink showed no significant seasonal variation during the NPF periods and the daily maximum H 2 SO 4 concentration was slightly higher in summer than that in winter. In all four seasons, condensation of H 2 SO 4 and (H 2 SO 4 ) nn (amine) nn clusters contributes significantly to the growth rates in the sub-3 nm size range, whereas it is less important for the observed growth rates of particles above 3 nm. Therefore, other species are always needed for the growth of larger particles.

The Synergistic Role of Sulfuric Acid, Bases, and Oxidized Organics Governing New‐Particle Formation in Beijing

“…Such low concentrations suggest that organic vapors are not the main driver of particle growth at the smallest size (e.g., ~2 nm). Consistent with this, an independent study based on H2SO4 measurement also indicates that H2SO4 and its clusters contribute significantly to the particle growth at 1.5 -3 nm (Deng et al, 2020).…”

Sources and sinks driving sulfuric acid concentrations in contrasting environments: implications on proxy calculations

“…Sulfuric acid (H 2 SO 4 ), which has a very low saturation vapor pressure and strong hydrogen bonding capability (Zhang et al, 2011), has been found to be the major precursor of atmospheric NPF (Weber et al, 1996;Kulmala et al, 2004;Sihto et al, 2006;Sipilä et al, 2010;Erupe et al, 2011;Lehtipalo et al, 2018;Ma et al, 2019) and is often used in global models for simulating the occurrence and intensity of new particle formation events (Dunne et al, 2016). However, atmospheric measurements of gas-phase sulfuric acid are rare, mainly due to its low concentration (10 6 -10 7 molecules cm −3 or below) that can only be measured using state-of-the-art instruments (Mikkonen et al, 2011), such as the chemical ionization atmospheric-pressure interface time-of-flight spectrometer (CI-APi-ToF) (Eisele and Tanner, 1993;Jokinen et al, 2012).…”

Impacts of coagulation on the appearance time method for new particle growth rate evaluation and their corrections

“…On the other hand, the particle growth rate is a key to investigating growth mechanisms. Theoretical particle growth rates contributed by condensing vapors are usually compared to measured growth rates to reveal the possible particle growth mechanisms (Ehn et al, 2014;Yao et al, 2018;Mohr et al, 2019). A non-biased and accurate determination of measured growth rates is an important fundament of these comparisons.…”